Supporting > Additive Machining

3D printed 1/16 scaled RC rotating tracked dumper

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ddmckee54:
Have any of you have been following Designs in Orbit's video series Rebuilding the Clinchfield?  They've been documenting the rebuilding of the 40+ miles of CSX railroad tracks that were destroyed by the hurricane Helene flooding.  If you've been following it then you've seen the little-ish rotating tracked dumpers in action.  They caught my eye, and unfortunately they were bright and shiny enough to catch the attention of my project Muse too.  Ever since that happened I've been nagged at that "WE" needed to 3D model one to build an RC model.  The majority to the tracked dumpers in the videos are Terramac RT14R's.  I said they were little-ish, they're only about  by 20' long by 10' wide - but they've got a 28,000 pound payload capacity. 

After being nagged by the Muse for several months, I finally broke down and started to work on the 3D model.  I found a 3-view drawing on Terramac's website, scaled it to 1/16 because that's the scale the rest of the fleet is going to be, and started drawing it out.  I had it in the back of my head that I could save myself a LOT of time and trouble if I could use off the shelf tracks - like Bruder's replacement tracks for their CAT excavator.  I'd been working on the frame for several hours when I finally got around to checking the scale track width, it was over 60mm.  Well, that's that, this project's over.  I told the Muse that this project wasn't going to happen, 40mm tracks on a machine meant to have 66mm tracks would just look ODD.  Then the Muse started crying and whining that it'd seen an RT7R on Terramac's website, and it was pretty sure it'd seen at LEAST one of them in the videos - what about a 7R?  So, I downloaded the 3-view drawings, scaled it to 1/16, and checked the track width.  Son-of-a.... 43mm.  Well that's close enough to 40mm that it wouldn't be noticeable, I guess we're doing this thing.

For those of you that are curious, this is what a Terramac RT7R looks like.

Cute little buggers aren't they? 

Well the Muse has been cracking the whip for the last 4-5 weeks, and this was the state of the 3D model a couple days ago.

It shows the engine bay door open because that's where the main power switch and the cooling fan are going to live.  The rest of the really important stuff like batteries, receiver, and the ESC's for all the motors are going to live in the rest of the engine bay and in the area for the fuel/hydraulic oil tanks that's just in front of the engine bay.  I was worried about the slew ring and the slew bearing, then I stumbled across across an Ebay listing for NOS Kaydon and Fafnir slim-line ball bearings, when I found out it had what I was looking for I couldn't hit the "Buy It Now" button fast enough.  I figured out a way to 3D print the slew gear using the profiles for a 6mm GT2 timing belt, like the belts used in 3D printers.

I barely had the cab finished before my operator was demanding that I print out the seat, so he could see how well it would fit his butt.  I did, and he did.  When I asked how it fit, I was told in no uncertain terms that the seat back needs to be tilted back, the headrest needs to be tilted forward, the armrests need to be lengthened because the joy-stick locations are under his wrist - NOT in the center of his grip, and that the top 1/3 of the headrest needs to be lopped off - because it just looks stupid.


Sooo.... I fixed all the items on the operator's punch list, heck I even gave him joy-sticks - with cushioned grips.  There shouldn't have been any complaints - but... there were.

The operator was whining that it was a little snug on his hips.  I told him he had 2 options, deal with it - or diet.  The other guy was so PO'd that he only got the "reject" chair to sit in that he said he was gonna hold his breath until he turned blue.  So far he's managed to turn his clothes a lovely shade of blue, does that count?

Next up on the hit parade?  Finish up the clean-up work on the cab and bed, then start printing the yellow parts.

Don

wagnmkr:
This is looking like a fun project for sure. What size of a build plate is going to be required?

Oh, and I'd tell the whiny guy to make his own seat!

 :cheers:

Tom

cnr6400:
 :ThumbsUp: :ThumbsUp: :ThumbsUp: :popcorn: :popcorn: :popcorn: Looks like a great project! Got the popcorn ready. Re the seat - maybe make one with projections upward like little traffic cones, and ask Tim and Terry Mack the operators which they liked better... :Lol:

Great that you found a Bruder track that was close enough. You're right, that will save a pile of time.

crueby:
Very cool!  I've never seen a dumper that rotated like that, should be fun! You can get slip rings to take the wires down through the slew ring and let it rotate without winding up the wires.   :popcorn:

ddmckee54:
wagnmkr - My go-to printer is a Wanhao D6 clone with a 200 x 200 build plate.  I may have to get a little creative, but everything should fit on that build plate.

cnr6400 - I got the idea of using the Bruder tracks many years ago.  They were building a new electrical sub-station and upgrading the power lines along the route I used to commute to work, and they were using a Morooka 1500 non-rotating dumper on that project.  I started to design a model using the Bruder replacement tracks and parts cut from 1/8" and 1/4" plywood on my CNC router.  Then that router died and life got in the way so I never finished it.  My project Muse has been hinting that we need to revisit BOTH of those projects.

crueby - My 6 channel 2A slip-rings showed up 2 days ago.  I would have preferred something with a little higher ampacity, but my main drive gearmotors stall current is supposedly 1.8A - so the 2A slip-rings SHOULD be OK.  The main drive motors are the only thing on the main frame that needs juice so I've got 2 spare wires if something goes belly-up in the future.

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