There are two things that I didn’t design well when I built #10 (okay, there are more than two, but I’m going to write about two tonight) — weights and wires. Weight, even on the first iteration, was largely composed of scraps of lead that I squeezed into nooks and crannies wherever I could. On the other hand, #10 effectively had no room for wires at all, and the result was no working headlight.
For 622, I’m going to improve the design, especially since I’m now in a phase where I’m mostly waiting for parts. So, it is that I’ve been thinking about out how the model will be weighted. 3D printing offers me some new opportunities. For example, the image above shows the front boiler weight, which I think I will get printed in steel.
The weight is hollow so that I can fill it up with Cerrobend, which is about 20% denser than Shapeways steel (or maybe even lead for 40% more!). Incidentally, that neat hollow shape is a doddle to make with OnShape’s shell tool: simply select the faces to remove, and specify the wall thickness.
There are two wire runs on either side of the weight to allow 4 30-gauge Silicon wires to pass up to the front of the locomotive for the markers and headlight. That should save me some foil-based aggravation in about a year’s time.
There will in fact be three weights in the boiler. The front one above, and two in the rear section of the boiler. The upper (grey) one will be sandwiched between layers of the boiler used to make the wagon top. The lower (light blue) weight will be glued to the top of the boiler. To make the rear weights, my plan is to create either a master for molds to cast them from metal, or to get the molds 3D printed themselves.
The grey ring in the middle of the boiler will be printed in “Elasto Plastic.” The intent is to stop the motor from trying to jump around inside the boiler, while allowing it to move with the wheels. In this view you can’t see them, but there are holes through this part for the wires too.