Cat 340D Excavator build
 

Hi all, been a while since I joined, finally gotten a chance to start building something (after learning a lot from yours on this site! ). I am starting a 1:14 scale RC model of a Cat 340D excavator, based on this die-cast model that I found:


https://i.postimg.cc/DZch0Lgb/IMG-6610a.jpg


I took side/top/bottom/front photos, and traced them into a 3D design in Fusion 360 so I could scale it up and print out model-size patterns to build from. I would love to make it fully hydraulic, but thought I would give a lead-screw based electric version to see how it works out, mainly for cost reasons. After finding the leadscrews and gearmotors over on ServoCity's website, and doing some experimenting, I wound up with this design for the pseudo-hydraulic pistons:


https://i.postimg.cc/YSYMcJLR/Piston-Cutaway-View.jpg


The leadscrew is the pale blue down the center, the follower is the pink bit inside the orange tube. The piston tube and the cylinder were made from DOM steel tubing, which are a loose telecoping fit. At the back, the red part is a steel turning, riding in a set of ball bearings to take the forward/back thrust. The light green section fits around the bearings, and connects to the main cylinder tube. Here is what the finished parts look like:


https://i.postimg.cc/bJP8q3Qh/IMG-6597a.jpg


And as assembled into the first full unit:


https://i.postimg.cc/vZpbNQTD/IMG-6596a.jpg


I put a u-joint on the drive rod on the end (the red part in the drawing above), so I can put a gearmotor down inside the boom. I'll put limit switches inside the boom on the pivots, to keep it from over-extending, and drive the piston with a ESC from the radio. As a test of the power it has, here is a short video showing the movement with it driven by a variable power supply set to 9 volts:



https://youtu.be/fryEKQaH3uY


It worked quite well, lots of force in both directions.


Now that I know it will work well, I'll make up the rest of the cylinders, and start in on the booms which will be framed in steel and clad in aluminum sheet. Progress on this will be a little spotty, since I am in the middle of a build of a 1/4 scale Stanley Steamer auto engine. If you are interested in that, am posting a build log over on the Model Engine Maker forum. There is also a build of a model of the Marion Model 91 steam shovel (not RC) that is near me in LeRoy NY, built at 1:16 scale.


Chris

Re: Cat 340D Excavator build
 

Great looking leadscrew cylinders!

This will be really cool to watch come together

Re: Cat 340D Excavator build
 

Hi Chris

Excellent idea on the lead screws and workmanship. I’ll be following your build with interest as I think an excavator will be my next project.

Good luck

Rob

Re: Cat 340D Excavator build
 

Thanks guys, glad to have you along for the ride on this one.

Re: Cat 340D Excavator build
 

Getting the rest of the cylinders assembled, couple more set screws to go...


https://i.postimg.cc/SsxhftQd/IMG-6623a.jpg

Re: Cat 340D Excavator build
 

Got the last bits on the cylinders done, time to start working on the booms. This morning got the side panels cut from some 1/8" aluminum plate:


https://i.postimg.cc/7PT094HQ/IMG-6628a.jpg

Re: Cat 340D Excavator build
 

And started riveting on the angle stock to hold the top/bottom panels. Those will be screwed on, with screw blocks inside the angles since the angles are just aluminum. This will let me access the insides to get at the gearmotors.


http://listerengine.com/coppermine/a.../IMG_6631a.JPG

Re: Cat 340D Excavator build
 

Its coming along nicely!

any reason for using aluminium?

how do you know your rams will act fast enough? can you speed them up if required with more voltage?

keep up the good work !

Rob

Re: Cat 340D Excavator build
 

Thanks Rob!



I am using aluminum for ease of working plus cost, plus I already had a couple sheets left over from some fixtures we built before I retired. Normally I use 303 stainless on most of my steam engines and such, but for these booms the ali will work out fine - at 1/8" thick its pretty solid, especially once made up into the box. I'll be putting in some strengthening parts of steel around the cylinder bases and the ends with the pivots will be steel on the inside.


I timed the rams at different voltages, should be good but if too fast or slow I have other gear ratio motors. These are 176 rpm at 12v, also have some 90-some and 56rpm motors that are the same size. Servo City has a whole range of different gear ratios in the same motors, all swappable. I'll be running speed controls on the motors, and can always tune them back for lower speed too. There will be limit switches on the pivots to keep from over-running the travel and locking them up.


These will not be as powerful as hydraulics, but should work out okay, good way to get into this branch of the hobby (I hope) at lower cost to start. I've been in RC boats forever, have plenty of radios, speed controls, and batteries already.


FYI - here are some pics of my last big build (year of research plus two of building), the Marion 91 steam shovel over in Leroy NY, all live steam and working engines (not RC though)



https://i.postimg.cc/MKgNJ7CH/DSC-8432a.jpg


https://i.postimg.cc/NjGff8pp/IMG-5593.jpg

Re: Cat 340D Excavator build
 

More work on the booms, rough cut the top/bottom pieces and have started forming them. The ends will be solid steel milled to shape.


https://i.postimg.cc/vmy48Tcx/IMG-6632a.jpg


The pieces were bent using the bench vise, clamped the end in and bent them by hand, the curves took some finessing but came out pretty close. A little filing on the sides will get the seams to close up.

Re: Cat 340D Excavator build
 

Wow; That Marion Type 91 is very nice! I would like to see it in person someday.
Any build pictures?

Re: Cat 340D Excavator build
 

I did a full build log over on the Model Engine Maker site:


http://www.modelenginemaker.com/inde...ic,7530.0.html


There will be an article series with full plans of the build starting around the end of 2020 in Live Steam/Outdoor Railroading magazine. It will be a long series, for a model like that - 4 double-acting steam engines, gear trains, winding drums, boiler, frame...



The shovel is sitting outside the quarry it worked in from 1906 to 1949 in Leroy NY, on Gulf Road. It is fenced off, so you can only get within about 20 feet of it (I worked with the historical society to get full access to get in and photograph and measure it a number of times to draw up the plans for it). It is the last remaining Model 91 - if you search for it online you will likely see references to it being used on the Panama Canal. NOT true, this one was working in the quarry here before the canal was started, and I've been able to account for where all the ones at the canal went later on. Its in remarkable shape considering that its been sitting out in the open for so many decades, the wood spacer blocks in the boom are half gone but the rest is there, aside from small parts that have been stolen. It was originally on railroad trucks, in 1923 it was converted to crawler tracks using Marions 'kit'. About 75 feet long, over 100 tons, it dug limestone in the quarry for use in railroad beds, roads, and dams.

Re: Cat 340D Excavator build
 

Chris

wow ! I have just been looking through briefly your steam model build thread and I must say the detail is amazing. 3 years in total? how long do you expect the excavator to take?

I think the excavator should be a walk in the park in comparison !


Rob

Re: Cat 340D Excavator build
 

Thanks Rob - the Marion build was in a whole different league than this one, everything was scratch built on the Marion, thousands of parts, this one I am using off-the-shelf parts wherever possible and am not being as minutely fussy with pure scale details. The tracks/sprockets will (initially at least) be RC tank parts, which will save a ton of machining time - can always replace them later with home-made ones. This build will likely be in months rather than years, at least to get it to the point of doing some playing with it. The detailing/refining stage can go a lot longer, but the initial shell and working mechanisms wont be as long (retirement helps timelines a lot!) as the other build, modern sheet metal designs vs older forgings/castings styles helps a lot. This build is sharing time with a 1/4 scale Stanley steam car engine build, so it will go in bursts - right now waiting on some taps/dies on the engine so am working more on the excavator.

Re: Cat 340D Excavator build
 

The two booms are further along, got the four sides bolted together, ready for the steel pivot plates. They are quite rigid, dont think I will need any internal steel framework other than the plates at the pivot points.


https://i.postimg.cc/V62CK3tw/IMG-6633a.jpg

Re: Cat 340D Excavator build
 

More done on the main boom, made up the steel plates for each end which will hold the pivot bearings/rods. They were milled out of 303 stainless bar stock and screwed in place.


https://i.postimg.cc/sXQvSbSd/IMG-6659a.jpg


Still need to do some trimming on the ends.


https://i.postimg.cc/W3Bt7S6D/IMG-6660a.jpg


After that is done, will make up the extension plates at the top of the outer boom that the hydraulic cylinder attaches to, and make up the pivot rod bearings.

Re: Cat 340D Excavator build
 

That's really looking great

Re: Cat 340D Excavator build
 

Wow! very nice!

Kerst

Re: Cat 340D Excavator build
 

Thanks guys! I've been getting the plates for the cylinders to attach with patterned out, hope to get enough together soon to test moving the outer boom with the motor.

Re: Cat 340D Excavator build
 

This is an AWESOME scratch build!

Re: Cat 340D Excavator build
 

Thanks guys!


Got some shop time on the excavator again, made up the plates for the top of the outer boom:


https://i.postimg.cc/0QtFBmsp/IMG-6719a.jpg


Next up is to make the plates that hold the base of the hydraulic cylinders...

Re: Cat 340D Excavator build
 

Got started on the plates to hold the cylinder bases to the booms:


https://i.postimg.cc/BbYGFbk4/IMG-6732a.jpg


Test fitting, needs a little trimming on the mating surfaces and some sanding on the top curves...


https://i.postimg.cc/NGptSCMS/IMG-6733a.jpg


These will get bolted to the booms, then will get started on the pivots.

Re: Cat 340D Excavator build
 

Fabulous looking machine!

Re: Cat 340D Excavator build
 

Your making great progress on the booms ! Have you got plans for the undercarriage yet?

Keep up the good work

Re: Cat 340D Excavator build
 

I've got a slip ring to get the wires down to motors underneath, plan on having a pair of gearmotors to run the tracks. To start with, will use some metal tracks and sprockets that I got from an RC tank that are the right general size, and see how it all works before I take the time to make my own tracks (have done them for other models, a LOT of work!).

Re: Cat 340D Excavator build
 

Got the plates on that hold the cylinders, next will start on the pivot bearings and rods at the joint. Then can start on getting the motor into the boom and give it a real test!


Here it is propped up next to the die cast model I am scaling from:


https://i.postimg.cc/YCwcg2FY/IMG-6741a.jpg

Re: Cat 340D Excavator build
 

Coming along very nicely! Your making rapid progress too

Re: Cat 340D Excavator build
 

Been away from the model for a few days, this afternoon made and installed the pivot bearings/rod to connect the booms together. Nice to see some parts attached and moving! A couple small fasteners, then I can work out the motor mount inside the lower boom to power the cylinder. Actually, that brings up a question - what are the proper terms for the two booms? Lower/Upper, Inner/Outer, Fred/Ethel?? Must be a name for them...


https://i.postimg.cc/DwtYPwD7/IMG-6773a.jpg

Re: Cat 340D Excavator build
 

Crueby:

The curved part is oddly enough called the "boom", the other is called either the "bucket arm" or the "stick". There is sometimes a "thumb" that the bucket can pinch against to pick something up, like your thumb and fore-finger. I have seen REALLY good operators that can pick up a wine bottle and pour a glass of wine with an excavator - and hardly spill any. This thumb can either be fixed, usually at about 90° to the stick which restricts bucket rotation, or it can be hydraulically operated to allow almost normal bucket rotation.

Don

Re: Cat 340D Excavator build
 

Thanks Don!!

Re: Cat 340D Excavator build
 

Those look really sweet. Glad to see you're even doing bushings. Keep up the progress!

I usually hear the arm parts called 'boom' , 'stick' , 'bucket'. I think naming is a carry-over from the design of the cable machines. If you'd rather lower your Fred to get more reach with your Ethel to take a scoop, i'm not going to argue, it's your machine.

Re: Cat 340D Excavator build
 

:lol:

Re: Cat 340D Excavator build
 

Back on the excavator today - I already had some Octura flex cable that I considered for use to connect the gearmotors to the cylinders, but it was too thin and twisted up under load. So, got hold of some of the thicker version, at .187" diameter, That is able to take a much higher force without twisting in either direction, and is still flexible enough for the gentle bends that I need to get out of it. This stuff is very handy, can transmit power without the noise of universal joints. I made up a set of ends for it, enough for all four cylinders, that have setscrews for the cable and the cylinder/motor shafts. Here is one set in place with one motor and cylinder:


https://i.postimg.cc/y6nCMYTV/IMG-6804a.jpg


Here is about where it will sit, inside the boom and extending out to the bottom end of the cylinder:


https://i.postimg.cc/CL1pSTvb/IMG-6805a.jpg


Next I will get the motor mount holes drilled, and also need to make up the final shaft stubs for the clevises on the cylinder ends (been using some temp bits that happened to fit out of the scrab bin). Then I can wire it up to the speed control/radio and give it a real test. If all goes well, will get the other cylinders/motors installed.

Re: Cat 340D Excavator build
 

And another bit done this evening - made the pivots for the cylinder ends, and milled the opening for the first flex shaft (to move the stick). The motor has been mounted, ready for some wiring to test it all. Here is a view inside the boom:


https://i.postimg.cc/44MyD5P4/IMG-6806a.jpg


and where the flex shaft comes out and connects to the cylinder end, to drive the leadscrew:


https://i.postimg.cc/j2Gjyx2n/IMG-6808a.jpg


So, still need to wire up a ESC to the motor and hook up to a channel on the radio, and it will be ready for a trial run to see what kind of force it can put on the booms, and see how the travel time is. I've got some faster and slower gearmotors that I can switch to if needed to dial in the max speed and force on the cylinder. Hopefully it works well enough to continue on without having to change the leadscrew out.

Re: Cat 340D Excavator build
 

Very nice!
Just one question, how are you going to lubricate the lead screws?

Kerst

Re: Cat 340D Excavator build
 

Hi Kerst,


The leadscrew bases are held in with sealed ball bearing units, so that end is good. The screws themselves are polished steel with bronze followers, so they are designed to be able to run dry in the robotics world, but given the loads on the model I figured I would give them a thin coat of CopGraf for good measure. By pulling the crosspin on the tips of the cylinders, the piston can be unscrewed from the leadscrew and removed for access.


Chris

Re: Cat 340D Excavator build
 

will you put shrink tubing on the wires so they look like hydraulic hoses more ? and your doing awesome work :cool:

Re: Cat 340D Excavator build
 

I had not thought of that, nice idea!!

Re: Cat 340D Excavator build
 

Chris:

When you going to introduce these guys to the shop elves?

Don

Re: Cat 340D Excavator build
 

I was hoping they would stay over on the other forum with Zee! :)