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MG Midget and Sprite Technical DIY Panhard Rod BBS discussion at MG-Cars.net
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MG Midget and Sprite Technical - DIY Panhard Rod
| Hi, Just wondering if anyone has made their own rear PR, or anti tramp bars??? I was thinking it can't be too hard???? Has anyone got any pictures? Cheers jon |
| J WHITE |
| Quite simple. Was waiting for respray to dry so me and mate made one up using square tube, MGB steering rack parts and other bits and pieces. It was started, painted and installed in around 3 hours. Although this time would have been better spent in the nearest pub, the improvement in handling was noticable. Will email some pics (should have taken some when we were building it...) I should say my mate is a top fabricator and sprayer (and guitarist, pig-keeper, tree-planter, JCB operator, house-builder, and beer-drinker). A |
| Anthony Cutler |
| I made my own for my car, anti tramp bars were simple to construct using steel tubing and some spare spring shackle bushes. Just dropped brackets from the lower spring plates and the front spring hanger. Used spring shackle bushes because I wanted a bit of give in the bars to keep the ride smooth for a street car, yet effective axle control is still there. I used Poly bushes to keep movement to a minimum. The panhard rod was a bit more involved, I mounted it rather high which isn't the best but I didn't know better at the time. Used a mount welded to the bump stop bracket on the axle and a bracket bolted under the shock on the other side and rose joints to allow for some length adjustment. It does keep the rear axle centered but the roll center isn't the best with the high mounted bar. |
| Bill Young |
| The other parameter you will want to keep in mind is that the bar should be as parallel to the ground as possible with the suspension in a neutral state height-wise. This way the amount of deflection is minimized. David "some of the kits assume the car has been lowered" Lieb |
| David Lieb |
| Here is a photo, of ""My Plan"" for tramp bars I am going to make, But with with the panhard rod linkage built into it and adjustable cerrara tube shocks instead of levers to attach to my RX7 rear axle Unfortantly some Moron did the tramp bar portion of it 1st...I cant BELIVE some idiot was thinking the exact same thing as I was, That photo still ticks me off every time I see or think off it...At least I know My idea/plan will work Mind readers...Kill them all! LOL Prop....I even already have the rose hymn joint bars for over 5 months  |
| Prop |
| To follow up on davids comment....some kits "Assume" the car is lowered, is CORRECT. If you get the Panhard rod kit from winners circle, you will have to remake the axle shackle for everything to line up ...or lower the rear end But it IS SO worth it. Prop |
| Prop |
| Prop, Dare I ask why you want to go to such extremes as cutting down an RX7 axle when youre only (in theory as you still haven't started the engine) running 1275 (or slightly modified) power through it. Have you ever seen a Class B or C midget race? These seem to cope just fine with the standard axle and little or minor rear suspension mods. By the way I don't like the look of the shape of the rear springs in the photo you posted above! |
| Matt 1275 Bucks |
| I'm with Matt, It looks like the tramp bars (I hate tramp bars) are adjusted up too short and are distorting the front half of the spring- I bet it handles not so well. Also in my humble opinion the p/bar is mounted too high for this setup- it should be about 50mm lower than that. Don't forget if you are making your own-- Make it as long as you can possibly make it Mount it to the body on the drivers side and diff on the other side and Get it the correct height for YOUR car Willy 10.30 Friday night here It's a three day weekend that I was really looking forward to and guess what - it just started raining-- great |
| WilliamRevit |
| ...."to the diff" ? I thought they went to the opposite end of the axle casing or spring plate? Guy |
| Guy Weller |
| I think those are offset springs causing an optical illusion. |
| Trevor Jessie |
| Yes, I agree - offset springs so you can run wide tyres inside a SWA shell without external modification. That said I would have thought a combination of tramp bars and panhard rod make the car a twitchy ba$tard... Matt's right - you can go a long way with standard Midget suspension - even on the Class A cars they run with Spridget axles albeit with modified location. Prop - just get your bloody engine running! |
| James Bilsland |
| Matt Willy and james, The photo is someone elses car..Not Mine, But the idea is mine ... Or I thought it was...I agree the spring is a little twisted, but I think its because the car is jacked up for the photo Why the RX7...Its rated to 250 Hp, bullet proof, has an LSD, wide range of aftermarket gears, disk brakes and lighter in wieght then the midget axle. All at a fraction of the price to make the midget axle the same quality >>>>>>>running 1275 (or slightly modified) power through it<<<<<<< HAhaha...Now thats funny! Been trying all week with the nice weather to get the engine to start...But hoping to have it running for this weekend... Prop...still tracking down the Hidden gremlin |
| Prop |
| Prop, The RX7 axle assembly is significantly heavier than the spridget axle even after you shorten it. You don't get something for nothing, it's stronger by virtue of it being larger and heavier. |
| David Billington |
| David.... Hmmmm, I havent looked at my notes in a LONG time But I thought the 1st generation was lighter by 10 pounds...But you may be correct as ive got a 2nd gen with all the goodies, but i was thinking the wieght would have been the same becuse of the drums converted to disk and all the other junk welded to the axle ground off. but still I think its a good trade off...its a great axle design that Ill never have an issue with once installed Sorry but this mod is already set in stone and is going to happen...No turning back now. Prop |
| Prop |
| Prop how much power are you expecting from that mild (yes mild!) 1275? but since you will never get that engine started you wil not have to worry about japanese junk axles ;P |
| Onno Könemann |
| Oooh, oooh, Is it my turn to take a jab at Prop? Here goes... Prop doesn't want a high performance car, he wants high performance "specs" for bench racing. ;) |
| Trevor Jessie |
| I agree with David, I have looked at / measured / weighed quite a few axles now and and nothing gets close to the weight of the Midget axle, it just gets expensive very quickly to uprate one. Midget axle complete (wet) 37 kg 'English' 105e saloon axle, discs, (dry) 44 kg Ital axle (as used on early Lotus '7')45 kg 'English' Escort axle, std, depending on spec 46 - 50 kg 'Atlas' axle scaled to same width as Midget ~ 50 kg '4HA' axle (some Escort rally boys use them) ~ 90 kg!! (data off t'internet) Volvo 1033? popular bullet proof axle I couldn't pick it up kg's!! I think people underestimate how much an axle change can add in weight Anyone know the actual weight of the RX7 axle? Increased torque handling / longevity / bending resistance only comes with more material, wider gears / teeth, thicker shafts, thicker walled casings etc... Cheers Spencer |
| S Deakin |
| A further 3 - 4kgs can be saved on the 'English' with an aluminium 'pigs head', works out at about £100 per kg saved! |
| S Deakin |
| Spencer, "Ital axle (as used on early Lotus 7)" cannot be, because Lotus 7 production finished in 1972 which was before the Ital came out ! My 1968 Seven had a Standard 8 axle ex-factory.... |
| David Smith |
| Lotus '7' as a generic term used Marina / Ital axles for a number of years. I guess it depends what you term 'early' Spencer |
| S Deakin |
| I think 74 ish onwards used them S3? Again I use the term "Lotus 7" as a generic description of the '7' Caterham etc... and I also group the Ital / Marina axle all as one as they are essentially the same in power handling terms and mechanically. |
| S Deakin |
| Apart from the RX7 axle case being larger to accommodate a larger final drive unit and higher loads, the final drive unit (US pumpkin ?) is iron and the internals larger. The spridget final drive is aluminium so weighs somewhat less. I wonder if the US export final drive housings were cast in aluminum?. I wonder what one of the cast aluminium Peugeot rear axles weighs, might be troublesome to narrow. |
| David Billington |
| Yes, BMC imported genuine aluminum to use for the US diffs. The tacky aluminium was good enough for the Brits, but it simply did not stand up to the continuous high-speed driving we yanks put them through. David "I guess it IS Friday..." Lieb |
| David Lieb |
| Ah, Caterhams 'not proper Lotus then' ;-) Quite possibly S3s had the Marina axle - certainly they were strong, many used in Marlin trials cars and they don't break often. |
| David Smith |
| Midget axle complete (wet) 37 kg 'English' 105e saloon axle, discs, (dry) 44 kg Ital axle (as used on early Lotus '7')45 kg 'English' Escort axle, std, depending on spec 46 - 50 kg 'Atlas' axle scaled to same width as Midget ~ 50 kg '4HA' axle (some Escort rally boys use them) ~ 90 kg!! (data off t'internet) Volvo 1033? popular bullet proof axle I couldn't pick it up kg's!! those are All probably good axles ...BUT those axles here in the USA are as rare as snow capped mountians in iowa. My RX7 rear end should be arriving late march if it dosnt snow and ice over agian in fairfax VA., Ill give it a good wiegh in at that time and let you guys know what I find. Prop |
| Prop |
| Hi Prop, It wasn't really mean't as a list of suggestions, just ones I had come across and everyone was heavier than the Midget one, which was a suprise as the Anglia 105e wasn't exactly a fire breather :) Initially I hadn't thought too much about the weight not thinking there could be that much difference, the Volvo was the first axle I went to look at / buy until I couldn't physically pick it up! They are very strong and come with LSD's if you pick the right one and are remarlably cheap here. So I looked at the 'Atlas' next but everything pointed to it being around 50 kg's and very expensive. I'd regard changing the rear axle as a last resort but with 170 - 180 bhp / 170 lbs.ft it seemed pointless trying, without spending £1000+ on the Midget axle. What Hp / torque are you planning? K series? Rotary? If the RX7 axle is lighter than the Midget axle I will sell the 105e and get one (assuming ratios are somewhere near) as this axle slipped under the radar if it's lightweight. This is a nice 'English' type axle: http://www.spcomponents.co.uk/gpage5.html Cheers |
| S Deakin |
| Wow this thread has really grown while I've been having a little sleep- Guy - You are completley correct -- I said diff meaning diff assy. We just call them diffs over here, So to be more precise the bar should be mounted as far out towards the end of the axle housing as possible. Sorry if there was some confusion there. On diffs I've had a good run with a Anglia 105e housing and axles with Escort 3.77 lim.slip centre and Escort brakes Cheers Willy ---and I still hate tramp rods------ |
| WilliamRevit |
| WilliamRevit, you are right this thread has blossomed, so much so it has very little to do mwith my original post - however if anyone has any measurements or photos I would be more than grateful Cheers Jon |
| J WHITE |
| I made my own. I made the pr as long as possible, and tried to have it horizontal when the car was on it's wheels at rest. The car suffered from unpredictable oversteer in autokhanas. I have a standard diff, and about 115hp at the flywheel. Sometimes it would step out on the way into a corner, sometimes on the way out. it just went so quickly, that my skill was not enough to save it. trying just resulting in wild fishtailing, leading eventually to a spin. I have now removed it, and it is definately more predictable. I run alloy anti tramp bars that I made using rod ends. I removed the front spring mounts, and cut off the uprights that mount the spring eye. I then welded a peice of flat bar that protrudes up and down from the plate,and braced it. I drilled the spring mount higher, to lower the car, and drilled the bottom for the anti tramp bar mounts. Hope this helps. And leave Prop alone. We all enjoy modding and working on our cars. I probably enjoyed building mine as much as driving it. Some people need religion in their lives, we need our projects. What is life without ambition? |
| Shawn |
| Jon, The rules for a Panhard are simple, some as stated already: Make the Panhard rod itself as long as possible as this reduces the amount of lateral axle movement with vertical wheel travel. It must be parallel to the ground for the same reason as above, but you need to decide on the conditions when it being parallel to the ground is most important. For a road car I would just make it parallel to the ground under your normal loading conditions, say with the weight of the driver and half a tank of fuel or if you always have a passenger then at that height. For a race car this can mean it isn't parallel at static ride height but at some nominal cornering condition usually imperically derived. A quick Google found these pictures: Mounted near the axle centreline as I would choose, from memory the leaf springs are about 880mm apart so this is the approximate length of your Panhard rod.  |
| S Deakin |
| As the whole point of a Panhard is to improve lateral axle location then you need to pay a lot of attention to the mounting to both the axle and the body as unless these are suitably stiff a lot of the lateral control is lost through deflection. The other side of the same car: As you can see it's difficult to give more specific dimensions as the system shown could mount where your exhaust system is? Also don't go over board on the rod end sizes (if you plan on using them), the lateral force generated by a road going Midget can be sustained easily by pretty modestly sized rod ends. No idea what is going on with the hose clips around the leafs? Holding it together or additional leaves to add stiffness? HTH Spencer  |
| S Deakin |
| William (Revit ? - what a great name for a driver!) Just to say I am sorry. I wasn't intending to be "picky", I thought perhaps there was some different arrangement than I had seen previously. Just a minor language variation then! Guy |
| Guy Weller |
| The height of the panhard should be near the spring height otherwise you introduce contention between the springs and the panhard rod as it'll be trying to force the springs sidewise, that leads to an effective stiffening of rear suspension. It a problem when using them when the cart spring have been kept, you end up with to forms of lateral axle location. |
| David Billington |
| Cool, Thanks for the info - I'm looking at making up either and or both anti tramps and a panard rod, whilst I have some spare time... Jon |
| J WHITE |
| Guy No offence taken-- Clearly I wasn't clear enough with my words Spencer The p/bar in the pics I would think to be a bit too high We've been through this subject a few times in various threads but here we go again--eh Shawn The mod Shawn has done to his car is in my opinion one of the best things to do to a Midget to get consistent handling-- By lifting the front of the springs up high in extended spring brackets it greatly reduces roll steer (turn in understeer) and makes the car feel a lot more predictable when driven in anger.A side benefit of this mod is that you can run a larger front bar than normal without the dreaded understeer. If you really must have a p'bar----- Make your bar as long as you can possibly make it Mount it to the body on the drivers side and to the axle housing on the other side and out as far as you can get on both ends. Now the important bit that is nearly always overlooked. With your car at normal ride height (as suggested driver on board and half a tank of fuel) Run a stringline from the centre of a front springeye (rear spring) to the centre of the rear springeye on the same spring--- The point at which the stringline passes the vertical centreline of the diff tube is the roll centre height for your car (rear)-- Measure up from the ground to this point-- This height and no other is the correct p/bar height for your car. To explain why--- This height is the natural roll centre built into your rear suspension and if you have a p'bar mounted at any other height than this your car will in effect have two roll centres-- the result will be that when pushed into a body roll condition the two R/Cs will fight against each other and the result is a tightening up in the rear suspension resulting in the big spinout and the faster you go the worse it will be. Hope this helps Cheers Willy ---- I still hate tramp rods ---- |
| WilliamRevit |
| Hi Willy, I understand the concept of kinematic roll centre descriptions although I prefer force based roll centres (although that is an entirely different discussion) Are you then saying that all the RTL equipped cars out there are going to crash? Frontline quote: "The results are stunning. In addition to the above, the roll centre at the rear of the car has been lowered and we have achieved zero lateral body-to-axle movement" Or the Watts equipped, cart sprung MK2 Escorts that have the Watts mounted on the axle centreline (pivot is in the middle of the axle) Light hearted discussion, please don't take it any other way ;) How's Symmons Plain these days? it's been a long time since I last visited :) 15 years! Spencer |
| S Deakin |
| Spencer, I think the GP4 Escorts used coil springs on the rear rather than the leaf springs, if that's so then the Watts linkage is the only thing providing lateral location and you could place the RC where you like as there's nothing for it to conflict with. |
| David Billington |
| Hi David, How do the RTL equipped cars get on? As the primary purpose (in my eyes) of a Mumford is to lower the roll centre (as well as the axle location) and Frontline state that they do lower it with the RTL? Your right, the Escort comment may be playing tricks on me mind now but I thought I had seen cars with both, but there does seem to be a few RTL Midgets around? Cheers |
| S Deakin |
| Spencer, I can't comment on the RTL in use as I haven't got one, hopefully someone will chip in with their experience. I have a Watts linkage on my mk1 sprite and it works very well, pivot mounted to the body. FL may mention lowering the RC but how much is important, they may not lower it enough to be significant or maybe the increased roll moment counters the tendency to stiffen the suspension. BTW the worse case of contention I've encountered was on a quarter elliptic car where the owner had fitted a panhard rod from just below the boot floor to just below the bumpstop, maybe 6" difference between the springs and the panhard vertically. I didn't drive the car but it felt awful from the passenger seat, bad oversteer when turning. |
| David Billington |
| David, I agree an over constrained system (contention?) is bad and can cause the mechanism to 'lock up' making the expected vertical wheel rate variable and much greater than expected. For me the biggest unknown is the actual roll centre height to any degree of certainty, we have the geometric construct of a roll centre from the intersection of various points / axes and this gives us what most people refer to as the geometric roll centre height. Which is why in my earlier post I didn't talk about the positioning of the Panhard rod at the leaf sprung / live axle geometric roll centre as described by Will. When we talk about 'roll centres' we are really talking about how much of the roll moment / force is resisted by the 'geometry' of the suspension links and not by the road springs / arb's. To this end we have what is known as the force derived roll centre height and is found by testing a vehicle on a Kinematics and Compliance rig like those at MIRA / Lotus, Michelin and most OEM's etc... When we compare force derived and geometrically derived roll centre data there is often large descrepancies between to the two. I am not aware of any OEM that uses or looks at geometric roll centre data in preference to force derived data. The problem for those who can't afford a K&C test @ £8000 or to develop a fully correlated CAE model which can calculate the same information is that all we then have is the geometric roll centre. My recommendations remain as stated in the previous post, the axle centre line is a close enough position for the Panhard in the abscence of force based data, the only thing I would add is that both the axle and the body have a few options in terms of height adjustment for this reason, then imperically find what suits you but stick to the rule of keeping it parallel to the ground and as long as possible. I suspect the RTL either through design / testing or fortune has ended up with a RC near the forced based RC which is why everyone who fits it seems to like it and it is without any obvious vice despite its RC height being some way below the leaf sprung RC. Cheers |
| S Deakin |
| Spencer, I agree that the geometric RC is not ideal compared to force based, especially for modern production car suspension systems with all sorts of compliant bushes etc. Geometric will work well with the likes of non compliant suspension bearings as more often used on race cars. The main thing I was trying to get across was regardless of where the effective RC is, if you have 2 locating mechanisms on the same axle and their constraining geometry is different, you'll get problems. In the case here with a Watts/Panhard/Mumford and the RC is away from that dictated by the cart spring you end up trying to deflect the spring sideways, which is their strongest direction. Given that the spring bushes have some compliance the movement may be acceptable upto a point. I think you understand all this. Best bet is to ditch the leaf springs and go for non locating coil springs and one can do what one likes with the RC position, in the case of retention of the leaf springs the RC should be kept close to the original for happy co-existence. |
| David Billington |
| David, Have you got any pic's of your Watts setup? I have been mocking the 4 link bits on the car today, well the longitudinal mounts to the body part anyway. I used to have have a rear outer bulkhead but not anymore What have I done!!!!!!!!!! |
| S Deakin |
| Spencer, The pictures I have are mainly of a Watts linkage I made for a mate for his Austin Sprite and are here http://www.metal-arts.co.uk/temp/Watts/ . The actual picture of the Watts linkage and the mounting bracket http://www.metal-arts.co.uk/temp/Watts/wattslink.jpg are that of the one I produced for my 1/4 elliptic sprite. The difference was mainly that the semi elliptic version was mounted slightly higher and had a cutout to clear the fuel feed and some different fasteners such as countersunk socket screws as there was less clearance on the handbrake. Some things I would do differently these days as I have better fabrication facilities, in those days what I had was limited so I tended to use standard sections, or parts of them, as far as possible. |
| David Billington |
| Jon - This has got big There is the KISS theory (keep it simple stupid) and unless it's a full on competition car ----- Spencer-- Symmons Plains is great now-- It was mostly resurfaced a few years back and the corner at the end of the main straight widened a bit with a shute off it to the pitts which is now on the outside of the circuit and rejoins the track after the hump. Fantastically fast track for a high speed car. Both Symmons and Baskerville are now run by an enthusiasts group and the MG club is a part of that and runs some of the open events as well as our own clubdays. We had our first full historic meeting last year with great success and that looks like being an annual event now. Over and out Willy |
| WilliamRevit |
| It's very interesting to see the differentthoughts and experiences. Ive just bought some westfield trailing arms and pan rod (cheap!!)- I was thinking I could cut and either lengthen/shorten them so I could use them as experimental upgrades. I have never even driven my Midget on the road so It's a little premature - although Im at an ideal stage where Im grafting on the rear wheel arches and welding up stuff pre paint... Jon |
| J WHITE |
| Prop, and anyone else interested. The photo above showing the race car setup is actually running Gullwing Offset Springs to allow the use of a wider rim without body modifications. These are available from the Winners Circle although i have no idea on price for them. Pete |
| PJ Moore |
| I have a home made Panhard rod on my car. Some details here: http://www.pjprofili.com/?page_id=243#081301 |
| Phil ('66 Sprite) |
| I have Frontlines RTL on my 1275, and am very happy with it. Straight line stability is better, and as they say, power can be applied earlier coming out of a corner. I have not noticed any detrimental effects at all. Dave |
| Dave Barrow |
| Dave, How about your bank balance?. |
| David Billington |
| "How about your Bank balance ?" There has to be some compensation for getting ------- old . Dave |
| Dave Barrow |
| I was only 31 when I got my RTL from Frontline, worth every penny!! About the bank balance... some invested it in Isave and i bought a RTL... I still have my RTL and the others lost their money. ;) |
| Arie de Best |
| The younger you are when you spend on your treasured car, the more years' benefit you get from it and the lower the annual cost. Unless of course you fritter away the benefit by having the car off the road for months on end whist you bu88er about with the engine. Now who could that refer to.....! |
| Guy Weller |
| Thinking hard... no, I give up! Who is it Guy? :) No engine problems this year(yet!!!)only diff and electrical maintanace and addition of extra electrics(cruise controll and soundsystem). Months I had to start it and as usual I find myself in a hurry now to get ready. I hope i get wiser and plan better the older I get... but i dont think so. LOL!!!! |
| Arie de Best |
| Where's Tarquin got to? He has been very quiet for a few days. Maybe he is locked in his garage. |
| Guy Weller |
| Most stuff I've read goes on about how good a Panhard is especially when running wider tyres. Would there be a noticeable benefit on a 145 section tyred 1275? I keep mulling over making one, but would the effort be wasted with skinny tyres? |
| G Hawkins |
| The Panhard eliminates side-ways movement of the car body over the axle (actually more complex than that, but will do for now). This movement is caused by cornering forces ... if you toodle around, maybe you don't need it. On larger/stickier tyres, cornering forces increase and sideways movement is visible and noticable through the seat and also the steering wheel. Whether you need one depends on your dirving style. IMO they make the car safer (more predictable) for emergency manoeuvres at speed. Some also find benefit in centralising the car body on the axle when they fit larger tyres; and prevent tyre running esp for square arches. A |
| Anthony Cutler |
| So, does anyone have a sketch and dimensions for making one? In particular, the mystery seems to be with the actual design of the spider-shaped mounting bracket that bolts to the car body. Anyone got a design for this? |
| Guy Weller |
| It's easier than you think. The main strut we made from square tube; weld a bolt in the end, thread out; put a repair washer on the thread, and stick through boot floor with washer/nut on top. Near other end: weld another piece to hit the rear boot floor; add tang on end so you can bolt into one of existing holes (eg used for ex mount); similarly, tube from lower end across to other side of car, drilling though tang to mount on forward part of boot floor. Etc. A |
| Anthony Cutler |
| So it is just a 3 -legged spider then? |
| Guy Weller |
| yes; the design is quite simple. Once you've made the frame, then you can turn your attention to the rod part; I used old MGB steering rack and some thing steel tube. This part can be thinner than you think, since the stress is along its axis assuming ball-joints at both ends (and I used TREs). A |
| Anthony Cutler |
| I was thinking of using something like this: 160366914786 (e-bay item number) |
| Guy Weller |
| For daily driver, I'd use a protective boot. A |
| Anthony Cutler |
| Yes, one can get a boot to go over them. I wasn't sure if an alloy one like this would be strong enough. Commercial ones are often just a short piece of tube welded across the end of the bar and fitted with a Metalastic bush. But I like the idea of the adjustability of a rose / track rod end fitting at either end. Why I was looking at something like this rather than just a TRE was so that I can use some rubberised sleeve in the eye and maybe reduce transmission of any road harshness |
| Guy Weller |
This thread was discussed between 04/03/2010 and 20/04/2010
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