Double Banger Tandem Project Update: Cut em’ up!!!

The last time we talked about the full suspension tandem, we were still figuring out the final details on what it’s going to take to build this tandem. I headed over to Nick D’s shop and we did some measuring and some cutting.

One of the things Nick D wanted to do was measure our 2Fast4U tandem and improve on it’s geometry on the new tandem.
tandem mountain bike

Not sure what this tool is called, but it some how measures the angles of things. So far the old tandem is sitting at 71 degrees. We want the new tandem to sit at 69 degrees. Don’t ask me how, but Nick D has it all figured out.
tandem

This is what we call our Pink Prints. This has a photo of the old tandem with measurements. One thing Nick and I remember from racing with it was the Stoker cockpit was a bit too cramped. Adding at least 2 inches to the rear would solve that problem.
mountain bike tandem

The following morning, we went for a ride. All that thinking makes my head hurt. Here’s a photo of Doc Thunda fixing Nick D’s busted chain. I would have helped but I didn’t want to get dirty.
aliso woods

After the ride, we went to the metal shop to get some tubing for the tandem and for the jig that Nick will build.
full suspension tandem

Here’s what I call the “Felt so wrong but oh so good” moment. Nick D, started cutting the frames. There’s just something naughty about cutting a perfectly good working frame…but it felt good to cut them. It was like a hot knife through butter.
cutting bicycle frames

Here’s the aftermath…OH THE HORROR!
bicycle frames

Now that the frames are cut, we wanted to get an idea on how it would look. Check it out!
home made full suspension tandem

The next step would be to create the jig, mount the frames and start fitting the tubes. We’re pretty excited to do this project and I have to say, out of all our builds, this one takes the cake!

4 Replies to “Double Banger Tandem Project Update: Cut em’ up!!!”

  1. Alright!
    A very cool project. But a questions! It appears that both of the frames that you are using are Aluminum. Are you going to heat treat the finished tandem? Do you need to? I asked this question every chance I get. One because I am not a metallurgist, and would likely consider using JB Weld (weld in a tube) if I thought I could get away with it.

  2. Moses:

    You are correct about both frames being aluminum. That allows them to be light and strong. This makes it easy for us to modify. The aluminum tubing we are using is 6061-T6. The lower tube is .120 wall 1.75″ dia and the upper is .120 wall 1.5″ dia. We will be adding a 1.375″ .083 wall diagonal tube for additional strength. We chose the 6061-T6 as its very affordable and the most readily available tubing. Ordering 7005 would have cost us more and needed to be special ordered. Although the heat treating would be pretty cool, it is not needed. With the larger wall thickness tubing, along with the bracing, it will be well overbuilt for our use. The tubing is artificially aged now to T6 so it does help.

    You can see more about T6 here:
    http://www.thefabricator.com/article/aluminumwelding/achieving-t6-designation-for-6061

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