Ive been riding an old beat up thrift shop free spirit 3 speed as a commuter bike to work and around on the train for a while now. It's a sturdy little bike, The lettering on the wheel says "Shimano 3 speed hub Cartridge type US patent 3021729" From what I can tell this is a Shimano model 333...
So Ive had an original swing bike for a couple of years, the thing is a blast to ride. Ive been thinking about building one with a 10 speed drivetrain, just wondering if anybodys tried anything like this.