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MG Midget and Sprite Technical - Panhard Rod

Next upgrade, in an effort to stop the tyres rubbing on the arches, I made a Panhard Rod!

Me being me, I wanted to do my own thing rather than just buy one. That way I could choose my on mounting points so that I could maximise the length of the bar, pick strong points on the boot floor for mounting and make sure it was dead level at rest. Also, the bits only cost a grand total of £42.97, plus a bit of paint, welding consumables and some tube borrowed from work :-)

It sure makes a difference to the stability of the car when powering off roundabouts! It feels a lot less wibbly wobbly at the rear as the weight transfers about.

The big test will be at Curborough a week on Monday when I can try it out with my fatter semi-slicks. Can't wait :-)

Hope everyone is well. Cheers,
Malc.






Malcolm

Your design and installation has also lowered the roll centre so that will also improve handling. Lowering the roll centre is the advantage the Panhard Rod has (when designed that way) over the Watt's Linkage.
Daniel

Looks good Malc.
A while back I was looking at using an A frame approach for axle location as the panhard rod causes an assymetric lateral displacement of the axle.
A prototype frame was tacked up with intention to use front wishbone inner bushes at all required positions.
Body attachment was to use existing hole in each inner wing to provide location with a strengthening corner bracket between bulkhead panel and damper mounting plates each side.
A mounting bracket would also require welding the axle casing and would probably need to be quite robust to withstand potential loading.
Yet another item requiring further work !
Cheers
Steve
S G KEIL

@ Daniel, yes, I read up loads on roll centres, did various calcs, pondered custom made brackets etc. etc. then decided sod it, I will just copy what everyone else does and weld the attachment to the damper mounting plate, make it horizontal and call it done and the RC will be what it will be.

@ SG, yes, in theory you end up with an asymmetric movement of the axle. But it's (theoretically) +/- 1mm over +/- 35mm of axle movement and only up to 4mm on extreme droop (i.e. I am airborne and the axle is hanging off the straps!!) So for the sake of a millimetre here and there, I am happy with the simpler and lighter approach :-)

Cheers,
Malc.
Malcolm

Malcolm
I made a Panhard rod just like yours for my Mk2 Sprite (1/4 elliptic springs), fitted it almost 20 years ago. Made an unbelievable difference, car feels so much better.
Made it as long as possible and reckon get about +/- 0.4mm lateral movement of the axle per +/- 25mm vertical movement. This is probably less than it would move normally with 1/4 elliptic springs!
Les
Les Robinson

Hmmm-I must be the odd one out here-not a fan
William Revit

Here is mine, also homemade. Uses fuel tank mounting points with longer bolts instead of studs. Other end rose jointed to axle bracket.


Les Rose

What' the advantage of a Panhard rod over a watt's? 😉
anamnesis

Panhard sounds more sexy then Watts...? LOL
A de Best

I think in theory the Watts linkage has some advantages over the Panhard rod - no change in roll centre (must admit not sure what this is!) and no lateral movement of the axle.
In practice you would be hard pushed to see any difference between the two, especially on a road going car.
In terms of application, the Panhard rod is easier to make and fit and to my mind has no disadvantages.
Les
Les Robinson

@-------Your design and installation has also lowered the roll centre so that will also improve handling. Lowering the roll centre is the advantage the Panhard Rod has (when designed that way) over the Watt's Linkage.
@-What' the advantage of a Panhard rod over a watt's?
@ - no change in roll centre (must admit not sure what this is!)

lol ---- just another pub session --here we go
William Revit

@ ?
anamnesis

oooo pub! I can agree with that! :-D

Willy, yeah I saw your comments on other archived discussions on the topic. I'm inclined to agree, but don't have the time/desire at the moment to get all design-y and novel with things. The Panhard is a bit of a fudge of a fix on top of an already imperfect system. But if it (mostly) works, I'm gonna run it for a while. The car spends too much time in bits and not enough being driven.

Cheers,
Malc.
Malcolm

All good Malc. Having fun is the main thing. let's do that.
Cheers
willy
William Revit

The figure of 8 Curborough course should be an ideal test for your new modification and good to see one that'll probably improve the handling for such a small outlay.

Some of the other cars at Curborough (July 10th) will also have had significant upgrades so be interesting to see how they all perform.
Tim Lynam

On a Sprite/midget the roll centre is in the centre of the rear axle. Fitting a Watt's linkage does not change that but provides lateral control.

With a Panhard rod the roll centre is at the height of the rod itself so if the rod is at the centre height of the axle nothing changes. However if the Panhard rod is lower than the centre height of the axle then the roll centre is lower than standard. You also get lateral control.

My experience is that the Sprite Midget does corner better with a lower than standard roll centre (all other things being equal, meaning on the same car which is lowered already etc).

The disadvantage of the Panhard rod is that it has to move in an arc as the axle rises and falls and this can cause rear wheel steering. If you doing any speed over the national speed limit you'll know this when it happens!
Daniel

Daniel,

With a Watt's linkage the RC is the centre pivot so it can be adjusted in height just like with a Panhard rod. I fitted my pivot to the body to achieve a constant roll moment. If retaining the standard springs you can't move the RC about too much anyway or you'll get contention between the springs and Panhard/Watt's.
David Billington

Nice job Malc. Better than anything I could come up with.

I've been considering one of these, on and off, for a number of years. I don't race or hill climb, just spirited driving on some of our windy roads. 59 Frog with standard suspension, front anti-roll bar and 6 inch wide wheels. I'm not good at welding so the prices are a bit high. Speedwell Engineering in California is asking $385.00 for their version. I'm sure others are in the same price range. Would one of these really be worth it? Awaiting 12 different opinions.
Martin

Martin
Agreed, Malc.'s a thinker--and I like what he does.
As far as your bugeye goes, yeah most sprites/midgets are a bit squirmy in the rear and apart from replacing all the bushes etc in the rear a bar of some sort will make it feel more solid--it'll feel like it handles better but really it only stops it moving about--it won't make it grip any better to the road- and as Daniel noted at high speed on undulating road it'll feel crap--this feeling can be minimized by having a Watts linkage instead or if using a panhard bar the body mounting must always be on the driver's side to eliminate the scissoring feeling that is felt in the steering/seat if it's on the other side
Also Daniel mentioned the roll centre is in the centre of the axle housing---horizontally correct but the roll centre height of most midgets i've measured up ends up about level with the bottom of the side tubes but varies from this depending on ride height----on a bugeye because it's 1/4 eliptic the spring is deemed to be a solid bar and the roll centre height is at the point where the spring mounts to the housing
Also, back to Daniel-he said a fair bit in a single post-impressive--yes midgets tend to like lower roll centres but there's a limit where the new introduced lower roll centre can be too far away from the natural roll centre and cause a binding with body roll the result of which is sudden increased oversteer on the limit where you least need it
As you can probably see I'm not a fan of them but on a roady bugeye with a squirmy rear end there would probably be an an improvement in the way the car feels to the driver---but--make sure the body mounting is on the driver's side
now where's my beer
ahhhhh--that's better
willy

Malc.--a suggestion if i may
Maybe you need to fit a larger flat washer under the head of the mounting bolts for your end joints--If the teflon lining pops out of the joint(and it will eventually) you need a washer big enough to prevent the link dropping off--easy to do now but a pain to have to do at the track on the day when the scrutineer points at it---cheers
William Revit

Willy,

Since my frog is left hand drive the mounting would be right behind me so that's not a worry.

I once installed a rear anti roll bar. That lasted about 2 months. Way too much oversteer. It always felt like the back end was going to come around on me. Right now it's pretty stable with my current setup, just thinking if I could improve it a bit. The biggest factory keeping me away is the cost. Sometimes I wish I had Malcoms skills. Alas, not to be.
Martin

You did well to last 2 months Martin---would have been a tail happy little jigger to drive I reckon---did you get to drive it in the wet--i guess not, you're still here---
William Revit

This was down in southern California during the summer. Long periods of no rain but in the wnter when it does rain it really comes down in buckets.
Martin

Thanks Martin, very kind. Not sure about skills, I have a grinder, a MIG welder, enthusiasm and an unhealthy belief that I am better off doing things myself rather than paying someone else to make the same mistakes I would make anyway!

Tim, there wasn't much ahead of me last year. (Not that it is a competitive event ;-) ) The Modsport racer, Rob Armstrong's K and a couple of Zetecs. This year I have 20% more power, lower, a stiffer ARB and now the panhard rod. It should be a laugh!

Yes re: flat washers. I want to put in some slightly longer bolts too, so those wee bits are on order.

Cheers all.
Malcolm

" -- but really it only stops it moving about--it won't make it grip any better to the road- "

Hi Willy,

I haven't a clue other than what I read about watt's and panhards.

But if what you say is true, why do people bother to fit them?

If you don't get any more grip, why not just get used to, and get to know better, the limit at which you lose grip?

My Sprite is standard suspension. I don't race or the like, but I usually 'know' when the ar*e end is going to lose it. I've felt it, and lost it more than once. Lol

Would a panhard or watt's have changed that?


anamnesis

an.--neither will make your std suspension grip better, if it's always the rear letting go on your car then going up a size on the front bar will reduce that--if it's an issue for you.
I can see an advantage for Malcolm using a bar to stop the axle moving making the tyres rub on the guards. If he's really lucky he 'might' gain a bit of drive out of corners from the slightly lower roll centre- maybe. the main advantage will be tyre clearance and the ability to drive the wheels off it without having to worry about that.
We'll be hard pressed to know though as there's also more power and stickier tyres going on at the same time, it's going to be faster anyway------we hope. The stopwatch will tell-
William Revit

Thanks Willy. Nah, I don't need to change the grip, only road use, and it grips well enough. Plus, I like being able to get it's end out. Lol.

But yep I see, the tyre rubbing issue if they're close.
anamnesis

Anam,

The following is all very theoretical waffle speaking in generalities... but from my point of view and the feel sat in the drivers seat, it's not about increasing the grip but about making the available grip more usable and predictable.

If you imagine two different cars (any car not just Spridgets), one has a very high peak grip but is more "on-edge" and the other has a lower level of overall grip but a wider and more forgiving operating window.

A pro driver would be faster in the first car as they have the skill to exploit the higher grip level without losing control. Whereas I (as an over enthusiastic novice) would be faster in the second car, because I need something that is more forgiving. It might have less grip overall, but I can use more of it because it is more predictable and confidence inspiring. If I were in the first car, I would spin, lose confidence in it, get scared and drive slower.

So the Panhard allows me to exploit what grip I have better.

As it's only a couple of bolts, I might do a couple of back to back runs at Curb' with and without it.

Cheers,
Malc.



Malcolm

" -- because it is more predictable and confidence inspiring. "

Yep, I can see that makes sense.

Be interesting to hear the results of you doing runs with and without.
anamnesis

Can I just throw this into the discussion ?
The normal arrangement for the semi elliptical spring mounting uses a pair of rubber mounting pads each side.
Whilst these can also be sourced made from polurethane I have also made a few sets using both aluminium and Delrin with the possibility of improving axle location.
Might be a bit 'noisy' for general road use and perhaps more suited to track work.
Cheers
Steve





S G KEIL

How much difference do poly pads make? My rubbers are knackered, only replaced a few years ago.

Rather than more poor rubber replacements, I'm considering poly, but don't want a harsh/noisey ride.

Does poly give a significant improvement, at the expense of increased noise/harshness?
anamnesis

Loaded question an.
Originally all the poly bushes were colour coded to indicate their hardness/flexability with red and yellow about the same as rubber then blue - dark blue - black with black being the choice for competition cars
Then along comes retailers that want all their bushes the one colour to match their trade name and it's all stuffed up-
But basically for the road red or yellow
race-black
For spring pads I'd go black(hard) anyway as you've got rubber bushes on both ends of the spring to gobble any possible extra noise up
but-----be warned i've seen polly bushes fall apart on cars in storage, although they were probably lubed with incompatible grease maybe
Found this for you to look at---

https://www.powerflex.co.uk/product-details/POWERFLEX+MATERIAL+DEMONSTRATOR/11710.html
William Revit

Thanks Willy; I think. 😅.

I kind of knew there wasn't a simple answer.

If only we could get the original rubber that was used. No need for poly as it used to last for yonks and yonks. Why is it/are (rubber susension components) so comparatively crap today?

How about a company called Superpro? They claim theirs, all blue, is a 'special' poly, that isn't harsh or noisey. Is that merely retail bull faeces?



anamnesis

Superpro have got a good name here especiaally with the outback 4x4 lot and their stuff seems to last well---but---they are one of the colour coded companies that have everything blue, but in saying that they do seem to have different hardnesses of blue------------why can't they just stick to the colour formulas so we know exactly(or roughly) what we're getting----but yeah, if you can believe what they say they match the hardness to the application
Another mob is Redline who sell--guess-------red bushes
but at least they promote them as road/touring bushes, and also sell blue for competition and black which they call solid--which it is
I put a set of black rear shackle bushes in my mate's MGB road/racer and it made a hell of a difference to the feel of the car's squirminess but then the old bushes were knackered anyway---didn't seem to transmit any extra axle noise with the hard bushes-this was probably8-10 years ago and they're still good and have had a fair workout in that time

willy
William Revit

I use the Blue Superpro middle hard quality for about 15 years and 100.000 km everywhere in the car . It was a direct fit. Last year I had to take some suspension parts apart. They were as new. 15 years ago the Powerflex bushes were no direct fit. I guess they are much better now.
A very interesting discussion about the Panhard rod!
Yes the car, a ¼ elliptic, drives much mor easy with the rod when cornering hard, it goes straight on the highway over ridges. Without it I had to make fierce corrections.
After I assembled the Panhard I had to diminish the front ARB because it oversteered on entry. With the thinner ARB there was more feeling in the steering.
I have been driving with and without Panhard rod on circuit days. With is much faster in slow corners.
I use rod end bearings on the Panhard. So I hear the diff better than before. When they are gone I will try silent blocks.
Flip
Flip Brühl

The one problem with those metal mounts Steve is there is a rule in the MSA blue book that says something along the lines of "rubber bushes must be rubber/polymer".

So *technically* breaking the regs if you use them for sprint/hillclimb etc. But then I doubt they would check/care.

Cheers,
Malc
Malcolm

I’ve got Superpro urethane bushes all round on my mk3 Sprite and they have improved the handling of the car, but with the rear axle pads I found that to get the U bolts tight enough to ensure correct axle location, you squash the pads almost flat so it’s difficult to feel if they are doing any good or not. I think most of the improvement comes from the front bushes and rear spring shackle bushes.
Bernie.
b higginson

It lasted less than a week before I bent the bar in a jacking related piece of feckwittery!

Sometimes I should not be allowed in charge of spanners.

Malc.
Malcolm

I need to remember “feckwittery”.
Philip Sellen

Ooops.

Explain the jacking incident Malcolm. 😉
anamnesis

Ali axle pads as mentioned by Steve are available from Peter May:

https://www.petermayengineering.com/product/alloy-spring-pad-set/

I have them in my road Midget and they seem fine.

HTH
Doug Plumb

This talk of axle location has me thinking ;-)

Is it true that the quarter elliptic cars have better longitudinal location than later semi elliptic cars, because of the radius arms stabilising the axle?
Bill Bretherton

You'd think so Bill. The rotation of the housing is well under control and as long as the U bolts are nice and tight and the spring bush mounting to the housing is good it should be well under control.
William Revit

Mk. 2 now on (finger tight, waiting on some longer bolts and spring washers). This time it's red! :-D

Re: the jacking incident... as you may or may not know I have two sets of wheels/tyres. Some tall skinny bicycle tyres for general use, and some wide, low profile semi slicks for the fun stuff. The semi-slicks are about 20 - 25mm smaller in radius.

I jacked up the car on the pumpkin to put on the track tyres for a final check of arch clearances etc. The trolley jack only just slid under with the tall tyres on, so when I dumped the car down on the lower tyres without thinking, the panhard landed on the jack!

As I said. Dumbness of the highest order!

Malc.



Malcolm

Apart from complexity, how does a Mumford link compare to a Panhard rod or Watts linkage?

I note that Frontline sell them for Midgets. Are they too much for a road car?
P Peters

a mumford link is more or less a watts linkage with a rocker link on one side, lots of moving parts---in the interest of keeping things simple--panhard bar--or if you're intent on a watts type linkage, it can be made/bought with the pivot mounted on the body and arms to the axle---doing it this way the pivot point can be made height adjustable to raise/lower the rollcentre to where you want it
William Revit

Malc,

How did the your Panhard Rod perform yesterday, did you see a difference?
16 runs certainly gave it a good test!
Tim Lynam

This thread was discussed between 28/06/2023 and 11/07/2023

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.