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Old 08-30-2021, 12:44 PM
dremu dremu is offline
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Default Re: 1:10ish Alvis Stalwart 6x6 high mobility carrier, wrongest of the wrong

Quote:
Originally Posted by jerry56 View Post
WOW...just WOW
You are right... that is a complex machine.... beautifully done...
Heh, thanks! It's not perfect by any means, flubbed a couple bits, and some I had to take liberties with. The crane, particularly, isn't exact, but like I said the cylinders (actuators) only come in specific sizes.

I tell you though, I sure breathed as sigh of relief when the thing moved under its own power the first time. 3D printing gears is tricky at best, but there's no way I was gonna find off-the-shelf gears to work... so if mine didn't work, I'd put a bunch of time and effort into nothing.

Thinking of that, here's a bit I forgot... the innermost gears on the slipshafts, wasn't enough clearance to get a regular socket cap screw or even a button head on there as they were rubbing up against the longitudinal drive shafts. Ended up cutting space into the gear for a hex head:



and then loc-tite the snot out of that to stay bound to the shaft. As long as it's only turning one direction of course it stays tight, but the left shafts turn opposite from the right, never mind backing the vehicle up. I do NOT want to disassemble this thing to get to those shafts.

Anyway, point being this is the kind of customization you can only get with 3D printing, unless you happen to have an amazing micro machine shop at hand.

Also, thinking of it, the longitudinal drive shafts are also brass square tube, right, I should buy stock in K&S. But the 4mm was not only twisting along the length but starting to deflect under load Ended up sleeving the 4mm with a piece of 3mm inside, soldered up one end to keep them together. I suppose I could have used solid stock, but (1) I had the two sizes on hand, and (2) I swear I remember from materials engineering that tube can be stronger than solid. That may not be true for rotational loads, maybe only for bending, now that I think about it, but ..shrug.. the combined shafts don't deflect and carry the rotation load. If I run the truck into, say, a chair, the gears skip, but you figure something has to be a "fuse", and I'd rather it be the plastic gears that I can reprint than the pinion or those dang slipshafts.

-- A
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I mean, how hard can it be?

Last edited by dremu; 08-30-2021 at 01:08 PM.
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