As I reported in an earlier post I am selling the bicycle I had on display at this year’s North American Handmade Bicycle Show that integrated a real time GPS tracking device inside the down tube. The concept needs more development, so in the mean time I am going to sell this frame to help with some of the operating costs of Maietta Cycling. To imbed the device in the down tube I made a mixed material carbon/steel down tube with an S&S coupler. I did not feel 100% comfortable selling the frame as it was, so I decided to replace the down tube with a more standard/conventional version (a much lighter version as well). Over the next few posts, while I’m on a buisness trip in Manitoba I am going to photo document the process of replacing this tube and adding a coupler to the new one. The picture below shows the frame as it was showed at NAHBS.
The tools needed to replace the tube are pretty simple: an air powered cutoff tool and some files.
The process starts with very carefully cutting the down tube. Great care needs to take place; for your own saefty because the tool will jump on you if you don’t hold it very secure and so you don’t cut into the adjacent tubes. The tubes will pinch the cutoff wheel, which makes the work even more hazardous.
You’re left with stubs on either end. One thing to note in the picture below is the complete seat tube weld. When I build the frame I do a complete circumfrence weld on the seat tube before the down tube is welded. This ensure a more robust joint, and helps to keep the seat tube perpendicular to the bottom bracket. A customer will never know this unless the down tube is removed like this, so its one of those unseen features that goes unheralded. Things like this are the difference between good work and poor work.
After I’m left with a large stube like this I will go back in with the cutoff tool again and remove as much as I can without getting too close to the other tubes. When I’ve down as much with the air tool as I can I will go in with hand files and get it to the point that you would never know a tube was there in the first place. I prefer to use hand files here because the amount and speed of removal is much more controlled. Using files is a lot more work, but its the only safe (for the other tubes) way to do it. I then strip all the paint off in the sandblaster and re-install into the Anvil frame fixture.
The next installment will show the mitering process for the new tube with the S&S coupler and review some of the logic behind the placement on the tube.