Another RC model side project

[crueby]

Well, its finally here! I was able to keep this one a secret from the shop elves till now. They saw the box coming in, smelled gear oil coming from it, and attacked the box with a knife to get it open:

they were really intrigued when the first layer of packing came away...

with the bubble wrap off, the cheering started

they were able to elf-handle it out of the box and onto the table...

and they flipped it over to get a better look at the underside too

Here is what its going to be:

A while back I had found sources for copies of some of the old Ruston-Bucyrus cable driven excavators, the RB-19 and RB-22, very similar to each other but with different cabs. I had found that the Magom HRC (company in Spain that makes RC excavators and trucks with full hydraulics operating them) also sells parts and subassemblies for some of their models. This one is for a 1:16 scale modern excavator, but its the perfect track length/width to make a 1:12 scale version of the RB-19. Rather than the hydraulics, I'll be making this a cable shovel powered by a set of GoBilda robotics gearmotors, which are available in a whole range of speeds, all quite powerful - the bucket lift cable will have a power of at least 60 pounds on this model. The Magom chassis comes with metal tracks, the motors inside the tracks to power each independantly, as well as a smaller gearmotor to spin the turntable on top. I did not buy any of the rest of the model, I'll be setting it up with these three gearmotors (I 3D printed the motor holders and cable drums), making my own booms/bucket and cab:

It may look like the motors are too big, but the cab for the RB-19 is wider/longer than the top plate the chassis came with, so plenty of room for the motor, radio, and overhead pulley system it will need. The chassis has a slip ring built in for the wires, so it can spin the cab round and round without messing up the wires to the track motors. I have a bank of speed controls for all the motors (6 of them), plus one servo for the bucket door tripper. There is one motor for each track, one to spin the cab/boom, one to tilt the main boom in and out, one for the bucket crowd movement, and one for bucket hoist. A friend of mine who casts bullets gave me a box of 1 pound lead ingots he had left over with lead that was too soft for his use, I'll seal them with epoxy and use them for counterweight on the back of the cab. The main boom is 18.75" long, dipper stick is 14.75" long at this scale. The manuals I have include detail parts drawings with enough dimensions to make everything accurate.


I picked this cable shovel partly due to the way Ruston did the crowd mechanism - all cable operated from winches in the cab, the dipper stick is a large square shaft running in a pivoting long bearing on the boom, the cables run up to the bearing and out to each end of the dipper to move it in and out. Also found some videos on YouTube of real ones in action, plus the Ruston patents with details of the crowd mechanism.

Should be a fun project! This chassis is something I COULD have made, but Magom had it all ready to go out of the box, very good engineering on it, and saves me a LOT of time just to make the tracks. When done, it should be plenty strong and heavy to do some digging in a sand/gravel/dirt pile, though not enough to dig through sod. Have to set up a sandbox for it! I have some Gauge 1 gondola rail cars for it to fill, also have an old RC offroad truck that could be refitted with a new body to add a vintage dump truck.

This will be a good side project alongside the Kearsarge winch/windlass engines that I'm currently building - that still takes priority over this build. I wont be doing a full build log on this, but will post progress now and then as it comes together...

Chris
 

[ozzie46]

Oh boy Oh boy Oh boy! Another great thread coming up

Ron

[cnr6400]

  The Magom chassis and the mount / drum printed parts look great Chris! Look forward to seeing this model come together with your cab and dipper parts. 

[crueby]

Thanks guys! 

Did a little playing around with laying out the parts (radio, speed controls, batteries, motors, etc) on top of the cab floor plate (allowing for the fact that the RB-19 cab is a little larger) and decided on a plan forward for it all. Well, at least an approach to making the plan!    

I'll put the electronics/batteries on the floor level, and make another floor above it to hold the gearmotors/cable drums. Otherwise things would be too crammed in and hard to work on. The cable drums dont have to be aligned directly to where they leave the cab - they can be routed through a pulley or two if need be. I really want the layout to be structured such that its reliable and easy to maintain. The motor floor will be removeable from its supports to allow easy access to the electronics level.

Will need to take a bunch of measurements and model it all up in CAD - lots easier to move things around there till a good layout is laid out! Sounds like a start on a good tongue twister!    My old favorite: How Much Work Could A NetWork Work If A NetWork Could Net Work?   

[Kim]

What fun!  A new RC project!  Looking forward to following you on this one too, Chris.  Look's like a very fun project.   

Kim

[simplyloco]

I look forward to following this. My late father used to drive stuff like this, plus CAT D9s with scrapers. At age 7 onwards I used to go to work with him during the holidays. I even learnt to drive the big CATs!
Great fun!
BTW the weather here in Spain is wunnerful! I just have to endure another 35 days of it...

[wagnmkr]

This will be another fun project to watch Chris. You are saving a massive amount of time the way you are doing this.

 

[Vixen]

Hello Chris,

It's got tracks and intricate mechanisms, so you have got my full attention from the start.

I found the magonhrc.com website. What a treasure chest of components and sub assemblies? That will take a few evening to go through. Already making a wish list.   

Hope you decide to do a full build log as a lot of other members would enjoy the ride.

Cheers

Mike

[tghs]

very cool cool stuff, but will they put an order in an old beat-up box so you can claim that I've had this for years.. 

[crueby]

Okay - sounds like enough want a full build log on it, will do! It will be slower progress than the Kearsarge build, but there is less to do on this build, so that evens out I guess?     Already am rethinking the double-decker approach, after looking at the specs on the original RB-19 cab. Its longer than I originally noted, so I may stack the electronics at the front of the cab and use the rest for the motors/drums. Came up with a way to shorten the motor/drum assemblies a bit, changing the way the limit switch section is put together. Am going to use a threaded rod/nut with post for the limit switches on the motors, a little like the steering engine did. The limit switches will keep the cable travel from going too far in either direction. Definitely will want to lay it all out in CAD first to ensure the arrangement will fit. I already have CAD models of the motors/drums/limitswitches as well as the speed control racks, which were already 3D printed. Just need to measure and lay out the floor plate for the cab. The chassis has the slew motor/gearbox already in place, so things need to work around that.

The Magom site does have a lot of stuff, pricey but the quality is excellent, am quite happy with what I see on the chassis. The entire framework and all panels are steel, they have it CNC cut, all edges are crisp and clean, it already has lots of tapped holes in its top plate to fit their cab. They make some machines completely, some are designed to be conversions for existing Bruder toy shovels/trucks. The hydraulic versions are amazing, though really expensive. I shy away from them since I want to run them indoors, and I've seen (at Cabin Fever) how messy a hydraulic leak can be - very high pressures. Thats why I spent a long time researching cable shovels.


Simplyloco - I bet that was a great experience as a kid, to be able to run real heavy equipment like that! I'd love to get a chance to do that as an adult! Well, physically adult, still a kid inside...  Enjoy Spain!   

TGHS, just mail it to yourself a couple of times, I bet the post office can beat up the box for you!   

[crueby]

Measured the chassis top plate, which is the cab floor, and drew it in Fusion with the outer walls extended to match the RB-19. Printed that out full size and cut out the outside to use as a pattern. Laying the motors, drums, and radio parts on top of the paper pattern shows me that I dont need two levels. Thats great news, much simpler. All I  need to do is stand the speed controller racks upright, and make a holder for the main battery above the motors, easy to do. There are six speed controllers, with all their wires, so they are bulky.


Planning is progressing well!

[crueby]

Had an idea to simplify the boom tilt function, which sets the angle of the main boom for digging trenches vs reaching up high. Its also done with a cable from the cab up to the top of the boom. Was going to use same type of gearmotor setup as the crowd and hoist, but with much less travel needed.


I remembered that I had  made a tilt mechanism for a  model a few years ago, using a sail winch servo turning a worm gear set. It has 9.5 inch pounds of force from the servo, through a 28 tooth wheel and single start worm. Plenty of power. Its a 4 turn servo, giving about 40 degrees of output arm travel. Being a worm wheel, once in position, force on boom doesn't  transmit to servo. And its much smaller than the big gearmotor rig, plus eliminates a speed control and wiring.


Design is continuing...

[Roger B]

Splendid     

I will enjoy following this one along and also need to look at the magonhrc website.

[Vixen]

Splendid     

I will enjoy following this one along and also need to look at the magonhrc website.

Roger, a word of warning about the magorhrc website; it's another expensive rabbit hole. Maybe you should only risk one eye looking at it.

Chris, sail winch servos make perfect sense for any application that needs big line pulls and the ability to lock out. You can play around with the drum diameter to trade distance against force.

Cheers   

Mike

[crueby]

Splendid 

I will enjoy following this one along and also need to look at the magonhrc website.

Roger, a word of warning about the magorhrc website; it's another expensive rabbit hole. Maybe you should only risk one eye looking at it.

Chris, sail winch servos make perfect sense for any application that needs big line pulls and the ability to lock out. You can play around with the drum diameter to trade distance against force.

Cheers   

Mike

And pairing the sail winch servo with the worm gear, it gives a LOT of pull, and no big loads from the boom while digging will get back to the servo. SHOULD work out well. We'll see!