Made for 80 and 75 cf tanks, this cart is fairly overbuilt, with 1 1/2 x 3 x 1/8 rectangular tubing, 3 x 3 x 1/8 square tubing, and 1/4 plate as primary components. Most steel came from the scrapyard for around $20. The wheels were slightly more expensive. I had originally run the axle inside the frame, but didn't like the balance. So, I welded on external ears and foot bars.
There's a haze of loose red overspray on the floor, even though I did the spray painting on a canvas dropcloth at the other end of the shop; it was bloody cold outside!