Drawings

[Dominik]

good day,

keep talking!
I learned a lot about this rear suspension from my books, Morris' build-up and input from R.Hudkins and of course Strictly P.
But my two buddies at chassis design in Germany say there is more to that rear suspension, which is actually amazing - if correct.

the topic "drawings" may not be the right place, but while I have your attention I fo for it :-)

1. the 40odd degree mounting anlge of the track rod is not critical, however the center of the mount is.
the distance from the center of the chassis and the heigth above ground.
the track rod angle dictates how much anti-squat you've got.

pointing at the center of gravity of the car (CG), actually lower than that, I guess 20% anti-squat.
the saying is, that those track rods would have ended up in the drivers back if mounted at full length.
a less heavy car having a lower CG, in theory, could have those track rod pointing at another angle.
people used to set up for acceleration (4-link in a drag cars) know what I am talking about.

2. the 12-odd degree angle of the LCA chassis mount is needed to slide the bolt in, and maybe to give the rubber bush a pre-twist? I don't know.

this rear frame is needed to have the LCA mount as far to the center of the chassis as possible to get a decent camber curve, and maybe to replace it easily after an accident.

the RC should be the same distance on the rear axle to the CG (of the rear axle) as the front RC to the front axle's CG.
If it is greater the car will loose traction on that end earlier. (of course: springs, shocks and bars play a role here also)
RC front: 5.5", RC rear 2 5/8" above ground. CG, I don't know, I estimate camshaft height in front, diff input shaft in the rear.

3. the 3,5 degrees of the UCA (upper control arm) dictates anti-aquat, moving the wheel rearward in bump (the upright turns clockwise looking from the side, (left in the "picture" is front of the car), BUT causing toe-in in bump (out in droop)
the control arm mount of the track rod pointing down supports that movement.

Now,
has this suspension originally been designed for a street car on skinny 205 tires, or for a racing car with little suspension movement and 10" tires?
I guess street.
still anti-squat is also a good thing for racing, if the suspension is not binding.

the original layout causes the outward wheel to toe-in in ROLL (bump) and the inward wheel to toe-out.
total toe is still "IN" but more, helping the car in the corner - and out of the corner once you push the pedal down.
toe-ing less IN, but not out!
that whole movement is also affected by the 3-odd degree of the UCA.

and this is what I would like to discuss with Klaus Arning, and which specs he had to follow when designing it :-)
I heard a current Dodge Viper's rear suspension follows the same idea.

which is turn, would make the 427 rear suspension a masterpiece, and worthwhile to copy it. It is quite comlex!
and worth the 2 years it took me to figure it out... - if not, I have another tequila ;-)

Opinion, thoughts?

(pic shows mock-up)

Dominik