Suspension Puzzle

Bob Goding · 07-10-2006, 09:20 PM

O.K. Suspension Gurus! Can someone explain to me how this system works?
I scanned the pics from the May issue of Racecar Engineering magazine.
The article is entitled Formular Vee and the the pics are
"US-spec 'zero roll'.rear suspension.
It looks to me as tho' roll might be the only thing it would do!
I cannot see how the coilspring/damper gets to work.

masraum · 09:37 PM

Wow, good one, whacky looking setup. The only thing that I can see is that when the brackets at the top of the carrier deflect left or right, the attachment points for the two rods on the ends will both go up or down by an equal amount. That to me makes it seem as if the rear end wouldn't be laterally fixed in the frame, but instead of roll, the suspension will just shift left and right and squat.

But that's just what it looks like to me, I don't know for sure.

Bob Goding · 07-10-2006, 09:51 PM

Steve, I dont see how it can squat ,with the link above the spring!
How can the suspension unit compress?

Bob

Willem Fick · 01:24 AM

Masraum, I agree. Great, simple setup!

Bob, I wonder if the link is a permanent fixture? Without the weight of the car compressing the shock/spring, the two pivot arms will be pushed apart once the car is lifted up. Perhaps the link is fitted temporarily for whatever maintenance requires the car to be lifted and wheel removed? I guess this si what they refer to as the "droop limiter".

Bob Goding · 07-11-2006, 01:35 AM

Ah ha! If the link slides thru its 'trunnion'[opposite end to the rodend ] it would allow the spring assy. to compress,and also act as the droop limiter in the situation shown in the pics,i.e with the weight off the wheels?
Thanks,Willem----- More thinking required!

Bob

Bob Goding · 07-11-2006, 01:39 AM

How would that look in the rear seat area of your old VW Beetle?
Ingenious.

Bob
'76 2.7

Willem Fick · 07-11-2006, 01:41 AM

Bob,

Brilliant! The link slides through the the "bit" indicated in the picture I attached. You are right - it slides freely during "normal" suspension operation, but the moment the wheels go airborne, they are prevented from drooping below a pre-determined level.

Joeaksa · 07-11-2006, 06:24 AM

Interesting...

serge944 · serge944's Garage

The top link serves as an additional guide or support so that when the suspension compresses, the brackets holding the damper dont deflect fore and aft. After all, the attachment points on the frame wouldn't be able to keep the assembly in place on their own.

Pretty neat design actually, and cuts down on the weight of at least one additional damper and spring. Race Tech and Racecar engineering are my favorite magazines.

djmcmath · 07-11-2006, 03:52 PM

Still not sure I understand how they call it "zero roll." It seems like an upward force on one side, but not the other, would result in just pushing that shock over to the un-pushed side. There must be something I'm missing?

Dan

serge944 · serge944's Garage

I think the whole point of this suspension design is that both wheels are loaded equally at all times. As one side absorbs the centripital force, it pushes it up through the spring and pushes down on the other side.

bell · bell's Garage

Quote:

Originally posted by djmcmath
Still not sure I understand how they call it "zero roll." It seems like an upward force on one side, but not the other, would result in just pushing that shock over to the un-pushed side. There must be something I'm missing?

Dan

not an engineer......but if one wheel compresses the shock, then the energy not absorbed by the shock will transfer to the other wheel, resulting in more traction for that wheel, and it should also counter the chassis roll associated when one wheel is moving upward.
interesting stuff

Owain · 07-12-2006, 08:25 AM

Quote:

Originally posted by bell
not an engineer......but if one wheel compresses the shock, then the energy not absorbed by the shock will transfer to the other wheel, resulting in more traction for that wheel, and it should also counter the chassis roll associated when one wheel is moving upward.
interesting stuff

Yeah, I think that's it. A portion (regulated by the spring rate) of the "cornering force" (or the weight transfer) is transfered back to the "inside" unloaded wheel. I seem to remember reading about this sort of thing on F1 cars as long as 15 years ago. It's not a new idea, but it is pretty neat

artplumber · 07-12-2006, 01:48 PM

Quote:

Originally posted by bell
not an engineer......but if one wheel compresses the shock, then the energy not absorbed by the shock will transfer to the other wheel, resulting in more traction for that wheel, and it should also counter the chassis roll associated when one wheel is moving upward.
interesting stuff

The damper is there to serve just as any damper - reduce the rapid oscillation of road irregularities, whereas the spring serves as the ride height/left to right loading. The linking of the left and right suspensions serve to keep the inside tire down and partially loaded, but only as limited by the spring length and rate.