I'm lucky to have a great trike builder here in Raton, who has a tubing bender for the 1" DOM tube I made the frame with. He is JP Rodman (look him up online to see what he builds) & does some incredible trikes. Here's the frame in it's rough starting stage. I'm not a great welder, it's been 40 years since I did any metal work, so I'm a bit rusty. It's still rewarding to have some progress. Having a shop to work in makes a huge difference for a build, having some basic tools helps as well.
The front end is made with 7/8" DOM & seems to be plenty strong. It's a bit stiff on bumps, since I'm used to riding an old Baja Warrior with front suspension & softer tires.
The rear axle is a 1" X 16" steel type with a 1/4" keyway cut along one side, so it's a live axle. It's a standard setup for karting, but hubs, tires & other parts can be a problem at times. I'm running a dual piston hydraulic unit with a steel hub from GoPowerSports (MB200-2) which is pretty good for braking. I use a cross-drilled rotor & it has good stopping power so far. The rear sprocket on the live axle is a 48 tooth steel one for 420 chain.
For now, the rear tire is a 19" Kenda 572 Road Go with pretty heavy tread. It's certified in Europe for 43 MPH, but I will be turning it a bit faster than that. The rim is an aluminum Douglas which is 8" in diameter. When I set up the axle, it didn't balance well at all. The tire kept turning until it stopped at the same place each time. I had to use adhesive weights along both sides of the rim to finally get it balanced correctly. It spins well now, but again, I need to keep an eye on it in the future.
PMR jackshaft on the output side with #35 primary drive & 420 secondary to the rear wheel. I need a better clutch!