Thread: New to the site - Questions about my '31 Model A

Tweet

Been studing the build pics of the frame and finding that it doesn't have any bracing or triangulation for torsional flex was baffling me-then I discovered the site of the frame builder and that explained it-He really is a builder of v8 chopper bikes-also of course with a single front wheel there aren't any steering geometry issues as in a four wheel vehicle ( caster, camber, toe in, bump steer)

Jerry,

The car is in a 12' x 32' garage and no I have no way to lift it. Mac builds hotrods and has for quite a while. I did a lot of reserch on him before hiring him. THere are so many guys out there with this chasis as he honestly builds rollers and just recently he started to build trikes. I am beside myself upset about this whole thing. If you want to call my house # I messaged you last night with it and maybe we start by talking on the phone. Let me know if you did not get it

Rob

Originally Posted by jerry clayton

Been studing the build pics of the frame and finding that it doesn't have any bracing or triangulation for torsional flex was baffling me-then I discovered the site of the frame builder and that explained it-He really is a builder of v8 chopper bikes-also of course with a single front wheel there aren't any steering geometry issues as in a four wheel vehicle ( caster, camber, toe in, bump steer)

No steering issues? Motorcycle and bicycle steering geometry is fairly complicated. You do have caster (called rake by motorcycle builders and head tube angle by bicycle frame builders). In addition, you have fork offset on both bicycles and motorcycles. Motorcycles can also have raked trees, to increase offset and reduce excessive trail from a large rake. In the end, the builder is striving for a particular TRAIL. Trail is the horizontal distance between a line through the steering axis, intersecting the ground and the actual contact point of the tire, with the ground. Unless the caster angle is zero, there is always some amount of trail. Cars have a trail value, and it's simple to calculate. All it involves is caster and tire diameter. Trail = tire radius/tanC, where C is 90 minus the caster angle. A lot of car builders only think of caster and not the affect of tire diameter on the trail. The larger the tire, the more trail and the more caster angle, the larger the trail (for a given tire diameter). A google search on rake and trail will bring up a lot of articles.

rake and trail