Originally Posted by
clubman
My clever mechanic friend clamped an SA cog to a 22 hyperglide cog. He traced it out and then demel-tooled the excess metal and cleaned it up in about 20 minutes. I have one, it works fine with narrow or wide chains and sounds easy to do. I'll try it next time I need a big one.
Your LBS can order either SA or Nexus for around $10 or less. My local Co-op carries them plus the local used bike place has them.
I tried using ordinary cassette cogs on a single speed and folded it over and broke it. The larger cogs on a cassette are laterally supported by the other cogs.
Granted, you won't be riding a 3 speed as hard as a single speed.