Anybody familiar with compensator on rear suspension of old Mercedes 108 chassis

[jimr]

Seems the older Mercedes were a swing axle design, much like the VW design.

I was looking at a microfische of the rear axle design on an old 108 chassis car (like a 280SEL 4.5), and Mercedes had a hydraulic-compensating device that kept the wheels from going negative camber under weight transfer or extra load. It was a horizontal shock that mounted on diff, and utilized rods that mounted to brackets on ends of swingaxle housings. According to some Merecedes specialists i have discussed it with, the system worked very well. However, it was very expensive to repair (the shock) if it failed.

Why am I talking about Mercedes parts?

Looking at the design of the Benz, it seemed it would be pretty simple to engineer a similar system for a swingaxle VW, that could aid in keeping maximum contact patch with the pavement under hard acceleration/weight transfer, instead of going to extreme negative camber. Since the expense of replacing the hydro-compensator grew to be unbelievable, an update kit is offered by MBZ to replace the shock with a simple coil spring.

If a system could be arranged, with simple lever arms off of lower shock-mount/axle housings and mount some type of damper or spring horizontally above transaxle (around intermediate housing area?), would this help traction problems?

Your thoughts?

Jim Ratto

[Tom Simon]

I don't think swingaxle cars have an inherent traction problem. Street tires with stiff sidewalls and city streets are the bigger limitations IMO.

The different camber compensator devices I've seen were all meant to battle what I call "tuck-n-roll", where side loads (while in a turn) cause the swing axle to go over-center, jack the rear up higher raising the CG of the car and helping it onto its lid. I hear it was common in the 60's for some racing sanctioning bodies to require some type of camber compensating device on anything with a swing axle. There is an older book (likely out of print) "Designing cars of tomorrow" that covers swingaxles and camber compensators/zero roll devices pretty well.

The best modern systems I've seen oddly enough are on the rear of newer design formula vee race cars...

[jimr]

I don't think swingaxle cars have an inherent traction problem. Street tires with stiff sidewalls and city streets are the bigger limitations IMO.

The different camber compensator devices I've seen were all meant to battle what I call "tuck-n-roll", where side loads (while in a turn) cause the swing axle to go over-center, jack the rear up higher raising the CG of the car and helping it onto its lid. I hear it was common in the 60's for some racing sanctioning bodies to require some type of camber compensating device on anything with a swing axle. There is an older book (likely out of print) "Designing cars of tomorrow" that covers swingaxles and camber compensators/zero roll devices pretty well.

The best modern systems I've seen oddly enough are on the rear of newer design formula vee race cars...

The Mercedes unit prevented negative camber (squat), not the jacking that many of us are way too familiar with.

[jim martin]

that unit is no longer available it is replaced by a spring and bracket

[Tom Simon]

The Mercedes unit prevented negative camber (squat), not the jacking that many of us are way too familiar with.

I guess I'd have to see a pic to understand it

[alex d]

as I understand it, the MB system also does prevent swing-axle jacking, in fact the stock Z-Bar in 67 and later swing axles works in a similar fashion, the suspension is in fact stiffer when both wheels move up (for example accelerating), but when one wheel moves up and the other down (turning), suspension is softer and the outer wheel is less likely to go to positive camber.
the mercedes system is probably much more refined and efective, never tried one of those, but they did win the Montecarlo Rally, so they might be into something