Dinglespeed:
A type of bicycle that uses has a single cog in the rear and a double ring set up on the crank. A chain tensioning device, such as the Paul's Component Melvin or old derailleur, is required to take up the chain slack. The use of a front derailleur is optional.
Looking for an excuse to build another bike?
Do you have an old frame or bike languishing in a corner somewhere?
Then slap a Melvin or old derailleur on there and dinglespeed that bad Larry
thats what I did to my old 1983 Fat Chance