44-Year-old Cobra Wins Street Car Challenge

[Cobra #3170]

I made my own because of the critical ratio of upper and lower joints and wheel axis with relation to the chassis. The only thing I regret is not using a cartridge bearing. I started out that way but converting it to a pin drive set up would have taken a lot more time than I had that season. The set up that Kirkham has on their new design is very nice for the bearing and hub. If I were doing it again I would use a lot of their design and just modify upper and lower joint accommodations. I use a 1/2 Stainless NMB Rod end for the upper and a 3/4 spherical NMB for the lower joint. Mounted at just the right angles it gives me 5.5" of total travel with out binding at all possible steering angles, I did limit rack travel to avoid potential clearance issues. One critical design issue is getting the steering arm outer pivot far enough outboard to get the needed Ackerman, that in conjunction with relocating the rack rearward in car gave me what I needed. You can actually push this car at full lock with out a lot of resistance (other than the rear end clutch plates). Try that on a stock Cobra with big tires, you might as well put the hand brake on.

[D-CEL]

I figured the A arms and geometry were yours.
Are the “upright” forgings and steering arm factory Cobra pieces?
Do you use a suspension design program?

Jason

[Cobra #3170]

In the 1970's I bought a spare set of spindles, steering arms, and uprights from Shelby American. I used those as my starting point and modified the uprights and steering arms to get the right package. I actually used a mechanical drawing program to articulate the suspension for roll center location and movement, tie rod end points and length to achieve minimal bump steer. I have used a Ford Motor program in the past that was on the main frame called "Hfronts" that showed me all the weak points of the original design in the early 1980's. I knew pretty much what I wanted in terms of camber gain, toe change, Ackerman, caster, roll center height, antidive, etc. and also how much freedom I had in terms of inboard points so a lot of the input was a given because I couldn't cut or weld on the chassis. I just used the lower inboard pick ups and the tire patch location with respect to the frame and optimized everything else from there. If I were starting with a clean sheet of paper and did not have to preserve the original parts and just bolt stuff on it would have been a lot different. I have a poor motion ratio and that makes it tough to get proper shock control (like the originals). My Ford GT is close to .9 front and 1 in the rear which really helps the shocks do their job vs motion ratios around .6 or .7 especially when you square them.

Originally Posted by D-CEL

I figured the A arms and geometry were yours.
Are the “upright” forgings and steering arm factory Cobra pieces?
Do you use a suspension design program?

Jason