PWC Workshop: making a speedometer drive

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MAKING OF A P/N - TYPE RIGHT ANGLE SPEEDOMETER DRIVE

Did you know that Jay Leno makes parts for his older cars using the same process I do? I'm sure he started this method before me, but he has a deeper wallet! I was fortunate in having received an original speedometer drive with my PB. The housing was all cracked and nothing turned but all the pieces were there for me to recreate it.
My first attempt was simply making a new housing from aluminum billet transferring the existing steel pieces to make an assembly. It was OK but did not look authentic and took a lot of time to make, photo 1. So, the seed was planted to make a pattern to have housings cast quickly.

3D solid modeling software was used to make an electronic model of how I wanted the part to be cast with added features to make machining easier to suit my tooling. My next step was to find a company that had a stereo lithography printer, sometimes called a 3D printer. This printer behaves just like your ink jet or laser printer at home but prints in space making my pattern in 0.004" layer of ink each pass. This process is called rapid prototyping. It is very popular in the automotive industry having a prototype part made of plastic. I now have a pattern that I can take to a foundry to have castings made, but where?

Over a few OSH I discussed my little venture with Bob Grunau who has a long standing source for aluminum castings. I passed on my pattern and in a few weeks had 6 pieces that I could play with. Fussing around with them proved useful. They weren't that good! The casting was fine but the pattern needed correcting. I went back to the PC and electronically edited the pattern. My final pattern arrived from the printer with Bob taking it to the foundry. A few weeks later and I had 6 new castings to machine. Success! I was now satisfied with the housing pattern for the speedometer drive. Casting cost for the 12 "prototypes" was not cheap, but it gave me an easy to machine and decent looking final part. 

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