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:


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

[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...


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

[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:


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

[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.


http://listerengine.com/coppermine/albums/userpics/10043/IMG_6631a.JPG

[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]

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)



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


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

[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.


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.

[9W Monighan]

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

[crueby]

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/index.php/topic,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.


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

[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.


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.

[frizzen]

That's really looking great

[kerst]

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

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!

[crueby]

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...

[crueby]

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.

[skeeter]

Fabulous looking machine!

[Originalrob]

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

Keep up the good work

[crueby]

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

Keep up the good work


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!).

[crueby]

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

[Originalrob]

Coming along very nicely! Your making rapid progress too

[crueby]

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

[ddmckee54]

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

[crueby]

Thanks Don!!

[frizzen]

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.

[crueby]

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.


:lol:

[crueby]

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.

[crueby]

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.

[kerst]

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

Kerst

[crueby]

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

Kerst
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

[jack van]

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

[crueby]

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


I had not thought of that, nice idea!!

[ddmckee54]

Chris:

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

Don

[crueby]

Chris:

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

Don


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

[crueby]

Got a chance to wire up the motor and reassemble them boom, to give it a first motion test. This test was done with a 98 rpm gearmotor, I have faster and slower ones to let me dial in the max movement speed. After testing, I dont think I'd want it any slower (its on a speed control on the radio so it will do slower speeds depending on the joystick movement).


https://youtu.be/_X8LaI4TmHg


The intermittant clunking noise when the stick is coming in is the flex cable just rubbing on the edge of the slot in the boom - need to grind back the slot end just a little more. Also, I checked the force it gives, and that seems reasonable (didnt have enough hands to do that on camera, did not have the tripod handy). Overall, happy with it for a first run! Work will continue on the bucket linkages and that cylinder, also need to rig up some limit switches on the movement to keep from over-running the ends of the leadscrew. A little insulation in the boom should knock down the motor noise some too.


:)

[Originalrob]

That’s absolutely amazing ! Can’t believe the progress your making and now I feel like I’m slacking 😂
Are you going to swap the motors out for faster ones and test ?
Looking really good

[crueby]

Hi Rob,


For the stick I am tempted to leave that motor in place, have been online looking at videos of real excavators at work, and the stick speed is about like that. If I go faster, it wont be by much. The bucket speed may need the faster motor. Guess I'll find out when more is together, and see how it all looks working as a system. I need to open the side of the boom up again anyway (sure it wont be the last time! ) to fix the cable rubbing issue and do the limit switch work. Six screws and the side panel will pop off, so that is easy (glad its not painted yet). There is enough room in the boom that I may go up a level on the gearmotor to a stronger one, I think that I have to stick with this size for the bucket motor, the stronger ones wont fit there.


Chris

[ddmckee54]

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

Not a chance, they're like bacteria - they spread. Or was it that they're like 2 year old's and they get into everything - never can keep that straight.

Don

[crueby]

Not a chance, they're like bacteria - they spread. Or was it that they're like 2 year old's and they get into everything - never can keep that straight.

Don

Sounds more like us than the shop elves!

[crueby]

Started in on the mechanisms in the stick, got the motor mounted - tight fit...


https://i.postimg.cc/qgfYVy3m/IMG-6839a.jpg



the opening for the drive cable from the motor to the cylinder:


https://i.postimg.cc/QNBdDD75/IMG-6841a.jpg


and also drilled for the bushings at the bucket end for the linkages:


https://i.postimg.cc/brSMB3sD/IMG-6840a.jpg

[crueby]

Some more work done on the excavator - working on the linkages from the cylinder to the bucket. The side links were milled from flat bar stock on the rotary table:


https://i.postimg.cc/RVy82TZm/IMG-6859a.jpg


The solid link from there to the bucket is being pieced up from a thicker piece of flat bar and two round bars with slots milled in. They will be silver soldered together and then more shaping done.


https://i.postimg.cc/KvRw9WFQ/IMG-6860a.jpg

[crueby]

Got the bearings and rods for the bucket links made...


https://i.postimg.cc/xjMck9XV/IMG-6862a.jpg


and silver soldered up the blank for the end link, ready for further shaping:


https://i.postimg.cc/bNPdk4nD/IMG-6864a.jpg

[crueby]

End of the link shaped...


https://i.postimg.cc/HsWdjJ8n/IMG-6865a.jpg

[crueby]

This morning got the pivot rods threaded and nuts made, and installed the motor in the stick. Here is a quick video of the motion test for the bucket linkage - better get started on the bucket!


https://youtu.be/qg6FHjgabfc

[crueby]

Been a bit since I've made any progress on this build, it is still happening, but I've been focussed on the final parts for my Stanley engine model, should be back on the excavator next week. I got some steel plate for the bucket, need to make up a bending form for the curved center section, then will trace the actual part to cut the sides out. Most likely it will be all silver soldered together since I do not have equipment or the know-how to weld it.

[crueby]

Getting back on the excavator build finally - started with some 3/32" steel flat stock, and bent the center section of the bucket over a wood form. The side plates are rough cut. The parts will be silver soldered together once ready. Still a number of pieces to shape out...


https://i.postimg.cc/Kj3m7Xfp/IMG-6959a.jpg

[crueby]

Got the bucket shell silver soldered up today, and the extra metal on the outside ground off:


https://i.postimg.cc/5NHCyXtc/IMG-6972a.jpg


Next will shape in the open part of the sides, and start adding the plates on the outside....

[crueby]

the side plates going on too....


https://i.postimg.cc/qR2YXJwj/IMG-6974a.jpg


Next up will be the plates on the top to link to the stick, and the plates for the teeth at the bottom...

[skeeter]

That's a nice looking scratch built bucket!

[crueby]

That's a nice looking scratch built bucket!
Thanks Skeeter! Just about to post some new pictures, now that the forum is back up...

[crueby]

Here is a shot of the boom/bucket assembly for the excavator all assembled and ready for the base bracket and lower cylinders.

https://i.postimg.cc/8c4d6h4m/IMG-6984a.jpg
And a shot of it painted. The yellow is actually from rattle cans of Cat paint, they sell it for touchup and repairs, covers amazingly well for a yellow paint. This is one coat. The black is Duplicolor ceramic engine enamel.
https://i.postimg.cc/L52B5yts/IMG-6985a.jpg
Underneath the boom you can see the little die-cast model that I am scaling up from. Next parts are the steel plates that form the framework that the base of the boom attach to, rough cut plates are in the lower left of the photo.

[crueby]

I am getting the base for the booms pieced together - from the weight of the boom assembly, I am wondering if I'll be able to use the same gear motor for it as I did for inside the booms, given how heavy the parts are. Even with the two cylinders, I may need to go to a larger/more powerful motor for this last one, but fortunately there is plenty of room inside the cab block. May wind up with a car seat motor or something like that. Possible that just another gear set will do - the two cylinders need to be kept in sync, so will be driving both from one motor with a line of three gears, motor on the center one. That gear set could be a 2 or 3:1 combination.

[crueby]

Okay, catching up on this side project build - been busy setting up a new computer, and all the time that always takes! Will be better suited for all the CAD work I am doing these days, so well worth the time. Anyway, I got the part in to switch the cylinder pair that holds up the entire boom assembly over to single-start Acme threads vs the original 4-start threads, which were just too aggressive on the movements. Here is the base assembly:
https://i.postimg.cc/d3MrRf2v/IMG-6991a.jpg
Each cylinder has its own drive shaft - in the picture the one on the right has a small drill chuck on it to make it easier to turn by hand. With the new leadscrews I can turn the shaft and lift/lower the booms with just one cylinder and a reasonable amount of force. Before, that was very difficult. The two shaftws will come back to a common drive gearmotor, have not decided if I'll do a gearbox to link them or use a small chain drive (leaning that way at the moment).
Here is a picture showing the entire assembly, bucket lifted off the table - stays there now, before it could spin the leadscrews and lower itself back, which meant that it would have been putting constant strain on the motors.
https://i.postimg.cc/xCNLzQbt/IMG-6990a.jpg
Lots of spare shafts and couplers in the foreground from figuring out the whole thing.
Here is a shot showing the part for holding and spinning the cab - there will be a lot of side force at times, so I wanted a strong way to connect things. Wound up with a spare set of tapered roller bearings from a trailer - figure it will be more than strong enough! The gear will be mounted to the track unit underneath, and a motor drive gear in the cab will engage it and turn the cab. There is a slip ring unit there to take the motor leads for the track drive motors down from the cab to the lower unit, but still allow the cab to turn as many full circles as it wants. The spindle will be home made, hollow unlike a normal car axle end to allow the wires through.

https://i.postimg.cc/90GTLBb9/IMG-6992a.jpg

[crueby]

Got the sprocket assembly for the chain drive started - using some .250 pitch chain and sprockets from Servo City for these, nice fine chain for small spaces but plenty strong. They sell the master links and link pin removal tool too. I am going to use the same chain for the track drives too. So far have the sprockets on hubs, next will make up a support to hold the sprockets. The output of each shaft will go to one of the cylinders on the main boom via a shaft with universal joints. The input will be from a gear motor onto one of the shafts. So, one motor will frive both cylinders at a matched speed and direction.


https://i.postimg.cc/MGZ5S3d6/IMG-6994a.jpg

[skeeter]

It's good to know I'm not the ONLY one that winds up with spare parts left over when doing a custom project!

[crueby]

It's good to know I'm not the ONLY one that winds up with spare parts left over when doing a custom project!

Got a bunch from this one, lots of experiments. Ones that are not reusable wind up as ballast in rc boats.

[crueby]

Few more parts - got the linkages from the ends of the lower cylinders back to the chain drive sprockets made, including a guide rail in the center to keep the u-joints from flopping around. This will only run at slow speeds, running the main boom up and down. Next need to make the holder for the shafts on the chain sprockets and the motor mount...


https://i.postimg.cc/3NKMyTKV/IMG-6996a.jpg

[crueby]

Some more done on the excavator - cut out the outline of the cab floor plate on some aluminum sheet stock, and made up the shafts/holders for the lower boom cylinder drive. While laying things out, realized that I should do the holes for the cab spindle (whatever that is called, the thing the cab spins on over the track assembly) at the same time, save some assembly/disassembly rounds. Here is the floor plate with the parts set on top:


https://i.postimg.cc/jShWdVbn/IMG-6998a.jpg


So, back to Fusion 360 to model up the spindle parts. I bought a trailer wheel bearing kit with 1-1/16" center hole size to use, knowing that regular whel bearings are set up to handle all the side/twisting loads. These should be MORE than strong enough for this purpose! Using the measurements of those parts as a starting point, modeled up the assembly. In all these screen grabs, we are looking at the bottom side of things - the square grey background is the bottom of the floor plate, the track assembly will bolt to the flange at the top of the darker grey 'hub'.


https://i.postimg.cc/5t76Lwjx/Spindle1.jpg


Now, to show things better, some more shots with parts peeled away. Here it is with the hub removed, showing the two bearing races/cups inside. The red spindle is hollow to hold the slip ring for the track drive motors. Sides are smooth, end threaded for the spindle nut.


https://i.postimg.cc/sxSXkqmX/Spindle3.jpg


Spindle with bearings removed:


https://i.postimg.cc/KzCjsxnw/Spindle4.jpg


And the hub itself - the step in the center on the inside goes between the bearings, holding the bearing cups apart.


https://i.postimg.cc/hGPXXCDy/Spindle5.jpg


This is all laid out just like the trailer axle/hub would be, just slightly different shapes to bolt to the cab floor and the track frame. Should work, as long as I didn't forget some important part...

[crueby]

Been some 'boring' days lately, boring out and turning the spindle and hub for the cab rotation bearing assembly. The spindle/hub are steel, the washer and nut are brass (just since I had some offcuts the right size, otherwise would have been steel too). The gear was bored out as well to fit the hub, there will be a gear motor inside the cab by the boom base driving a spur gear against the big gear. The big gear and hub stay stationary with respect to the track frame, and the spindle/cab spin around on that. All fits well, and the hub spins freely without play - no grease in the roller bearings yet, just since it will be handled so much for a while. Here are some pics of the top/bottom of the assembly.


Bottom view, the end with the nut will face downwards in the final assembly.

https://i.postimg.cc/1zjZyJh2/IMG-7001a.jpg


Top view - the inner spindle will bolt to the cab floor.
https://i.postimg.cc/nz9frBnz/IMG-7002a.jpg


With these parts done, now I can lay out and start drilling the patterns of holes in the cab floor for the spindle as well as the boom base and its drive motor....

[crueby]

Getting the floor plate drilled for the mounting screws, and test fitting the parts....


Bottom view:


https://i.postimg.cc/DzQwFZ1R/IMG-7004a.jpg


Top:


https://i.postimg.cc/pT2XdHZr/IMG-7005a.jpg


Need to open up one hole for the base frame, missed that one by a little bit. Then get the spacer block under the motor drilled/installed, and add the angle-aluminum around the rim to hold the cab shell on. The cab is most likely going to be a wood frame clad in thin plywood, set down over the top.

[crueby]

Got some more done on the floor plate, riveted on the angle pieces around the edge to hold the cab in place, and bolted down the motor and boom base parts.


https://i.postimg.cc/W32PD56S/IMG-7007a.jpg


closer look:


https://i.postimg.cc/GttwK9fy/IMG-7008a.jpg


The vertical motor at the lower right of the boom base frame is to turn the cab around on the track base. It will drive this spur gear (once I make the shaft to connect it) against the large gear on the hub. The hub and the large gear will be bolted to the track base.



https://i.postimg.cc/hjpRVV2n/IMG-7010a.jpg

[crueby]

Started in on the framework for the undercariage - this will hold the spindle/hub for the cab on the top, and the tracks out at the lower arms.


https://i.postimg.cc/CLpWWJdc/IMG-7011a.jpg


lots of drilling/tapping later...


https://i.postimg.cc/mkCKP1p3/IMG-7012a.jpg


Still more holes to go to get the lower arms on...

[skeeter]

How come you went with motors, rather than hydraulics to for this excavator? It's still an AWESOME scratch build, but I was curious.

[Mikem]

Skeeter that’s because he is a steam guy and couldn’t find any steam powered hydraulics !

[crueby]

:lol:
Mike is sorta right, not enough room to fit the boiler in the cab!




Actually, its a combination of cost and mess - having seen what happens when a hydraulic line leaks, and I want to be able to run this one around in the house. Also wanted to see if it could be done - kind of a middle ground between the pure hydraulic machines and the plastic-geared 'toy' ones. The gearmotors and leadscrews are an interesting combination, seen them used in some of the builds here (especially in truck dump beds). It seems to have enough power in initial tests, but it could always be converted to hydraulics later on if need be.

[crueby]

More done on the undercarriage - getting it skinned with aluminum sheet. All are roughed in, ready to do final trimming/blending on the edges.


https://i.postimg.cc/cJqFKwLk/IMG-7015a.jpg


The spindle unit is sitting on top - need to bore a large hole in the top sheet so it will sit down on the top sheet.

[crueby]

Bored out the hole for the spindle assembly:


https://i.postimg.cc/3JQf9W0D/IMG-7016a.jpg


and test fit in the base:


https://i.postimg.cc/8PdKYDLX/IMG-7017a.jpg

[Originalrob]

Looking absolutely amazing !
Really impressed with the speed of the build too
Keep up the great work ����

[Zabco]

Very nice work as usual! What is the boring head you are using on your Sherline mill?

[crueby]

Looking absolutely amazing !
Really impressed with the speed of the build too
Keep up the great work ����


Thanks Rob! Got some paint drying on the base parts, hope to start assembling it to the boom tomorrow, then can start wiring up the motors to the speed controls and do some full motion tests, see how the twin cylinders at the base handle the weight of the boom assembly.

[crueby]

Very nice work as usual! What is the boring head you are using on your Sherline mill?
Hi Zabco,


That is an APT boring head - it takes the same 3/8" boring bits as the Sherline, but is a much more rigid and accurate head. The Sherline one just pushes on the moving portion of the head in one direction, so its easy for things to slip when tightening it down. The APT dial moves the head both directions, and there are adjusting screws on the dovetail to tension it all - I've had much better luck with it. They do not make it to match the Sherline headstock threads, so I had to turn down an adapter and mount it in a mill cutter blank holder with a 1/2" hole. Taller than the stock one, but I think it works better. I do have the taller column on the mill, so it can handle the extra height for most parts.


Chris

[skeeter]

Skeeter that’s because he is a steam guy and couldn’t find any steam powered hydraulics !
LOL! :lol:

[skeeter]

:lol:
Mike is sorta right, not enough room to fit the boiler in the cab!




Actually, its a combination of cost and mess - having seen what happens when a hydraulic line leaks, and I want to be able to run this one around in the house. Also wanted to see if it could be done - kind of a middle ground between the pure hydraulic machines and the plastic-geared 'toy' ones. The gearmotors and leadscrews are an interesting combination, seen them used in some of the builds here (especially in truck dump beds). It seems to have enough power in initial tests, but it could always be converted to hydraulics later on if need be.

Very true! The hydraulic machines DO get messy! I believe the operating system you went with is far less expensive than a hydraulic system. For indoor operations, I too wouldn't want a hydraulic machine.

[crueby]

Got the cab/boom assembly bolted onto the track base this morning:


https://i.postimg.cc/8kWn44jH/IMG-7019a.jpg

As expected, needs some counterwieght at the back of the cab to balance out the booms. The cab rotation drive gear meshes okay:


https://i.postimg.cc/WbvYHZZP/IMG-7020a.jpg

Good place to park the die-cast model:


https://i.postimg.cc/kXvY35NR/IMG-7021a.jpg


Next up is to do a bunch of wiring for the radio/speed controls, and I can do some testing!

[Zabco]

That is an APT boring head - it takes the same 3/8" boring bits as the Sherline, but is a much more rigid and accurate head. The Sherline one just pushes on the moving portion of the head in one direction, so its easy for things to slip when tightening it down. The APT dial moves the head both directions, and there are adjusting screws on the dovetail to tension it all - I've had much better luck with it. They do not make it to match the Sherline headstock threads, so I had to turn down an adapter and mount it in a mill cutter blank holder with a 1/2" hole. Taller than the stock one, but I think it works better. I do have the taller column on the mill, so it can handle the extra height for most parts.


Chris
Thanks very much for info. I have a Sherline mill also and really like it but the one accessory they make that I really don't care for is their boring head for the reason you stated. I will have to look into getting one like yours. Keep up the great work, I really enjoy following your builds.

[crueby]

Got enough wired up to do some testing - the bucket and stick motors working well, the motor that drives the two cylinders on the main boom does need an upgrade though - with the weight of the booms and bucket extended out, it is really struggling. So, I need to either add some more gear reduction or swap out to a different motor with some more oomph. Still need to wire up the cab rotation motor and test that one...

[crueby]

Got enough of the wiring done to test things out, and swapped the main boom motor for a slower/stronger one which is pretty close but could be a little faster. Here is a short video testing the different functions out, moving slow so I didn't whack anything on the table and so I could learn which stick did what!


https://youtu.be/xkGL3TcqJPY

[crueby]

Another major assembly almost done - got the track frames/tracks assembled this afternoon, moving quite well. Still some more trim panels and brackets to go on, and need to pull the tracks off one more time to install the drive chains and sprockets on the inside. The chain sprocket on the center of the track drive sprocket is there, but there is another one in the center of the frame that still needs to be fitted. The drive motors will sit on the inside edge of the track frames, under the middle of the cab (one per track). As mentioned early on in the build, these are NOT true scale tracks for this machine, but are re-purposed from a RC Tiger tank model - getting me running a lot sooner, to see how the whole thing functions. They can be replaced later with better scale tracks if I get the time for it.


https://i.postimg.cc/Jnh9Xd9r/IMG-7023a.jpg

[crueby]

More done on the tracks - got the frames painted, chain drives installed, and fit to the frame. Here is a test assembly of the whole thing, will pull the cab/booms off again to turn the track assembly upside down to fit the motors to the bottom. It definitely is more stable now with the extra width and length to the footprint.


https://i.postimg.cc/ncDwXwFJ/IMG-7024a.jpg


https://i.postimg.cc/P5nVYzJ8/IMG-7025a.jpg

[crueby]

Got the motors mounted to the track undercarriage, ready to wire things in...


https://i.postimg.cc/KjQ15yhH/IMG-7028a.jpg

[frizzen]

I like it on those tracks on it, looks kinda like it's set up for extra stability or lower ground pressure

Are the motors running track from center, or does it chain drive to and end sprocket?

[crueby]

Hi Frizzen, there is a chain drive inside the tracks, with a 1/4" pitch bike style chain. Sprocket on the shaft with the motor, chain up to another sprocket on the track drive wheel. The drive wheels were two part castings, so I trimmed one side to make room for the sprocket in the center of the hub. That way the chain is not visible without looking inside. Having the chain inside made for some trade-off with the design of the track road wheels down the length, had to make them a little larger so things would clear.

[crueby]

Got the bigger/stronger gearmotor installed for the main boom raise/lowering, had to rearrange a few things to get it to fit in the cab. It works much better, the original one was barely able to raise the boom assembly. This one could be just a little faster, may swap up to the next rpm range on it (they come in a series of gear ratios). This one is quite a bit longer, so it has to sit sideways in the cab, and have a bevel gear set to attach it.



https://i.postimg.cc/vZRcK2kP/IMG-7030a.jpg


https://i.postimg.cc/ZKvWVz7B/IMG-7029a.jpg


The shop elves are measuring things up to make a rack to hold all the speed controls, they are just temp wired in using some terminal blocks to test things out, want to have them all in a row and the wires neatened up from the current rats nest.



https://i.postimg.cc/pLDpMYtP/IMG-7031a.jpg


https://i.postimg.cc/DznmvJ2L/IMG-7032a.jpg


I was able to test out the crawler track motors, went for a long trip of about 6 inches back and forth on the bench. Looks good there too.

[Originalrob]

Looking great ! your progressing very well and will be digging soon !

keep up the good work :)

[crueby]

Thanks Rob!


I was taking a look at the travel on the bucket, it is not opening up as far as it should, looks like I need to adjust the positions of the links and cylinder a little bit to get the proper travel. The cylinder needs to move up the stick about 1/2", and the pivot hole for the bucket at the end of the stick is a little too far out the bucket, which messes up the geometry somewhat. That hole can be re-drilled farther in towards the upper lip of the bucket and the old hold trimmed off, so that will be easy. The cylinder moving will just need moving the mount holes for the upper brackets, and shortening the flex shaft to the motor. The joys of scaling up from such a small die-cast model!

[ddmckee54]

Chris:

If you move the cylinder are you still going to get the curl on the bucket that you need in the other direction? Don't want to be dropping bits out of the bucket when trying to stack the dirt on top of a tall pile.

I warned you those Shop Elves would weasel their way into this site, told you they were just like germs and that they would spread.

Just don't tell anybody on this site where you've hidden the elves' explosives, or their booze, and you should be OK.

Don

[crueby]

Chris:

If you move the cylinder are you still going to get the curl on the bucket that you need in the other direction? Don't want to be dropping bits out of the bucket when trying to stack the dirt on top of a tall pile.

I warned you those Shop Elves would weasel their way into this site, told you they were just like germs and that they would spread.

Just don't tell anybody on this site where you've hidden the elves' explosives, or their booze, and you should be OK.

Don


Yes - I took the bucket off, and held it to the side of the stick and moved the cylinder piston to both ends to figure out how much to change the pivot points, so it SHOULD be good now. I hope.... Before, the bucket was reaching the furthest-curl-in point with the cylinder only partway out, and would not go to the furthest-open point at all, stopping when the piston bottomed out - this should re-center things. Also, the distance between the pivot holes on the plates attached to the bucket were too far apart, moved them in so that the travel angle is higher. This should make it match the real machine closer, I had mis-measured things initially and did not understand the geometry of how the movement worked.


I have the changes made, and the parts have been given a respray to coat the new cut edges. Tomorrow will be able to reassemble and test the movement again. In the meantime, started making the rack that will hold all the speed controllers for the motors in a neat row. The rack is plywood, with notches cut in on the sides for the ESC's to slide into. The sides are glued up on a baseboard, when that sets up I can drill mounting holes to screw it to the cab floor plate and start the wiring.

[crueby]

Some more progress to show - the wiring is pretty much done, still want to bundle up some of them but all is functional. Re-tensioned the tracks, since it was fine when the drive wheel was pulling the tracks from underneath, but going in the other direction where it was pulling the tracks over the top, the plates were bunching up as they went under the track rollers - just needed another 1/8" of movement outwards on the idler wheels. Also started in on the cab - making it out of a thin ply skin and shaped wood formers for where it angles in at the top, plus ply frames around the back:


https://i.postimg.cc/tT2p0xCX/IMG-7034a.jpg


Next steps will be to add the inner walls and top panels, then can start on the operators cab.




On the background project, have gotten a lot done on the Mann Steam Wagon - 3D CAD model is pretty much done, and I've decided on a 1:8 scale for that build, with a 3" diameter gas fired boiler. The 3D model was done at full-size dimensions, will make a copy of it and scale it down to 1/8, then start generating the 2D drawings for the parts. Here is a screen capture from Fusion:


https://i.postimg.cc/dtMvbwJZ/3-D-model-1.jpg




https://i.postimg.cc/TYrGGFP7/3-D-model-2.jpg

[ddmckee54]

How do you work that fast in Fusion? Is it practice, practice, practice? Fusion still feels slow and confusing to me, but then I really haven't logged that many hours in it yet - only a few.

I'm used to Autocad 2D, and most of the 3D work that I do is in Designspark3D. At the time I was first learning 3D CAD, that was easier to understand than Fusion 360. Still is, but I know it's not nearly as powerful as Fusion 360.

Don

[crueby]

How do you work that fast in Fusion? Is it practice, practice, practice? Fusion still feels slow and confusing to me, but then I really haven't logged that many hours in it yet - only a few.

I'm used to Autocad 2D, and most of the 3D work that I do is in Designspark3D. At the time I was first learning 3D CAD, that was easier to understand than Fusion 360. Still is, but I know it's not nearly as powerful as Fusion 360.

Don
Hi Don,

Yes, I have been getting a lot of practice in Fusion, first started using it a few years ago for my Lombard log hauler model, then for the Marion steam shovel which was a huge project, plus several rc submarine and small engines. I never used any CAD programs before, which may have helped with nothing to unlearn on other workflows. I only use it for modeling and drawing, don't use any of the other functions. With all the practice it does feel intuitive now, at first was very confused till I watched some of thier tutorials. Doing as much as possible in sketches then extruding or rotating helps a lot since changes to the sketch get propogated forward to the parts. I still run into problems now and then, some bugs, but overall I really like it.

[skeeter]

Great job with the excavator. The steam truck will be phenomenal when you get it finished!

[crueby]

Great job with the excavator. The steam truck will be phenomenal when you get it finished!


Thanks Skeeter! Between sessions of gluing/waiting for glue to dry/painting/waiting for paint to dry/repeat on the excavator cab, I've started generating the 2D drawings from the 3D CAD model of the Mann truck. LOTS of sheets, LOTS of dimensions to place. Once that model starts the build log will be over on the Model Engine Maker forum, where I've done most of my other steam models.


More to show soon on the excavator, as the cab comes together. I'd be playing with it in a pile of sand by now, but I am waiting on some electrical bits for the radio system. Turns out that having this many ESC's on one receiver is an issue - there is some interference and possibly ground looping between them. Found out this is a known issue with the Mtroniks ESC units, they have made an opto-isolator unit for them, which plugs inline with the radio lead, that goes from electrical wire/signal to an optical signal and back again, that both boosts and isolates the signals and eliminates the cross talk. What I was seeing was once I had at least four ESC's all plugged in there motors would start glitching, even if only one was turning at a time. Any three ESC's in any three channels, no problem at all. Tried different radios (different brands too), same thing. So, got a handful of those on order, but it may take a little while since they are coming from England to the US. Will continue on the cab for now...

Chris

[avel]

I love these self built machines. Always amazed at what people can build at home. Looking good.

[crueby]

Going to call this one just about done, and start playing with it! Got the last of the wiring bundled up and out of the way so the cab would go on, and set up the radio. Just need a lot more practise to train myself which lever does what in which direction. Here is a video of the first digging run, using a mortar mixing tub and some 'scale gravel' (AKA kitty litter - NEW, assuming the shop elves didnt do anything nasty in it).


https://youtu.be/oimbHLx2Kkk


And a couple photos of where it stands:


https://i.postimg.cc/gkp3XFB7/IMG-7079a.jpg




https://i.postimg.cc/kgX8sNCF/IMG-7083a.jpg


Elfric at the controls:
https://i.postimg.cc/hP0TVykt/IMG-7082a.jpg