No apology necessary. The Bat and his son won the national competition for human powered vehicles some years ago. I consider him something of a mechanical genius. A few years ago he took a bunch of leftover bicycle parts, a rejected controller from a golf cart, and a worn out Scott 1hp motor and proceeded to stomp the competition in Electrathon for the next two years! Then he went quietly back to building hotrods at his home in Miami.

I use 1/2 inch o.d. tubing from ACE Hardware to make my kingpin bosses. It has a 3/8 inch i.d. which is perfect for a 3/8" grade 5 bolt that I use for the kingpin. For my steering knuckles I use 1/4" x 1 1/4" flat stock. I tried 3/16" x 1 1/4", but had trouble with it bending under stress on the tight courses. For the spindle shafts I use either 1/2" or 9/16" (depending on which hubs I'm using) grade 8 bolts, 5 inches long. My cars have hit concrete curbs, parking bumpers, and other cars. I have had the front axles bent numerous times and broke or bent rims several times and I am yet to ever break a spindle.

I haven't tried the hydraulic brakes because they usually come as a sealed unit (can't bleed them) and the hydraulic lines are either too long or too short. So far, the ones I've seen were too pricey for me to experiment with cutting and splicing lines, trying to bleed them, etc. If you can get some freebies and make them work they should be great.