Here’s our latest “garage fun” project - a 20” tandem for kids, made from two inexpensive single-speed kids bikes.  One bike was a girls version that my daughter outgrew.  The other bike is a boys version snagged from the neighbor’s garbage pile on junk day.  The bike was “well-loved” but functioning with tires that were holding air.

To start with I cut off the rear frame portion on the boys bike (intended for the front of the tandem), and removed the handlebars, stem, front wheel and fork from the girl’s bike.

The headset tube from the rear bike fit nicely over the seat post tube of the front bike, so I did that and ran a bead of weld around that spot.  I then connected the two bottom brackets with a chunk of 1” square tubing.

For the rear handlebars I just cut a gap in the bottom portion so that they would slip over the rear bike frame, and I welded them in place.  I was able to keep the front seat height-adjustable by using a length of threaded rod for a seat post.  I welded a washer/nut combination to the top of the rear bike headset tube, and added a second nut to tighten the seat in place.  The seat needs to be removed in order to change the height, but it’s a small inconvienence.

Here is the bike getting a test-fit by the intended victi....uhh....riders.

Here is the bike with pedals and chain added back on.  As you can see the droop in the bottom portion of the chain was an issue:

The solution was to take the spare rear wheel apart, and cut down the axle/sprocket to use as an idler sprocket on the tandem’s lower frame - although the chain still isn’t engaging the top of the sprocket as I’d prefer.  Another sprocket might be in order.

And the inaugural test ride - in 35 degree Michigan winter, with a fresh 2” of slop on the roads and a light rain falling:

And the boy going for a solo test ride.  The two kids tried riding it together but the snow and rain proved too big a distraction for learning the “coordinated launch” required:

Update:  Here’s the latest chain arrangement which seems to be working (until a stray pantleg helps it off the sprocket).  I added a small gear from a junk derailer that the local bike store donated to the project:

And finally, success from the target users of the bike…

So far it’s been a fun and cheap project - all I’ve had to purchase is a fresh bottle of welder gas.  Once the weather gets warmer we’ll sand down the frame and shoot a fresh coat of color on it - maybe it’ll look less like the results of a kids biking accident…

Update: And here’s the finished product after a $10 paint job and $12 in new handlegrips.  The color is Rustoleum Safety Blue: