 Motorized Bicycle Spring Loaded Chain Tensioner
I was having a problem keeping my chain taut, and was very unhappy with the stock chain, so off to Tractor Supply for some #41 chain. Got the chain and got to browsing and also picked up a really sweet ball bearing, rubeer coated chain trensioner, AND spring, it is sold seperatly. After mounting the chain I took some 3/8 althread rod, heated it up and bent it into a U shape to fit around seatpost. I cut a strip of metal ( out of stock tensioner mount) to secure allthread. Then I just mounted the spring tensioner to the end of the allthread, the ID of the tensioner seems to be a good fit on 3/8" rod. Then a little adjustment and done. Spent $40. on everything including new chain. I have put a couple of miles on it an it is a lot quieter, and very smooth... | 
