1:10 M1070 and M1000 HETS

[dremu]

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

Had more free time lately, so I figured I'd liven things up a bit here and do up some picture threads of my builds vs actually building. Might give ideas to the next guy, might stimulate discussion for good ideas to change up this build or for the next one.

Bit of background: I've been building things of many sizes for years, ranging from scale models to RC vehicles to a 1.5ton ride-on backhoe with working hydraulics. I hate hydraulic fluid.

I've done a number of 1:10 builds, starting with a Cross RC kit (nice, but kinda dry and boring) to a partial scratch build HEMTT/PLS and then to full-on scratch builds. One of those was an M1 Abrams, which reminded me why I don't like tracked vehicles and didn't quite turn out as well as I hoped. It does move under its own power and looks more or less like an Abrams, so I guess it's a qualified success.

https://rctruckandconstruction.com/s...ad.php?t=13837

In any event, if you have an Abrams, it only makes sense to have a prime mover it for it too, right? I mean,



Well, like the Abrams, harder than you might think. Partially that's because the trailer has to cope with the tank being ridiculously heavy (over 50lbs.)

It's fairly close to the 1:1. I've seen a couple other builds here that are more accurate and better models, but favoring function over accuracy seems to be my thing. The truck will pull the trailer loaded with the tank, at least on flat terrain with good traction, so again, a qualified success.

The regulatory money shot, all six feet and, I dunno, 80 or 90 pounds of it:



Frame and drivetrain are basically the same as my previous HEMTT/PLS, save that this one is 8x8 instead of 10x10.







The cab also rides a lot higher on this one, so the hood hinge is waaay low. On the PLS, I had to hide the battery in the cab which is a pain to get to, have to undo screws. (We call this a "learning experience" ) For this one, the battery goes under the hood, coupla snaps, boom.

The cab is mostly sheet from the local plastic place, with square tube down the corners. It's done up as an armored cab, so the doors and windows have printed frames with tinted acrylic



The hood is 3D printed because it's stupid shaped, and to give detail like the grille, air intake, etc.



Bars are glued temporarily to keep the thing square.



Greebling is a mixture of printed and fabricated. Fuel tanks are ABS drain pipe, with printed rings and brackets to mount to the frame



Toolboxes and the platform behind the grille are printed.




Exhaust is just plastic tube and bar from Evergreen, with a printed heatshield. I don't have the patience to cut that many holes by hand!



Winches are, duh, winch servos, nice metal gear ones (learned my lesson about buying cheap ones when I built the forklift!) The drum-cable-hook setups are off-the-shelf Chinesium of matching spline count. The outer end sits in a brass tube which goes into the 3D-printed box. This gives the drums a nice double-shear mounting so they don't flex. An M4 bolt below the drum acts as a convenient stop for the hook. They have enough pull to load a truck in neutral up the trailer, but won't grab anything stuck, especially the Abrams.

They're set up on an Arduino. The TX has one up-off-down momentary switch to winch in/out, and another left-center-right to select either or both winches, so as to pull evenly if the load is off-center.

The controls are only vaguely representative of the 1:1; the switches aren't hooked to anything, but the light bar blinks when the winches are enabled. I do like me my blinky lights.

This one has a ton of electronics, some by necessity and some just for fun.



There's two Arduinos, one for the winches and one for lighting. They could be combined, but they're only a coupla bucks, it makes the programming for them MUCH simpler, and there's certainly room in the truck.

There's also two DC-DC "buck/boost" converts, aka BEC's, one for 6V and one for 5V. There's also a servo distro board (orange plate, top) and power distro (yellow, bottom). The power one has a relay so that when the ESC is switched on, it brings battery power to the DC-DC converters and Arduinos and such.

As with all of my scratch builds, I'd first drawn it up in CAD to check clearance and fitment, design all the printed parts, etc.



However, some of the mechanical parts, you just kinda guess and say "That sounds like it's the right gearing" ... and then you find out once it's built that, mm, that's not enough gearing.



Middle is the motor I started with, as compared to a 3S LiPo.



Some testing with a load (teaser there of the trailer) said that it didn't have enough torque, so the final version uses the motor on the left. Here it is next to a 540 for scale:



Had to do adapter couplers as the motor has 10mm shafts and of course the driveshaft ends are much smaller, but those are off-the-shelf mechanical components, then a solid rod inside with some drilling and filing for the setscrews, et voila.

The motor proper is a bit bigger, and then there's the gearbox. The first motor was 250rpm unloaded @ 12V. The second is 100rpm unloaded @ 12V and has like 4.5x the torque, woot!



(yeah, yeah, I know torque isn't power, it's rotational force, but still funny.)

Mostly assembled, it gets a cat scan



I'm actually kinda amazed the fifth wheel came out as well as it did. It's printed parts with some springs from the assortment box and a paperclip for the release handle. It tilts side to side and yaws fore and aft just like the 1:1, and the latch mechanism works. And, most importantly, actually holds the loaded trailer (score one for 3D printed parts!) There's better pix of a duplicate in this post about the trailer dolly.

Coat of paint and some more detail work, and it looks mostly like an M1070:

[dremu]

I've seen several M1070 builds, but not so many M1000 trailers. Not only is there not need if you don't have an Abrams or other crazy huge thing to pull, they're a complicated setup.

Five axle rows, with independent bogies each side, each bogie having four wheels. The really tricky part is that all of the bogies steer, but at varying angles. The fronts turn a little, the next ones back turn more, all the way to the rears turning a lot, and the outer ones turn a bit more than the inners. Here's a 1:1 in action

https://www.youtube.com/watch?v=f7jHBH_zrDs

No way I was gonna do that purely mechanically, especially when doing it electronically means that turning ratios can be changed at the push of a button. As always, draw the thing up first in CAD (donno what the red block is, musta been testing something)





Arduino (top), servo controller (middle), and a power distro board down by the big capacitor at the bottom. Had some issues getting enough current to run all the stuff (servos, lighting, outrigger legs), so there's a separate lager-gauge power wire in addition to the smaller trailer signal wire. The M1070 has matching plugs for both, but if it's being pulled by a smaller truck, a battery directly connects to the trailer power.

Also, that many servos create some serious spikes on the 6V side when turned quickly and/or under load, like enough that they'd brown out the Arduino Thus the big filter capacitor for the Arduino (and servo controller board and the LED string).

This one is more mixed-media than most of my builds. The trailer frame is welded steel



Bare steel, being clamped and tacked, and the two white plastic things are 3D printed servo mounts to keep all the crossmembers aligned.



and the bed is wood of various thicknesses



That's the bed and the frame. Doesn't look like much yet!



there with the PLS on it. When I was working on the trailer, often had to borrow a second pair of hands to flip it over as it's so unwieldy. (Why did I pick 1:10 again? Just so my builds match? Ugh!)



Doing individual pieces of different thicknesses of wood allowed me to do the center rib with the pockets on each side, without having to try and route the pockets or the like. Also means it's less prone to warping as it's not one piece. (It's also glued-and-screwed, using Tite-Bond glue, which I found to be downright nuclear in its adhesion.)

Hard to see, but the neck is an engineering challenge as well. It's a number of printed pieces, glued together (again, bit surprised it can handle the load placed on it.) It's hinged at the base (lower white piece with two holes, the left/lower hole being the hinge) and then a short shock absorber acts as a dampener (right/upper hole, shock goes down underneath.) Filled the shocks up with fluid so they're pretty tight, just enough travel to hold the neck in place with a bit of give.



The bogies mount on 608ZZ bearings (I love those things as they're cheap and mount nicely on an M8 bolt or rod), and then there's a servo inboard to turn them, on a 3D printed mount.



Again with the cat scans. That second one was when I was doing turn testing, and she just HAD to check out what all the noise was.

Each bogie has an M8 threaded rod axle, and then a very stiff vertical spring. They have nice flat ends and fit into rings printed into the upper and lower bogey halves. As previously mentioned, I use pool noodles for tire foams. However, I discovered after the fact that when loaded, the trailer tends to pop the tires off the rim, so apparently I should have cut these rather wider. Sigh.



It's very hard to get motivated to redo 42 wheel-foam-tire setups.

Though you don't really see them, the bogies are actually pretty close to the 1:1, both in appearance and function. The upper and lower halves are hinged on a piece of 3mm brass rod.



The wheels also have 608 bearings. Each "dually" is actually printed as one, with the inner face being solid save the cutout for the inner bearing. The outer face has faux lugs printed, the joys of a dual-extruder printer. There's a washer on the inner face to space the bearing out from the bogie just a smidge, gives the tire clearance, and then nylocks on the outer faces/bearings to actually hold the wheels on.



A small spring keeps the lower half from dropping and the blue spring from falling out when it's not held in place by gravity.



Each servo has a steering stop to prevent the bogie from turning too far and getting locked up. To the right is an M8 bolt holding the upper bogie to the frame via the 608 bearing; the ring outside it holds the big suspension spring in place. The lower bogie has a match ring.



The stop has two M4 threaded inserts; adjust via turning the bolt and lock in place with the nut.

Front and rear have outrigger feet, vaguely similar to the 1:1. Unlike the 1:1, they're not independently adjustable; mine only do front and rear, but I've found that's enough. When hooking up the fifth wheel, I raise the rear of the trailer, which puts just a smidge of pressure on the kingpin, enough to latch it.

Here's the front, sorry for the errant thumb



and the rears



Aluminum channel down the center keeps the servo and outrigger actuator wiring mostly in check. The lighting is strung around the outside; they're the "NeoPixel" style, so are point-to-point.



Another design compromise is that the feet stick down too far and get caught up when the trailer is on any real incline. However, these are the shortest actuators I could get in that strength rating, and even the next ones down wouldn't fit much better.

The rear ramps hinge on 3mm brass rod, and are width-adjustable for the Abrams, or for narrower loads like trucks. They're not counter-spring loaded or powered or anything, as I just couldn't find any clever way to do any of that in the space available. Instead, there's those chain-binders made out of left over bits, small turnbuckles, chain and hooks, threaded rod, and vacuum caps.

Another thing I'd change if doing over again is the length of the ramps. These are made to be close to the 1:1, but are a bit steep for the Abrams (it teeters, and then when it comes down, the trailer bangs a bit and lifts the truck up just a smidge.) It's better loading the tank backwards, which IIRC is how the 1:1's are done, but it's still hairy.



And there it is without the tank. Hard to see, but there's a pulley at the back that just about matches the 1:1 sheave, rescued from my junk drawer. I think it used to hold up clothesline, but slightly justifies my hardware hoarding habit

[dremu]

As with the Abrams, this build isn't quite what I'd hoped. I don't expect perfection; I lack patience and I'm not a rivet-counter. In addition, I also enjoy my builds being functional, so they're not just a static model or even a mobile RC one, but can actually *do* whatever they're supposed to do. It's that last requirement that sometimes bites me.

What I found with this build is that yes, the truck will pull 20+ pounds of trailer with 50+ pounds of tank ... on flat ground, with traction. To aid with traction, I welded up some scrap steel to put inside the frame, adding weight over the axles (about 4 pounds over #3 and #4, and about 6 pounds over #2.) That helped some, but it also made the driveshafts pop out, doh. Also, as mentioned, when loaded, tight turns make the trailer tires start to dismount, ugh.

The truck itself came out pretty well, though, and I'm pleased with some of the parts being close to the 1:1 AND being functional (the bogies, for instance, are simple, but look mostly right and are strong enough to hold up, well, anything.) The trailer steering is actually great fun to watch, as the Arduino does its scaling magic. It's harder to drive than a regular trailer because it slides sideways due to the active steering; I'm used to trailers being passive and just following the truck. The HET's rear having the reversed steer also means you can jack-knife the thing in a heartbeat. My lovely wife is very understanding, but even she got tired of me testing the apparatus in the hallway and banished me outside.

I can say I learned a lot; my OpenSCAD skills are definitely improving, I can plastic-fab stuff with some expectation of positive results, and overall I had fun. Which I suppose is the important thing. Just wish the dang tank wasn't so heavy, and geared better, and ... =))

[frizzen]

Wow! That's an awesome looking beast!

Sounds like you may need to look at some better rock crawler driveshafts?

It the trailer tire foams can hold the weight, why not just glue the tire beads?
Sounds like a guy that's good at programming could really get fancy and make the trailer able to switch between stuff like the scaled normal steering, less turn-assist, crab... or even just a Gain setting to adjust how much steering help it gives, maybe off a pot channel on tx?

That thing looks stunning! Just watch out those motor-pool guys don't suddenly decide it needs unit markings or camo.

[dremu]

Originally Posted by frizzen

Wow! That's an awesome looking beast!

Sounds like you may need to look at some better rock crawler driveshafts?

It the trailer tire foams can hold the weight, why not just glue the tire beads?
Sounds like a guy that's good at programming could really get fancy and make the trailer able to switch between stuff like the scaled normal steering, less turn-assist, crab... or even just a Gain setting to adjust how much steering help it gives, maybe off a pot channel on tx?

That thing looks stunning! Just watch out those motor-pool guys don't suddenly decide it needs unit markings or camo.

As always, thanks for the good words.

Wrt driveshafts, part is my fault for them being a bit short, and part was fixed by loc-tite on the set screws.

I think gluing the tire beads would keep 'em on the rims, but they'd still be squashed, like an under-inflated tire in the real world, if that makes sense. This is why I think a wider foam would do the trick. Maybe that AND gluing them. Or even just narrow rims. Regardless, it's such a pain with so many. I don't know how Bo Wallen does his magic with eleventy-bazillion tires!

You actually hit the nail on the head with the steering programming. I have it set so one of the TX switches chooses between two different scalings. Another switch selects whether the trailer steers with the right stick, same as the truck, or the left stick, independent of the truck. That definitely requires a neck strap and careful wrist motion. The "tail wags the dog" phenomenon you get in 1:1's, like going downhill without trailer brakes, is absolutely the case here. If I get it wrong, the trailer will push the truck all over the place, especially on the hardwood floors in the house. Did I mention I was banished outside?

Actually, using a pot for scaling would be really clever, but I think all the aux channels are used on the TX it its fairly modified state. I do have a mod for them to add more switches/pots, hmm. You have me thinking again. However, I gotta admit I'm kinda ambivalent about actually *using* this setup. It's just so bloody unwieldy; the tank and trailer have been banished to the garage, as they don't fit on any of the shelves inside. Another reason I like the fork and the Rover and even the Cross M809, as they're smaller and don't require back-breaking labor to set up =))