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Back when I was 14 or so, I really wanted a tandem bicycle. When I saw how expensive tandem bicycles actually cost, I decided to make my own.
The first tandem bike was two mountain bikes bolted together. It worked fairly well, but it flexed a lot, which caused the chain joining the front rider's crank to the rear to come off. Unfortunately, I do not have any pictures of that one.
A year or so later, I built another one using the same technique, but used 10-speed road bikes instead of mountain bikes. I also make a much stiffer frame, although some flexing still remained. This bike was also very top heavy, making it difficult to ride.
The second tandem. Top heavy, ugly, and somewhat flexible.
I stopped biking in general for a few years, but when I got back into it, I decided to build another tandem. I knew it had to be welded to be stiff and lightweight, so I learned how to weld (somewhat) and then got to work.
I started by collecting bike frames in decent condition from a nearby scrap yard. It cost me $10 to bring home a few frames.
The donor frames.
I then began to cut them up into what I thought would be a good layout, but ended up having some problems. It was such a lame attempt at making a frame that I didn't even take pictures.
I eventually realized that welding cheap metal frames was not going to be easy, so I decided to keep as much of the original welds on the frames as possible. I also had to make sure that all parts of the frame were formed by triangles so that they would not deform under load. Basically, the bike would have to look like a truss on wheels when it was done.
Another thing that I had to consider was the angle that the frames met each other. The previous tandem bikes had a bit of a "sag" in the middle, which gave them bad ground clearance and made the steering heavy (from the added caster). For this frame, I made a jig that held them at the exact angle that they would be at if they were individual bikes. This kept the steering caster the same as a regular bike, and was decent for ground clearance too.
Day one of welding the frame.
The frame was taking shape quite nicely, but because some of the tubing was so thin walled, it was difficult to weld correctly. I decided to add a few reinforcement places to help keep the frame together.
Detailed photos of the frame.
Once the frame was done, it was time for painting. There is not much special to report; I removed all of the original paint and then primed it with grey rattle can primer. I went with a dark blue for the frame colour.
Frame is painted.
After the frame was painted, it was time to put the actual components on. I went with components that I had lying around, which was a mistake.
Bike with random junk components on it.
I decided to go with all new components, which ended up raising the price of the bike considerably.
New components.
The bike is too long for standard length brake and derailleur cables, so I had to join them end-to-end using the connectors for center-pull cantilever brakes, as seen below.
The long chain that joins the front driver's pedals to the rear has always been a problem area. On the old tandems that were bolted together, the frame flexing was enough to make the chain come right off when accelerating hard. The welded frame still has some flexibility to it, and the length of the chain alone is enough for the chain to misalign and pop off.
The only solution was to setup guides that would keep the chain from even having a chance at coming off. To do this, I welded some metal tubing near the gears and placed some plastic pipe tees from a hardware store on them. The guides only need to be placed where the chain approaches the gears. Assuming that the bike is going forward, this means one goes at the top for the front gear, and the bottom for the rear gear. Below are some pictures showing the setup.
Chain guide setup.
To help keep friction down, I decided not to tension the chain. Instead I have an idler gear that holds the slackened bottom section of the chain, and I shortened the chain to an approximate length. If the chain ever stretches, I can just shorten it and/or relocate the gear slightly.
Chain idler gear setup.
With the chain dealt with, the bike was finally done. It was totally worth it too!
Part | Cost |
|---|---|
| Bike Frames | $10 |
| Misc bits (metal stock, fasteners, paint) | ~$75 |
| Cables | $8 |
| Pedals (3 pairs) | $15 |
| Shifters (1 pair) | $70 |
| Rear Derailleur | $15 |
| Handlebar Grips | $15 |
| Cranks | $87 |
| Stem | $5 |
| 7-Speed Freewheel | $15 |
| Total | ~$315 |
| Savings | > $1000 |
Ongoing Issues
The tandem is not perfect. With two riders on it, the wheels and tires have a tough time with the weight. The cheap steel wheels that I originally put on bent very quickly. The expensive replacement aluminums wheels are holding up better, but they already have a wobble to them.
The chain that drives the rear wheel has broken twice, leaving us stranded and having to walk the bike home.
The rear axle is bent from the weight, which hasn't really been a big deal so far, but I have the feeling the bearings will not live long.
More Pictures
More pictures of the tandem can be seen in the tandem bike image gallery.
