Simple MTB Tandem - Page 1 of 4

Figure 1

If you have a pair of similar mountain bike frames lying around your scrap pile, then why not whip up a simple mountain bike tandem? You can complete this project in an afternoon using a single mountain bike for parts, along with a second frame of similar or equal size. If you can find a pair of identical parts bikes, then the geometry will look perfect and all of the transmission components will match, but this is not absolutely essential as any pair of similar frames can be welded together. You will need two frames, two sets of cranks, a front and rear wheel, front forks, two seats, and two pairs of handlebars for this project.

Figure 2

The plan is very simple - cut join the front triangle from the first frame to the rear triangle of the second frame using the leftover frame tubes as shown in this photo. If the leftover frame tubing is of differing diameter, then use the larger tube to join the lower part of the frames between the bottom brackets, and use the smaller diameter tube to join the top part of the frames between the seat tube stems. Cut your frames and lay out the tubing so you can see how your final frame will look.

Figure 3

Once you have worked out your frame tubing, the top and bottom joining booms will need to be fish mouthed at each end in order to make a joint that can be welded properly. The top boom tube will have to conform to the seat tubes on each frame section and the bottom boom tube will conform to the two bottom bracket shells. Both seat tubes on each frame should end up parallel to each other; this is how you will know that your frame geometry is correct. The distance between the two seat tubes will be about the same as the length of the front frame top tube (the tube between the head tube and seat tube).

Figure 4

Weld your frame together, making sure that the alignment is correct as viewed along the length of the frame. Weld all the way around the joints, being careful not to strike the inside threads on the bottom brackets. You can leave the bottom bracket cups screwed in while you weld in order to protect them from accidental strike and welding spatter. Your tandem frame is almost complete.

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You can build it yourself from our easy to follow DIY plans!