Designing the Satchell Link

[boodlefoof]

Hey guys. Sorry for another long post (I've gotta break that habit) but I could use some help.

I've been pouring over old threads for awhile both here and on CC.com. I think the Satchell link design for my Datsun 240-Z project is coming along well, but I would like any input you might have.


The car: 92'' wheelbase, 62'' track width both front and rear, and I am guessing it will come out to about 2000 - 2200 pounds when done. Front suspension has an RCH of 3''.


The Satchell link (current design):

RCH is 10.9'' in its present iteration
Upper link axle housing mount = 16.5'' high (3.5'' over axle CL)
Upper link frame mount = 15.5 high''
Upper link down angle from rear to front is 1.7*
Upper links are parallel in plan view and 34'' long
Lower link axle housing mount = 8'' (5'' below axle CL)
Lower link frame mount = 9.75''
Lower link up angle from rear to front is 3.5*
Lower links are at a 45* inward angle and are 28.3'' long
Side view swing arm length is 72.5''
Anti-squat is 101%

There appears to be mild understeer, but I am unsure of how to calculate a percentage. For example, in a 3* roll, the axle housing has moved about .17'' (forward on the outside axle relative to the roll, rearward on the inner axle relative to the roll). By 5* of roll the axle has moved .3'' at either end.


The questions...:

1. I'm unsure whether this is or isn't too much roll understeer... based on what I've read, I'm shooting for around 2-3% roll understeer. I can easily increase or decrease the understeer by adjusting the angle of the upper arms in side view.

2. How high of a RRCH would be acceptable? It seems that I've read posts describing anything from 8''-15''. There is lots of info talking about FRCH, but RRCH seems more of an enigma.

At present, the lower arm axle mount point only gives me about 2'' - 2.5'' of clearance from the flat belly pan design, thus limiting my suspension droop to 2'' (as would be regulated by axle bump stops). I would like to raise the lower arms an inch to give myself some extra clearance, but doing so raises RRCH to about 11.6''.

On a side note... man this Suspension Analyzer program gets buggy when dealing with the rear suspension!

Thanks for any help all.