The Chopper Compendium

Rubber mount Evo softail in a Paughco Twin Cam frame (no center downtube). I just wrote up a long complete description but lost it when I went to preview it, and found out that I couldn't go back to add more pics without losing everything (lacking serious PC abilities!). If you are interested I will talk more about it. For the present I will just post it, and can explain later if anyone is interested. I have 5000 miles on it currently.

I am interested. Thanks for posting.

One of the main challenges in building this was due to the relativley poor rear suspension design that a softail has. Because the rear shocks are located underneath the eng/trans, the attachment point for the shocks to the swing arm is very close to the pivot point of the swing arm, something like 8" or 9" (23cm). On a "normal" rear suspension, that distance might be on the order of two feet (61cm). Because of this, the shock springs must be much more stiff (higher spring constant), on the order of three times greater than "normal" rear shocks (for the same amount of return force). The downside of this, is that those high spring forces will be applied the rubber mount system. This is the primary reason that other rubber mount softails out there have had difficulties with their life cycle (failed). The two stiff rear springs will just eventually mash the rubber in one direction, failing it in the worst case, or minimizing it's effectiveness in the best case. My rear bushings are polyuerathane with a DUR A rating of 70 (too high for my liking). They were sourced from automotive, and were designed to be used on the leaf springs for an older model Ford Mustang. I did not modify the size of the holes in the frame where the swing arm pivot axle goes through, so there is 1/16" inch clearance that allows for poly bushing movement, and acts as a maximum allowed bushing displacement. (The stock swing arm setup has some steel bushing that passes through the frame.) See crosssection. More, later, thx for responding!

Nore pics