A local tandem enthusiast, Wayne Sulak, whom I had met at the Great Southwest Bike Swap some time ago had approached me about converting a steel tandem to 650b. “Sure!” was my immediate response. Then he asked how I felt about removing the lateral tube from a tandem. That one I wasn’t too sure about as I have not built any tandems yet and don’t have extensive knowledge of them, so my response was “Uhh, I don’t know about that one.”
Over a little bit of time we discussed it more. Wayne told me that his reason for wanting to do this was because he always found his, and most tandems for that matter, too stiff. The lateral tube is essentially there to stiffen the frame up as you are essentially doubling the load with not necessarily that much more tubing. I was aware that lateral tubes were not always used and a lot of classic design did not have them. One day when I was out for a short ride I saw Wayne and his wife out on one of there tandems. The two of them are extremely lean, I think Wayne said there combined weight is 280 lbs. Thats not a whole lot for 2 people, and I began to see why he would find his bikes too stiff.
Wayne was on the look out for a donor frame, and eventually found a Santana frame which is one of the big names in the world of tandems. I was still a little reluctant, but we made a compromise. Wayne would cut a slit in each lateral tube, rendering the lateral tubes effectively useless, but still attached to the bike. He would then try it out to see if he and his wife liked the feel of it. If they didn’t I would make some kind of sleeve, a lug of sorts, and rejoin/patch the tube. If they did like it I would completely removing the tube and do whatever filing and clean up necessary. It turned out that they liked the new feel and it was time to do a tandem chop.
After removing the tube I had to plug the air expansion holes that were drilled to aid in the original welding of the frame. Also, were the lateral tube met the head tube it also slightly touched the top tube and down tube. The frame was originally TIG welded, which essentially fuses the tubes together. That made it a little difficult to tell were one tube stopped and the other began. So on one side of both the top and down tube I laid a little brass fillet for extra security.
In addition to removing the tube I add quite a few water bottle braze on’s to make up for the ones that were lost. The cool thing about this is that it will be a lot easier to get a bottle out and back in with the extra tube making things cramped.
Like any custom project or frame repair/alteration one is always faced with various instances requiring great problem solving skills. There were a few of those with this project. Probably the most entertaining one was how to remove the flux from the frame. For those who don’t know, flux is a paste like substance that aids in the brazing process. Typically I run the frame under hot water from the sink. Sometimes I soak it in a bucket. The flux I use is from Cycle Design group, and I swear by it. In the case of the tandem, the frame would obviously not fit in a bucket or the sink. So, I ended up putting it in the shower and using the hand held shower head to remove the flux. No, I did not wear a shower cap.