I see no need to make a complicated, spring tension adjustable chain tensioner. I made mine similar to abikerider, post #43 except that I welded it to the bike frame; no movement whatsoever. Some slack in the chain is desired; like said before me, a tight chain puts additional wear on all components in the system. I adjusted my chain when I completed my tensioner, and I have many miles on it now and I have not had to make my second chain adjustment yet! BMF