I've been working on a home-made tandem for a few weeks, and tonight I pedaled it around the block. It still lacks rear handlebars, brakes, and cables, but the drivetrain seems to work fine and it rides well.
If anybody's interested, I'll try to take pictures in a few days when I've had time to get it cabled and fabricate some sort of rear handlebars. I had to tell somebody about this stupid thing!
I started with an old Centurion road bike frame and a Huffy (whoo-hoo!) mountain bike frame for the rear. I modeled the frame after a couple shown on
Sheldon Brown's web site. I cut the front of the Huffy's head tube off, welded it to the seat tube of the front frame. Then I cut and bent the chain stays of the front frame to mate with the down tube of the rear frame and welded them.
I didn't want to use an idler pulley so I ordered an eccentric bottom bracket from Nova Cycles (a frame builder supply), and machined it to fit in the rear bottom bracket shell. I split the rear bottom bracket shell, fabricated pinch bolts and welded them to it.
The drivetrain is a single sided setup with 42 tooth chain rings and a double on the back; modeled after one shown on
John Allen's site. If anybody knows where to order longer chainring bolts and spacers, I'd appreciate a source; I have them bolted together right now with hardware store stuff and would like to find some 15 mm long chainring bolts and 4 mm spacers.
Total cost so far has been about $80 for used cranks and chain wheels and a new chain. The road bike was a $10 flea market purchase originally, and the Huffy frame came from a scrap pile. Wheels, derailleurs, etc. came from the road bike. My goal is to ride it in the MS 150 ride in September with my wife.