Posted this in the Mechanics forum, but it was suggested I post here also.
Original Thread
Hello all,
Shop recently built up a Surly Big Dummy for me. I moved over most of the drive train parts from my Breezer Uptown 8, which previously had the standard xtracycle kit attached. Drive train is internal hub red band nexus 8 speed with single 38t chainring.
When this was setup on the Breezer/xtracycle combo the chain was tensioned using the forward facing horizontal dropouts on the breezer frame, moving the xtracycle free-radical attachment back in the dropouts to tension the chain. However, the Big Dummy frame has standard vertical drop outs, so to use the same system some sort of chain tensioner was needed. We decided to use the surly singulator to accomplish this.
With this singulator setup on the Big Dummy I'm experiencing chain popping/slippage when putting power to the rear wheel. Under normal pedal it's OK, but as soon as I stand on the pedals or put much power (usually up hills) the chain starts popping. This happens frequently, with no extra load on the bike, and I'm concerned that with the singulator there isn't enough chain wrapping around the cog to ensure a complete connection. This is complicated by the hub's cable/shifter arm posing an obstruction to the singulator. I've noticed that some use the singulator in a "push up" mode opposed to the standard "push down" mode but the configuration of the Big Dummy's chain stays prevents this.
With the old setup on the Breezer frame I never experienced this problem, leading me to believe this is a result of not having the chain in contact with enough teeth due to the use of the singulator. I haven't found any other feedback, so any suggestions would be greatly appreciated. Maybe the singulator isn't the cure to my problem... should we consider an eccentric bottom bracket like those used on single speed mountain bikes? Would this provide enough movement to properly tension the chain (long, long chain) to use this internal hub on the Big Dummy?