Mo,
Most tandems use a standard bottom bracket, some older Burely tandems used a special rear bottom bracket. Are you looking for a eccentric bottom bracket to build up a singlespeed? (I see singlespeed in your link) Something like this
http://www.tetcycles.com/Specials/specials.html
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Bentbaggerlen
"When the spirits are low, when the day appears dark, when work becomes monotonous, when hope hardly seems worth having, just mount a bicycle and go out for a spin down the road, without thought on anything but the ride you are taking." - Arthur Conan Doyle