My neighbor gave me this. It's an early 70s Schwinn Heavy Duty. He said his brother used it on a paper route. The frame and fork are solid and straight. I believe this is the start of my first rat bike.
The only thing heavy duty when that bike was new was the spokes. Every other part was standard Schwinn stuff. It has a clip frame, which means you could set it up with rear hand brakes and a Sturmey Archer 3 speed...or not. Gary