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.)

[dremu]

While greebling detail is not my strong point, I try where possible. One example is the wheels. RC4WD had a good military-tread tire that matched my scale, but I wasn't able to find anything remotely close to accurate for wheels. And even those that were available were crazy money. I got busy with the CAD then, and printed these up:



They're a beadlock, and a fair visual match to the 1:1.



Mind you, they're five pieces...



...and take half a day each to print, so doing 11 of them took a while. Not too bad, as once the design is set, you just hit "print another copy" ... but getting the dimensions Just Right to fit the tire lip took a lot of trial and error.



That's a slice view, and ouch, my head still hurts thinking about it.



The inside has a drive hex to match the axles, and then smaller hexes to press-fit M3 nuts into for the beadlock. Assembling beadlocks is hard enough, gotta use two long bolts to draw the halves together, then use shorter ones to assemble, without having to continually drop nuts off the back.

Jumping the gun a bit, found that the foams inside the tires were waaay too soft when the truck was laden. Being frugal and enterprising, I found that pool noodles can be had in about the right diameter, are cheap, and are easily cut with a foam wire cutter.



Again jumping ahead, those are actually for the trailer, but you get the idea. I've since switched to exclusively using pool noodles. With a bit of searching you can find them in different diameters, even solid-core ones sold for yoga or exercise, so you can use them on any size wheel.

Here's before





and then after, same force applied (using my carefully calibrated fingers.)

[dremu]

As I said, my styrene fab skills aren't fantastic, but in 1:10 the bits can be big enough for me to manage. In parallel with building the truck, there's also a conex ("shipping container", "ISO", etc). As drawn in CAD:



And then start to assemble:



Starts out as just 3mm styrene sheet from my local plastic shop, then 3D printed hinges, latches, and twist locks for the corners.



The latches actually work, if you're careful with them. The yellow splotch is a hinge for the handle; it's a piece of 3D print filament pushed through (1.75mm diameter), then melted on the end with a soldering iron to mushroom it in place.



Rather than actually corrugate the sides, I faked them with printed inserts glued into place. Rustoleum hides many sins.



Add some stickers, et voila.

This in turn fits onto a "flatrack":



to end up like this



As with the conex, the flat rack starts out life as styrene sheet, then has stuff added:



Most of the "stuff" is 3D printed, like the red A-frame on the left, but the tool box is left over from the body kit, and the tie downs on the sides are Fleabay Chinesium. They're so cheap that it's just not worth my time to try and print them, plus even the chintzy aluminum is stronger than printed plastic that small. The corners have snaps for the twistlocks on the conex:







They're so small I couldn't figure a way to actually make the lock twist, and in the end the thing weighs enough (just the conex empty is like six pounds!) that gravity holds it down just fine.

Like the 1:1, the back has rollers to facilitate loading and unloading. These are printed, and roll on a length of spring steel (aka a straightened paperclip. I've discovered that paperclips are amazingly useful in this hobby!)



The white blocks are added as I did some testing in the real world. My CAD design was nice and all, but keeping the flatrack aligned both fore-to-aft and left-to-right, while being able to load and unload it, turned out to be more of a challenge than I'd thought.

At the rear of the truck is a mechanism to not only roll the flatrack, but guide its frame rails on the angled rollers to keep it centered.





See highlight on the 1:1; not the same visually, but same idea functionally.

[dremu]

While I like build RC stuff that's accurate to the 1:1, I'm not remotely a rivet counter. I also want mechanical functionality, so I'm willing to to tweak things as I see fit, either for my own taste or to allow the thing to *work* like the 1:1, even if doesn't exactly LOOK like the 1:1.

One case in point is the suspension. The axles came with links and I could make them fit; I couldn't find a way to make leafs fit nor did I have any on hand. Another is the lift mechanism. I hate hydraulics in 1:1, so there's no way I'd do them in scale. That meant using linear actuators, though fortunately they can be easily controlled by an Arduino (see above wrt the RX and Arduinos.)

Here's a 1:1 moving a flatrack. The mechanism is actually compound. It has two sets of actuators, one to lift the main a-frame and another on the hook to bend backwards.



Learning to model that in CAD was, well, let's just say I tore out a substantial amount of my limited supply of hair

After many iterations, the design ended up like this at rest



Extending just the top, hook actuators looks like this



and then extending the bottom lifts the whole thing



Took me forever, but got all the sizing and angles worked out and it moves like this



That middle piece, the lift A-frame, was nightmarish to print, talk about a learning curve. It's too big to print at once even in my big printer, so it had to be split in two and then glued and bolted together.



and rendered for printing



For those not familiar with 3D printing, however, you don't magically get a nice clean piece straight out of the printer. What you get has supports and, unless you have the temperature and speed settings just right and the planets are in alignment, little melted bits and will require tons of sanding and filing and drilling to make perfect (or even good.)



That's an early iteration of the bottom half of the lift A-frame. After removing the supports and said sanding and such, the final version looks like this:

[dremu]

With the loading mechanism sorted, the next trick was the center loading crane. While it's not used to load the conex, it can be used to load stuff onto a flatrack.

This uses more linear actuators to lift up and down





and then another to move the arm in and out, with a 9G continuous rotation ("sail" or "winch"), with a little drum on the end to spool up the cable (well, string )

That all in turn is mounted on a skateboard bearing, with a 3D printed worm gear assembly driven by a regular size winch servo, pink and purple in the mockup. I find it handy to use the proper colors (ie olive drab) for parts which are "done" and then obnoxious colors for the parts I'm working on to more easily locate them.



and in the real world, getting a cat scan. Projects in this house get a lot of cat scans.



Actually setup, down:



and then checking clearance over the hook:



With moving parts like this, geometry comes into play more than I'd like. Turns out that when the crane is lifted so it clears the hook, the reach is reduced. As mentioned, ended up with a switch to choose one of three crane positions, one with reduced height but at an angle to give maximum reach. It will rotate over about 270* of the cab, and drop loads into the flatrack to about half the length back.

[dremu]

As mentioned, I get happy with lighting on my projects. Arduinos lend themselves very nicely to these programmable LED strings popularly called "NeoPixels". Instead of a star topology where you have to wire every LED back to some central point, you just wire the RX to a controller (in this case, an Arduino), which goes to the first LED, to the second, etc, in a line. Makes the wiring much tidier.

These LED's come in several forms; the traditional round style in multiple sizes, flat ones, bars, and various shapes. One of the latter I enjoyed is a small circle:



which can be programmed as a strobe (slow motion)



End result:

https://youtu.be/IeSNXUt1nA4

The LED's aren't actually limited to yellow or white, they're full RGB, so you could just as easily do red or blue or whatever for emergency vehicles

https://youtu.be/o6m2hWx5NkE

And, because they're software-driven, making blinking patterns or traffic directors or strobes just requires different programming, no hardware changes.

Here's the backup lights; center of the rear bar stays white, and corners and the edge markers strobe.

https://youtu.be/SD8kimBdvOQ

Brake (center red) and left turn (sequenced)

https://youtu.be/eJ4eigj61xc

And traffic director when loading or unloading

https://youtu.be/AndqlGcuIp8

[dremu]

Some other details: The hook for the flatrack is hinged on the 1:1 to reduce height for airlift:





Again, paperclips serve me well. The hinge proper is a bent paperclip, and the lynch pin that latches it is a piece of brass tubing from the LHS, with some Dremel work to hook yet another paperclip.



The nose of the body kit was set up for the "OSHKOSH" logo, but didn't actually have it. Odd of Chinesium to respect trademark ..shrug.. Anyway, grabbed one from the company's website, resized it, and printed one up to blue onto the front.





Got some metal shackles, but they didn't match the hangers that came with the body kit



Coulda Dremeled them down, but to get all the cuts I wanted, was easier to print



Et voila



On the 1:1, the hole to the right (left side of vehicle) is for the driver to see down. I re-purposed it for the power switch for the ESC, as it's exactly the right size and well-hidden, yet easy for a finger to reach.



Also did some other little stuff, changing LED sizes and added one set to the sides to make it closer to the 1:1. New buckets for the front, and drilled the sides and added a second set (grey ones)



It's tight in there to fit 8mm and 5mm LED's across the front and then two 5mm's each side, but the good silicone wire bends well. The only problem is that the programmable LED's have four wires, so proper labeling (colored heatshrink) is a must.

That puts the truck at about here, all the bits completed but not painted.



The antennas are a combo of fabricated and printed. The first two are just Evergreen round rod with printed middle and base:





And then the thicker ("RCIED") one is printed in like ten pieces, with a piece of 1/8" rod down the middle to keep them all concentric.





There's another view. In addition to the flatrack, I used the body kit's bed to make a side-drop rack. However, the bed wasn't big enough, so that's actually the bed kit's front and back, with new sheets for the bottom and sides, and then more Evergreen rectangular stock to match the side detail. Hinges are from the local plastic place; they're a bit clunk but again, I like the thing to *work*.



All of that took many weeks, on and off, to design and build ... and then was like one afternoon to tear it down for paint. Bit depressing.



Coupla days in the paint booth, and we have primer and then OD green (hard to tell in the dark)



Reassembled with some printed greebling and hand painted detail, like the fire exinguishers and fuel tank caps, and as teased above, this is the finished truck:



Next up is the trailer, which fits the same racks

[jerry56]

Impressive....
I see more and more people using Arduino I think I should learn more about how to use it along with 3D cad.
Looking forward to seeing this one finished.

[dremu]

Thanks for the kind words! It's definitely a learning curve, especially if you're not coming from a programming background. But both are increasingly pervasive, especially the Arduino stuff. There's TONS of tutorials on the web, and the hardware is cheap. This truck has sixteen channels of servo control (and could do another ten or so), plus support for several hundred LED's, and the boards were less than 20USD total.

Plus, if you want to do something, chances are somebody else has done it, and Arduino being open source means that they've published it on the Internet for you to use, modify if you like, whatever. Lights are trivial, and even sound effects are simple with off-the-shelf cheap modules. I had one truck done up with an MP3 player that uses a little SD memory card like you use for digital cameras. You could put any number of sound effects on it, so you just google that you want an truck horn sound or the engine startup sound or the hiss that air brakes make when they release or whatever, and you can put all of those onto the chip, and then the Arduino plays whatever sound(s) you want when the throttle goes up or down or stops or whatever.

The CAD is a must if you're printing parts. Thingiverse and such are great to get started, download somebody else's parts, but you'll find very quickly that you want to customize them. Being able draw your own is priceless. OpenSCAD is free, and again, many tutorials on the web.

Some stuff does make sense to fab old school because it's easier/quicker/simpler/stronger, like the basic box for the conex. But doing the detail work is SOOO much easier with a printer; once you get it dialled in, you just keep pressing the "print another copy" button. The ribs for the conex are like that, all eleventy-bazillion of them.

[frizzen]

Great looking truck!!!

The loading system and crane look like they'll work really well. Doesn't look like any fun designing those...

Oh no, another of those crazy Fiero owners?

[dremu]

Originally Posted by frizzen

Great looking truck!!!

The loading system and crane look like they'll work really well. Doesn't look like any fun designing those...

Oh no, another of those crazy Fiero owners?

"Crazy Fiero owner" is redundant, btw

The problem I have with the load/unload -- besides, yeah, the weeks of designing them and having to recall high school trigonometry! -- is actually doing it. It's just two dials on the TX, but for some reason I can only do it while looking from the left. If I'm on the right-hand side of the truck the dials are "wrong" in my head.

I've found it best to move the hook up as the A-frame goes up, then down while still moving the frame up, then the hook goes back up again, to get a nice smooth movement without tipping the load at too great an angle. Harder than it looks, and gives you respect for the folks who do this on 1:1's.

I took some video early on, with the parts in place but before paint and with crazy messy wiring:

https://youtu.be/7gGnfUmpqAM
https://youtu.be/oZ4iLoMdgig

You can see sometimes I move the hook up when I meant to move it down; when the arm is down, twisting the hook dial one way moves the hook "up", but once the arm is up, twisting the hook dial that same direction moves the hook "down". I think even if I changed the dials out for momentary switches I'd have the same problem, as for some parts of the arc pushing the switch "up" would move the hook "down." Ow, my head

After the truck was finished I did some more videos. Here's picking up the flat rack, with the Cross RC truck tied down:

https://youtu.be/G1gigDKLBgU

and driving around loaded

https://youtu.be/tIGJTuGSd-E

eagle-eyed viewers may notice one of the front marker and turn sets is munged in this video.

Unloading the flatrack with the conex on it

https://youtu.be/3_SnaMT9GGc

The outrigger feet in the back aren't just for looks. Even with the pool noodle tire foams, the weight and force of loading anything really pushes the back end down.

Sorry for the crappy video, apparently it was dark in the garage. Outside looks a little better

https://youtu.be/Vl4-64sQ4DQ

And my dad having fun (and some trouble with steering)

https://youtu.be/EMaO3L1g0b0

Leftover gravel, river rock and roof shingles from various house projects can become a playground with a little effort. The bridge is a broken-down pallet (remember Bridge Over The River Kwai? This is Bridge Over The Railroad Tie.)

[dremu]

In comparison to the truck proper, the trailer was pretty straight forward. There's not a ton of information on the web about them, and there's some variation, either due to multiple manufacturers or multiple contracts. In the end I opted to make something that basically looked like the 1:1, and would also work with the PLS and my existing racks.

The CAD layout looks like



same aluminum C channel frame and 3D printed crossmembers as the truck. The leaf springs are actually 3D printed as one piece, but if you don't look closely pass muster.



Axles are just M4 threaded road; the wheels then have brass tubes of ~4mm ID to act as bushings to spin freely on the axles.



a little snap on cap for the hubs



and they're a close match for the 1:1



The tired tread isn't quite right, but I couldn't find a closer match in the right size.

There's still a few tricky bits to this design. One is the front axle, which is mounted on a turntable (again with the skateboard bearings, cheap/widely available) so that it steers somewhat. However. for load/unload operations, it has to lock, so there's a hole for a brass tube to do so.



Further, to load and unload, the trailer has to be tucked very close to the truck's rear bumper, or the truck's arm can't reach. However, at that position, the trailer can only turn a few degrees before hitting the rear bumper. The trailer's drawbar must therefore telescope to allow two different positions (again, latched by brass rod from the LHS.) The 1:1 actually works the same for the same reasons.



This is the drawbar extended, but right about center of the pic you can see the second hole to latch it in closer. Yes, those are safety chains, and yes, they work. I discovered this when testing the trailer out in the driveway and something came unglued, and the chains kept pulling the trailer, just like they would on a 1:1

[dremu]

So what's that thing on the back, you ask? Why, it's another kind of rack, a "Hippo" (used for water or fuel delivery.)



As always, we start with a CAD



This one has no electric stuff nor much in the way of moving parts. Frame is plastic tube, and bottom, and box are just styrene sheet. The tank was trickier to make; it's printed, but it's a weird shape (ie irregular, not just a squashed cylinder.)



Also 1:10 scale means it's big, so had to be printed in chunks even on my big printer. To give the illusion of the rings on the tank, just printed short chunks scaled slightly larger; that's the grey glued onto the blue.




More cat scans, and then it starts to come together



And some greebling and paint later



Has the same rollers and underside frame as the flatrack and the drop-side boxrack, so they're interchangeable on the truck or trailer alike.

[frizzen]

Originally Posted by dremu

"Crazy Fiero owner" is redundant, btw

Nope, don't know anything about that.


I'm not suprised running the loading arm makes a lot more sence one direction, i've learned that my dragline crane is easier to explain and run from the Right side of machine.

Since you've got the basic Conex already, modding one into a CHU should be a pretty simple additional load to print.

Glad the machine passed the cat-scans.
You build really fast!

[dremu]

Originally Posted by frizzen

Nope, don't know anything about that.

I'm not suprised running the loading arm makes a lot more sence one direction, i've learned that my dragline crane is easier to explain and run from the Right side of machine.

Since you've got the basic Conex already, modding one into a CHU should be a pretty simple additional load to print.

Glad the machine passed the cat-scans.
You build really fast!

Sweet mini-me Fiero! At least you don't have the Indy go-kart. Or do you? There's those guys on Pennock's with three or more sizes of Fieros. Which is almost as bad as having multiple full-size ones. (I mean, they're fun, but keeping up on my one is enough for me!)

I looked at the CHU, but given the weight of the conex and its leverage, I'm not convinced I could make the CHU work in plastic. Seems like it would either snap the corner twistlocks off the conex, or just break the CHU. That's why I stuck with the flatrack and let gravity do the work.

Since then I've actually also built a reach stacker for the conexes (conexi?), but it's a combination of metal rods on roller bearings with printed bits, so as to carry the weight.

Also, the build was several months. Just looks easy with the summary writeup I have some free time these days, so I'm finally getting around to doing build threads vs. actually building.

[dremu]

Since I had the big box rack and a crane, needed to make stuff to fill it up. Some printed, some fabricated, bits bought off-the-shelf (because, again, Chinesium can be so dang cheap it's not worth it to build.)



Rigging hardware: metal chain and shackles, and some ribbon from the craft store with heatshrink on the end for straps.

The little printer has two heads, so can do two colors. Here are various size options, doing the Goldlilocks thing:



And then a variety of colors (orange is most common here in the US, but overseas you see the neon green, on the street as well as on Kraftwerk album covers, in addition to the other colors.)



Got a mixed bag of balsa at the LHS and went to town. Hadn't done anything with balsa since I was a kid, but was great fun, other than having to be very careful with the miter cuts to get the angles just right.



Had some rotted old tires, so they went on a pallet:



The pallets are sold as drink coasters, I kid you not, and were like a buck and change apiece, another of things where it just doesn't make sense to build. The net is a standard LHS thing.



55 gallon drums come right off the printer, and are then shrink wrapped onto a pallet with longer versions of the straps above. The missus was surprised when I asked for Saran Wrap, and laughed at how long it took me to get it wrapped tight around the drums. They're sneaky little buggers.



Another place the "print another copy" is handy. You want different colors? No problem. Feed in another spool, push the button, boom. These are actually hairy to CAD up as the military Sceptre-branded ones are stupidly shaped, but I have a set out in the garage to work from. Note the blue water one is a bit different from the others. The "20L FUEL" label doesn't quite some through, maybe a bit of X-act knife work would help.



This one's an IBC, printed in several pieces and then glued. The main transparent piece in the middle is one block. Each of the grille side faces are separate, and then the base looks like this



And a coupla bars across the top.



Some greebling for the faucet and fill and it's as seen above.

Did up a pile of these guys



and also some Pelican-style cases in various sizes and colors



I was surprised that the crane's winch is strong enough to lift these, even without a snatch block



The pallets can also be moved about, and loaded onto the boxrack, using this



There's some more pix and videos of the fork @ https://rctruckandconstruction.com/s...d.php?p=170566

[egronvold]

Awesome truck!

[dremu]

Originally Posted by egronvold

Awesome truck!

Thanks for the kind words. It was definitely a labor of love. While I'd set the scope in CAD and was reasonably sure I could complete the project, I was not 100% sure it would have enough strength to actually LIFT the conex and racks when they were laden down. I was smart enough to order the slowest ( --> highest geared --> strongest) actuators, so it all worked out, but some of my builds have not been so lucky.

[Wombii]

It's you! Nice to see the build thread alive again after the scale4x4 crash.

[dremu]

Originally Posted by Wombii

It's you! Nice to see the build thread alive again after the scale4x4 crash.

LOL, yeah. Still nowhere near the detail of many builds -- I'm thinking of a RNoAF crash tender in particular -- but still fun.