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the patterns are being made in my spare time after work. I had hoped that
I would have at least one half of the cases cast at this point but I have
ran into a few unforseen events which are unrelated to this project. Although
I have made significant progress the last few weeks.
The pattern methodology can be seen from the pictures. I took the CAD drawing of the cases and sectioned it into different layers which are cut out from the wood pattern material and then fit together to produce the patterns.
The minor details such as fillets, pattern draft and bearing bosses will be finished by hand after the main assembly is glued together. As you can see there are 8 main pieces which are sandwiched on one plane and two other pieces for the cylinder deck areas which are on a separate planes. The two cylinder deck pieces are each made from two pieces. I chose this methodology based on the equipment I had available and previous experience with other patterns. It is easier for me to make a pattern using this method than to try to turn the major diameter out on a wood lathe and then fit the remaining pieces onto it's curved surface.
These pieces are fixtured in a jig to hold them in alignment as the pattern is assembled. Some of the fillets will be added before the entire pattern is glued up to facilitate sanding. The jig uses a series of dowels, on a template which corresponds to various bolt and shaft hole locations on the cases. The holes for the dowels will be filled in after the pattern is glued up.
Most of the pieces in the drawings have been cut out. Some are already glued together. I had help from KaulCraft, a local furniture manufacturer, for planing and sanding the material to the correct thickness. If you need mission style furniture, KaulCraft makes the best. KaulCraft is run by Rev. Kaul, who it turns out, has performed a lot of ceremonies for the local "biker" community. He was very receptive to helping me and interested in the project. I am going to utilize his resources on several other projects.
This wood pattern uses a double shrink factor. Once the pattern is finished, I will cast an aluminum master pattern from it. An aluminum master pattern will stand up under hard use, be adaptable to modern molding equipment and be able to be machined to better dimensional accuracy than a wood pattern allows. An aluminum pattern also is easier to withdraw from the sand and will allow a smaller draft angle. In the unlikely event that the demand gets out of hand for these cases, I can turn over the wood master pattern to a real foundry and they can cast any type of molding machine matchplate pattern they want.
Some of the outlines for the pattern layers are common to both right and left cases. Because of this, pattering the left case will go quicker. Once both halves are completed, I will send a set to Jim Wall and Rick Abbott. They will machine them and make recommendations. If Mr. Abbott is able to write a CNC program and is agreeable to it, we will solicit the list for orders.
Currently, I have both primaries, mag opening cover, and the cam cover available in unmachined form. After these case patterns are finished, I'm going to investigate a four speed transmission case that will fit Sportster 4 speed gears and kicker. The case will have a trapdoor similar to the Sportster where the gears can be slid in as an entire assembly. I need to do some basic investigation first and might need help from the list. I think this is the best solution for the 4 speed tranny problem. That is, using highly obtainable transmission gearsets which can be used in a custom set of cases. My next step after the transmission housing will be to produce an entire top end. I can either reproduce the flathead design or modify an existing OHV design. The foundry and pattern work will be a little different for the top end as I intend on using core boxes or lost foam casting. Either method I have only limited experience with. Although investigations and experimentation are ongoing.
I have subsequently found out that a number of local firms are capable and willing to do the machining on any of these items. Although these firms are highly experienced and work for major manufacturers, I would rather keep as much of this work on the list and money changing out of the picture.
Until these patterns are finished, I have cut myself off from the electronic world and the unproductive distractions it offers. At the rate I am progressing, the right case pattern should be close to finished by the end of the month.
April 2000 Warpath update