Anybody??

I am building up an ulster rep at mo and was wondering whether it is worth trying to improve the road holding by putting either a panhard rod on or locking a front spring shackle ,or by other means??. Theoretically the combination of a lowered chassis with proper front axle location should make for extremely good road holding(relatively speaking!!)???

regards nick

I think the short answer is "yes", Nick. I would also suggest improving the damping if you can; you will have seen the typical set up in the "A7 Companion" with separated damper arms.

Regards, Stuart

Hello Nick - Tim Myall does an 'off the shelf' mod with two damper arms, much shortened from the original mounted on a central extended bit of angle. Not pricey in my view. The connections to the axle beam are still through ali s/a links, but the ability for the front axle to move about is much reduced. Just bolts on in place of the original with no further mods. Hope that helps? - Hugh

Nick,

Cut sections from the tread of an old tyre (canvas construction) or block of rubber to insert through the spring shackles and down the gap between the axle and the end of the spring. This gives fantastic location and is by far the quickest way of locating the front axle. It is also barely noticable.

Rob

I would be wary of the rubber block method if your front spring is not almost flat, if you have a standard spring it will need quite a lot of shackle movement to accomodate full defelection when you hit a bump, the spring needs to have room to grow in length, if both ends of the spring have got rubber bump stops it could put some strange stresses into the spring or make the ride very harsh.
With a flat spring the opposite should happen, the spring will curve the opposite way and it gets shorter when you hit a bump.

I have just tried the simple mod of removing an alloy link and attaching one of the shock absorber arms directly onto the axle stud, it has made a noticable improvement to the wandering problem on rough roads, the only downside I can see is the possible stud or hole wear due to metal contact in that area, if I get round to it I might arrange a rubber bushed version, but that would make it a non reversible modification unless I use a spare set of arms.

Phil

Phil, I go along with Rob about the rubber blocks, I first saw these in use in New Zealand where there are still many miles of 'dirt road' with the inevitable potholes and corrugations on the bends.

In NZ they tend to find remains of lorry tyres and cut a suitable block for each side. I use a dense foam rubber ( the type used for trainer soles, it came as packing around something! ) After seeing the way my car rides several other Cornwall Club members are doing the same.

It certainly transforms the riding ability of the car and normally there will be enough 'give' in the rubber to allow the spring to act normally.

I understand that some people locate one of the damper arms onto the axle without a swinging link. In my view this must be the worse way of stopping axle tramp.

Phil,

My dad has been running standard cars with the rubber blocks for years, there was some teething trouble with using them on his box saloon in that he found he could corner so hard (boy racer) that it broke both front hubs in the space of a few months. Has not been a problem having eased off. The other problem is the sudden revert to the original poor handling if a rubber block should fall out (has only happened once). No problems with ride.

Granted would not work so well with a sports spring.

Rob

Like Phil I locate one arm solid to the axle without the swinging link. Mine corners very well in my humble opinion, although I have not compared it with anything else! Not sure why Malcolm doesnt like it? It is basically a crude form of panhard rod , which is a very common way for manufacturers to provide transverse axle location. I was always under the impression "axle tramp" was that experienced by 70's rear wheel drive cars whereby a grunty engine gave enough torque to wind up the rear semi eliptic springs into an "s" shape which gave rise to a viscous cycle of events that caused the axle to skip up the road. Ford actually fitted "anti tramp radius arms" to the high performance Escorts.

I do like the sound of the rubber blocks, and wasnt aware of this technique, you must have been keeping it quiet Malcolm!! . If I did another one I would consider using the blocks that you and Rob describe because I guess its cheap and very simple and fully reversible if you change your mind.

Ref the spring movement, I do find mine very stiffly sprung as the car is light and the spring rate probably to high? I did wonder if the short shock absorber arm acting as a crude panhard rod was stopping suspension movement as a result of the arc it swings through conflicting with the spring shackles, but this does not seem to be the case in practice?

As many people in published books report success with all these different methods why not try them out for yourself and make your mind up with some testing? theres more than one way to skin the proverbial rabbit!

Regards

Steve

A very good point Steve there are any number of ways to do it. I think if i were building a racing special i would use a watts linkage to locate the front axle as it acts the same in both directions (would put one on the rear too). An ideal panard rod needs to be as long as possible to avoid bump steer effects ie attach to one end of the axle and the opposite side of the chassis.

If you were to use the twin front shocks as discussed there is probably space to mount a watts linkage on the shock absorber bracket.

See http://en.wikipedia.org/wiki/Watt%27s_linkage

Regards

Rob

Yes I agrre with all the comments above, there is certainly always more ways than one to achieve results, and no one idea can be assumed to be the best.
The proof is in the pudding, if it works OK in practice then the theory goes out of the window.

How about some photos of said rubber blocks so we can see what sort of size and shape we ought to be making.

Phil

Whats wrong with the front axle as designed in 1929?Austins were very happy with it ,they did very well in the TT,Double Twelve,500 Mile Race Etc etc etc..
They were going faster and further than we will ever do.

Dave
Are you refering to the axle with the rotating joint in it? Was this not because the radius arms were located on the chassis and not on the centre ball pivot as standard? .

Ref the Watts linkage.... We fitted one of these to a friends rally car (on the back)and it transformed it. For those not aware it allows straight line motion instead of the arc the panhard rod moves in. They are also used in a slightly altered way on some kit cars as the longitudinal locating arms for the rear axle, were they produce outstanding levels of grip.

For other unusual and strange ways of locating axles just look at a clubmans car like a Mallock! Arthur Mallock came up with many variations of linkage that are interesting .

I also remember that a sliding link was used on a car of some kind to locate the axle transversely, where the axle was "guided" up and down in a track/groove?

Steve

Steve, my 'negative thoughts about fixing one damper arm to the axle are based around the fact that it is too short to be doing a 'good' job and puts strain on the joint to the axle and the chassis in a way that was never designed. As the joint is metal to metal without inbuilt lubrication system it would seem to be a high wear point.

As already mentioned rubber blocks are a simple method, easy to install, easy to adjust and easy to remove if required.

thanks for all the advice guys!!!

Has anybody got any good ideas about the other end ?

you get all sorts of weird things happening as the car leans over on a bend, the outer spring gets longer whilst the inner gets shorter causing oversteer as the rear axle is no longer at 90° to the centre line of the chassis.

I dont actually mind that quirk too much, in fact quite often I use a technique of accelerating half way round corners to "add a bit" when it is under-steering.

Short of a radical re-design I think we must accept it as is.

Phil

Phil,

I have seen cars with rear spring shackels and radius arms to prevent this. On a sports car however, with flat or inversed curvature springs the rear axle roll steer goes the other way and puts the slip angle on the tyre rather than taking it off. This makes the handling of the car far more predictable.

Regards

Rob