1:10 10x10 "HEMTT" (actually M1074 PLS w/ M1076 trailer)

[dremu]

[Side note: if images don't load, see https://rctruckandconstruction.com/s...7&postcount=16 ]

Bit of background: I like to build things, large and small, and a while ago I got a Cross RC kit (their 6x6, which is a fair approximation of the M809-family 5-ton.) Was fun and all, but basically you have all the parts and just put them together. I did a bunch of customization to the lights as I'm an Arduino guy and love me my LED's, but still, pretty straight forward.

I also dig 3D printing, so I figured the next project would be a mostly-scratch build. My styrene-fab skills were kinda weak (still aren't great), but I found a HEMTT body kit, with no mechanicals, to jump start me. It also came with a bed, which was later used elsewhere.



its ad pic, and a closeup of the cab



Read up on the many variants of the HEMTT



and decided I'd go for the 10x10 flavor, the M1074 PLS (see https://en.wikipedia.org/wiki/Palletized_Load_System )

Projects can be a slippery slope, and many end up languishing for years or never finished at all. (I should know: I own a Pontiac Fiero!) I was very careful, therefore, to scope this all ahead of time, make sure it was all doable. A key part of that was designing the whole thing in CAD; not just the parts to 3D print, but the body kit and mechanical components and such. I mean,



As it turns out, not impossible, but certainly time consuming and certainly had a learning curve. As a teaser, though, here's the end result:



Integy has axle kits for 8x8, so two of those did the trick for 10x10 with spares left over in case anything went awry, or for other projects:



Cheated a bit by using the link suspension that came with, vs the leafs that the Oshkosh trucks actually use. I fiddled with it in the CAD and just couldn't make the leafs fit in the space available.

Started with drawing up one axle's worth of frame and suspension



Then moving on to the whole thing (front of truck to right)



Here's a printed mockup of the forward frame section with the first two axles. Note both have tie rods, as axles #1, #2 and #5 steer (see below.)



This allowed checking clearance of the tires to the frame and the cab and placement of the cab on the frame.



Once the axles and suspension were sorted, could move to the actual aluminum frame rails and do a quick drive test



It's not obvious here, but there's some challenges to the steering. The #1 axle can turn farther than #2 due to clearance, and of course #5 turns opposite the fronts. Instead of servo scalers and reversers, I opted to use an Arduino. This made scaling and reversing the servos trivial and easy to adjust. I've fallen in love with the Flysky FSi6 transmitter; there's third-party firmware for it to expand to many channels with extra features like you'd get on a much spendier unit. The RX also spits out iBus, essentially a serial connection carrying all channels, which can go straight to the Arduino.



Right stick controls the truck proper; left stick the center crane. Dials on top move the load/unload mechanism (more below), and switches for the crane's winch in/out and height and the outrigger feet. The crane arm has three positions for maximum reach, maximum height, and down. Oh yes, and lights. Must have lights (again, more below.)