I’m currently collecting parts and materials for a small-scale functional prototype. I’ll be using 6″ diameter wheels up front and from that I’ve been scaling down dimensions from my design graphics to match that proportion. Presently, my small-scale prototype will be 22% the size of the real deal. That’s not quite quarter scale, and should be plenty big enough for me to build most components in about the same way they’d be built in full size. If I also scale my materials as much as possible, it’ll give at least some idea of structural rigidity (although not material rigidity). More importantly it’ll hopefully reveal the majority of mechanical complications. I’m going to use brass tubing because it’s inexpensive, readily available, and I can solder it together similarly to how I’d weld the real thing out of steel. I can also easily bend curves and other complex shapes without too much effort
So at 22% scale, my equivalent brass tubing sizes are as follows:
1″ steel tubing (the majority of the structure) = 7/32″ brass tubing [rounding to 1/4″]
1-3/4″ steel tubing (the heavy bits of the roll cate) = 3/8″ brass tubing
1/4″ steel plate = 1/16″ brass plate
These materials should be lightweight enough to be easily workable. Once it’s all soldered together, it ought to be pretty sturdy. I’ll be able to find small bearings, bushings, and other hardware at the local R/C car shop. Now that I have both a working band saw and a drill press, I should be able to fabricate pretty much anything at that scale. I wonder if I could even mill parts on my dremel press from solid brass if I take small bites. We’ll see.