The Shay, Part 2: The Crankcase Once I finally complete what's universally considered the toughest part to make—which is proving to be true!—everything else should be a walk in the park by comparison. The next logical part to tackle will be the crankcase, since it needs to be designed to precisely match the crankshaft (much easier than the other way around). After learning what a Shay crankcase looked like inside and out, I came to the conclusion that this wasn't going to be quite as simple as I'd thought. It's a highly unusual shape, with many convoluted curves and surfaces, not to mention non-parallel sides. Remember, too, that it needed to be assembled from at least two parts so that the crankshaft could be installed inside. For reference, the real crankcase measures 56 inches long, 22 inches high and 16 inches deep. In Z scale, that's 0.25 inches long, 0.10 inches high and .070 inches deep. That's not very big!
As a kind of game, I'm documenting my plans for its construction in advance of building it. When it's done, I'll compare the actual process with my plans to see how well I did divining a way of making the thing. I've spent quite a long time working on this design, so it's not as if I'm just taking a shot in the dark. The principle concept is to make a sandwich of three layers. The inner layer comprises the bulk of the crankcase, and has three slots for the three connecting rods. The center layer is also cut short of the bottom of the crankcase, even with the crankshaft. Over this center layer is two outer layers that will be drilled out to make the crank openings, and filed down to form the tapered sides of the crankcase. Then, after slicing the finished crankcase from the center layer, four tiny wedges are glued into the slots between the cranks to secure the crankshaft inside. Since I imagine all of this is difficult if not impossible to visualize, I rendered a series of illustrations showing how all of this is supposed to work. |
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