Purple Nurple: ~1:12 Frobeliner cabover scratch build

[dremu]

Freightliner, Globe Liner, take your pick. Like the name, the build is a mish-mash of things: drivetrain is off-the-shelf, frame is Home Depot, body and accessories are 3D printed. In the 1:1 world rarely are two trucks exactly alike, so mine is customized to ... me. It's scaled to match the rest of my fleet, a bit bigger than your regular Tamiya. I haven't done an RC in a few years, so wanted to get my brain and skills back again before I start on my mega-project, a rotator wrecker.

Lots of it ain't perfect, but I had fun making it. I like to make things.

First up is to design the thing in CAD to test fitment (which will still be wrong) and to export printed parts.



Eventually a design is settled on and the chassis emerges.



Tried various color options, and ended up liking this purple, thus the name Purple Nurple.

[dremu]

The drivetrain is pretty conventional using off-the-shelf components. Front axle is your basic Tamiya type passive, and yes, that means I'm mixing ~1:14 manufactured and ~1:12 printed parts, but I don't think it's noticeable to the naked eye. (If you're breaking out the ruler or calipers to my builds I've got bigger issues =)) Rear axles are from Integy, a type I've used on other builds. They're a bit blocky, but I like that the parts are interchangeable, ie the through axle is the same as the end axle, just with a blank diff cover instead of one with an output in it. Same for the steering axles, so for my 10x10 HEMMT I had two steer axles in the front plus one in the back. All the same axle means designing the suspension is easier.



Front suspension is leafspring, using the Chinesium "D90" springs as I had some on hand. Rear suspension is linked, which always annoys me and yeah, maybe I shoulda done airbags, but the axles come with links. Did require custom link lengths, but was able to print new center tubes and reuse the rod ends. Getting the link lengths right always drives me nuts, and this build was no exception. I really shoulda done leaves or leaf+links like the Lesu pre-made box, but the Integy kit came with all these links so it's another "How hard can it be?" moment.



The rear driveshaft was a nightmare; ended up just sleeving some square brass tube inside U-joints. Soldered the ends of the tubes so they didn't squish under the setscrews.

Also always seems painful to find shocks which have enough rebound for my taste but fit into the desired space. Both front and rear use Chinesium shocks, but with new much stronger springs on/in them. (Particularly in the rear as I know that's a horrible shock angle, but again, getting everything to fit was a major pain in the watoosi.)

[dremu]

In the past I've used a dual-extruder printer, which allows two colors, but they're a pain to keep the extruders aligned. Lately been using a Bambu printer, which only has one the one extruder, but can switch colors mid-print. There is a performance hit if you do it a lot and/or have many layers with multiple colors, so it takes careful planning. Otherwise a piece that prints in 30 minutes in one color suddenly takes four hours with a coupla colors :O The bumpers and brushguard did well for this because there's only a handful of layers with the colors, mostly the silver. The inlays are "transparent" (I'd call them translucent, whatever) red, orange, and white, so the LED's behind them shine thru.

[dremu]

Top of the cab gets lights in multiple pieces



The orange then glues on in front. Horns are actually genuine Tamiya and mostly look right; 1:12 and 1:14 scales are close enough to fudge mostly.



Headlights are just switched via the RX, some nice bright "straw hat" shaped 8mm's.

Turn signals and the rear lights are driven by an Arduino



Because in RC, I find rarely is there a problem that can't be solved with an Arduino =)) The front turns actually annoyed me, as I couldn't find T1-sized LED's I liked, or otherwise make it bright enough to just use one LED, so there's that stupid tube with an LED on each end. I may change them up to a WS/SK2812 "NeoPixel" style once I get some in that are clear vs frosted.

Anyway, the Arduino gets the iBus data from the RX, and decides if it's turning left or right (in which case it blinks the appropriate turns), backing up (reverse lights), moving forward (turns off brake lights) or stationary (turns on brake lights.) There's also a switch on the TX for hazards which blinks both sides' turns.







Some printed greebling; there's also some wheel chocks somewhere that I printed, and then some stuff from AliExpress that's just SO ADORBS because it's SO TINY but the ratcheting straps and loadbinders actually work! Pix those with the trailer later.

And then the regulatory cat scan



Duke Leto Atreides II has to check the thing out and decide whether to be frightened of it or chew on it.

[dremu]

So that's how it sits as of now.



Yeesh that is one ugly fireplug of a man.

Next up is trailers, because what good is a semi if you have nothing to tow? More to come.

[Zabco]

Looks really good, nice job. Just out of curiosity, why 1/12? The inside of that cab is huge, I wouldn't know what to do with all that space. I agree with you on the use of arduinos but because of size constraints in most of my builds I have to use the nano, pico or feather versions.

[dremu]

Originally Posted by Zabco

Looks really good, nice job. Just out of curiosity, why 1/12? The inside of that cab is huge, I wouldn't know what to do with all that space. I agree with you on the use of arduinos but because of size constraints in most of my builds I have to use the nano, pico or feather versions.

Thanks for the good words. As with any of my projects, there's always stuff I coulda differently or better, and there's always somebody else here who's done one far more amazing. This does what I need, though, and since it's been a few years since I did a build, I needed the practice on a relatively simple one.

The cab on this one does have tons of space, but I built this truck to be a "casualty" for my next truck, the mega-project of a rotator crane/wrecker. That one will end up with ZERO extra room anywhere (think of a TX that requires an extra Arduino, and four Arduinos on the truck proper.)

Anyway, my other stuff is mostly about 1:12, so I try and keep them matching.

It's not so bad for this truck, but when you think to yourself, "Self, I should make a 53' trailer." In case anyone wonders, a 53' flatbed is very, very long.

After that I'm only doing 40 footers.

[ddmckee54]

What motor/gearbox are you using in the Nurple?

[dremu]

Originally Posted by ddmckee54

What motor/gearbox are you using in the Nurple?

Mmm, you ask a good Q. This was made with a lot of things left over in the cabinet that didn't get used for previous builds. Then there's a gearbox on the end of that, what's described as "Axial 1:10 scale" in the ads, with the driveshaft outputs. This truck is only rear wheel drive so I'm not using the front output, but you get the idea.

If memory serves it's a 55T 540 with a 4:1 planetary reduction box. Gives it enough torque to pull a trailer and not be stupid fast. Weather has not been conducive to actually going outside for much testing, but soon.

[ddmckee54]

Duke Leto Atreides II? Somebody's a Dune fan.

[dremu]

Originally Posted by ddmckee54

Duke Leto Atreides II? Somebody's a Dune fan.

Good catch. To be specific, I dig Frank Herbert proper. However, should I ever meet David Lynch I will murder him on the spot. I actually think I woulda enjoyed Jodorowsky's interpretation, and the more recent film adaptation I was fine with until the third act of Dune 2 where they whacked up Alia's plotline and changed who killed the Baron. And then IMO the son's work is paid-by-the-word fanfic. It's like Majel Barrett trying to capitalize on Gene Roddenberry's name after he was gone with "Hercules In Space", I mean, Andromeda.

Anyway, my wife's cat but I named him, go figure.

[dremu]

Also occurs to me that doing 1:12 allows me to fudge using parts from both 1:14 and 1:10. Gives me a little more leeway in what Chinesium parts I can use/repurpose.