The Excelsior Project, 8: Handlebar Casting

This is the pattern being made for the handlebar casting. Pieces are individually machined from steel and Tig-tacked together. Notice they're held to a 1/2" x 2" cold-rolled flat bar with two 6mm allen screws. The edge of the flat bar lines up perfectly with the edge of the pattern; this makes alignment very simple. The hole saw is set to rough cut the centre section, then a boring bar will take the final cut to fit the last piece.

The pattern now has all its pieces, and is ready for bondo and primer. Below it is the Excelsior handlebar casting I can buy. It's poured from ductile iron, which certainly machines beautifully. It's better than cast iron, which is known to be brittle. I'd rather have mine in 4140 steel. It's tougher to machine, but I know it won't break. Do you see how the hole on the right is a little thin on the inside?

The pattern is coated with high-fill primer, and now needs sanding with 320 paper, followed a shot of glossy Imron paint. Can you see the pattern is 1.021 percent larger than the standard part? Shrinkage (remember the shrinkage episode on Seinfeld?) is 1/4" per foot for steel in a casting...

The bike is slowly starting to take form. The gas and oil tank shapes were made from cardboard and held with masking tape. A little bit of experimentation was needed to get the shapes right.

I couldn't find a sheet metal brake to buy, at least not one of good quality. I wanted a straight leaf brake with an adjustable apron. A friend very kindly lent me this one. The "leaf" has been removed, and a 1.25" shaft welded to 1/2" flat bar, as shown below. This is what the 18-gauge steel is bent around. The "adjustable apron" makes this possible—see the adjustment on the left, underneath. The piece of wood is to sight down > to line up the end of the wood, the round stock and the mark on the sheet metal to make every bend as consistent and accurate as possible...


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PO Box 401Lynden WA98264

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