# Adventures in tube mitering.



## Huguenot (Jun 14, 2019)

30 or so years  ago I saw a line drawing of a Pedersen bicycle in the book Bicycles & Tricycles by Archibald Sharp. (BTW this book is well worth a look if you are not already familiar with it.)
Fast forward to about 2012 and I found myself with the time and equipment to give building one a shot, just for fun. I was very bad about taking regular photos, when deep in a project it's far too easy to just keep going, and I admire the guys who are disciplined enough to regularly document things. But I do have some, and at the request of another member I'll piece together how it went. The photos are actually of 2 separate frames under construction but it's hard to notice.
I had not ever seen one of these bikes in person, so I worked from pics on the web, blowing them up and using a protractor to get some angles and dimensions by using the rim diameter for scale. By the time of the second frame I had found Dave Doctor (US importer of Euro built replicas) and he graciously sent me some of the critical dimensions also sold me some of the replica seats.
The frames of most modern replicas seems to be 14mm tube, which is not easy to find. Aircraft Spruce has 9/16", which is close, but was 4X the cost of 5/8"-which is used a bunch in light aircraft manufacture and was readily available. Since I was making a large frame and the whole thing was an experiment anyway, I opted for the cheap route. It required 32 feet of 5/8" diameter .035" wall (16mm x .9mm) 4130 tube.
The challenge, and what I like best about these projects, is the fixturing. Regular frame building jigs are unusable here, so I started from scratch. The idea was to suspend the important stuff -head tube and the lower steering pivot, axles and bottom bracket- out in space, and then whittle the connecting tubes to fit.
I'll break the build into a few different posts, so here are some pics of how that was achieved.





So it begins. A big aluminum plate and the raw tubes. The only "official" bike tubes are the Columbus SL chain stays on the right, and it took every mm of them. On later frames I made my own chain stays.



Fit and measure.
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I figured out ways to miter some of them in pairs. Starting with the longest tubes, in case of "oops".
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An quality hole saw and slow feed/speed works surprisingly well.
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Coming together. The head tube junction was a particular challenge, but the current replicas just squish the ends of the 4 tubes and bolt them to an ear welded to the head tube. Cheaters.
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That is a lot of tubes coming together, almost ready for brazing.
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And eventually we wind up with this.




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