Cat 340D Excavator build

[crueby]

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:





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:





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:





And as assembled into the first full unit:





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

[frizzen]

Great looking leadscrew cylinders!

This will be really cool to watch come together

[Originalrob]

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

[crueby]

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

[crueby]

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

[crueby]

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:

[crueby]

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.

[Originalrob]

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

[crueby]

Originally Posted by Originalrob

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

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)

[crueby]

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.





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.

[9W Monighan]

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

[crueby]

Originally Posted by 9W Monighan

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

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.

[Originalrob]

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

[crueby]

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.

[crueby]

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.

[crueby]

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.





Still need to do some trimming on the ends.





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.

[frizzen]

That's really looking great

[kerst]

Originally Posted by crueby

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)

Wow! very nice!

Kerst

[crueby]

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.

[skeeter]

This is an AWESOME scratch build!