The control-arm style suspension systems fail to keep the wheel at the same camber angle to the road over their length of travel (i.e. rotation). Just curious if a parallelogram suspension system design has ever been used in a car so the camber angle remains constant? Or is the rotating arm type actually better for cars?
Almost all double wishbone suspensions have shorter upper arms vs bottom to increase camber when suspension is loaded. Not exactly a secret.
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If a parallelogram suspension is used, when the body rolls 3 degrees from corning, the tire will camber the same 3 degrees in the wrong (out at the top) direction. That will reduce cornering grip.
If the upper arm is shorter, the tire will camber in the correct direction to maintain grip in the corner. How much is defined as percent roll compensation. 100% would keep the tire upright with 3 degrees roll. 50% would camber in 1.5 degrees with a 3 degree roll. 100% is never used. Makes the car twitchy and compromises braking.
Parallelogram types have been used. One example is an early 30s Tatra. A rear engine V8 car, this was done to promote understeer.
Early VW Beetles had parallel and equal length trailing arms on the front suspension for the same reason. Car rolls 3 degrees, so does the tire. Tail happy rear engine car so promotes understeer.
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I enjoy your comments but why did the late 60’s, early "70’s have a tendency to “Tuck and Roll”/
Would you explain Tuck and Roll? Are you thinking of the Corvair and similar?
Yes, my understanding was that the IRS rear suspension was responsible for the terrible handling at extreme points for the Corvair, VW, FIAT 850 and even others like the TR 5 and would result to rollover.
Please enlighten me, Thanks
The Corvair and others used a swing arm rear suspension. The half shafts were solidly connected to the wheel… no u-joint or CV joint. The end connected to the differential had a u-joint that was the axle swing point. There was a control arm solidly mounted at the wheel that runs forward to a bushing mounted to the frame or body.
When the car corners, the outside tire can tuck under and spin the car. It was unlikely to flip the car but it would spin. It does this because the u-joint pivot is too high and it makes the roll center too high as well giving the car a tippy tricycle-like feel
The solution was to add another control arm under the driveshaft and add a u-joint to the wheel side of the half shaft. This can push the pivot point formed by the 2 arms much lower and far outside the car. This is called an virtual instant center point. It also lowers the roll center to eliminate the tippy feel.
Swing arm suspensions were not so bad when cars were tall and tires very skinny. VW Beetle for example. Lower cars with fatter tires make the problem much worse. The Corvair.
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