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MG Midget and Sprite Technical - Bad words!! Wishbone's given up the ghost....

oh well.

Managed to limp it back home like this after noticing it in Tesco's car park.

How's best to stop this happening on t'other side as well?

Perhaps time for some -ve camber wishbones..


Rob Armstrong

Blimey! I've run wishbones into the ground before now, but never had one split like that.
Lawrence Slater

I literally ran one into the ground (a wheel fell off) and it didn't die like this one has. It made itself aware by feeling like a balance weight had fallen off. Drove back very boingily with the dampers set as soft as they would go.

I blame Nigel, they were his springs. Sabotage! lol. ;) :)
Rob Armstrong

It happens. 40 year old steel probably subjected to rather more stress than it was originally designed for.
Not the first incidence of this failure I've seen. I think Arie had one split as well.
Guy W

Have changed a few with the same crack that one has/ and likely had when you fitted the springs. They bear close examination, and the hugely increased loading from the dampers makes examination more necessary. Damping loads are far higher than spring loads, and some reinforcement might be called for.

FRM
FR Millmore

"It happens. 40 year old steel -----"

Yup that sounds right, and makes the case for not getting refurbed wishbones -- use new instead.

Anybody still thinking about replaceable bushes in the wishbones?
Lawrence Slater

I am now.

thinking along the slightly different lines of propshaft UJ cup bearings

Idea being there'd be a 'yoke' part on the wishbone, and the kingpin would lock to the modified 'crosspiece' using the cotter pin still.

Circlips and pressing would be the method of changing the small needle roller cups on the wishbone.

Wonder if that'd be strong enough..
Rob Armstrong

Not sure I'd trust a circlip to keep my front suspension together.
Dave O'Neill2

Stiffer suspension not only makes the ride harsher for the people in the car but also the rest of the car. If you have soft suspension and you hit a bump the wishbone goes up with the wheel and the suspension absorbs the bump in a gentle manner as it was designed to do. With stiffer springs in the wheel still wants to go up but the springs provides greater resistance. With standard suspension parts something has to give. Are they standard rating springs? If not then it's so not surprising it's torn just the way it has.

Does it look like a new crack? Surely you would have noticed it when yoy put the springs in. I wonder if it happened after that?
Greg H

As FRM points out, - its the damper load.
Using those Frontline systems transfers all the damper load from its designed point acting directly on the top of the kingpin, to a mid point on a bit of pressed steel pan. Not surprising they fracture.
Guy W

I've had one go in an identical manner. It's a problem to keep an eye out for and a reason to buy new wishbones rather than reconditioned.
Daniel Thirteen-Twelve

Looking at the picture I would expect most of the problem to be that the lower damper mount appears to be cantilevered off the side of the wishbone so putting twisting into the side causing it to fail.
David Billington

Rob, about the needles; Needles are not really meant to be used in a non-rotating application. As the kingpin rotates only a few degrees it will always be the same few needles that carry most of the load, and will soon give in.
Alex G Matla

Alex,

The problem with what you say is that propshaft UJs use needle rollers and last fine if sized correctly. It is advised that the joints have an angle so the joints move a small amount but IIRC less than the suspension articulation on a spridget. Original Mini upper front suspension arms use needle rollers and they last fine in that application.
David Billington

The mini arms are where I got the idea from.

Will have to think about it a bit more, I don't think the UJs are designed for any kind of sideways force that would happen with them in the bottom joint.

What I'll probably do is just stick a new one on here, with perhaps a mod to the damper pickup to spread the load a bit, then I can use the knackered one to play with.

The damper mount at the moment is fitted to a bracket that looks like a hollow wedge. Perhaps it is asking a bit much of the original bits, when I get it off I'll be able to see better how it's broken and a path to making the new one stronger.

If it comes apart, that is....
Rob Armstrong

Duck tape ???...or JB weld ???

Hahaha

If it wasnt the wish bones then it was going to be the king pin, iy looks almost as bad in the photo

At least it and you are safe at home

Prop
Prop and the Blackhole Midget

duck tape'd probably fix it ;) I'll just wrap it round the bottom lots, job done!

Just a bit of surface rust on the kingpin, nothing too serious.
Rob Armstrong

Is that damper mount welded to the wishbone? Looks like a homebrew thing from this angle.
Tarquin

it is indeed a home brew thing, and needs a redesign as it's part or all of the problem

here's a pic of the wishbone off the car, looks like (quite a big) crack has developed from the flex on the damper mount, as well as the one from the end.

Rob Armstrong

here's the inside, also not fantastic

(apologies for poor camera phone pics)

Rob Armstrong

and here's the soon-to-be-redesigned bracket

I think it needs to go all the way across the whole bottom of the pan, hopefully in a way that still allows spring changes

what do you guys think? I'm not going to be putting it on like that again, asked a bit much of the original components. I'll be doing the other side as well. And the shock rubbers.

Still, it all came apart nicely, took me an hour and a half to get the lot out.

Rob Armstrong

Rob,

What's your upper bracket. Are you going to lower the pick-up or just arrange for a brace under the wishbone also. Whatever you do you want to make sure you have enough travel that the damper can't go solid at the extremes of travel.
David Billington

Upper bracket is through the inner wing with a largeish plate, in the same style as the spridgebits conversion but a lot beefier. It's also connected to the bracket that I've got on top of the lever arm. It could move down if needed, but I think i'll just brace across the pan while still using the current height lower bracket, unless there's a benefit to having the damper mount lower on the wishbone? I obviously want to avoid bottoming the damper out...
Rob Armstrong

Looks to me like the length of the pin extending from that bracket has provided enough leverage to flex the wishbone until it fatigued and cracked. The stock ARB mount, for example, uses the same holes, but keeps all forces nice and close to the wishbone. I suppose this is why Frontline braces their damper mount with a bar running below the spring pan. I think you're right, adding a bar like that couldn't hurt.

-:G:-
Gryf Ketcherside

Mine cracked while traveling along the west coast in Scotland towards GlenCoe.
A great area to drive arround but not to have a broken wishbone on a sunday afternoon...
Local shipyard helped me out the next day with welding it up to be bullit proof.

Mine was also a reconditioned one, but howmanytimes was it reconditioned(wleding new bush in and sandblasting it)?
No more reconditioned wishbones for me anymore!
To be honest I to have to say I run my on Frontline frontsusp. on a very stiff selection, 400lbs frontsprings and a big-brake conversion.
So its fait to say the wishbones get more to handle then they originaly have.

The new Barry Kings are the best available, new steel and reinforced.



Arie de Best

left a paint stripped stock wishbone and right the improved Barry Kings wishbone.
See the re´nforcement plate near the fulcrumpin.

Arie de Best

Arie,

I can't see anything different from a standard wishbone on your Barry one, can you get a better picture of the reinforcement.
David Billington

I can see it... a plate facing camera in front of the filcrum pin mounts, with shallow u-cutout top and bottom.

Would be interesting to see how this is welded to rest of structure... needs a zoom-in and plan view, too.

A
Anthony Cutler

I don't find it clear enough to see much detail in that region and the glare from the paint doesn't help. Maybe a close up shot and one from the outer end of the wishbone looking inwards.
David Billington

Here is a better shot David.


Diffecult to see on this photo are the double greasepoints(on both sides) on the fulcrumpin.
Sorry, I know im a bad photographer...

Arie de Best

Arie,

Thanks that is clear and now I know what I'm looking for I can just pick it out in the previous picture. I expect it is spot welded to each side of the wishbone and then MIG welded to the webs each side of the fulcrum pin.
David Billington

that's neat. Thanks for pics Arie - I might copy the frontline design on the bottom bracket a bit more in the next iteration of the damper mount.

presumably that mod can be applied to any wishbone that hasn't got it, though it wouldn't be nearly as neat. I'm a bit wary of welding the wishbone...

Actually bugger that I'll just get some BK ones if he's got any in.

Rob Armstrong

Hey arie

On your barry kings and frontline kit mating...did you grind both the wish bone and the FL surfaces or just one unit such as fl...what paint did you use to reseal the steel after grinding to make the2-units fit

My olan is to grind both contact surfaces to keep as much metal as possiable on both the FL and the BK wish bones

Prop and the Blackhole Midget

Prop,

You're nuts grinding on the wishbones as they're thin enough when the FL attachment plates are thicker. The place to grind if any would be the least loaded front plate of the FL attachment bracket.

Really as the Barry King wishbones are common and apparently slightly narrower than original then the nice thing for FL to do would be to have the laser profiler they use cut some shims to supply with the kit and make their standard bracket slightly narrower to accommodate the BK wishbones. Shims not required for the BK wishbones but added for originals. Might happen or is that wishful thinking. IIRC was it Arie that had some BK wishbones and FL suggested the use of a hammer to make the bracket fit, not really a well engineered solution in my opinion.
David Billington

ooh, don't make the wishbone any thinner! I was more thinking adding extra strength!

Is this the fitment of the lower frontline mount that's being discussed?
Rob Armstrong

Correct... The lower wishbone... Barry included a note to grind on his wishbones which im not wild about, and i certuanly didnt like the hammer idea....it looks like i only need to loose 1/16th of an inch or so from them to slip into place
I was wanting to seal the grinding with por 15, but no luck finding it
Prop and the Blackhole Midget

Prop, the picture of the bare metal wishbone and Barry king wishbone is my BK next to tarquins bare metall one.
I dont repaint the wishbones anymore as I was replacing them (pre-BK ones) faster then they would rust.
Actualy sofar im impressed with Barry Kings paint as it has survived two winters already.

I do about 12.000km's in the midget with some tough miles included so I find it normal that at some point things wear out on the car and need to be replaced on a regular base.
Therefore I see no need anymore to superpaint replaceble parts as my car is not a show &shine car to compete in concours-elegance.

The dry-fitting of the FL lower suspension mount in the BK wishbone didnt go very smooth, could very well be Davids explanation and his solution of adapted lower FL mount + shims would be great.
In the end a friend of mine replaced the wishbones for me before a midgettrip as I was to buisy with work.
He got them in without grinder or plasmacutter but it was a bit of a struggle/fidling to make it fit together.
Arie de Best

Yeah... My lower FL kit isnt going into the BK wishbones without some massaging, and i dont think a hammer is going to do the trick so im still thinking grinding off 1/32th to 1/16th of an inch off both surface is the way to go

But I have to disagree with you on the lack of paint....paint is cheap, it dosnt have to be pretty, but painting the bare metal parts that have been ground on will keep the rust bunnies at bay ....i just think rusting wishbones cant be a good thing... Esp for what barry king wishbones cost....$2.99 for spray paint vs $380 barry king wishbones


Prop
Prop and the Blackhole Midget

Hi just a quick reply to the comments on fitting frontline to our wishbones,the reason some of you have found the under bracket a tight fit is because since circa early 2011 the gusset brackets are made of heavier gauge steel for obvious reasons, to overcome this you need to remove 0.0020" /0.5 mm from each side of the bracket,you should not attempt to take from the wishbone itself or elongate ARB holes,we feel most people capable of changing their wishbones should have no problems overcoming this but if unsure ask somebody that is,we did make a batch of 100 WBs with a percentage of the std gauge brackets which a lot of you bought at the show near peterborough when asked if you were fitting FL,but in our experience approx 1 in 20 pairs we sell seem to have FL fitted so not really a major issue,we do now make this known to buyers of our wishbones hope this clears the issue.(not such a quick reply!) P.S are many of you going to the MG sandown park show in October? We plan on having a stall would be good to meet you in person all the best Barry
bp king

Hi Rob,
I think it more likely the cause was oversized low profile tyres than those springs :)

I see from the photo neither of us got round to putting a bit of touch up paint over the Trustan 23, I wonder how long the Trustan 23 will last there under the car, where I've forgotten to cover the Trustan 23 on the bodywork it's lasted over a year

as you probably know by now the LB, I mean FL damper fitting is a bit more robust than yours and I'm sure somewhere there's a link to the fitting instructions for it, if not email me as I have a copy if you want/need the info

having had to temporarily remove my 11/16" ARB (with end stops) but testing my new magicmidget.co.uk 360lbs standard ride height(+) springs in Wales I think I'll soften my dampers down even more (they're on 2 or 3 clicks from softest now) and get just a little more tyre wall with 155/80 tyres later (155/70 now)
Nigel Atkins

;)

not sure I'd describe 175/70 as low profile..

The car certainly handles a LOT better with the new springs on.

Got some -ve camber wishbones on the way from Barry (Thanks Barry!) so will stick them on with a better bottom bracket arrangement.
Rob Armstrong

>>not sure I'd describe 175/70 as low profile.<< that because you're young :)

>>The car certainly handles a LOT better with the new springs on<< great to hear, do you think that's because they are newer than the previous ones or set the front of the car lower or the uprated poundage or a conbination of all three(?)

BTW - if anyone wants a barely run-in, pre-tested and pre-settled set of standard CHA129 front springs I have them

once again all Waxoyl will be removed and these I think feel lighter so perhaps a less expensive postage rate
Nigel Atkins

:P

reckon the handling improvement is a combination of all 3, but mainly the lower and the harder. Much reduced body roll into corners, more stable, less understeer.

For those that are wondering, here's a shot of the top arm I'm always on about:

It's all being spruced up now it's in bits. Kingpins and fulcrums are in perfect condition with no play (a little bit in the pin on the stuffed wishbone) after 4 1/2 years, probably about 30-40K fairly tough miles. Came apart completely down to the bare wishbone in 1hr..





Rob Armstrong

on a slightly related subject, what have people found that works to keep the grease in as an alternative to corky washers?
Rob Armstrong

Slices of high density foam pipe insulation, as sold in 1 metre lengths at B & Q etc. Cut slightly wider than the gap, shaped to fit, split across one radius and then slipped into position. Keeps the worst of the grit out - which is more important than keeping the grease in. Regular greasing still needed, not because it runs out or dries up, but to flush out any grit that does get into the bearing surfaces.

Nigel - I doubt very much if stiffer road springs were the cause of the wishbone fracture. The problem is relocation of the damper reaction from direct action on the top of the kingpin, to working mid way along the pressed steel lower wishbone. And then compounded in Rob's case by having a mounting bracket which induced repetitive flexing of the side flange of the wishbone, eventually causing metal fatigue.
Guy W

cheers Guy, I remembered something like that. Will use the rest of the pipe stuff to make a mock roll bar :)
Rob Armstrong

Nigel, a 175/70 tyre has more sidewall height than the original 145 tyres... and only 1.5mm less sidewall height than a 155/80 (i.e. negligible - a 1/2 worn 155/80 will be shorter than a new 175/70).
Andrew F

Hi Guy and Andrew,
I was having a joke with Rob about the tyres causing it rather than the springs you see in the original photos as they were my old springs that Rob bought from me

I couldn't remember what tyres Rob had other than they were a bigger size and when I was a young girl and it was all fields around here a 70 aspect tyre was considered low profile :)

now . . .

of course we need to consider if the original tyres were 80% or 82% and that the dimension given for any make and model of tyre are nonimal and . . .

:)

as usual I'll put this and this -

http://www.carbibles.com/tyre_bible_pg4.html

http://www.carbibles.com/tyre_bible.html

BTW - if anyone wants a barely run-in, pre-tested and pre-settled set of standard CHA129 front springs I have them

once again all Waxoyl will be removed and these I think feel lighter so perhaps a less expensive postage rate

Nigel Atkins

BK nice blue wishbones are here, and looking much better than the old ones!

that's tomorrow sorted then!

Rob Armstrong

well they've made a huge difference. Still a little tracking to sort out so it feels 'right' but what an improvement!

Looks like plenty -ve camber, but car is much more planted, even in the wet. Front end now goes exactly where you point it, no hint of understeer as yet and no tramlining now the tracking is close. Would recommend them (Barry's still got a few sets left!) :)

Rob Armstrong

What did you do about your shock brackets?
Andrew F

Shock mount strengthening arrangement:

1) make some pretty monster brackets, built up on the old wishbone that wasn't cracked.

Rob Armstrong

2) add a bit of pretty strong channel bar, tack into position on car. Also tack (old A series cylinder head) stud into one end

Rob Armstrong

3) weld everything on a lot stronger, and fettle to fit to car

Rob Armstrong

4) clean up nicely, and paint.



Rob Armstrong

You've been busy.

And lucky you, you've got a pit. Wish I had one. I've been thinking of digging one in my garage.
Lawrence Slater

This thread was discussed between 08/09/2012 and 01/10/2012

MG Midget and Sprite Technical index

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