Transverse rear spring rate adjustment ponderings.

Update: Received the spring from Jim a while back (Thanks! (y)). Digging under the bottom cushion I saw some writing that indicates it is in the vicinity of the rate I was looking for. Been busy getting the car back together for a track day this weekend, but I'm also mocking up some ideas on a spare rear end to adapt this C3 spring to fit the C4 D36 batwing I'm using under my '69. Hopefully I'll be able to get some serious progress made on it next week.
 
Well, got some aluminum pieces cut for the spring mount to adapt this spring to the batwing. The top portion of the mount will locate/center the spring and transfer the force/weight to the batwing. I'm still kicking around ideas on the bottom/clamp portion.
 
I was never quite clear on VBP's measurement of spring rate on dual mount springs. The cen to cen distance of the spring mounts is 18" and with 4 holes, spaced 1/2 apart. VBP said that moving the blocks, that are clamped onto the spring, out 1/2 inch would increase the spring rate 25lbs. I think the issue with these springs is that, as the spring is loaded (static weight of the car) at bends into an arc (between the clamp centers) causing the spring chord length to increase and cause the spring to slide back and forth through the clamps.

I think I solved this problem but I don't have any miles on my car so maybe not. If that fails, I might try to use a C5 style design. A C5, which also uses a dual mount spring with compliant rubber cushions molded onto the spring. This was a good discussion on this (starts at post 161):

www.vettemod.com/threads/long-overdue-progress-rebuild-doors-latch-mods-10-02-24.11639/page-9


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