Miatav8,MstrASE,A&P,F wrote:
I see the ifs is canted for caster. Otherwise spitfire lcap and ucap geometry but no anti-ackermann rack position and eliminating the trunion?
(lcap/ucap = upper/lower control arm position?)
I haven't positioned the rack yet, I figured I'd deal with Ackerman and bump-steer by mock-up and measurement once the control arms are in place. What I don't know is what I'm aiming for in terms of Ackerman. Like most suspension questions, probably a matter of compromise? I'm sure it's been discussed at length here but I haven't delved into it yet. Any recommendations for a starting point?
By eliminating the trunion, do you mean converting the Triumph uprights to a lower ball or heim joint?
I used vsusp.com starting with the lower control arm and upright as constants. With the components I'm using, I'll have an adjustable upper control arm for camber but everything else will basically be as-built. Caster is 5°, camber -1°. With vsusp, I was able to get a pretty stable roll-center, but with Lotus type geometry, the caster is achieved by the difference between front and rear control arm mounting points (as you noted), and I don't really know what effect that has on everything else.
All that said, I know the original Lotus setup is not ideal, but it's kind of what I'm going for for now, optimized a bit. I figure I can upgrade to fully adjustable control arms in the future.
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F7_CHASSIS_Frt-Susp.png