Progress has been made! The linear actuator fiasco has finally been solved (or at least, most of it). I have upgraded the linac with a Leopard LBH3650 with a KV of 1185 (that's a measure of RPM per volt supplied in case anyone who doesn't know reads this - not kilovolts. I was originally going to get the original helical pinion off the old brushed motor and somehow 'cabbage' it onto the new motor's shaft, but it really didn't want to come off. I'm sort of glad too, because I think that would've been a lot more work. Instead, I removed the old motor AND another two gears in the train, because I'd ordered a mod 0.6, 25-tooth gear for testing anyway that happened to line up almost perfectly with the next gear in the chain and the shaft-hole. You can see what I mean in the pics linked below. All I had to do then was drill some new holes to match the motor's mounting holes, which are closer together than the old one's. I messed this up a bit the first time as you can see in the pictures, but it's not really a problem and when I basically drilled holes in-line with the existing ones, it just took a little bit of adjustment to get the gears to mesh. The result is a faster linac. Much faster than before, though I'm not sure about the power since I've dropped a part of the gearbox. However, I purposely ordered a higher-power, low KV motor, so it should hold up. Here's hoping it works when I test it in anger! Next step is to finish making the limit switches with the Arduino (which I think is mostly a matter of software) and then finally do a bit of metalworking to make the Hardox parts fit into the chassis.

Little imgur album of the linac images:
http://imgur.com/a/4VD9X

Test video: