I have a tandem which has a tensioner/idler pulley. I'd like to get rid of the tensioner, but the standard way of doing that on a tandem, using an eccentric BB, may be cost prohibitive with this frame.

I measured the BBs and they are exactly 25" apart (c-c). It seems like it's got to be possible using the right chainring sizes and possibly a halflink to get a chain that doesn't need a tensioner. Currently there are 40t chainrings on it and the chain has a lot of slack even when made as short as possible

it seems like exactly 140 links should be on the chain.. 50 running on each top and bottom (at 2 links per inch), and another 20 around each the chainrings. but as i said there is a lot of slack.. is there something i'm not taking into account? it's a brand new chain so no chain stretch