MG Midget and Sprite Technical Lower fulcrums, and Gas grade PTFE BBS discussion at MG-Cars.net

MG Midget and Sprite Technical - Lower fulcrums, and Gas grade PTFE

It’s been a while since I needed to do anything to my wishbones. Years ago when these were much cheaper to replace outright, wear meant replacement, irrespective of the fact that they don’t last long due to the poor design of the lower fulcrum. However, now I’m fed up with the scrap and replace method, just on the principle that it annoys me, and I’m looking at a way to extend the life of these, either by a modification, or by other means. Having just picked up a complete set, both sides, of very good condition 2nd hand front suspension, including wishbones, other than constant greasing, which only works up to a point, I wish to extend the life of the wishbones. I’ve been thinking for example, about how you might take up the wear in the threaded bushes. The pins being extremely hard, don’t seem to wear much at all. Looking in the archives, I was amazed to see that a thought I’ve had about wrapping gas grade ptfe tape around the threaded pin and forcing it in, seems to have been tried already. What I’d like to know is, has it lasted? David, Guy? Has it lasted?

Lawrence Slater

I tried it some time ago. Tightened up the clearance OK but just got shredded in use.

F Pollock

I seem to remember that some commercial vehicles - maybe the A35 van, used a one shot pressure feed system. Each time the car was started a slug of grease was fed to the tread and bushes.

F Pollock

Hi Lawrence, Yes, I used PTFE tape on mine. I put it in as an experiment as I couldn't see it doing any harm. I did partially dismantle the suspension again some while later - about 5000 miles I think it was, and was surprised to find the tape more or less intact. At least there was still a good deal of it wound around the pins. I haven't looked again more recently I am a real believer in greasing those lower fulcrum really regularly. I do mine usually once a month, maybe less often in the winter if the ground is wet! The reason is not in order to lubricate the bushes - the grease would last way longer than that! - It is to pump any grit that has worked its way in there back out again as the fresh grease comes through. I also replaced the thin cork washers which are supposed to keep grit out, with disc slices of dense foam pipe insulation. These I cut over-length so that they compress in and make a better seal. Whether any of this actually makes much difference I don't know. But it is cheap, easy to do and makes me feel as if I am more in control of the entropy that is my car.

Guy

I used PTFE to get through MOT on one side. On the other side PTFE was not enough, so I used lead/tin and soldered the thread of the pin before putting it back together. I was/am planning to alter the lower pin and make solid pin and bushes for it, but stranded on getting the old threaded bushes out of the donor wishbones. Have to get back to that project soon.

Alex G Matla

Thanks Guy, Fergus, Alex, I thought it was only me that tried "mad" things. The other day, I used my blowtorch and some plumbers power flux, and did the same as you did with lead solder. It's tightened up the pin a great deal, but I haven't put it on the car yet, as I'm really only experimenting with these spare wishbones. It seems to me that there ought to be a way to improve the longevity of these bushes. I don't think it's just road grit that causes the problem. The pin is way harder than the bush, and with all the weight and forces at the front of the car resting on those bushes, it's not surprising that the bushes wear. Greasing both ends obviously helps, but still the grease gets squeezed out of the way, to the open centres, and the pin grinds away at the bush. Hence the need to grease very regularly, probably weekly. A real pain in the butt. Or as Fergus mentioned, a squirt of grease, every time the engine is started. On my motor bikes, I used a Scott-oiler, a device that fed a drop of oil to the drive chain every so often, and was adjustable as required. Without that, the chain and sprocket wore out at the normal rate. With the scott oiler, the chain and sprocket lasted at least 10 times the usual, because the chain was washed and lubed constantly. It did bathe everyting else in oil as well though, as it flicked off at speed if the flow was too great. :) Take crankshaft bearings. Hard journal against a soft bearing, except that it's not. A constant feed of oil under pressure keeps them apart. So if a way could be found to keep the pin from being in contact with bush, the bush would last far longer. That's what prompted my thoughts about the ptfe tape, and obviously other before me. If the bushes were bigger, and lined with these new Igus type materials, or a hard ptfe bush, I wonder how long they would last. So a thought I've had, is to modify the wishbone in some way, that would allow the bushes to be lined with a replaceable "plastic" inner bush. Another thought is to modify along the lines of what David B has already done, removable, renewable bushes, but retaining the original pin, as it's freely available and doesn't wear much. Other cars from the BMC stable of similar years, used replaceable bushes in the lower wishbone arms. Unfortunately none are a direct fit for Spridget lower fulcrum pins. But getting them made should be pretty easy I would think. Then it's a case of adapting the wishbones to accept removable bushes, again similar to the way David B has done it. I could of course just buy the cheaper standard pans, and add another grease nipple at the end, or buy the much better BK wishbones. But I'm in the mood for modifications now. :). It's a poor design, and everybody, even a poor non-engineer like me can see that, and how to improve it. I suppose the reason that someone hasn't made a commercially available modification, is the relative cheapness of the replacement wishbones, but other than that, I am surprised that some bright spark hasn't come up with a decent solution, that's caught on.

Lawrence Slater

My plan is to make some bushes on the lathe, from bronze or steel, dunno yet (oilite perhaps?) Then take a huge cilinderhead bolt (10.9 or 12.x quality) and put that in the lathe as well to make a new pin with grease passages to both sides. That way, the (stupid) construction of swiveling on a thread is eliminated.

Alex G Matla

Apart from the way I did it, I met a guy years ago who mentioned having done a few conversions to use Triumph Spitfire lower trunnion components. I think they comprise nylon tophat bushes and steel sleeves and a few other components. If you go like I did then you have to be aware that the OE spec kingpins are not available new since the early 1990s, unless someone has put them back into production. The difference is that the OE kingpin had the bottom faces around the trunnion bore faced and the aftermarket ones typically didn't so that face isn't accurately flat and square to clamp against. Not a difficult job though if you have appropriate machining facilities.

David Billington

David ,what did you do then?

Alex G Matla

BTW, the threaded bushes are brazed in the wishbone aren't they? So with a acetylene torch it should be able to loosen them? 'Cause this didn't work for me.

Alex G Matla

Just a point with he design - the "thread" on the pin isn't actually a thread. At least it isn't in the normal application of a thread. It is effectively a means of increasing the surface area of the bushes at either end. Sort of like a concertina'd plain bush. Doesn't make it any better as a design though! A common arrangement for that on modern cars is a hefty ball and socket, in effect replacing both the Spridget fulcrum pin function and the lower king pin bush. Although these are often integral to a bottom wishbone arm, some cars use a replaceable component that bolts to the end of the wishbone. It then has a vertical tapered pin up into the hub carrier where it is further clamped by a bolt through a notch in the pin. I think Renaults Clios and possibly earlier VW Golfs were like that. I think it would be difficult to convert the Spridget swivel hub to take a ball joint pin, but there may be another way. Given the form of the Spridget king pin I imagine it wouldn't be that hard to machine a new king pin to match the stepped bearing part, but with a block at the bottom end in place of the horizontal fulcrum pin hole. This block would then need a vertical tapered hole, clamping slot and cross cotter pin /bolt. Sized to take a standard ball and socket unit which would then bolt to the end of a normal wishbone pan.

Guy

Alex, http://www.metal-arts.co.uk/sprite/frontsuspmods/index.html Questionable these days as I understand that technically welding a wishbone is an MOT failure and I can understand why with modern wishbones and metallurgy. Guy, Interesting idea but I think it would have to be bent inwards at the bottom for the joint to clear the disc. Also IIRC many VW and similarly Porsche use a straight stem on the ball joint but then that's easier to make.

David Billington

Actually. I was only speculating. I wouldn't ever do that as a) my engineering isn't up to it, b) I would have no way of testing other than use/ destruction testing and I don't want to be destructed c) It would no longer be a Spridget - a modification too far I think! I might however go as far as using some more modern/ technical replacement for the wishbone bushes if something were available. In the meantime I will keep on with the grease gun. I am beginning now to factor in the number of times I may still need to do some of these recurring jobs on my car. There is a sort of formula of reducing mileage (down from around 10K to 8K per year already) and increasing age (mine rather than the car's) that should save me from a future of too many front suspension rebuilds to come.

Guy

Guy, I think a balljoint has more degrees of freedom than the midget, so I suspect using a balljoint could be a very bad idea.

G Waite

Hi, As I said, I don't plan to do this. But I am not sure exactly what you are getting at? Clearly a ball joint will pivot through a greater range of movement than the Fulcrum pin and king pin combination, but the actual amount that these move through isn't limited by their design anyway. Surely it would just mean that only a part of the available movement in the ball and socket would be used? Maybe I have misunderstood the point you are making? It might help others to explain a bit more.

Guy

As is often said around here, no point in re-inventing the wheel. But maybe improving it is good idea. As regards welding the wishbones. Exchange pans are still available, as well as new, so some degree of welding/brazing is allowed I assume. I'll keep the kingpins as the are as they are long lasting if greased, and not difficult to change. It's the threaded bearing that's the problem, so that's what needs the attention. The only bit I want to alter is the threaded bush, either by lining it, or by replacing it with a renewable one. With the exchange units, somebody removes the exsiting worn bushes, and welds/brazes in new ones. One idea would be to put in oversized bushes, into which could be inserted replacable threaded bushes. That way, as long as the remainder of the wishbone remains sound, you could change the threaded bushes easily at home, and indefinitely. The bushes in the picture are clamped into the lower arms of the following cars. Austin A55 Mk II & A60, Morris Oxford Series 5 & Series 6, MG Magnette Mk 3 & Mk 4, Riley 4/68 & 4/72, Wolseley 15/60 & 16/60. Something similar with the appropriate internal threads, could be made to insert into the Spridget wishbones. Either by clamping as with these, or even an external thread, so that they could be screwed into the oversized threaded bushes I mentioned above.

Lawrence Slater

Smart idea Lawrence. For a while, and not so many years ago, it was common practice to supply the bushes loose as a replacement item. The idea being that you (or your mechanic) softened the old braise with a torch, knocked out the worn bushes, and then braised in the replacements. This involved aligning the two parts using an old fulcrum pin, and then taking care not to let the braise run in the wrong places so that the pin couldn't be undone! Actually quite a simple procedure.

Guy

PS, the reason for the thread isn't only to increase the bearing surface. The thread controls the pin endfloat. With plain bushes, you would have to provide for the bearing surface David mentions on the side faces of the kingpins. I think beefed up and replaceable threaded bushes, could be a relatively simple answer.

Lawrence Slater

Guy, does anyone supply the threaded bushes?

Lawrence Slater

Great idea - Lets do that. I'm going to try and get a spare wishbone to practise on - the ebay hunt begins. Then its a case of machining up new oversized bushes and the disposable ones - sounds like fun!

C L Carter

Just had a look but cannot find any now. I haven't seen them for a while. Last time I recall this being discussed was in the USA where they were still available, maybe 8 or 10 years ago. My guess is that they have dropped off the bottom of the stock lists as few would choose to do that job when "reconditioned" wishbones were cheap enough.

Guy

Original design from around 1953 I think. You would expect that with modern materials there would be something one could make in a hard Nylon or similar that would just push into place as a liner for the old bush. I could imagine reaming the inside of the old bushes out to an accurate size and then just in a new replaceable liner, to take a plain pin. Then maybe some shims to take up any fore and aft thrust otherwise controlled by the old screw fitting pin as Lawrence commented.

Guy

I've got some ;o)

Dave O'Neill2

So where do the reconditioners get their new bushes? Do they just get some steel tube and have them made? If so, then that's the way to go. Get some thicker walled steel tube, and cut an appropriate internal thread, and an external thread. Also get some larger steel tube for the external bushes, and cut internal threads. Weld the external bushes into wishbones. Screw in internal bushes. In other words copy the bushes in my picture below, but with the addition of an external thread. Or copy the bushes below, and arrange for them to be clampled into the spridget wishbones, in the same way they are clamped into the lower arms of the cars listed below.

Lawrence Slater

Guy, I also thought of exactly that. Drill/ream out the thread and insert a bush. But would the existing bush still be thick walled enough to support the pin? Here's a serious suggestion. Suppose someone here, with both the knowledge/skills and the access to the required machinery, could be persuaded to make the prototype internal and external bushes? Who might be interested in a joint not for profit venture to fund this, for the sake of ALL spridget owners? After that of course other arrangements would be needed to make them in the quantities required. PS. How many have you got David?

Lawrence Slater

I'm not sure how many bushes I have. I will have to check when I get home. I have 60+ wishbones, though!

Dave O'Neill2

I take it you used to recondition wishbones then Dave? Or is there some other reason you collect wishbones? :)

Lawrence Slater

I will happily machine up a prototype system and then can ask nicely a friend (perhaps with a small fee) who can CNC out as many bushes as we need. Dave, I'm going on tour in the midget on Saturday and will be staying the night in Birmingham on Sunday night, if you are willing to part with a set of wishbones then I could collect them enroute on Monday morning/midday? Also, why on earth do you have 60+ wishbones? Does that sound okay?

C L Carter

Barry King ought to know a lot about the wishbone design and what works / what doesn't. It would be interesting to take your final creation to him and get his input (and, if it works, maybe he'd be interested in productionizing it?) On the other hand, if I have to replace my wishbones every 40k ~ 50k miles, then it will take me the rest of my life to wear out the ones that I've got and so maybe the question is moot? Norm

Norm Kerr

I understood at Midget50 that Barry King's bussines was for sale? And I think that the wall thickness left after removing the thread isn't enough. Based on the fact that I could look through the bottom half of one of mine 8^0

Alex G Matla

Hi Norm, From my experience, whilst you can make the wishbones last 40K miles, with very regular greasing, it's long before that, that wear in the threaded bushes becomes annoying, and constantly greasing the fulcrums is annoying in itself. Until now, I've just lived with the shake rattle and roll until it annoyed me. However as I said earlier, I used to scrap the wishbones regularly as they used to be much cheaper. Now I'm in the mood for a more eloquent solution. I can't see how it won't work. What's not to work? The BK wishbones have an extra grease point, and solid pins, and must last longer. However, that doesn't get around the central issue, that the threaded bush will wear out long before it should, and then the you have to replace/repair the wishbone. Persuading someone who is already successfully making an improved version of the current wishbone seems an uphill task, as no doubt there is existing investment involved. Christian, I don't have access to machinery, or sufficient skill on those machines to do this myself, but I'll gladly share my bad ideas and research with you. Either that or I'll go local, and get my ideas made up. A new pair of standard pans is circa 100 quid. I reckon I can get internal and external bushes made for that kind of money. I also wonder what size the bushes I pictured are. One will be too big, as the threaded pins used on those cars, are the same thread diameter on both ends of the pin. But if one fits, then it's only a matter of having it copied, with a smaller internal thread, and then designing a clamping method to fix them in the wishbones. Not an insurmountable task I wouldn't have thought. This isn't for everybody, but I like the idea of fixing an annoying problem. I agree with you Alex. I was playing this afternoon. by the time you ream out the thread for an internal bush, the wall is too thin for any margin error. It needs new oversized thicker walled bushes. I also tried the thick gas grade ptfe tape. I was surprised at how well that took up the wear. I wrapped a couple of layers of the tape around the pin, and forced it in. it turns with a stiff interference, but turns smoothly. I wonder how it would perform on a brand new set of bushes?

Lawrence Slater

Well seeing as I'm about to do a front suspension overhall myself, and this is a problem - I'm keen to have ago at fixing the problem - and if it works am happy to roll off a few more at cost, for those who want them. When I get back from holiday (hopefully with some wishbones if Dave is willing to spare a couple) then we can arrange a weekend where I come over to RTwells and we ponder ideas. Sounds like a plan gents

C L Carter

Although I see where you are coming from, I don't think your proposal as it stands is going to reduce the maintenance requirement at all. Yes the screw in replaceable inner bush will be easy to renew once the initial work is done, but it will still wear if not regularly and frequently greased. I thought the original concept of using new materials - solid PTFE; Nylon, whatever, - that are in effect self lubricating, would be a better solution. It does make one wonder why they didn't originally go for a Metalastic bush arrangement of some sort? Maybe the direct impact pounding that they will get would have just destroyed the rubber bonding.

Guy

About seven years ago, I had one of the first three Westfield (Lotus) Elevens, and it ran A series motor, Sprite axle and also Sprite kingpins/stub axles & hubs. What it didn't have was the wishbones as these were tubular, and the kingpins were bushed but I can't remember how. I never had any trouble or had to take them apart, so didn't get to see exactly what was done. I'm busy modifying my rear axle to take Caterham coil-overs, and would be interested in doing something clever with the front too. Have access to a lathe and a good operative.......

D le Versha

Christian Drop me a mail daveo138 at yahoo dot co dot uk

Dave O'Neill2

Guy, I'm not fixed on this, but to keep costs down and use what is easily available, and is hard wearing, I favour retaining the threaded fulcrum. This also has the advantage of not needing to invent a method of endfloat control, as it's in the threads. I'm essentially lazy, and if there's a solution already in use on another car that works, I'm happy to copy it. The bushes in the picture I posted, are much heavier, and from what I can tell, last far longer. The spridget wishbone bush is frail and soft by comparison, and so wears prematurely. My idea would be to use a harder threaded bush, such that the wear would be reduced. Playing around tonight in the garage with ptfe tape, I also realised that it's possible to reduce or maybe eliminate grease loss. If this can be done, then not only will the bush last longer, but the greasing interval will be reduced greatly. Winding an extra thick wrap of ptfe tape around the forward end of the large diameter thread on the fulcrum, and around the rearward end of the smaller diameter thread, effectively prevents the grease from being pushed out to the centres under pressure, and also has the side benefit of keeping grit and moisture from entering the threads. If this works, even the current bushing arrangement could last much longer. However, I think it's well worth finding a simple and readily available way to fit replaceable bushes. "Maybe the direct impact pounding that they will get would have just destroyed the rubber bonding." That's the nagging doubt I have about trying a hard plastic bush too. We don't know how much pounding it could take. To alter the wishbones to take a modern plastic bush, and then find it doesn't last long enough, would be somewhat annoying. At least we already know the longevity of the current spridget bushes. All that's required (at least by me), is to extend that life, reduce the greasing frequency, and make it much easier to replace the bushes when the time comes. But I'm all ears to a better idea. Yup get together sounds great Christian. Have to be after end of April for me, I'm off to South East Asia for a little sun shortly.

Lawrence Slater

"but the greasing interval will be reduced greatly." I mean the greasing frequency reduced, the interval will increase. :)

Lawrence Slater

Lawrence, To me there was an attraction in the idea that somewhere out there is a modern material that would do this job, not wear, not shatter, need minimal maintenance, etc etc! Probably doesn't exist! Probably a good idea to use the heavier duty items that you have found used on those other, heavier and more robust cars. I think that is in effect a modified redesign of the same thing, developed and used on the later and heavier cars in the group. The Spridget version was introduced on the A30 at the start of the '50s and is clearly a minimum simple solution job when materials were in short supply and vehicles not expected to do more than 40 or 50,000 miles in a whole lifetime. So the design was "adequate" for the expected use. Interesting too that Special Tuning didn't, as far as I know, come up with any development for that specific part during the early racing and rallying days. I am interested to see how you get on with this. I am sure others must have tried some ideas before, but yours has the merit of simplicity and use of existing tried and tested components. I still think they will need pretty regular greasing but although a chore, it is so simple to do it isn't really a problem. Incidentally, I have grease points at both ends of the pin as without that the thin end never gets enough grease injected directly into it to force the grit and muck out.

Guy

The regular greasing isn't a major chore (on the vintage vehilces we use - we grease every 100miles... and by hand!) The point is this is an engineering challenge that we can solve. This is just a random thought that I haven't thought through - but what about a replaceable steel bush - I was thinking 2 top hat style arrangements which thread into each other through the wishbone? Else we could go with Lawrences dual bush idea - and instead of using a rubber/poly replacable bush - use a phozzy bronze one, expensive, bush if well greased should last a good while. Food for thought

C L Carter

The other issue to resolve is the fulcrum pin seizing in the bottom of the kingpin.

Dave O'Neill2

Guy, after stripping the FL suspension conversion, and becoming aware of the new Igus type bushes, I too would like to use a modern material to replace the threaded arrangement in the spridget wishbones. But it requires experiment, and I think this needs a more tried and tested solution, for the reasons you gave about the pounding it will receive. I agree too, that the lower suspension arrangements on the later cars, has to have been an improvement, as well as being more robust for the heavier cars. My feeling is, that if the heavier bushings lasted longer on an Austin A55 and cousins, then those bushings or something very similar, will last far far longer on the comparatively light weight spridgets. It's annoying that we are not able to simply use the A55 bushings directly. The trouble is, we are constrained by spridget kingpins, which need a thin fulcrum pin to go through the eye in the king pin. Otherwise we could use the fulcrum pin and bushes from the A55 et al. One option might be to use the A55 king pins too, and then turn them down to fit Spridget stub axles. But following this route is to practically replace the whole of the spridget front suspension bottom end, when most of it is really not bad at all. In fact apart from the often poor rebuild quality of the front shocks, and the relative weakeness of the threaded bushes in the wishbones, it all works ok. So for me, I'm happy to replace the weak link in the simplest way possible, with the minimum alteration. I agree Christian. This is a problem that should be solved. Had I been an engineer, and the wishbones more expensive in the past, I think by now I would have done something about it. I'm really quite surprised nobody has produced a comercially available mod to this. Trying to stick to the idea of minimum alteration, and minimum use of non standard parts, I still favour the threaded solution, but nothing should be ruled out. 1) The wishbones have to be altered to contain a receptacle for the replaceable bushes. 2) The receptacles and replaceable bushes have to be made. 3) If replacing with a smooth fulcrum pin, the smooth pin has to be made, and the king pins have to be faced, or other means devised for endfloat control. 4) Grease points at both ends essential, but also block the hole in the thin end of the fulrum. This then forces grease around the threads, instead of it being pumped to the fat end. I'd retain the hole at the fat end though, as this allows grease to be fed to the thin end threads, via the smaller side hole in the thin end of the fulcrum. Christian, your suggestion of steel top hat bushes or the like, sounds like David Bs solution, except that he used oilites instead of steel. David also pointed out that the king pins would have to be faced to provide a bearing surface for endfloat control. In fact, David if your still following this, I've been meaning to ask. I've looked at the pics on your website, and wanted to know how your oilites solution to this has fared. Are you still running this mod in your car, what kind of milage have you got from the oilites, and how much wear developed? Edit, Dave, spot on, Im just working on freeing one now. The only way seems to be prevention. Copper slip or the like. Got to prevent mositure ingress in the first place I think.

Lawrence Slater

On the seized fulcrum pin in the kingpin, I've been thinking of reaming the kingpin eye a thou or 2. Just sufficient for a coat of paint on either or both the pin and the kingpin eye. Sounds dodgy at first, reaming the Kpin eye, but I've driven on Kpins that were revolving around the fulcrum because the cotter came out, and had oodles of play due to wear. Rattled a lot, but didn't fracture the eye of the Kpin. I think they could stand a bit of reaming. A rat tale file or a very slightly oversized drill would do it in the absense of a reamer. If of course there was a decent handle on the the fulcrum pin you could put a socket on it, and turn it free from the kpin. The slot in the end is hopeless, even if you make a tool --- I have. Edit. If the hole at the fat end of the fulcrum pin would take an allen key, that might work better.

Lawrence Slater

I wanted to save a good kingpin which was attached to a worn wishbone, but I couldn't remove the fulcrum pin. I cut through the pin on either side to free the kingpin, but no amount of heat or hammering would remove the remains of the fulcrum pin from the eye.

Dave O'Neill2

These are 2 different problems. I would only attack one at once. The King pin issue - easy solution is to whack copperslip on it - the copper will prevent it from bonding. A more permanent solution would be to use 2 different materials (bronze on steel) - but that involved accuarately reaming out the hole and pressing a bush in... I'm not sure any of this is necessary - because its not supposed to rotate is it? It has a key for the cotter to hold it in place - the threaded portion rotates and thats what we are trying to solve yes. I think a 15 tonne bearing press would remove the seized pin Dave... if not I can borrow my friends 250tonne press he uses to press brake drums out of 1/4" steel plate... that would shift it =]

C L Carter

Back on the other problem though, Lawrence, you are keen to keep the "threaded" pin... I've haven't stripped mine down yet so have never seen how this arrangement fits into the wishbone. Nor have I seen how endfloat is controlled. I would much prefer not to use a threaded pin... I've been inspecting my rebuild kit and the threads are extremely sharp - these must be causing wear... its like jumping on a bed of nails. I would think a smooth pin with a coarse shallow spiraling groove cut in (like in an old main bearing) would work much better - although this may be reiventing the wheel a bit. I need to strip down a wishbone to see the arrangement more clearly. That all said, the pins are probably hardened or made from hardened steel - EN8 or upwards... EN24... Maybe it would be better to make hardened bushes (EN 36) - which are harder than the pins, so that the pins wear instead of the bushes... pins are easier to replace!

C L Carter

I've always thought the threaded bushing/pin was a bit dodgy. This joint is supposed to be the primary means of keeping the king pin at proper inclination (the upper shock link helps very little). Yet the very nature of the threads requires a bit of float for assembly. As we observe, the float becomes greater with use despite regular greasing. So, if I were to undertake this project, I'd look for solutions that also improved the "rigidity" of the lower joint. Actually, I think a tubular lower A-arm would be a better solution than modifying the stamped one. However, that is a slippery slope and before long the car is no longer a spridget. Carry on, gentlemen.

Trevor Jessie

I agree Trevor, but I also agree that going tubular is a step too far.

C L Carter

Dave Did you get my email this morning? Christian

C L Carter

Tubular is either heavier or way too expensive in case of lighter material. I think. This thread is making my hands itch to continue whit my plan! I think I'll have a try tomorrow to get the old bushes out.

Alex G Matla

Yup, agreed, the seized fulcrum in the kpin is a seperate problem, albeit in the same basket though. The 1st answer is prevention. The 2nd is freeing it, if it is seized. I have the great satisfaction to report freeing one today. Firstly, I don't like being beaten. I'm a bad loser. These are two seperate dumb bits of metal(unless someone welded them together), and I command they seperate. For the last few days, I have tried rotating it, -- hopeless, heating it --- hopeless, freezing it (entire wishbone in the freezer)---- hopeless, acetone/brakefluid and atf --- hopless, Plusgas ---- hopless, and all combinations of the above. I was about to resort to cutting either the kpin or the fpin. But I don't like defeat, and like Dave I didn't want to destroy either the kpin or the fpin, or the bushes in the wishbone for that matter. So I thought a bit more. If you can't turn the fpin in the kpin, then move the kpin along the shaft of the fpin. How? Hammer it. How to stop the bushes in the wishbone being ruined by the hammering? Support the fpin, so that all the force of the hammer blows is taken on the ends of the fpin. It helps if you have wishbones with grease nipples at each end. If you don't, then drill a hole in the blind bush, and add a grease nipple later. 1) Remove both grease nipples. Of course the cotter is already out. 2) Insert a hard bolt through the grease nipple hole. 3) Place wishbone on it's side, so the head of the bolt just inserted, is on a hard very surface. 4) Use a suitably sized drift and hammer, to bang the kpin along the fpin. Use a little heat to assist. Might take a few(hundred) blows. 5) Turn w'bone onto other side. Use bolt again to support the fpin, and bang on the other side of the kpin. 6) Repeat the process as often as neccessary until movement appears. 7) Once it starts to move, it's just a case of repeating until movement is greater. Heat again. Hammer again, plus gas again, suddenly it moves a lot, and then you can finally turn it. Bingo I have a freed, previously extremely seized fulcrum pin.

Lawrence Slater

Back to the main event. There are quite a few solutions out there to this already. But apart from David Bs solution, they all require much more major alteration than I am looking for. Not for purity, but for simplicity, I want to retain as much of the original as is possible. I already have 4(2 sets of w/bones) lower fulcrum pins. These pins are very hard, and don't wear much, if at all. They are also circa 10 quid each. I'm tight, and also have a pathological hatred of wasting anything that isn't worn out. The pins are not the cause of the problem. The bushes are. They are too weak, it's those that wear, so those that need the remedy. I'm not that clued up on the different types of steel, but I agree a harder steel for the bushes is the obvious way to go here. That appears to be the case in the pictures I posted of A55 bushes below. Perhaps if a harder steel were employed in the first place (non removable bushes), that might be all that's necessary to fix this. Perhaps we don't need renewable bushes at all, just harder wearing ones. I agree Christian, keep the original pins, and use a harder bush, so the pin wears first. Would a harder bush be too brittle? Would there be a risk of fracture?

Lawrence Slater

Lawrence, Regarding your query about getting PTFE tape in around new pins I doubt you'd have much joy as new pins in new bushes can be a very good fit. Years ago I was told that the correct way to do the bushes was to braze in new unthreaded bushes then tap with a special tap to unsure alignment and the correct size threads. I have never seen one of the taps though. Regarding the longevity of my wishbone modification I have done about 70k miles on them with little wear so I'm happy with the result. The car hasn't been on the road since 1997 but did about 85k miles in total in the 12 years I had it on the road since 1985.

David Billington

It is possible they could fracture - they do get a shock loading. I'm not suggesting we use tool steel or anything that hard... but as long as its harder than the pin. If I get some spares then I'll do a vickers hardnest test on them both to see what they are made of. If fracture really is a concern then we could just case harden them. But I've never heard of 24 or 36 fracturing. Lawrence can you post a photo of the current bush in the wishbone - I've never seen the arrangement and I want to know how the pin fits into it and what stops it coming out!

C L Carter

Yup Christian pics are on my list of things to post. Will post a couple later.

Lawrence Slater

Hi David, I just looked at your website, and didn't realise that you had put the mileages on there already. Teach me for not reading it thoroughly. If your oilite mod has lasted upto 70k miles, that sounds like a good solution to me. Oilite bushes are not very expensive. So as much as I would like to avoid extra work --- having a smooth pin(s) made --- 70k miles between bush changes, sounds good to me. As regards facing the Kpin sides, I reckon that could even be done on a stone in the garage at a push. The pair of Kpins I've just removed are unfaced, but it would be a pretty simple job to smooth them. Have the steel sleeves over the fulcrum bolt worn much/at all, or is the wear confined to the oilites? So you also do away with the cotter pin, as the steel bushes clamp tightly to each side of the Kpin? That resolves the issue of seized in fulcrum pins.

Lawrence Slater

David, the special tap you mentioned for the w/bone bushes was probably made by Churchills, like the kpin reamer, and would have been stepped too. Does anyone have the original BMC workshop manual for Spridgets? I wonder if the tool section in there lists it.

Lawrence Slater

Nope, no sign of any stepped taps in there.

Dave O'Neill2

I don't remember any garages refurbing wishbones, only replaced them with new or bought in refurbed ones - so probably very specialist tooling by reconditioners if they actually exist. R.

richard boobier

Yes, there's also the challenge of getting the beginning of the thread in the bushings exactly right, in such a manner that the pin will screw in. Ofcourse that isn't a problem if the thread is cut in afterwards.

Alex G Matla

As I mentioned earlier, there was much discussion on fitting those bushes as replacements on the USA based Autox-Spridgets forum, maybe 10 or more years ago. Pretty sure that the bushes were supplied ready threaded so a tap was not needed, and that the method was to fit them loose, using a fulcrum pin to align them (and the thread start positions) and then just braise away. Perhaps Gryf will remember?

Guy

Here's a link to a bit of a discussion in 1998 which mentions a modification. http://www.team.net/html/spridgets/1998-08/msg00041.html I will keep looking, I might find more that I had forgotten about!

Guy

Guy, I dislike that forum organisation. Anyway after "Basically, it uses a modified high tensile bolt and some delrin bushes. You have to remove the existing threaded insert from the end of the wishbone." Did anything come back regarding that mod, sounds a bit like the Spitfire trunnion mod I've been told about before. Lawrence, For the mod I made it is fairly important that the sides of the kingpin are faced square to the bore. Not difficult with the right tools but I wouldn't try it on a stone in a garage. I suppose it could be done with a gauge and spotting blue but time consuming.

David Billington

David, I hate archives at the best of times! I rarely if ever find what I want. I was quite surprised to come up with that particular, though brief reference from 1998. There is almost certainly a lot more on it than those half dozen related messages - I will see what I can find. The Autox site goes back a long way and was a pretty primitive form of e-mail exchange at least in its early years, even more so than the BBS was!

Guy

Mark (the guy that runs autox.team.net) is having to rebuild the archives, so it may not all be there at the moment.

Trevor Jessie

That's maybe why I am only getting hits from 1998 - 2000 on my searches. I am absolutely certain that the topic was discussed off and on over a much longer period than that! Interesting to see some of the names from way back then though - many still around and just a few notable ones now gone>

Guy

I've been discussing this with a friend of mine and we've decided that oilites are probably the best (user friendly) way to go. I'm very keen to get rid of this nonsense threaded issue - so yes a smooth pin would need machining. In order to remove cotter... My original idea was to machine bronze bushes instead of Oillites and keep one end shallow with a D flat and then have a corresponding D flat on the pin to prevent rotation but I think that might be taking it a bit far. Cotters are okay anyway - not great - okay. The pin I would make such that it takes 2 lip seals to keep the grease/heavy steam oil in and the crud out. The pin/oilites or bushes would require a release groove for the grease. Also an idea would be to use 2 shorter oilites with a gap in the middle to act as a grease resevoir (not a huge gap a few mm) I'm going to draw something up and make a prototype - but I'd be keen to have the pins professional made so that they can be made from a hard but tough steel (EN8) then case hardened and ground to size. They would drill and tap the grease nipple holes and the release holes and grooves. I think if I had a batch made they'd be reasonably priced by a local company I know - probably no more than the £10 a side that Lawrence says the new ones cost anyway. Bit more design work first.

C L Carter

I may not have grasped the way the thoughts are developing, but here is a suggestion that may be worth considering: Why not have a fulcrum pin that is fixed in relation to the wishbone and use a single bearing bush that is set into the eye of the kingpin. It would be easier having a long hardened bolt that passes through the two wishbone bushes and is tightened to fasten there, and have an oilite bush that is a tight interference fit into the kingpin. It would need to be just slightly wider than the kingpin to provide thrust faces on either side. I wish I knew more about modern materials. I find it hard to believe that there isn't some suitable plastic type material that has been developed over the last 60 years from which a suitable bush could be cheaply made that would just be a push-fit into the hole in the bottom of the kingpin

Guy

I do not think there is enough space to fit a suitable size pin AND bushing into the kingpin.

Trevor Jessie

ha ha, you beat me to it trevor. :) Hi Guy, In order to fit a bush as well as a bolt/pin through the eye of the kpin, I think you'd have to ream out the eye to an extent that the wall of the kpin would be pretty thin, and hence prone to breakage. Christian, I think I follow you, be interested in the drawings. I agree about the oil seal, that's what I meant earlier when talking about my experiments with the ptfe tape sealing the grease in, and peventing it being squeezed out at the centres. Something else I've noticed. The larger of the two w/bone bushes, appears to wear more than the smaller. At least that's how it is on the pair of w/bones I've been playing with. Although both are grease nippled at each end, both appear not to have been well greased in use, as they were both filled with gunge. Probably not greased often enough. However, I would have expected them to both wear the same amount if both get the same amount of grease. I'm wondering if orientation on the car causes more wear on the front or rear bush? How about my comment on just replacing the standard w/bone bush with a hardened one? If the existing bushes were harder, they would wear less, and hence the problem would effectively go away. As the bushes have to be replaced/modified anyway, if simply using a harder bush fixes this, then that has to be the simplest possible solution. Agree/disagree?

Lawrence Slater

My issue with the threaded bushing/pin is the inherent play that exists to allow installation.

Trevor Jessie

Lawrence If the larger of the two bushes wears more, orientation can't be the cause, as the N/S is to the front and the O/S to the rear. I have also noticed more wear on the larger bush. The system that Guy describes is similar to what is used on the MGB. There is a bush in the kingin eye, a steel tube inside the bush which is clamped between the two arms by a long bolt. The MGB 'wishbone' is in three pieces, with a separate spring pan and two arms bolted together.

Dave O'Neill2

Presumably then Dave, the MGB kingpin has a larger "eye" at the bottom, to take the bush as I speculated earlier. I can see the point though, there isn't a great deal of meat on the Spridget kingpin. Why are Oilite bushes so chunky? All the ones I have seen have quite thick walls, when obviously it is only a thin surface that does the bearing support function. Perhaps to retain sufficient oil within the material? If one were to compare it to an engine bearing it would only need to have a thin wall, backed by the steel of the kingpin. A bit like a Speedy-sleeve, though maybe rather thicker than that! Regarding replacing the bushes with something harder: Can someone explain the logic with bearing surfaces. Some applications use similar, very hard materials on both surfaces. An example would be a ball bearing. Other applications use a hard and a soft material - such as on a big end where the white metal is really soft, but still doesn't wear away. At least not for a long time. I still think that the main cause of wear in fulcrum bushes is from the abrasive mix of grit and grease that gets in there. If one fitted new standard bushes, well aligned and then had a means of sealing them from any road dirt I think they would last a good long time. I had thought about cleaning off all surface grease and muck from between the kingpin and the wishbone bushes, where the cork washers normally go - I think early applications used felt washers which I would have thought worked better than cork - then filling the whole void with a thick plug of silicon. I wonder how long that could be made to last?

Guy

I agree lawrence that would be the simplist solution - but if the job is being done - its worth doing properly and the threaded arrangement is clearly the source of the problem - I can't see any tribological sense in it! Guy - The balls in a ball bearing are actually slightly harder than the races. Now in laymens terms I'm going to try and explain the difference between Hyrdrodynamic lubrication and Elastohyrdrodynamic. Hydrodynamic uses the principle that 2 relatively hard surfaces generated an oil film between them under pressure. This is what happens in a journal bearing and a ball bearing. Elastohydrodynamic lubrication occurs with a soft material against a hard material - it is used frequently where you can't generate enough speed to get a high enough pressure to seperate the 2 surfaces as in hyrdrodynamic. The idea is that the softer surface deforms elastically therefore increasing the surface area. Many think this is the case in white metal engine bearings but most of the time its not becauase you get hyrdrodyamic lubrication. Here is a party trick you can do to demonstrate the principle: Take a hard boiled egg. Find a clean slippery surface like a lamintate kitchen top. Put some water or better still soapy water on the surface. Take egg and gently send it along the surface. The hard boiled egg will roll through the water because there isn't enough pressure to build up a film of lubricant Now remove shell of egg and repeat! See what happens. Alternatively you can insert hard boiled egg into a French letter and repeat - it should have the same effect. This is why we use soft materials in areas like this - so that you get a film seperation!

C L Carter

OK, So in the case of the fulcrum pin there isn't enough (any) movement to build up a hydrodynamic film of lubricant. So it uses a relatively hard pin and a soft bush. What effect will making the bushes from a harder metal have - won't this defeat the object? Although the screw arrangement enables the king pin to be adjusted and set between the lugs of the wishbone, accounting for the fore and aft loads, I still believe that the other function of the screw is a clever way of massively increasing the surface area between the components. Changing to plain surfaces is going to have some other effects and this will need to be addressed, presumably by choosing the right materials. Everyone criticises this fulcrum pin arrangement, and yes, it probably can be improved. But the engineering expertise available at the time was pretty good - there were far more sophisticated engineering applications already in use in all sorts of situations. So it was not a lack of engineering knowledge in 1950 that led to this design. I think it was an item designed for a specific relatively light duty application, to a cost, with an expected life span and a maintenance regime which was common place at the time. We now view it differently, expect components to last much longer, cope with higher stresses and do so with minimal maintenance. It is our expectations that have changed. Life was very different in 1950, and pottering a few miles through rural roads at 25mph in an A30 is what the original design envisaged. It is some testament to the much maligned design that it was retained unaltered in production for 30 years and in much more demanding use. But I am sure it can be improved!

Guy

Not just me then Dave. So why does the large bush wear more than the smaller of the two? If not orientation in the car, then something to do with the greater circumference of the larger bush? You’d think the smaller might wear faster, so I’m intrigued that the larger appears to wear faster. Maybe the larger bush sheds/leaks grease faster? Which brings us to the topic of sealing the bushes, rather than the current total loss system. Yup Guy, I remember felt washers too. I posted earlier, “Winding an extra thick wrap of ptfe tape around the forward end of the large diameter thread on the fulcrum, and around the rearward end of the smaller diameter thread, effectively prevents the grease from being pushed out to the centres under pressure, and also has the side benefit of keeping grit and moisture from entering the threads. If this works, even the current bushing arrangement could last much longer.” So combine sealing the bushes, with installing harder bushes, and the problem might well go away. If so, then there is no need to make any other alterations. I (we?) don’t like the threaded system because of two issues. 1) It requires frequent greasing, 2) it wears prematurely. However, when first installed, when new, it performs well enough for my needs (road use). Reduce the greasing frequency, by making it more effective, by reducing or eliminating grease loss, use harder bushes, and problem solved. If what Christian has explained about hardness in bearings is true, and I have no doubt it is, then the question is, why were the bushes not originally made harder? Guy probably already explained this earlier, talking about materials choice in the A35. It seemed adequate at the time for a short lived car. Little did BMC know. Or probably they did, and used harder bushes on the later A55 stable of cars. I’ll always go for the simplest solution to a problem, no matter how sophisticated the alternatives are, tribologically speaking. – :) Great word Christian, I had to google that. Typical engineer baffling us poor laymen lol. I’ll find a way to use that on someone this week. :) As regards eggs in French letters. I can barely speak French, let alone write about oeuf in French.

Lawrence Slater

Here's a pic or 3. This first one, is of a crude attempt to line the worn bushes. I cut a couple of slithers of thin tin plate, -- from my tobacco days ---, and insterted them into the large bush, whilst screwing in the fulcrum pin. You can see the results. The play was taken up very well, and the pin still turned quite smoothly in the bush. I'm going to make a single wider liner (say 75% of the circumfrence of the of the pin, to allow the grease to penetrate) and try that later. If it works as well, I might just install it on the car and trial it for a few hundred miles.

Lawrence Slater

Here's a couple of pics as requested by Christian. The white bits at the edges of the bushes are gas grade ptfe tape.

Lawrence Slater

And another showing the pin partially screwed in. Again the white bits are the remains of my experiments with gas grade ptfe tape, after I removed most of it. That tape is actually reasonably difficult to get out of the grooves -- it hugs them, after it's been squeezed inside the bushes. Quite useful in fact, I think.

Lawrence Slater

And one of the smaller bush with added grease nipple hole. These w/bones appear to be home/garage modified. Crude but effective, and great for the cheap price I paid, including very serviceable stubaxles/kingpins, and original no free play RHP wheel bearings in the hubs. :).

Lawrence Slater

Increaseing the hardness of the bushes will not remove the problem. It will not help with lubrication at all. It will have the following beneficial effects. 1. It will reduce wear for a given lifetime in use 2. It will transfer the wear to the less hard and easier to replace pin rather than the hard to replace bush But I don't want to go down this route - You're right, the idea of the thread probably was to increase the surface area and you should double it with a standard pitch thread. But I'm not convinced it works because the angle of load is constantly changing and hence the pressure field is too. I'd love to meet the engineer who perfomed the Reynolds equation calculations on this thread type bearing surface. He must be a clever clever man.

C L Carter

And for completness.

Lawrence Slater

Thanks for the Pics Lawrence. - That confirms exactly what I thought. Presumably some sort of cap then covers the end?

C L Carter

Hi Christian, Yup , grease nipple covers the end. If hardened bushes extends the life of the the system "significantly", that's good. If it causes the pin to wear, rather than the bush, that's also good. Harder bushes don't need to help with lubrication, sealing the bushes will do that, and thereby add to the extended life of the bushes, and the fulcrum pin. I also wonder about changing the angle of the thread pitch, if that's the right interpretation. The thread pitch is shallow, so that the pin does not move much laterally. You don't want the bottom of the kingpin moving forward and back much, relative to the top of it it.

Lawrence Slater

Going back to my first picture, of the tobacco tin lid tin plate. If that works (once the bushes are worn), and if it lasts a decent amount of time, then they effectively become very cheap and easily installable bush liners. Replaceable bushes in other words.

Lawrence Slater

I think if its worth going to the effort of machining new bushes then improving the design is important. If you wanted to increase the surface area they could just have made the bushes longer... there is plenty of space!

C L Carter

True - but its a horrid solution!

C L Carter

Horrid solution it maybe, but "Replaceable bushes in other words", -- satisfies my original post in this thread. How to take up the wear in the bushes. I agree Christian, they could have done all kinds of things, but for whatever reason chose not to, or an apprentice was left to design this and it got used. I also agree if it's going to get redesigned, might as well do it thoroughly. However, then it becomes a more involved and costly adventure. Everybody has different expectations and desires. Mine is only for the simplest effective way of not having to keep replacing the wishbones. If by fitting hardened bushes, with grease seals, I can make the wishbones last for say for 100k miles, that's a good enough result for me. If by fitting replacable threaded bushes with seals, I can make the system last for 100K miles before new replaceable bushes need be inserted, that's even better. I don't see (through an engineers eyes) the need to do anymore.

Lawrence Slater

Hi Christian, I don't mean to imply a damper on your enthusiasm to come up with a much better system for the outer end of the wishbones. You're an engineer. If I had your skills, and access to the machinery to employ them, as opposed to a surplus of bad ideas, I too would rework the whole lot. If you come up with a complete working solution that's exceeds the current design, I reckon everybody, including me will be very interested. So please keep your thoughts coming, and post the drawings you do. Just one thought though. This could be a commercially viable developement. There are plenty of spridget owners out there who might well be happy to part with some dosh, for a one off fix, for a future problem that they will without doubt encounter, if they keep and drive thier Spridgets long enough. So you might feel that you want to keep your developements to yourself. On the other hand, I'd like to see a solution that didn't become very good, but overpriced, in the sense that it exploits people.

Lawrence Slater

I think the threaded bushes and pin should be "given the boot". When new the amount of play is barely acceptable, and while you might yet 50,000 miles of use before they become too worn out... I'd estimate that by 20,000 miles they are worn enough to affect handling (especially under breaking). And while I'm making unsubstantiated claims, I also suspect that they cause dampers to fail (leak) earlier.

Trevor Jessie

"If you wanted to increase the surface area they could just have made the bushes longer... there is plenty of space!" That's also a good idea to incorporate into a new design. It was under-engineered, much better to over-engineer if cost isn't a great issue.

Lawrence Slater

Trevor, Not sure if when new they are barely acceptable, -- do you race- ? I find when new they're ok for my road needs. Otherwise I agree with you. By the time you've done 20k, they are certainly rattling and annoying. Transposing the movement at the bottom of the kpin (because of the worn bushes), to the top of the kpin, definitely results in a lot of the movement at the top if the kpin, which must load the bush in the lever arm shock. But other than that, lol, they work great. :) Really I don't think the threaded bearing in principle is so bad, more perhaps the use of the "wrong" materials to impliment it. I guess it really comes down to --- Fix what you have, or replace it entirely.

Lawrence Slater

How about what Fergus posted very early on? --- "a one shot pressure feed system. Each time the car was started a slug of grease was fed to the tread and bushes." Maybe not automatically as above, but a manually driven permanently installed reservoir of grease, that you pump into the bushes whenever you feel the need. A minature grease gun(s) mounted on the inner wings, with flexible hosing connected to the grease nipples on the ends of the bushes. The equivalent of the Scott oiler chain lube system I mentioned earlier. Maybe even motorised? Hmmmm? How's that for an off the wall, and actually only 1/8th joking idea?

Lawrence Slater

Lawrence, I'm not interested in any commercial venture. I'm just enjoying the challenge. I also want a cheap solution. A solution which is easy to install and will last forever without the need to remachine parts in the future. So I'm keen to employ the use of replaceable oillites. Even if you have to replace them every 50k miles, that would be fine.

C L Carter

Thats a solution but not a fix. I wouldn't be interested. I'm keen to find a solution where the pins could be machined from a standard sized and available gudgeon pin and would fit standard oillites. The key part would be removing the current bushes and braising in newones and then reaming them in one step which would also parallel it up to the rear fulcrum mounts. I think I would build some sort of jig to mount the wishbone on my mill to do this.

C L Carter

I do not race, but I do use large sticky tires for recreational driving (I no longer use my cars as daily transportation since I have children to haul around). When I assemble the new units, and see the fore/aft movement at the top of the kingpin it makes me cringe because I know it is only going to get worse. Why is it acceptable to have the castor angle varying to such a large degree? We should ask Barry King about the installation technique of the bushings. Are they installed such that the crest and roots are centered? In my mind the forward flank of one bushing should be on the back flank of the pin and vica-versa for the other bushing. Sort of like a jamb nut scenario. This would make the pin very snug to install, but would reduce the free play.

Trevor Jessie

Do you know what. If you just set up the wishbone in its current state you could machine out the threads and slip in an oillite without having to remove the bushes. This would mean you would need a slightlty thinner pin - stepped to recieve the king pin... but would be a whole lot less work for the sake of a few mm. More food for thought

C L Carter

What then stops the kingpin from rattling back and forth?

Guy

The problem with producing your solution on a commercial basis is the issue of product/public liability insurance.

Dave O'Neill2

see what you mean - but a) would a thinner pin be strong enough? (wouldn't they tend to break at the step? b) would the oilite bushes be too thin-walled and posssibly break up?

David Smith

Also, the smaller bush would also have to be reamed to take a bush, making the fulcrum pin even thinner at that point. Much too thin I reckon.

Lawrence Slater

I keep thinking of liners. You re-line a block, so why not a bush? Christian, can you make tools? Could you make a stepped tap to the specs needed by the existing threaded fulcrum? If so, the existing worn bushes could be reamed, and a blank bush pressed in. The stepped tap could then cut the new threads.

Lawrence Slater

No I could not make a tap - my skills don't go that far. I'm sure you can get one made - but I doubt it would be cost effective. I really not think I like these threads. More to come from me when I've had a break

C L Carter

lol. Which threads don't you like? The ones here on the bbs, or the ones in the wishbones? :) Actually the fulcrums are so hard, that with additional flutes cut in them, they'd make a good tap I think.

Lawrence Slater

I meant the fulcrum threads lol - but it does sound like I meant the BBS lol

C L Carter

I am commenting on the end of long series of posts here so may cover something someone may have already said so here goes.. The problem I see with the fulcrum pin being threaded is the contact area will be small since despite precise thread forms there will be inevitably local aperities ( raised bits) in the surface and also misalignment in the bushes from side to side.. So I actually could imagine the contact area being quite small. The advantage the thread has is the thrust is taken via the thread - I think that must be why the design went this way.. NI pic I am trying to portray the fact that the contact between bush and pin threads will likely be line contact along a limited number of thread forms and so wear could be quicker - may actually be more area on a plain bearing? Stikes me that we should look at alternative designs which use plain bearings to get an idea of size and materials - I would be interested to take part in the project once car is back running of course..

John Barber

John, that's what was itching in the back of my head! But I couldn't put my finger on it! I agree.

Alex G Matla

OK, thinking on, with the post from John added to the mix, I'm warming to the virtues of going the extra mile to replace the threads. Christian mentioned gudgeon pins earlier. The small end of a conrod certainly lasts long enough, even with the pounding it gets from the explosions over it's head, and that's with only a splash feed of oil for lubrication. So with that in mind, if we go smooth, the thrust/endfloat question has to be resolved before anything else. And, with that in mind, how does adjustable thrust sound? How about this? New permanently fixed oversized internally threaded bushes, replace the current fixed threaded bushes in the wishbones. BUT, the threads are there only to allow replaceable, internally SMOOTH bushes to be screwed in, --- from the outside faces of the wishbones --- , and locked in place, by some means. Inside the new smooth replaceable bushes, at the deep ends of each, there could be a bearing material, either oilite or hard plastic, --- perhaps a disc --- up against which, the ends of the new smooth fulcrum pins would butt. This would stop the smooth fulcrum from moving back and forth. As the new internally smooth bushes are screwed into the wishbones, if endfloat developes, it would be a simple matter to screw the bushes in a little further to remove excess endfloat. Discuss.

Lawrence Slater

I was reading your post and was thinking as I read... I can't see the point of threading in the replaceable bushes... its a lot of effort for nothing... and then your last sentence explained why - I can't quite picture how it would work, how you would "lock them in place" and I think its more effort than its worth when you can simply press in oil lites or bronze bearings which you replace if they wear. There are plenty of ways to make pins with shoulders and top hats and threaded ends which clamp the whole lot up together with oil seals and all. Once I get hold of a wishbone, I will take some measurements and draw up a design that I think I can make. Then I'll post some concept drawings on here. Right. Off to pack the car and get ready for my tour! Bring on the good weather!

C L Carter

Some more simple thoughts on the potential design options in pic below... The shaded parts are the bronze /oilite bearings - which fit into steel bushes permanently brazed/welded into the wishbone. Important detail is they must have internal shoulders to retain the bearngs/bushings. Pin has a washer built in one one end and the other is held on by internal threaded blot with loctite to hold in place.. Big item is getting the steel bushings in place in the wishbone.. Thoughts /comments ?

John Barber

So Ive been having similar ideas. I'd like to use top hat bushes (hopefully that will push fit in from the centre taking the thrust from the king pin) I also want a grease nipple at both ends which spoils the simple end cap idea in your picture. I'd like to also incorporate a recess in the bush for lip seals or o rings if you're as tight as lawrence Then there are the release grooves and the design of lubrication to consider.

C L Carter

I was thinking of making a pin from a large allen key bolt (is standard from a higher grade steel), something like the drawing. Head of the bolt thrust one side, hard washer on the other side. Secured to the kingpin by the cotter pin. Bushes made from steel as well. Maybe some chambers for o-rings in the head and washer. John, I think there should be thrust washers in the middle as well, or the bushes long enough to hold the kingpin in the middle. I opt for the second. I don't think the cotter pin is beefy enough to hold the kingpin.

Alex G Matla

Lawrence, or anyone with a wishbone to hand. Can you please measure the space between the 2 bushes in the wishbone where the king pin sits. The king pin I've measured as just shy of 7/8 (about 21mm) - I'm keen to know if I can insert top hat bushes from the inside out.

C L Carter

Seems like this is coming full circle back to David B's modification.

Trevor Jessie

Is the kingpin eye ( bit that fits over the fulcrum pin) suitable for putting directly against a thrust surface of some sort? I didn't think it had a very large surface to bear against.. having said that all the thrust currently goes through the cotter pin with the std design....

John Barber

What is David B 's modification?

C L Carter

John, No its not - but I want it to be. I have a king pin sitting on my desk and its a cast surface. But I am planning on Maching both sides flat... not worked out how I'm going to make them perpendicular to the hole yet

C L Carter

something like this then CL ?

John Barber

Chris, make a jig on the lathe to secure the king pin on a milling machine? Mill the faces perpendicular to the hole.

Alex G Matla

C L Carter, http://www.metal-arts.co.uk/sprite/frontsuspmods/index.html Questionable these days as I understand that technically welding a wishbone is an MOT failure and I can understand why with modern wishbones and metallurgy. What are the dimensions of the standard threaded steel inserts and the trunnion pin? I think that smaller and thinner bushes could be used compared to what I used, I largely used similar to what I had already used for the upper link and rear Watts linkage.

David Billington

The bushes could be brazed like the originals I think? Using silver hard solder.

Alex G Matla

Just looking at your site David - this seems to be the ticket. Not sure I understand your point about wishbone welding - welding should be stronger than parent metal if done correctly.. Is it the parent steel you are concerned about ?

John Barber

John, As I understand it these days a wishbone or suspension link on a car can't be welded to repair it, to do so is an MOT failure. I think this is largely due to the metallurgy of modern components and that one doesn't know what the materials are so welding can be a dangerous repair. Wishbones can be of welded construction though. The mods I made have survived for 70k miles but technically could be rejected although I haven't run this by VOSA or anyone else as the mods were done before the MOT regs included these rules. I think most MOT testers these days wouldn't know a standard spridget wishbone from a modified one though. I would be inclined to do a mod close to the original in using brazed bushes but improving on the threaded bush design.

David Billington

Agree - most wouldn't know what a proper midget suspension was supposed to look like. Braze was originally used so it should be strong enough.. Not sure what you would need to do to get it approved of - so you could supply others...

John Barber

Yes - I think we are arriving at something like that. Great minds... Am roughing a quick model out now...

C L Carter

Here follow some ideas: Discuss. Note 2 things not included in design. 1. ends of pin would have flats or hex for tightening 2. O rings not present - grooves can be seen 1st picture is of the pin arrangement and cap which is threaded - this will pull whole thing together

C L Carter

This is a 3d model. You can see the end cap has an internal thread which allows space for a 2nd grease nipple

C L Carter

When pin is assembled - end cap does not form part of bearing surface - this is just for alignment issues

C L Carter

This arrangement shows the bushes - between which there is a small gap to act as a reservoir for oil/grease Also note there is an o ring groove. There will be 4 o rings in total

C L Carter

Here are all the bushes the pin is transparent so you can see the grease passageways and release groove

C L Carter

And the final assembly with 2 copper washers to seal against the king pin and the inner o rings. There would be the standard cotter too in order to prevent rotation

C L Carter

and a section view to show o ring seals

C L Carter

Chris. That's beautiful

Alex G Matla

Hail Christian. :) So good, I'll nip down to the garage and measure the central space between the bushes. However, I've already noted on many occasions, but forgot to mention it here, the installation of replacement bushes is often pretty hit and miss. Obviously they should be installed to placfe the kingpin centrally, I'm sure they were at the factory. But rebushed w/bones often have the kpin offset in one direction or other, fwd or rev. The pair I've stripped have the bushes installed placing the pin too close to the small bush. But actually, I think in the original setup, how close the bushes were to eachother didn't really matter, as long as the kpin was central, and didn't scuff on the bushes. Give me 5 mins (or so) and I'll get a measurement. Meanwhile a question. What locks the end cap in place?

Lawrence Slater

uhhmm, I've seen something like this elsewhere - http://www.metal-arts.co.uk/sprite/frontsuspmods/index.html I've very little idea of what you lads are up to now but if it works out and improves things I'd be interested in a set

Nigel Atkins

Just photoshopping the pics. Meanwhile. The MOT welding issue. I can't see this being retrospective to Spridget wishbones. If it is, then sussex, bhive, and Moss et al, will all have to cease selling exchange rebushed w/bones. Furthermore, all those owners whose Spridgets are currently sporting rebushed w/bones, will have to go out and by newly factory made wishbones, and swap them over, or fail an MOT. Hence I don't think it applies. Repeat question. How is the end cap locked in place? The central point of this mod, once the basic mod had been done, is to make this a simple owner dependant operation. In the current installation, when the bushes wear out, there is little other option, than to have someone to replace the bushes for you. Your dependant on a supplier. So as long as the top hats, or whatever the final arrangement is, can be installed and removed without the need to take the w/bone to a machine shop, or the need for anything other than regular toolbox equipment, then it looks very good. Edit, yes your right Nigel. DavidB is stamped all through this discussion, in the moving away from the threaded fulcrum and bush setup.

Lawrence Slater

Here are the pictures showing measurements between the bushes, and also between the internals of the wishbones. No point being too exact, as they are both different. I’ll call them brass and oxide. Brass bushes distance between, 25.4mm, 1” Oxide bushes distance between, 24.9mm, 0.976” Brass wishbone internal faces, 30.2mm, 1.19” Oxide wishbone internal faces, 29.2mm, 1.15” As you can see, two different wishbones, two different sets of measurements. I’d bet you’ll find the same results on every wishbone you measure. Maybe even new factory w/bones aren’t that accurate. They don’t need to be, since there is no requirement for either the w/bone, or the bushes to provide a thrust surface. The threads take care of that. So the problem arises, how do you spec the bushes for exact end float, to fit every wishbone, irrespective of these measurements? There will have to be some form of adjustment, and some exact guidance to each owner in respect of bush placement, when taking their wishbones to a machine shop for the fitment of the new fixed bushes. Internals picture first, bushes next picture up.

Lawrence Slater

Distance between bushes on both wishbones. Brass bushes distance between, 25.4mm, 1” Oxide bushes distance between, 24.9mm, 0.976”

Lawrence Slater

Let’s discuss the pounding the oiltes, or whatever new bushes are used, will get. The early FL front telescopic shock conversion, uses ¾” long oilites with an internal diameter also of ¾”, for the smooth steel swivel pin. This pin and bearing combination, doesn’t get anything like the pounding that the wishbone lower outer fulcrum/bearing gets. Yet, it shows distinct signs of wear, to the extent that the pin and oilite bearings need to be replaced, or modified, because the arm moves around too much. It’s reasonable to assume that the oilite bushes in the new design for the lower outer fulcrum, aren’t likely to survive any better, and will in all likelihood, probably wear far more than the FL situation above. Additionally, because of the relatively small size of the eye of the kingpin, the bushes used in the new modification will have a smaller internal diameter than the FL oilite bushes, and hence have a smaller bearing surface area than the FL conversion bushes. This will exacerbate the wear. I think it would be wiser(essential) to use a harder bush for the bearings. I also think the outer bushes should be longer to increase the surface area of the bushes, as discussed earlier today (yesterday that is). ;) The pin will still have to be harder than the bushes, otherwise it will wear, and become a major issue having to replace it, unless there is a large batch of them sitting around as future cheap spares. I acknowledge that David Bs conversion has done good mileage, but he does say “I have done about 70k miles on them with little wear”. How much movement at the top of the Kingpin does that wear translate to, and at what mileage did it become noticeable through the steering wheel? It’s that movement that causes the bushes to need replacing in the current setup. Even though they will be easy(easier) to replace, I don’t think it will be a decent solution, if at say 20k miles the wear becomes annoying, and a must change issue at 50k.

Lawrence Slater

Bonus question: while doing this conversion, can you find a way to move the fulcrum point outboard enough to change the stock +1deg camber to a more radial tire friendly -1deg camber? Norm

Norm Kerr

Why oilite? Maybe super oilite would be better (like used on farm implements). However, if these are being greased, why oilite of any sort?

Trevor Jessie

Just remembered the same reason, as mentioned earlier, that endfloat/thrust, has to be controlled at the ends of the steel fulcrum pin (if going smooth), and not at the side faces of the eye of the kingpin, if that's what is intended. Yes you can have the kingpin machined to flat bearing surfaces. But who is going to do this? When an owner installs this mod, he doesn't also want to be getting his kingpins machined. If he were to, then it wouldn't be worth machining old kingpins. He would have to purchase new ones. Later, when his kingpins wear, he would have to buy new ones, and then have them faced exactly to the dimensions of the old ones. If he were having a garage replace his stubaxles with exchange units, he would incur extra cost getting the garage to have his kingpins machined. Too much future hassle, too much future expense. That's what was behind my idea of bushes that screw in from the outside, and allow for control and adjustment of thrust and endfloat. Edit. That wouldn't suit everybody Norm. :)

Lawrence Slater

Chris' designs are looking good! As Lawrence has discovered, there will be a lot of variation in the positioning of the old braised in bushes relative to each other and to the wishbone. I suspect that the wishbones themselves also vary a great deal in the width of the two horns. But maybe this can be accommodated by varying thickness, or providing a shim pack, to go between the faces of the kingpin and the inner copper washers. Second issue - if you look at worn wishbones the wear on the bushes is almost entirely as a line along the lower length of the bush, where the grinding paste of road grit and grease has done its work. The joint only moves through a few degrees so all the wear is concentrated into this narrow strip, and in terms of spreading the load this is the only bit that counts. Not sure what that means in relation to the new design other than the grease/oil slots need to be positioned away from that wear zone. Third issue - the design needs to have a "Homer factor" built in. With the original, as the bushes wear they begin to rattle and clonk, the suspension and steering feels sloppy. One has maybe 10 or 20,000 miles to experience this and realise there is something that needs attending to; plan ahead, order the parts, get the car off the road... The replacement design needs to ensure that when it does eventually wear it isn't as a sudden catastrophic failure where the first you know of it is a sudden close up acquaintance with the nearest colony of amphibians.

Guy

Right, Don't know where to start.. 1. Thanks for the measurements L, That works fine. 2. Guy, in terms of slack - I was thinking shim pack in exactly same way as you. 3. In terms of machining Kings pin faces - this may not be necessary - if a cupped washer could be provided or tbh a copper washer will deform to fit the casting (its not perfect I'll admit) 4. In terms of materials, its important that the bushes are the replaceable item - Hence they need to be soft. So I was thinking pbronze is perfect - although expensive. because it will be a totally sealed system it will always be lubricated. I'm starting to think why bother with grease nipples at all! It could just be sealed for life like modern units. 5. Longer bearings at the outside - I'm still thinking about this. Yes I like it in some ways. However it requires a more noticable alteration to the wishbones, and I think more support else there is a high bending moment at the join - so It will definitely get pick up on I think. 6. What holds end cap in place? - At the moment its just threaded - but I could develop a grove to take a nylon ring - making it a nyloc - at the moment its 3/8unf so it would be easy enough to lift that component - It might be the case that the endcap is turned from a nyloc and has a cap welded to it to cover its end - crude but effective! 7. I've noticed an inherent design flaw in my solution. The outer 2 o Rings prevent 2 bearing surfaces meeting and will essentially lock the whole thing up tight - meaning those 2 o-rings will get destroyed in 20 miles time. Solution is to use a slightly longer or deeper bearing and insert 2 lip seals at outer edges.

C L Carter

So i've updated to include lip seal at either end - and also incorporated a longer out bearing if we choose to increase the bearing length as discussed. Time to pack up Midgely and fit the boot rack!

C L Carter

David B? I've just been looking more closely at your version. I like it. Its very simple. Your bolt - Is it hollow for grease? or do you not lubricate once installed because of the oillites? C

C L Carter

Lawrence, another thought on the locking end cap point. My design is overly complicated... why not just extend the pin and use a normal nyloc like David B did See pic... just add big washer and nyloc

C L Carter

I think we've come full circle to David B's idea now - with modifications for pumping grease in, increaseing surface area, and keeping grease out. Its a good idea and its worked for 70K miles. Am happy with that. However, another thought would be to go back to the 'alternative material' - no grease passageways = simpler design and cheaper to make. Still needs sealing to avoid grit getting in. But what about polymer bushers... PTFE is self lubricating - or Nylon which is tougher and also has lubricating properties - its also hard (relatively) compared with the PolyUrethene bushes we use elsewhere on the susp

C L Carter

The road to hell is fraught with good ideas, and all roads lead to Rome, or David B in this case. lol. Guy, there’s no suspicion about it. If you read my post, and look at the pictures, I did indeed identify a variation between the separation of the "horns" of the wishbones. I don't like the idea of shim packs to accommodate variations in the kingpin surface, and the width between the two horns of the wishbones. Too many fiddly bits to install, and then maintain when it needs adjustment. I also think, that however you arrange the thrust washers at the sides of the kingpin, this area will be subject to premature wear, and cause a problem that does not exist in the current threaded design. How are you going to keep road dirt and moisture from getting between the kpin and thrusts, and grinding away to produce end float? Like or loath the threaded bearing system, one problem that is virtually non existent, is end float. Even when the threads wear a lot, there is very little lateral movement. The problem is that the kingpin can tilt, and also move up and down relative to the wishbone. Yes a simple nyloc system to lock the end cap has to be a better idea. Keep the whole thing as simple as possible in my view. I also think the end cap should incorporate the additional function of adjustable endfloat and thrust. "(its not perfect I'll admit)" Ha ha. That’s the problem. Nor is the current system, but it works well enough, until it wears out. If the replacement is not nearer to "perfect", then I can’t see the point in doing it. As Guy pointed out, most of the wear takes place in a relatively narrow band along the bearing surface. I can see the potential for greater deformation, if the new bushes are not at least as hard as the current threaded bushes. I still don’t agree that it’s just road grit turning to a grinding paste, that causes the current bushes to wear. All you need is metal to metal contact to wear the bush. The threaded fulcrum is far harder than the threaded bush. When first greased, the two surfaces are separated by grease. The grease gets squeezed out to the centres, --- to the gap between the horns. Then, long before moisture and road grit get in, the fulcrum is grinding the bush (most of the wear is actually very close to the large cap that contains the grease nipple for the large bush). This then creates a bigger gap, and allows more grease to be squeezed out. Process repeats. The answer is to seal the grease in, or drastically reduce the loss. Finally, I too still wonder about biting the bullet and going hard plastic. However, as I’ve said before. We know the longevity of the current threaded system. We have no real idea at about how long a “MODERN” hard plastic bush would last in the same situation. I personally don’t want to experiment over several years, in an effort to find out. Yup if 70k miles is obtainable with the new system, with no wear until that point, I’d be pretty happy. But as I asked before, at what point does the wear start, and at what point does it become a problem? It’s not known as far as I can tell.

Lawrence Slater

How does this now compare to Barry King's design? (have I got that name right - I cannot find the link to his site) I think as well as dealing effectively with a redesigned fulcrum pin arrangement, his also involves a modified wishbone to give additional rigidity. Although interesting to see the ideas developed through the BBS discussion, why not just buy Barry's version?

Guy

Guy, I did consider the BK system, which is a distinct improvement. 1) It's a fair bit more expensive. 2) I don't race, and don't need the extra rigidity of the premium product. 3) Essentially, it's the same as the cheaper replacements, but is made to a higher quality. It's still a hard threaded fulcrum turning in a softer threaded bush. Hence, eventually it's subject to the same wear. As far as I am aware, there is no guarantee how long the bushes will last. Albeit that they last longer than the "standard" products. PS. The fulcrum pin is solid, no central hole, and there is a grease nipple at each end. So too with the grease nipple, on mine, and yours.

Lawrence Slater

Anyone have a spec sheet on Nylatron?

Trevor Jessie

"sudden close up acquaintance with the nearest colony of amphibians." LOL Guy. No I don't trevor, but I found this here, very interesting. http://www.azom.com/news.aspx?newsID=11751 Plastics are Replacing Phosphor Bronze, Stainless Steel and other Metals In the Mining Industry Published on March 31, 2008 at 11:06 PM High performance engineering plastics that don't corrode and never need lubrication are making inroads into mining and minerals processing applications once exclusively the preserve of metals. Their many advantages – including good wear characteristics, light weight, low friction, low inertia and long operational life - are why the super plastics are replacing phosphor bronze, stainless steel and other metals in applications where metals have ruled for decades. From conveyor impact beds to sheaves and wear blocks on draglines; from flow promotion liners on dump trucks to safety guards on machinery; from cranes and earthmoving equipment to chutes, bins and hoppers; the change is happening in a myriad of applications where long-life products such as the Ertalon, Nylatron and Polystone families of plastics are displacing costlier counterparts in grimy environments where reliability is at a premium, a smooth flow of material is essential, and downtime is an enormous liability. An example is custom engineered plastic sheaves, which can weigh as little as one-seventh steel equivalents yet offer longer wear life - and, importantly, give two to six times the rope life. Then there is safety equipment fabricated from polycarbonate Safeguard PC, which is among the strongest and safest rigid see-through material available to safety conscious managers, machine builders and OH&S safety teams. This rugged material has: • 250 times the impact strength of glass of equal thickness • has 30-40 times higher impact strength than clear acrylic sheet • maintains its high impact strength even after long outdoor periods • and is easily fashioned for applications ranging from guards on machinery to see-through doors and hatches So superior is the performance of engineering plastics in many areas of mining and resources that the only reason they are not used almost universally is habit and resistance to change. Ertalon and Nylatron Ertalon's scope is one of the broadest in the mining industry because each application’s requirement can almost always be facilitated by subtle variations in physical properties afforded by different additives in each grade of the product. The range of Ertalon (commonly recognised as nylon) stock shapes can be engineered to suit applications requiring high mechanical strength, stiffness hardness and toughness, fatigue resistance, high mechanical damping ability, good sliding properties, noise damping, electrical insulating, dielectric properties and excellent wear resistance. The complementary family of Nylatron thermoplastics can be similarly formulated for outstanding performance characteristics suiting different applications, such as wear resistance and fine motion control in production and processing. Nylatron®703 XL, for example, features ‘Zero Slip-Stick’ performance for precise and efficient motion control of machinery components including wear pads, bearing blocks, wear guides and linear bearings. Machinery equipped with Nylatron 703XL can accurately produce the smaller movements made possible by today’s sophisticated control devices. Telescoping or sliding parts – such as those in cranes and materials handling equipment – move smoothly over pads made from Nylatron 703XL, without sticking or jumping. Such precision is made possible by the material’s “Zero Slip-Stick Performance” in which static and dynamic coefficients of friction approximate each other at virtually every point over the product’s useful range. Members of the Ertalon and Nylatron families have been successfully employed as: • Wear pads on side guides, rollers, conveyors, presses and telescopic booms • Gears on winders, lifts and escalators, and in drives for processing equipment • Bearings or bushes, where the materials have found extensive uses in draglines, cranes, rolling stock, earthmoving equipment and processing machinery • Pulleys and sheaves for overhead cables, or as rollers for electric hoists, conveyor components, boring and bolting equipment, and heavy duty sections on draglines. Draglines themselves are host to a myriad of uses for Ertalon and Nylatron, which are virtually maintenance-free and hardly ever suffer from high wear, corrosion, lubrication breakdowns, dirt or dust effects, splitting or abrasion. Uses on draglines have expanded to encompass slap blocks for drag ropes, drag rope sheaves, deflection rollers, tower sheaves, fair lead sheaves, drag tunnel wear blocks, shoe alignment sheaves, walking shoe wear blocks and wear pads for pedestal and brake arrangements. Even in the harsh environs of foundries and open cast mines, Ertalon has been used to engineer replacements for existing steel bearings because of its impregnated lubricant. Whereas traditional roller bearings carry a wet lubricant that traps the abundant dirt and dust, Ertalon obviates this problem. The same result is achieved on conveyor systems and entry guides, which in many industries are subjected to similar working environments. Polystone for optimum sliding qualities The ultra high molecular weight (UHMW) family of Polystone plastics is especially formulated for optimum sliding characteristics and resistance to wear, abrasion and environmental stress cracking. This means it is ideally suited to mechanical transmission support products and to flow promotion. It displays some of its greatest benefits when employed as conveyor components such as mechanical chain guides and mechanical wear strips – or, in another form, as liners for hoppers, bins and truck trays. Key features and benefits of the material include: • Impact strength combined with light weight. It is easy to handle without special equipment (having a specific gravity of 0.93). • Weatherproof – it doesn’t absorb water • Chemically resistant – it resists corrosive material (such as sulphuric acid, caustic soda) • Abrasion resistant – rated better than carbon steel for sliding abrasion applications Common uses of Polystone include conveyor systems, for example, where chain guides and support profiles made from metals such as steel cause heavy wear on the link plates and rollers of the roller chains, and on the links of round link chains. Another important area in which UHMW plastics are increasingly important is in dump trucks, trailers, hoppers and bins for flow promotion where common problems include product sticking, rat-holing and generally clogging processes that require a smooth flow of material. The smooth paraffin-like surface of Polystone prevents the adherence of bulk solids to the walls of transporting and storage equipment. It allows regular mass flow patterns and consistent release of product. The surface friction properties of Polystone provide an economical way of ensuring maximum discharge. Dump truck liners made from such materials have evolved considerably with the availability of new sheet sizes, special grades and improved fastening systems. From independent owners and operators to large fleet managers, Polystone Matrox liners provide a quick return on investment.

Lawrence Slater

Lawrence, I never suggested that the wear is "just the grinding paste". But grit and dirt is most certainly a factor, which is why the sealed in system definitely looks like an improvement. Actually although I grease mine monthly to pretty effectively keep the grit at bay, they still wear, as one would expect with a metal to metal bearing system, with or without added grit! I don't think that shimming either side of the kingpin need be particularly fiddly. I don't think it needs to be to a very fine tolerance, just a couple of steel packing washers would do just fine. A selection of probably 4 washers each of 2 thicknesses could provide sufficient options (5?)to pack the kingpin centrally between the inner flanges of the new bushes.

Guy

Shimming the sides of the pins is not something I'd want to do. If you have to make an adjustment, you'd have to strip half the front suspension to do it. And if you think grit contributes to wear in the bushes, it would without doubt cause an increase in endfloat. I repeat, endfloat isn't a problem, why introduce the possibility of it?

Lawrence Slater

Just adding, that info on the use of plastics in the mining industry is interesting stuff! And if I am concerned about the grinding paste issue, then mining situations must be one of the worst imaginable for that! Maybe Chris' design is right, but the top hat bushes just need to be in plastic instead.

Guy

Trevor, try this. http://www.portplastics.com/download/pdf/plastics/BearingAndWear/bearingAndWear11.pdf

Lawrence Slater

Remind me why you think endfloat isn't a problem? I know that the threaded pins don't show much lateral wear on the threads, but there must need to be something there to stop the bottom of the kingpin slapping back and forth between the horns of the wishbone at every pothole encountered

Guy

Still don't agree Guy. Hard plastic, won't last longer in a grinding paste situation, than hard steel. In the mining environment, they must effectivelt seal the grit out to prevent the paste effect. Where it scores, is presumable it's tolerance to deformation under impact, and it's lack of need for lubrication. I favour end cap thrust control. Far simpler, and removes all posibility of grinding paste causing endfloat.

Lawrence Slater

Guy, it was you who reminded us that the thread is more then a screw. It's a bearing. The major loading is vertical. There is far less lateral loading, and the effective side load bearing area, (the walls of the threads) is quite substantial. even with all the grease removed, and with the amount of wear present in the w/bones I have currently stripped down, I can barely move the fulcrum pins back and forth. I've never found this to be a problem in any of my previous rebuilds. Of course in extreme wear cases, I'm sure it exsits. However, It's not a even a small problem in m y experience.

Lawrence Slater

Either we are agreeing, or maybe talking about movement in different plane. I am referring to movement of the bottom of the kingpin along the line of the car, not vertical or lateral. Have I missed a step?

Guy

We're agreeing. The kinpin can't move along the fulcrum pin because of the cotter pin. The fulrum pin can only move back and forth by very small amounts, because it is screwed in. If it had a steeper pitch it would move a lot. It has a shallow pitch. Thus with the very few degrees of rotation available it can't move very much at all. As there is very little side wear on the threads, this remains the situation.

Lawrence Slater

OK, Got it now! I was talking of shimming the kingpin because one of your original criteria was to do away with the cotter pin. I couldn't see what was therefore preventing the kingpin sliding back and forth on the new (secured by end caps), fulcrum pin.

Guy

No, I think someone else want's to do away with the cotter. Or was it me? :) The threads of the bush and fulcrum, provide very effective endfloat control.

Lawrence Slater

I'm being drawn back to improving the current threaded system, rather than replacing it.

Lawrence Slater

C L Carter, The main bolt I used is just a standard 1/2" UNF socket cap screw with no provision for greasing. It can be greased by removing the bolt and the washers and O rings either end, packing with grease and re-assembling. The washers and O rings will act as pistons to push some grease through when the bolt is done up again. As the spindles fit into the kingpin the bolt can be removed without the whole assembly falling apart. The main thing I wish I had done was add some provision to seal the thrust washers either side of the kingpin, probably just a thin O ring in the outer edge of the thrust washer would be enough.

David Billington

I have a feeling there is an insurmountable dichotomy of opinion forming with regards to how to improve this :) I described earlier, adding a seal(s) at the appropriate locations on the threaded fulcrum. This is what I mean. In fact, for the large bush, you could even insert an Oring deep into the bush from the inside. That would seal the inside of that bush.

Lawrence Slater

My compressed slices of dense foam pipe insulation do a pretty good job of sealing around there. Not up to the engineering standards of an O ring or lipped bearing oil seal, but not bad. Wouldn't an O ring just get trashed after a while? No one commented on my silicon seal idea. There is probably not much more than 10 degrees of rotation involved. Would a thick fillet of silicon flex enough for that, whilst remaining stuck top the adjoining metal surfaces

Guy

David, as you pointed out, your system has unfortunately been complicated by the lack of faced kingpins. This adds complications and expense, because they have to be machined. If the cotter is retained, and the thrust control relocated to the ends of the fulcrum pin, the complication goes away again. Yup Guy, I eluded to that. I agree. The trouble is we don't know how long a dollop of silicon would last. O-ring may indeed get trashed too. it's just a thought. But actually I think the 0-ring in the large bush would last a long time.

Lawrence Slater

Guy, your compressed pipe insulation keeps the grime out, but doesn't keep the grease in. The grease comes out, under a degree of pressure, exerted by the squashing effect caused by the loads on the fulcrum pin against the bush. What's needed is an effective seal that will resist the internal pressure trying to eject the grease. Wrapping a length of ptfe tape, around the trailing threads of the smaller end of the fulcrum pin, does create a seal that prevents the grease being squeezed out. I know this becuause I've tried it. If there is sufficient ptfe tape, the grease gun is unable to pump the grease through to emerge between the horns. Note, I have the dual grease nipple arrangement, and I blocked the central hole in the small end of the fulcrum pin. Thus forcing the grease to the threads instead of along the internal of the fulrum pin.

Lawrence Slater

BK wishbones. I forgot to add. 4). The extra stiffness of the premier wishbones, prevents/reduces the amount the w/bone twists under braking, and thus reduces the wear in the threads. Hope I have that right Barry, if you're reading. :)

Lawrence Slater

Re. the width of the horns; looks like one of the wishbones was rebuilt (the one with the copper welding), and so maybe not representative. If the fulcrum on that one was removed with an angle grinder it could have made the gap bigger? Maybe there must be more measurements taken. I'll measure my set tomorrow.

Alex G Matla

Alex, they have both been rebushed, and the bushes brazed in. Both from the same car. I painted one of them with red oxide paint. The point is, that apart from possibly new factory made items, that have not been rebushed, I think all of them will vary. Also, there was no requirement for the w/bones to be exact in dimensions at this point, and I doubt they were. If they vary by a few thou at this point, then making preset thrusts can't be done. Every wishbone setup would have to be unique. A real pain in the ar*e.

Lawrence Slater

I think that the tooling used yesteryears was a bit better then you reckon for lawrence, and the average tolerance between non rebuilt wishbones might be quite good. Hence the suggestion to measure more bones. So even if a wishbone was rebuilt, the gap between the horns should vary little, depending on press form wear perhaps.

Alex G Matla

Maybe Alex. But unless people are going to go out and buy new factory items, new old stock, if they can even get them, then they are likely to be driving around on rebushed wishbones, and that means likely variations. Furthermore. Even if the distances were uniform, they don't appear to be parallel either. They appear to fork out. But lets suppose the variation in distances between the horns is minor, and they are also parallel, there still isn't a bearing surface there. It would have to be formed by the new bushes. So you do that, and then you have to make a bearing surface on the sides of the kingpins too. It's all beyond the capabilities of the average owner to do that, and if someone is employed to do it, it becomes expensive and far more complicated than it needs to be. For you and Christian, with the equipment, and the skills to use it, all of this is a minor problem, but for others it's prohibitive. My intention in starting this thread, was to find a way to extend the life of the existing system. That then evolved into improving the existing system, by considering the addition of easily replaceable bushes, whilst keeping to the same basic, and arguably, very simple principle of the threaded bearing. There's no requirement for anyone else to follow this route. However, I think that if most other owners would like to be able to swap to an improved system, they are more likely to do so if it involves a minumum of alteration and it is very easy to do, using for the most part, the wishbones essentially as they are now.

Lawrence Slater

Out of curiosity I measured the end float of a pin in a used pan/pin. I took it apart and cleaned out the hard grease to the best of my ability. The pin was quite "wobbly" in the A-arm, so I expected a significant amount of end float as well. Surprisingly, it was only .005". The other surprising discovery was that the threads on the pin were worn appreciably. So while I can agree that the threads do a good job of controlling end float, I'm not convinced that harder bushings alone would slow the wear problem. And, I'll iterate that the new pans/pins still have too much slop in them to inspire me with confidence.

Trevor Jessie

Hi Trevor. Well you've confirmed what I've experienced for 35 years when taking apart the lower end of the wishbones. The fulcrums don't move back and forth much if at all. It's interesting that your fulcrum has so much wear in the threads though. Could the hardness of the fulcrums vary across the years? Were originals better quality? Did you have harder bushes to begin with? Do they vary? As hard as the fulcrums are, you can take a hacksaw or grinder to one, and destroy the threads in short order. If sufficient grit were to enter between the fulcrum and bush, the grinding paste Guy talks of, would no doubt wear the threads on both the pin and the bush. But in general, I've always found the fulcrum to be sufficiently harder than the bushes, and the wear less, to almost non existent on the fulcrumm, when compared to the bushes. If that is the case, then harder bushes ought to resolve this. On your last point, the idea is to replace the standard bushes, make the whole system tighter to begin with, and make it last longer whilst being far easier to rebuild when it does loosen up.

Lawrence Slater

Well ,I agree Lawrence, I think it is very difficult to get this commercial viable. Especially against the very good (so I hear) BK wishbones. I see this solution only applicable for people with access to the needed equipment (or are friends with people who have that) For me, if it was commercially available, it would be quite expensive, and as a dutch, well, you know what they say... And there is the "fun factor" and satisfaction of doing it yourself.

Alex G Matla

Hi Alex. I don't have access to equipment, or anybody "friendly"(free), with it either. So for me, the system I use to replace the current one, has to be simple enough for me to take the wishbones to a local metal works, to have the new fixed bushes made and fitted to the wishbones. I'll also get the replaceable bushes made up(future spares included), which have to be easy to install/remove myself, with basic garage tools. From an engineers point of view, I can see the fun side of designing and making a superior system. I hope quite a few people run with this. It'll be very interesting to see what evolves.

Lawrence Slater

Lawrence, If simple is what you are after, then how about: Keep the design of one bush being smaller than the other. Ream out the bushes just a minimum, but still keep them in position in the horns. Use a plain fulcrum pin that is stepped to match the two sizes of bush, such that when inserted, there is a shoulder that will but up against the end of the smaller bush. You could use a thrust washer of some sort here, maybe with an O ring around it. At the end of the f-pin have it stepped down again to a threaded bolt on the end. When assembled the f-pin is inserted through the larger bush and the k-pin. The thrust washer is slipped in before the f-pin is pushed fully into the small bush. Then add a second thrust washer and do up a nylock to take up the fore and aft slack. It is now held in position, but located only by being clamped in relation to the smaller end horn. This would get around the problem of varying spacing between the horns on different wishbones, and also avoid the possibility of any clamping action bending the horns inwards. Not sure how this leaves the issue of the actual bearing surfaces. Ideally one would have a thin walled liner of a harder metal that would just push into the reamed out bush and provide the new wearing surface. Akin to Speedisleves. Maybe they could supply something? All components as described would be easy to get made. Its is basically a lathe turned pin, two bearing liners and the thrust washers and nut. Modification to the wishbone involves line boring a small cut through the two bushes. One might even be able to do that accurately enough with a stepped reamer held in a hand drill? For greasing, one could either pump from a grease nipple at the fat end. Or it might be better to drill and tap for 2 nipples positioned in the sides of the 2 bushes? Whole thing may not be as elegant a design solution, but it is simple enough.

Guy

You've been reading my mail Guy. LOL. Your description is almost exactly what I've been thinking of for a day or so. My reservations are: 1) Concern about the residual thickness(thinness) of the fixed bushes in the wishbones 2) Sacrificing the threaded pins for smooth, in the event that the new smooth pins wear prematurely and then have to be replaced -- machining costs. 3) What material to use for the thin walled liners, and how to install and remove them for replacement. But otherwise, with a few other minor details to be worked out, I agree. I've been meaning to take a good look at resiting the grease nipples too. I think it would be far more effective to have them on the sides. I also wonder if the LM grease used, is too light. If oil were injected, it would run out. Thicker oil would remain longer. Hence thicker grease than the current LM, would better resist ejection. How about CV grease? That is designed to take much greater loads as I understand it.

Lawrence Slater

CV grease does take loads, but I think is quite runny - vague recollection from mini rallying days of the stuff pouring out when CV boots got split by flying stones! What are Speedisleves made from? They must resist wear quite well - maybe not hammering type wear but they stand up to the lip from oil seals that wear ordinary crankshaft grade steel. And the pins wouldn't be that expensive. You could afford to buy a small stock for future use. I think concern 1 is the major problem. One could always get new thicker walled bushes braised in first. But still then use a higher grade and replaceable lining. Problem is it takes the thing to the next level in requiring specialist input, whereas without that it is a DIY at home project once the machined pin and liners have been sourced. Whilst thinking outside the box . . .I wonder if one could one Helicoil the bushes and retain the screw-in f-pin?

Guy

What about brazing in a couple of these bushings and then use a cotter pin secured kingpin as std. Plain Fulcrum Pin tightened against the outside faces to contain thrust? http://www.ballisticfabrication.com/DOM-Sleeve_p_1453.html

John Barber

yeah I mentioned that idea earlier... just reaming out the threads and whacking a plain pin in with some seals... 1. machining operation needed on the bones I think I would at least sleeve these... so that they can be removed and replaced by anyone in their garage at a later date. Whatever you go for in terms of bearing surface... Lawrence has hit the nail on the head... its sealing thats important... the grease just comes out at the moment.

C L Carter

I'm not sure sealing is going to be the answer regarding grease but feel free to try. I'd be inclined to try an automatic oiler or greaser with the current setup to increase longevity. Other than that another approach to deal with the grease issue is to do away with it and use a bearing material that doesn't require lubrication, that leads to DU, Igus and some others.

David Billington

Interesting. Too many Ruddles to comment intelligibly, hence I'm in refrain mode. Hic. :)

Lawrence Slater

OK, Ruddles aside. How could material be replaced inside the current bushes? If it were possible, that would be an answer. If it were possible to screw in a helicoil type blank bush and then tap to the required thread, that would do nicely. Those bushes are also very interesting John. Weldable it says. Here's another thought that's been irritating my cells. Why is the fulcrum stepped? The kingpin eye is limited, and dictates the size of the fpin, as it has to pass through the eye. But why did BMC then increase the size of the remaining portion of the fpin? Why not a uniform size along the whole length? Did they find that one end of the fpin needed to be of a larger diameter? If so, that would suggest that the larger diameter end of the fpin and larger bush, should be installed either at the front, or the rear, according to the loading it was expected to get. I don't have a very early original parts list for the wishbone. But I wonder if they were originally side specific. Why else would there be a larger and a smaller bush? Could excessive wear be due to incorrect orientation of the larger vs smaller bush on the car?

Lawrence Slater

Interesting comment on Ruddles, I used to enjoy Ruddles County but Ushers killed that brew when they started brewing it in Trowbridge. A long dead brew as far as I'm concerned now.

David Billington

Lawrence, The Ruddles is giving you a different perspective on things! It has to be stepped, with a large and a smaller threaded bush; how else would the two threaded sections of one pin both engage with the threads unless the pin were threaded the entire length, including through the king pin?

Guy

After a few brews ... I've decided that it is time I make a some adjustable tubular A-arms.

Trevor Jessie

I don't follow you Guy. Even no longer being under the influence. :) If the pin was a uniform diameter for it's whole length, and smooth in the middle, it would still screw in. It's installed, small thread first, large thread behind. If the threads were the same -- small size-- at both ends, the bushes would be the same size too. For a reason no doubt, the rearmost thread/bush was increased in size. What was the reason? The pin in the picture fits all these cars. It's not stepped. We can't use it for the Spridgets, because it's bigger than the eye of our kingpins. If we could, we could also use the bushes I picture posted some days ago. Austin A55 Mk II & A60 Morris Oxford Series 5 & Series 6 MG Magnette Mk 3 & Mk 4 Riley 4/68 & 4/72 Wolseley 15/60 & 16/60

Lawrence Slater

Lawrence, Imagine a pin of uniform diameter, with a smooth bit in the middle. To install it you would need to screw the first end through the first threaded bush, and on into the second bush. But the smooth bit in the middle would bottom out when it met the first threaded bush. The middle smooth bit could be reduced in diameter to less than the root of the thread pitch. But then how do you get the kingpin on! And anyway, it wouldn't then be a uniform diameter pin would it? You could have the whole pin threaded and thread the kingpin hole as well, but that would be awkward and take longer to assemble, screwing the whole length of the pin rather than the designed version where you insert the pin and then only have about 1/3rd or less of its length to screw in. With that A55 pin I can only assume that you screw the bushes onto the pin from either end which may be why they are fastened differently, not welded in.

Guy

O/T Ruddles County when brewed at Langham in the fair shire of Rutland was a great brew - now brewed by Greene King it's nothing like and just a brand name

Nigel Atkins

Ah yes, got you now Guy. I think. However, except for the need to screw the first thread through the 1st bush, I don't see it the smooth bit would need to be reduced any more than it is now. So you think they made the rear bush bigger just to save screwing the pin through it? Doesn't seem sensible to me.

Lawrence Slater

Ah, see it now. you're right. :)

Lawrence Slater

So, do you think those A50 bushes are screwed onto the pins, before being fixed? I cannot see that one could screw the pin into the bushes if they were fixed first as with the A30 type. How are they held - some sort of collet or pinch bolt arrangement into that groove I presume? Some time earlier someone (David?) was saying that the threads wouldn't have only a point or thin line contact area because of irregularities. May be true, but it isn't a normal thread form. The pitch sides are very flat, deep and steep angled, so presenting quite a large spiral surface area for contact. But I cannot see that the design was ever very much good for maintaining a layer of grease between the metal to metal surfaces. Taken in section the threads form a sharp angled wedge which will very effectively squish the grease out away from the contact surfaces. Its definitely something of a camel in design!

Guy

Yup Guy, I think they are screwed onto the fulcrum pin first. Then the pinchbolts in the ends of wishbone arms are tightened. Anybody got an A55/A60 Austin Cambridge workshop manual handy? Have you cut a cross section through a bush or fpin then Guy? That would be interesting to see. Can you post a picture? I don't have redundant spares to cut up.

Lawrence Slater

No, I haven't. Might look and see if I have a sufficiently worn spare to try that. I do have some spares, but they are too good to cut up I think! It still feels like there ought to be a simple way of inserting a PTFE or similar bush that doesn't require lubricating and can be a firm press-in by hand (or vice). If a plain fulcrum pin was made to extended through the two horns and had a square groove cut into it -as on those A50 bushes, only in the pin. One could then have a C shaped plate that slotted into the groove where it protruded from the front bush and was bolted to the adjacent vertical face of the wishbone. This allows the pin to rotate, but restrains it from fore and aft movement. ??

Guy

Yes I very much agree. I keep thinking there must be a simple way to (re)line the existing bushes. If only they had been thicker walled. I wonder though, if what you said earlier is possible. There is already one large bush. So if that was reamed only to just remove the threads, a plain bush could then pressed in. The new smooth fpin, can be the same thickness as the smooth section of the existing fpin. So that takes care of one bush. Then there is only one bush to replace in the wishbones. I'm not sure I understand what you mean about the c plate. How would it be fixed? These are the A55 arms that the bushes sit in. There is a plate bolted between to hold the spring pan.

Lawrence Slater

Locating plate - I need to try drawing it for you. I know where I have seen the idea before though. And it will have a certain familiarity with you, well almost! It is the camshaft locking plate on a 1500 engine! It is part 38 on this Moss engine parts view. http://www.moss-europe.co.uk/Shop/ViewProducts.aspx?PlateIndexID=1377 Typical though! - it is obscured by the chain so hard to see. A plate like that could slot into a groove cut into an extended fulcrum pin. But maybe lubrication / wear would be a problem. Just having tea now but I may try a sketch of the idea later.

Guy

And one more thing . . . . That's another 200 posts!

Guy

What are the dimensions of the fulcrum pin? particularly the diameters. I know the centre is nominally 9/16" so the smaller thread will nominally be that but what is the OD of the larger thread and possibly the OD of the large bush. It looks like no Igus at 9/16 but some DU at 9/16 but apparently not flanged.

David Billington

The pin is 14.06 at the small end and 16.15 at the big end. Now what's that in English fractions...? 9/16" and 5/8 approx?

Guy

Yes I see what you mean Guy, but I think wear would be a big problem. It would be exposed, and all kinds of muck would get in.

Lawrence Slater

Yes. That is what l thought. I can't come up with a straightforward way of sealing them either !

Guy

Given that these were British measurements from the '50s/60's, I would say 9/16" and 5/8" definitely. We might well be limited in standard bearing choice too, due to the length these bearings need to be.

Lawrence Slater

Let's re-examine the existing system. Why doesn't the existing system last longer? Dirt and moisture can and does get in. The grease can and does get squeezed out. So, suppose you started with a new set of wishbones, and retrofitted oil(grease)seals to the insides of the horns? With the grease trapped inside, it will have a far greater chance of keeping the two surfaces separate from each other, and won't get contaminated. Also, you add a 2nd grease nipple -- to the small bush which on the standard item doesn't have one --, or you relocate the grease nipples to the sides of the bushes. You seal all the holes in the fulcrum pin, to force the grease only to the threads served by each grease nipple. How about the grease?. The book says, Castrol (or equiv)LM Castrol LM Grease Lithium based, high melting point grease, specifically designed as a wheel bearing grease for use over a wide range of temperatures. Also suitable for general purpose applications. However, maybe this would be a lot better. Castrol Moly Grease High melting point, lithium based grease containing molybdenum, providing dry lubrication under extreme operating conditions. Ideally suited for the following applications; King pins and bushes, shackles and suspension trunnions, bevel worm and peg steering boxes. I think a complete new design might not be needed, just improvements to the old, plus a change of grease.

Lawrence Slater

So carrying on from my last post. (in case someone beats me to the next slot). Take a used and worn set of wishbones. Have made, and fit, the same size and type of threaded bushes, but with four differences. 1) The bushes are harder. If the bushes are harder, the fulcrum pin will wear and the bush hopefully won't. If(when) the fulcrum pin wears, you just buy and fit a new one. 2). The new bushes incorporate the ability to fit replaceable oil seals at the insides of the horns. Grease stays in, dirt/moisture stays out. 3). The bushes are thicker walled, to facilitate side entry grease nipples, and in case you ever wanted to ream them. With side entry grease nipples, the holes in the fulcrum are less important, and can remain. 4). Fill the system with Moly Grease, instead of LM. To me, the advantages of this, as opposed to a root and branch re-design, is that the threaded system is tried and tested. We know it's weak points, and thus what to improve. It also works very well at end float control, so there is nothing new to design in this respect. We already know the exact sizes to have the bushes made up to. So no trial and error. Essentially, the existing system works. It just needs a few tweaks

Lawrence Slater

Why not renewable bushes? Harder bushes should cause the pin to wear first. In the event that the bushes do wear to the extent that a new pin doesn't take up the play, you are in a position to ream the thicker walled bushes, and try various replacement options. Also, this has the merit of relative simplicity. It's a lot easier, aka, a cop out :) A pair of new standard wishbones are circa 100 quid, give or take. I reckon the above could be done for less than that, and then you should end up with wishbones that will last a lot longer, and with options for the future to boot.

Lawrence Slater

Blimey. Nobody disagrees with me? :) Too many eggs to unwrap and eat no doubt.

Lawrence Slater

Well, after 200 + messages you seem to have come down to: fit harder bushes add improved grease seals in place of cork (felt) washers Use a different grease Add a second grease nipple at the other end (or side entry grease nipples) Hardly radical re-engineering is it? I have been using 3 out of 4 of those plus PTFE tape for some years now.

Guy

So, what would be a better way of sealing in the grease? Would O rings fitted either side of the king pin help, or would they just get shredded without making some sort of groove or housing?

Guy

Guy, I was thinking that some expert engineer(s) amongst us, could re-design the bushes, so that they incorporate a chamber to allow the fitment and removal of a properly made off the shelf oil seal. "I have been using 3 out of 4 of those plus PTFE tape for some years now." Have you used different grease? Has all your grease stayed in? Has any moisture at all got in? Would you mind awfully, taking your pins out to see if the ptfe is still wrapped around the f pin, after 5000 miles? :) :). Trevor. You mentioned wear on your fpin. "I took it apart and cleaned out the hard grease to the best of my ability" "The other surprising discovery was that the threads on the pin were worn appreciably." You were surprised at the very small amount of end float. Can you also tell us about the condition of the hardened grease? What colour was it? Rust coloured by chance? Was it course, embedded with metal/grit of any kind? Look at this and the following pictures of my fulcrum pin being removed from my bushes. This was with 2 grease nipples. Is it any wonder at all, that the bushes wear out prematurely? It's really a wonder, that the pin and bushes weren't completely destroyed. Actually the pin is barely worn, and the bushes are still(just) serviceable -- with ptfe wrap -- for another x number of 10s of k miles. Now imagine that there had been an "effective" grease seal in place, and harder bushes. More pictures follow.

Lawrence Slater

Rust and the remains of the grease, mixed with plus gas.

Lawrence Slater

The pin is barely worn. Even though it looks ruined.

Lawrence Slater

Finally, the bush up close. More and better grease, retained in place, and harder bushes. I think that's the fix.

Lawrence Slater

This is very interesting, regarding grease performance, and water absorbtion. I've cut a few bits out, but most of it is relevant to us I think. I'm becoming more convinced, that if we get the greasing right, and keep it there, the wear problem will largely go away. Whole article here. http://www.machinerylubrication.com/Read/272/general-purpose-grease Selecting a General Purpose Grease Without Compromising Performance ---- To maximize grease lubrication effectiveness, minimize cost and minimize risk of application-induced failure, lubricant manufacturers have made an effort to formulate greases that cover a variety of applications. These greases range from slow to high speeds, and from low to high loads, in an effort to provide a single product to meet a multitude of requirements. The result is general purpose grease. --- What is General Purpose Grease? A general purpose (GP) grease is designed to meet a broad range of requirements. It is grease manufactured to medium consistency with a medium viscosity base oil and medium wear, washout and oxidation resistance properties. Equipment Condition Considerations Keeping the objective in mind, a general purpose (GP) grease is used as a multi-application grease in a production process to reduce complexity and the potential for component failure due to misapplication. Consider the following operational characteristics when selecting the GP grease. --- Load As the load increases, the grease’s base oil viscosity must also increase to support the load. --- Atmosphere The three atmospheric factors that must be accounted for are temperature, moisture and airborne solid contaminants (particles). Although the influence of atmospheric factors can be significant, these factors are considered after the viscosity selection is complete. The atmospheric conditions have a greater influence on the heavily loaded components than the high-speed components. Heat causes oxidation and reduces the base oil’s viscosity. As the base oil’s viscosity decreases, its load-bearing capability is diminished. Heavily loaded components operating at elevated temperature are susceptible to inadequate lubricant film and aggressive wear. Water can do much the same thing to the oil film because water has very low load-bearing capability. If water is allowed into the bearing in a free or emulsified form, the film may be compromised, leading to corrosive, adhesive, abrasive and hydrogen-induced wear. A continuous grease purge is sometimes used to prevent water and solid contaminants from entering grease-lubricated components. Because most greased components are not constantly purged, there is potential for moisture and particles to enter the component cavities through seals and fittings. Silica-laden atmospheric dust and dirt particles that enter into the load zone can scratch and abrade surfaces, generating more abrasive particles (wear debris). The potential for particles to damage load zone surfaces increases in high-temperature and/or high-moisture applications. The combination of reduced base oil viscosity, free water and particulate at the load zone can be particularly detrimental. ---- Greased components require a constant supply of lubricant at the load zone to sustain the hydrodynamic film much the same as oil lubricated components. The reserve grease contained in the cavity in the housing serves as an oil reservoir that components draw from for lubrication. When grease is resupplied to the housing, the oil reservoir is replenished. The longer the duration between cycles, the greater the likelihood that the reservoir will deplete and the component will run to a semi-dry (mixed film) condition. The oil in the load zone is squeezed and pushed away over time. If the relubrication volume is insufficient, or the cycle is sporadic (greater risk with manual lubrication), the likelihood that the oil film will dissipate leading to mixed film conditions increases. When these conditions are prevalent, the grease selection must be one that resists the squeezing action and tendency to dissipate. Greases formulated with heavier viscosity base oils and chemical and mechanical film forming additives can be helpful in these circumstances. --- There are a few lubricant properties that influence lubricant selection, whether GP grease, special purpose grease, oil bath or circulation lubricated applications. Oil viscosity, oxidation resistance, wear resistance and corrosion resistance certainly qualify. Beyond this, the thickener type influences the dropping point and water wash resistance, both of which play a role in the selection of a GP product. Each of these warrants a brief look. Viscosity Given the relationship between speed, load and viscosity, and given that the viscosity of the oil in the grease is the primary load-bearing mechanism, just as it is with oil lubrication - the first selection criteria is the grease’s base oil viscosity. Because high-viscosity oil will reduce under load (fluid friction produces heat which locally reduces the base oil’s viscosity), then initially defer to the heaviest base oil viscosities the machine can tolerate and move toward lighter viscosities as high-speed conditions are considered. As noted earlier, general purpose grease base oil viscosities in the ISO 460-plus range may be seen in operations running heavily loaded machinery. --- Wear Performance Wear performance is also related to base oil selection, because the viscosity of the base oil at operating temperature is the primary determinant of lubricating condition (hydrodynamic, elastohydrodynamic, mixed film or boundary) that the component will experience. Where there is a strong likelihood of shock loading and extreme loading, chemical AW and EP additives can be useful in supplementing base oil properties to provide additional protection from wear and seizure. Inorganic additives such as moly, graphite and PTFE are often added to provide mechanical load support in addition to the chemical additives. Water Resistance Applications where the process employs water-based coolants or process chemicals have multiple problems to address. Water resistance is characterized by the grease’s ability to withstand one of four water-related problems, including: 1. Washout Resistance - the ability of the lubricant to stay in the bearing while operating partially or fully submerged (ASTM D1264). 2. Water Absorption - the ability of the grease to deal with the presence of water by either absorbing or resisting the washing and diluting action of the water. The grease may either absorb a large percentage of ingressed water and then de-gel (lose consistency but retain the water), absorb a lesser amount of water and retain consistency, or resist absorption of water altogether (which leaves water in a separate phase in the component or system). 3. Corrosion Resistance - the ability of the grease to prevent corrosion of surfaces when water is present (ASTM D1743). 4. Spray Resistance - the ability of the grease to resist displacement from a direct impingement of the water on the greased surface (ASTM D4049). The thickener, in large part, determines the grease’s response to moisture. If the thickener is particularly good at absorbing moisture, such as with sodium soap greases, it may form an emulsion that traps and draws water away from metal surfaces. The downside to greases which emulsify is that they can be easily washed out. Rust/Corrosion Resistance Coupled with water washout resistance, if the typical operating condition is constantly exposed to water, process chemicals or high humidity conditions, then an additional measure of corrosive resistance may be warranted. Some thickeners, such as aluminum, have inherently good corrosion resistance. If the thickener resists water, such as lithium or calcium soaps, then rust and corrosion inhibitors will be added to protect surfaces from water. If the grease is expected to remain in the bearing and prevent corrosion under wet conditions for a prolonged period (between lubrication cycles), then an added anticorrosive capability is highly desirable. Thickener Type There are several thickeners available for consideration. Generally, the criteria for selection of the GP grease thickener type will be compatibility with other greases used in a plant and the dropping point (which represents the grease’s temperature maximum range) that the thickener imparts to the grease. Lubricant thickeners are generally compatible with other similarly named thickeners. (Polyureas are an exception.) Lithium thickeners are compatible with other lithium- thickened greases, lithium complex with other lithium complex greases, etc. Table 1 shows typical compatibility characteristics. A second rule of thumb is that the complex thickeners can be used to higher temperature ranges, frequently to 400°F (204°C), with frequent relubrication. If the equipment operates at sustained temperatures above 400°F (204°C) then it probably would not qualify for a general purpose lubricant. The issue of the thickener type and dropping point is central to this decision because technicians are inclined to use greases when the oil won’t stay put. The thickener must remain stable over a sufficiently broad temperature range such that an incidental spike in temperature will not cause the grease to thin and bleed from the application. Finding an acceptable general purpose (GP) grease requires consideration of many aspects, including lubricant factors such as oil viscosity, oxidation resistance, corrosion resistance, thickener type and water wash resistance properties. There are key operational factors to consider as well, including speed, load, temperature, contaminant type, concentration and relubrication cycles. In food handling and processing plants, toxicity and edibility create a separate set of questions not addressed in this article. Selecting a grease to meet broad operational requirements requires an understanding of how the equipment runs and how the grease will respond to those operational factors. A well-reasoned and planned consolidation to a general purpose grease can bring dividends through reduced risk of contamination, reduced complexity and improved overall lubrication conditions. However, do not compromise needed machine reliability by force-fitting a general purpose grease into an application for which it is not suited.

Lawrence Slater

PS. I found a post on britishcars.net, a few years old, in which Mark Boldry, --- are you still around Mark? --- said much the same thing about the unsuitability of LM grease for our kingpins and the fulcrums, but in far fewer words.

Lawrence Slater

Read this too. http://www.machinerylubrication.com/Read/28517/grease-dry-out-causes

Lawrence Slater

I remember Mark was a strong advocate of usi9ng oil, not grease in the kingpins. Not sure (and doubt) thtat this applied to the fulcrum pins as well. I have been using Molybdenum grease in mine for a long time. The grease doesn't stay in in mine. largely because I keep pumping more of the stuff through to keep water and grit out. Don't know if moisture has got in, but I would be very surprised if it hadn't! I am not about to strip mine down to find out. - Or to check on the PTFE tape I used. That I know had survived reasonably well after 5K, but has done a good deal more than that since. I have front suspension to build up for my other car and have two or three pairs of wishbones to choose from. So depending on their condition and what eventually results from all this discussion - if anything - then I may try applying some of the principles learnt. Interesting (long) cut and paste there Lawrence. I note specifically this bit: A continuous grease purge is sometimes used to prevent water and solid contaminants from entering grease-lubricated components. Because most greased components are not constantly purged, there is potential for moisture and particles to enter the component cavities through seals and fittings. Silica-laden atmospheric dust and dirt particles that enter into the load zone can scratch and abrade surfaces, generating more abrasive particles (wear debris). That is what I have been attempting with my monthly greasing regime, but it is a bit of a chore, especially in winter when it is probably most important!

Guy

Lawrence, "The pin is barely worn. Even though it looks ruined." In that photo it is showing the surface of the pin that gets little wear anyway. The bit that wears is diametrically opposite the oilway groove, on the bottom. Usually the crests of the threads show the worst wear in a stripe around 240degrees opposite to the groove.

Guy

Here's a pretty clean pin from my project car. Not sure what age this would be, but I expect I shall re-use this pin. First photo is of the upper side with very little if any wear at all.

Guy

2nd photo is a closer up shot of the underside of the fat end of the same pin, where it wears most. You can see the flattening of the crests of the thread. But this is still in pretty good condition! (sorry for the poor focus, too close up for my phone lens to cope with properly!)

Guy

"A continuous grease purge is sometimes used to prevent water and solid contaminants from entering grease etc ---- " Yup, I picked up on that too Guy. The trouble is, a kind of purge is taking place all the time, but without the replenishment. The grease is being squeezed out, but not in at the same time. If there was an oil seal present, that was capable of resisting the internal pressure of the pin/bush squeezing, but not the pressure of a grease gun then the purging would be more useful. Note also: Wheel bearings don't get purged. They are far better protected from the possibliites of moisture and grit ingress. The grease survives inside the hub, for far longer than it does in the bushes of the wishbone, without either expulsion or the same extent of drying out. All becuase of an effective oil seal? I'll take a closer look at my fulcrum pins from the other side. When I measured them, -- albeit quickly -- they seemed to be the same all round. I've got a really good macro mode on my digital camera, so I'll post a pic of the wear present too. It would be useful to see others, just for comparison.

Lawrence Slater

An 'o' ring type seal would improve grease loss and we a good mod IMO, but we still use fairly basic grease that weve been using since the 50's or earlier. There are a lot of synthetic products out there now - some far more water resistant (some suitable for underwater use on feathering yacht props etc) - may be worth a bit of research. R.

richard boobier

You know guy, I was thinking how useful it would be to have a brand new fulcrum pin, to compare measurements to a worn pin, abd to screw into worn bushes to gauge the difference. I might take my worn wishbones to sussex, and ask if I might borrow a pin for that purpose, in the shop. Otherwise we need someone (Christian, on his UK tour unfortunately) with a new and older pin, and worn bushes to make the comparison for us.

Lawrence Slater

Richard I agree. And have just remembered that there is an O-ring at the base of the stubaxles/kingpin for the very purpose we are discussing. It's in very close proximity to the fulcrum pin, so it must get all the same water and dirt wash the fulcrum gets. The base of kingpins do get worn, and the grease contaminated, but not to the same extent in my experience.

Lawrence Slater

I have already talked about the sioces of pipe insulation that I put either side of the kingpin in place of the cork washers. Next time I think I will first assemble the fulcrum pin with an O ring either side of the kingpin. Then run a thick bead of silicone sealer around over the O ring - It should be possible to build this up to around 3/8" thick as a continuous bead around the fulcrum pin. If it is all cleaned down with thinners this should stick pretty well. Ideally I would pput a tiny bit of grease onto the sides of the kinpin and the exposed bit of fulcrum pin with a small paint brush so that the silicone bead doesn't stick to them, just to the end of the bushes and wishpan horns. That way it should seal, without being torn off by the movement of the joint. Then lastly I will fit my pipe insulation slices over both, with the ends fixed with a bit of superglue.

Guy

Guy, I've got some 16mm ID 28mm OD silicone rubber tubing I could cut up if you wanted to give that a try. I'd need to know how wide to cut it and where to post it. Also have some 14mm ID 24mm OD so that would be a nice fit.

David Billington

This is one of the synthetic greases - can't remember the marine ones at present - will need to dig it out. http://www.super-lube.com/synthetic-greases-ezp-44.html R.

richard boobier

I was thinking gun grade silicone that would stick to the end of the bushes but with a thin film of grease painted on it would not stick to the other moving parts and would then allow them to rotate without ripping the silicone out again. It will be a while before I need to assemble this for my project car (STILL welding!!!), but I think that a careful assembly with attention to this sort of detail will be well worthwhile. So thanks for the offer David but it isn't a job I am ready to do just yet!

Guy

Here's a link to a test report on the grease Richard posted a link to. http://www.super-lube.com/files/pdfs/Endurance%20test%20results.pdf On the spare set of wishbones I have for experimentation, I invisage a properly contructed cage on the internal faces of the horns, into which a lipped oil seal could be inserted. I'll do this without replacing the buashes. While the wishbones are off the car, now is the ideal time to try this. Then I'll swap these wishbones over with the ones currently on the car, which will be the pair to receive the new bushes, when the final outcome has been decided. --- If it ever is. lol.

Lawrence Slater

Taking Guys measurement of 14.06 mm, which I find is the same as the smooth unworn centre section of both my fulcrum pins, then Simply bearings stock an ideal size lipped oil seal. Inside Diameter: 14mm Outside Diameter: 20mm Width: 3mm £4.07 inc Vat and shipping. Going back to the distance measurements between the internal faces of the horns, there's room to fit these, as long as the holder isn't to thick.

Lawrence Slater

Guy, when you measured one of your fpins, you say the pin is 14.06mm at the small end, which is the same as the smooth centre section I measured on both my pins. By that did you mean across the threads, or across the smooth section? If across the threads, then my pins are more worn than I thought after all. Or rather, they look rusted away. Now I've cleaned them up, I can see distinct pitting on the crests of the threads, but other than that the crests appear uniform in shape the whole way around. Anyway, the diameter of the small thread, is less than 14mm on both pins, and is pretty much the same measurement all round. About 13.95mm. So possible wear of about 0.11 mm = 0.004". Quite a bit when added to wear in the bushes.

Lawrence Slater

Lawrence, I have re-measured the spare pin I have. Yesterday was measured with a dial calliper - not the most accurate means as the jaws don't automatically get the widest diameter and if taken across the pin can slip into the threads. So now with a micrometer. I only have a metric one I am afraid. The plain section, completely unworn, and from several diameters is 14.26 +/-0.01 The narrow end across the threads is 14.16 +/- 0.01 This is where it shows no wear marks. I can get a diameter as low as 14.14 at one diameter where it is just discernibly worn. The pin appears to have a sort of copper coating of some sort which is missing on parts of the inner/underside of the pin. The fat end of the pin is more worn. Unworn diameter is 16.22 +/-0.01. Worn diameter at worst point is 16.18. HTH

Guy

Lawrence, The problem with an oil seal is if you fit it in the normal orientation you'll likely just blow the seal out when you grease the fulcrum pins. Might be OK reversed.

David Billington

Yup good point David, I guess it would need experimentation with the grease gun. Guy, yes I noticed the copper colour of yours, and have had that type myself in the past. Thanks for extra measurements. If those are more accurate, then my pin is even worse. however, I only have a vernier caliper, and expect I too had the same problem with slippage. I'll take the pins to my local machine shop for a true measurement. But I also think I should invest in a micrometer too. any advice on the best type, that won't need a mortgage? There certainly appears to be very little wear on yours. It would be very helpful to know the exact manufacturing specifications of new bushes and the fulcrum pin. I can't find reference to these anywhere. As I wondered earlier, where do the exchange wishbone refurbishers get their new bushes and fulcrum pins? Whoever supplies/makes these, obviously has the original drawings/specs.

Lawrence Slater

This thread was discussed between 03/04/2012 and 09/04/2012

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