Wanted: Fiat 850 Camber Compensator setup

kmead

Old enough to know better
Wanted Fiat 850 rear suspension Camber Compensator

Likely not the best place to ask but perhaps someone has a line on one of these.

A few years ago an enterprising individual produced a reproduction of the old camber compensator set up for 850s which minimizes "jacking" of the semi-trailing arm suspension as the car leans excessively during heavy cornering loads. Sadly I wasn't in a position to buy one at the time.

So does anyone have a line on one of these fine contraptions, either a used old one or a newer one they would be willing to let go?

Alternatively drawings of the unit would be fine as I could likely have one fabricated in a local shop.

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Many thanks

Karl
 
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It takes the place of the sway bar. It is a subframe part that attaches to one of the sway bar mounts and to the transmission mounts. It creates a saddle and primary mount for what is in effect a leaf spring that attaches to the sway bar mounts on the semi trailing arm and keeps the rear from "jacking" while cornering.

These were very prevalent back in the days of the old swing axle VW Beetles and the original Corvair. Triumph Spitfires also suffered from the same jacking under braking and cornering which made them pretty evil. The 850 isn't this bad but I have seen one pretty jacked up during some spirited driving in the past.

triumph-spitfire-.jpg
 
It takes the place of the sway bar. It is a subframe part that attaches to one of the sway bar mounts and to the transmission mounts. It creates a saddle and primary mount for what is in effect a leaf spring that attaches to the sway bar mounts on the semi trailing arm and keeps the rear from "jacking" while cornering.

These were very prevalent back in the days of the old swing axle VW Beetles and the original Corvair. Triumph Spitfires also suffered from the same jacking under braking and cornering which made them pretty evil. The 850 isn't this bad but I have seen one pretty jacked up during some spirited driving in the past.

triumph-spitfire-.jpg

From the ancient tome "Racing Car Design and Development" by Len Terry and Alan Baker:

"Low roll centres mean low roll stiffness and, conversely if the roll axis passed through the C of G there would be no rolling moment at all under centrifugal force. Just the thing, you might think, but such a layout would be impracticable. A high roll centre results from a high intersection point of the wishbone axes, and this point can be regarded as the instantaneous centre about which the wheel is articulating on an imaginary swing-axle. The higher this centre, the greater is the tendency during hard cornering for the body to be lifted and the outside wheel therefore to tuck-under, with consequent further (and severe) reduction of cornering power. This phenomenon, known as the 'jacking' effect, is responsible for the well-known violent oversteer of swing-axle cars such as the Volkswagen and Triumph Herald, particularly if the driver lifts off in a corner and the weight transfer off the rear wheels raises the roll centre further."

So it is written, so it shall be.

Pete
 
I did a lot of searching this afternoon Karl, but came up empty. I found a link to an Ebay auction from 2012 that has a tiny picture of the parts and I found the picture you used in your original post. That's it. I do have a PDF of "Fiat and Abarth Tips by Greg Schmidt" which has a mention of the compensator and a sketch, but no measurements.

If you want a kit for independent front suspension on your 850, well, those are everywhere. :(
 
Thanks all.

Indeed Jeff knows, he just hasn't been around much of late. I will IM him. Merkel would be the other good source, knowing him he has three of them sitting on a shelf just in case...
 
Hi Karl,
i think is no good idea,
you must eliminate the reasons!! not build other problems

try get Roll center low as possible
try get CoG height low as possible
get sufficient wheel travel
measure and tune wheel rates

Radek
 
VW's solution from the factory on the '67 (if I recall) Beetle was the "Z-Bar". Effectively something of a 'reverse' swaybar. It attached to the outer ends of both axles like a swaybar. It had a single rod going from side to side, with pivoting mounting brackets like a swaybar. But the two ends faced in opposite directions, quite the opposite of a swaybar. And the end links had a 'sliding' motion in one direction but solid stop in the other direction, causing the bar to only act when the axle moved one way. Take a look:
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DSC04901.jpg
308819.jpg

Those German engineers are crafty little buggers.
 
Karl, If you end up finding drawings and need people to sign up for a run of these to get prices low enough to be practical you can count me in.
 
Not sure how I even stumbled it. But I too have been wanting to add one to my car. Looks pretty straight forward to make. But I am thinking that the transverse plates are actually leaf springs that would need to be sourced and of the correct temper, etc? Perhaps they are the same springs as the fronts? I'm sure the local 4x4 shop can whip some up right quick.
 
I'm just guessing but it looks to be the same principle as that VW item I referenced. However in this case the transverse plates pivot at the center, so as one side goes up the other side goes down like a see-saw action (that was the purpose of the "Z" configuration on VW's). The ends of the transverse plates can slide up the end links in one direction, but cannot move down past the lower end of them in the other direction (also like the VW arrangement). If all of this is correct, then the actual 'temper' (spring rate) of the transverse plates is not that critical. In fact it should be fairly firm because it is the pivoting action that gives it the desired effect on the rear axles. The 'flexing' of the transverse plates would be more to prevent binding/bending/breaking of the plates rather than to act like a "anti-sway bar" does.
 
Yes, I think the leaf’s could be sourced through a spring shop, they should be fairly soft. I will try and find some more info from a friend who I believe has one installed (in CA, so not something I can go and measure).

Yes that is how is intended to work. I will look for an image of an 850 “jacked” up, there are some movies of 850 Coupes on the ‘Ring’ going around some particular sets of turns which demonstrate the problem, several of them overturn.

At least three 850 Sport Coupes in this movie.

 
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