My axel is a 7/8th in allthread bolt that I took out of an electrical high line structure(Tear down) when I was a lot younger.. My wheel nuts i hand made(a lot of hand work) from the square nuts used on the pole structures. On the 4th photo you will see the roll of masking tape. It was what I used for the radiuses for the cut outs. The wood was clamped into the threads of the bolt plus a little epoxy.
I put a couple of coats of clear coat on the made nuts and use lock tite(blue) to hold them in place.
This is my paint station. The green tint is covering up the yellow tint from my Cat models.
The 1/4×20 seen on the ends of the axle are for attaching fenders and different tool attachments . I used self locking nuts so they will not be lost. The long all thread is to attach the axle to the main body later.
These photos show the axle attached to the main body. Enjoy.