The Excelsior Project, 3: The Headtube

Progress is slowly happening. A rear triangle is mated to a set of cases with barrels. The OHC frame is based on a 1914 rear end coupled with a 1919 "front clip". Bicycle frame terminology has no knowledge of "front clip", so I had to learn it was everything forward of the seat tube.

Here is the basis of the project. An 85 year old photo showing a 1000cc OHC V-twin with bevel drive in a heavy duty bicycle frame with no brakes… exciting!  Remember, when this bike was made, welding wasn't even invented. The rider I have ungraciously cropped is Joe Wolters.

The mock-up made it this far before I realized the bevel drive was split down the middle, plus a few other small details, so it had to be made all over again. Making the upper bevel drive covers has turned out to be difficult. There are only five photos of the right side, all from different angles, and the lighting is usually harsh. A shape that works in one photo might not work in others.

Back to the frame. Here the headtube is being machined in the lathe. I can't finish machine the inside for the bearings until all welding is complete. It's important to "think through" all the steps involved. I'll need a fixture to hold the completed headtube assembly when I bore the ID (inside dimension).

The headtube has been Tig-tacked to the rest of the dummy headtube castings. If this shape works well on the prototype, patterns will be made for future castings.  Everything is held in the frame jig; accuracy is important.


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