I currently have my cross bike set up as a singlespeed with one of the cheap chain tensioners like the Surly one (think my came from Nashbar). I was reading about the Paul Melvin being able to run a double ring up front, and was wondering if anyone knew about trying this with other tensioners?

I know that it is a question of chain tension and chain wrap. I think that it might work cause the tensioner is set to push the chain down away from the frame, and not up like some tensioners are set to do. I am just not sure if there is something special about the design of the Melvin that allows this and that prohibits other designs for doing or not.

Any suggestions?

The Melvin has two pulleys, so it is capable of taking up enough slack chain to accomodate two chainrings. A single pulley tensioner can not swing far enough to handle two rings, even in push down mode.

White Industries has the cool "Double Double" concept that has two front rings and two rear rings that allows a jump between 38t/16 and 35t/19 without changing the chain length. Pretty ingenious and good looking kit. http://www.whiteind.com/ENO-cranks-specs.html

Just need to step off the bike, pop the chain over and ta da, a different gear to take you over that hill. Unfortunately, I believe this is a freewheel double-cog, so fixies are out of luck.

White Industries has the cool "Double Double" concept that has two front rings and two rear rings that allows a jump between 38t/16 and 35t/19 without changing the chain length. Pretty ingenious and good looking kit. http://www.whiteind.com/ENO-cranks-specs.html

Just need to step off the bike, pop the chain over and ta da, a different gear to take you over that hill. Unfortunately, I believe this is a freewheel double-cog, so fixies are out of luck.Surly makes "dingle" fixed cogs. The 17/19T would theoretically work with the WI Double Double crank.