July 31
Engine construction continues on the B&CC over the last part of July. I finished up the frames - the assembly jig is just made out of poplar and used to hold the frames sides in place. The final design of the frames includes a couple of additional pieces of brass to provide cross support and I decided to split one of the top supports in two to provide a place to attach the cylinder block to (while I was originally planning on soldering it to the frame, I've changed my approach to use a nut/bolt to allow for adjustments and disassembly). The top support in the middle of the frame is to hold a lead slug to provide weight and also ensure that the flea motor doesn't tip forward (I still have to machine and add these). These thoughts have led me to rethink lots of what I was planning to do with a eye to future maintenance. The next step was to do a "dry" fit of all of the crankpin bushings ad side rods to ensure proper fit.
I've also assembled the cylinders (I'm using C-16 casts from PSC, which are slightly oversized to the prototype) and am improving the PSC cast crossheads - I've already soldered a small piece of brass over the guide channel to ensure the crosshead doesn't pop off due to torque from the main rod. This required filing down the Laird guides to fit and I intended to finish up the process with rubbing compound at a later date.
The next step will be to drill out the cast nubbin and replace it with a properly sized brass bushing to ensure that the main rod doesn't come off due to torque. This means that the crosshead/main rod will be a single assembly, but it can be removed by removing the crankpin locknut, removing the main rod and then sliding the crosshead off the guide and out of the cylinder. Once that's done, I can do a test fit of the cylinders, crossheads and main rod and determine how much to machine the cylinders and shim the frame for the resulting fit.
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