As of this writing, the M24 Chaffee tracks are in a minor state of limbo. They’ve been designed. They’ve been fit-tested to the available Chaffee sprockets. But I’m not ready to call them final until I can verify that they fit the sprockets of the upcoming Tamiya kit (and the Gecko kit for the 1/16 tracks).
But that also means more time to tinker.
A few days ago, I decided I’d go ahead and get a jump on packaging. Make sure the full set of tracks will fit in my track cubes, get a length of them together for product photography, that kind of thing. In the unlikely event that they don’t fit the Tamiya sprockets (or…since they were designed from scaled measurements of the real thing…if the Tamiya sprockets don’t fit them), it’ll be by at most tenths of a millimeter.
Sticking Point
The T72 links go together like butter. Mostly. But on maybe a third of them, the pins were sticking, typically near the middle of a length of track hole (technical term). If I had to guess, the culprit is resin bloom constricting the holes. Which would explain why it’s more pronounced toward the middle.
A Better Way
The laws of the universe being what they are, the fix for this basically comes down to – something needs to get bigger, or something needs to get smaller.
The pins are already about 0.65mm, and I’d rather not take them smaller. But I also don’t want to widen the track holes, either. I mean, most of the links are perfect.
Then it hit. Why not just widen the middle of the hole? That’s where the pins stick. Instead of using a straight cylindrical shape cut through the track, what if I introduced a very slight bulge toward the center?
A few minutes in Fusion and it was done. And this afternoon I got to see if this idea did what I intended. And it totally did. The tracks fit wonderfully, there are no more pin snags, but with the entry and exit portions of the holes their original diameters, the pins still fit snugly enough that glue isn’t necessary.
In retrospect, it seems a very obvious solve. But it’s the little things like this, the thought given to the experience down to that level, that really makes me fall in love with products (see: most Tamiya kits). And it’s something I really want to come through in my own products, as well.
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