Chapter Thirteen - Tandems

The only real difference between building a rear triangle for a single frame and a tandem is that a longer rear triangle fixture is needed for the tandem. If you are using a rear triangle fixture that has been built out of the plans for fixtures included with this book, you will need a longer base (Part # RTF-02) and a longer alignment bar (Part #RTF-12) for the rear triangle fixture. The plans for fixtures give the necessary dimension changes for these parts to convert your rear triangle fixture to a fixture with tandem capabilities. Those changes can be found right on the plan sheets.

With the dummy headset and fork mounted in the frame, install the complete assembly into the rear triangle fixture as shown in Figure 13-39. Follow all the rest of the directions on building a rear triangle outlined in Chapter Eight.

FIGURE 13-39: The tandem frame and fork jigged for building the rear triangle.

The chainstays will more than likely have to be indented on the inside faces for added tire clearance. The outside face of the right chainstay will probably have to be indented for chainring clearance. Figure 13-40 shows a special punch I have made to do this indenting. It's like a cold chisel, except the end that would normally be a straight cutting edge has been rounded and smoothed. I added the recess behind the head so that I could indent inside faces of chainstays on a completed frame. Figure 13-42 shows the indented chainstays.

I prefer building a lugless fastback seat cluster for my tandems. The fitted seatstays for this frame can be seen in Figure 13-42. The seatstays will more than likely have to be bent for added tire clearance; this was covered in the lugless section of Chapter Eight.

Follow all of the brazing instructions in Chapter Eight to tack and finish braze the rear triangle into place. (Don't forget the heat sync plug in the stoker's seat tube!)

FIGURE 13-40: Indenting the chainstays

FIGURE 13-41: Finished indentations

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