Step 1: Find the parts
- Some old bike chain. 12" or so will work fine. I find that the farther you wrap around the gear the better the chain holds.
- A welder or POSSIBLY you could put a hose clamp around the end and the middle to secure it. If using a flat bar, drill and bolt it.
Step 2: Assembly
http://bicycletutor.com/replace-cassette-cluster/ shows a chain whip in action.