Good idea... I'll do it right now.

A big problem is that there aren't any scrapyards within 100 miles of where I live, so finding spare motors might be a problem.

Luckily, my Uncle owns a company that produces SLA batteries, so I could get batteries from him for very cheap.

For a Co2 tank, I was thinking of using 2 700g paintball tanks.

I've found some stainless steel at a hardware store. might be able to use it.

I also found some nice lawn mower wheels, ranging from 5 inches to 8 inches in diameter.