The first order of business was to tack weld the eccentric bottom bracket (EBB), then build the jig.
To make the new tubes used to extend the tandem, Nick D. made fish mouth cuts to the ends so they can fit just right onto the bottom brackets.
After Nick D. built the jig, he mounted the two frames then tack welded the bottom tube. Notice the front, we had installed the EBB. Both bottom and the top extension tubes were measured to 29″. This will give the Stoker ample room in the rear without making the bike too long.
Here’s a shot where the top has been welded on. It’s starting to look like a real tandem!
After the frame cooled down, we wanted to mock it up and see how the frame will look. So we installed the rear suspension linkages, bottom brackets and cranks. The frame still has more work to do, mainly a cross bar that will go from the rear bottom bracket to the captain’s seat tube right underneath the top tube…make sense? We also still need to make shock mounts. Nick D. wants to run a design where we have multiple shock mount positions. That means depending on the type of travel we want, we can adjust it.
Here’s a different angle. Did you notice that the timing chain and drive train is on the same side? Most tandems have the timing chain on the left side. But I didn’t feel like spending a ton of money on tandem specific cranks. So I ended up using 34t chain rings on the front and rear timing, then I’ll have the drive train run on 32t/22t. With this set up, I am able to get enough clearance from both chains and still be able to shift. One thing I’ve learned with tandem riding and racing, you don’t need a big ring. So eliminating the 42t chain ring made sense and using that spot for the timing made even more sense.
Front timing chain with a 34t ring. Yes I know that it’s missing ring bolts, I have those in a box.
Rear drive train with timing gear.
A closer look of the timing and drive train system.
Nick D. was able to take some video footage of the build work. You can see them below:
The Double Banger Tandem Project has been sponsored by the following companies: