My uncle game me five 80 lbs weights from an old New Idea Uni-System, and a local business had a 175 lbs chunk of steel in their scrap, so I needed a way to mount them on my 3520. I used 2 1/2" square box (1/4" wall) to build the frame, and turned down some 2" steel rod to make the pins. I welded the large chuck of steel to the frame, but have the 80 lbs weights bolted on (they rest on an arm that is welded to the upright frame member). I gave it a shot of paint and it should serve me well for many years. With the frame, I think it weighs about 625 lbs. I plan to make a 8" tall, heavy duty cart to set them down on in my barn.
Fort Loramie, Ohio