Author Topic: Excavator side project  (Read 5711 times)

Offline crueby

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Excavator side project
« on: March 26, 2020, 05:33:51 PM »
After my Stqanley engine build finished, I went full(er) time on the RC model of a Cat 340D excavator, which I was documenting over on the RC Truck  & Construction forum. But, this past week that site seems to have gone into isolation in a cave somewhere, so thought I'd put the occasional photo up here at major milestones. The 3D CAD model of the Mann Steam Waggon is going on in the background too, will start a thread on that when it gets to metal cutting stage.
Anyway, here is a shot of the boom/bucket assembly for the excavator. The booms are aluminum with steel fittings, the bucket is steel. It is 1:14 scale, with gearmotors and leadscrews making the cylinders work rather than true hydraulics. For size reference, there is a 6 inch ruler on the table in the foreground. This will be a big-un. With the gearmotor drive, it will be able to dig loose soil/sand, not as powerful as with real hydraulics but this is both a LOT cheaper and without the horrible mess if a line leaks hydraulic fluid at high presssure.


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.

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.

Offline mnay

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Re: Excavator side project
« Reply #1 on: March 26, 2020, 06:13:59 PM »
that is cool!  keep us posted

Offline Vixen

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Re: Excavator side project
« Reply #2 on: March 26, 2020, 06:18:01 PM »
Hi Chris,

That looks fascinating. Are you able to give some details of the gear motor/ leadscrew 'hydraulic' actuators? They sound exciting.

Mike
It is the journey that matters, not the destination

Offline crueby

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Re: Excavator side project
« Reply #3 on: March 26, 2020, 06:37:09 PM »
Hi Chris,

That looks fascinating. Are you able to give some details of the gear motor/ leadscrew 'hydraulic' actuators? They sound exciting.

Mike
I have some gearmotors and leadscrews from ServoCity.com, Actobotics brand. Got a few sizes of their Standard Duty/Economy gearmotors, they are available in a range of speeds, the slower the stronger. Picked them for size, only about 1" diameter so they fit inside the booms. They drive a Octura flex shaft to the leadscrew inside the cylinder. The leadscrews are 6mm, 4-start threads, with matching followers. I designed up the cylinders using those parts:


The center teal is the leadscrews, with the red holder on the lower left end. That rides in ball bearings, yellow and purple, with a light green base piece. The tubes are DOM steel tube, with the moving end (blue) attaching to the part to be moved. They seem to work pretty well, will know for sure when the base is done and I can run it for real - done motion tests with the subassemblies and it seems strong enough. Power comes from a 12V NiMH battery, each of the six motors will have its own speed control unit and be on a separate radio channel. Channels: bucket, outer stick, main boom, cab rotate, left track, right track. The metal tracks/sprockets are from RC tanks for now, may make my own later on.

Here is a video clip I did a while back with a motion test, done with a 98rpm gearmotor. I have others faster and slower, can swap them to dial in the max travel speed vs torque.


Offline awake

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Re: Excavator side project
« Reply #4 on: March 26, 2020, 06:54:24 PM »
Very nice! A slick way to recreate the look of the hydraulics without the mess.
Andy

Offline Vixen

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Re: Excavator side project
« Reply #5 on: March 26, 2020, 07:32:33 PM »
Hi Chris,

Those servo actuators look very realistic and actuate realistically as well. I guess the size of the gearmotors set the scale for the whole excavator.

Mike
It is the journey that matters, not the destination

Offline crueby

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Re: Excavator side project
« Reply #6 on: March 26, 2020, 08:06:00 PM »
Hi Chris,

Those servo actuators look very realistic and actuate realistically as well. I guess the size of the gearmotors set the scale for the whole excavator.

Mike
Yeah, the scale was picked to match what most of the 'fleet' (herd?)  is at places like Cabin Fever's dirt pile, lots of detail parts, trucks, etc available at that size. I did have to widen the stick boom slightly to fit the cylinder parts in.

Offline crueby

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Re: Excavator side project
« Reply #7 on: March 26, 2020, 08:08:04 PM »
Very nice! A slick way to recreate the look of the hydraulics without the mess.
After seeing one with the real hydraulics at a show that sprung a hose, it was an easy decision! That and the cost of the hydraulics - wow. Amazing how small they can make them and how much power they get, though. This way wont be as strong, but should be fun to play in the sandbox with. Burying misbehaving shop elves....  :LittleDevil:

Offline vcutajar

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Re: Excavator side project
« Reply #8 on: March 26, 2020, 08:25:19 PM »
What a really awesome project.  I always wanted to do something like this but always ended up deciding it would be too complicated for me.
Keep it up Chris.

Vince

Offline Brian Rupnow

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Re: Excavator side project
« Reply #9 on: March 26, 2020, 08:52:44 PM »
Great project Chris. I did a six month design contract for a local company that rebuilds/refits excavators and bulldozers. Got to know all the good stuff about digging buckets versus ditching buckets, root rippers and loader buckets and cast replaceable teeth. There is an entire world of knowledge about these machines that the average person never comes into contact with.---Brian

Offline crueby

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Re: Excavator side project
« Reply #10 on: March 26, 2020, 08:56:03 PM »
Great project Chris. I did a six month design contract for a local company that rebuilds/refits excavators and bulldozers. Got to know all the good stuff about digging buckets versus ditching buckets, root rippers and loader buckets and cast replaceable teeth. There is an entire world of knowledge about these machines that the average person never comes into contact with.---Brian
I went to Cat's website a while back for pictures and specs, was amazed at how many bucket options there are. Lot more than the Big or Bigger that I was expecting!

Offline crueby

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Re: Excavator side project
« Reply #11 on: March 26, 2020, 08:58:46 PM »
What a really awesome project.  I always wanted to do something like this but always ended up deciding it would be too complicated for me.
Keep it up Chris.

Vince
Thanks Vince, there are so many off the shelf robotics parts now, really helps these kind of projects. The organizations like FIRST have really driven demand and options.

Offline gbritnell

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Re: Excavator side project
« Reply #12 on: March 26, 2020, 09:49:51 PM »
Man O man it's hard to keep up with you Chris! Looks like another great project.
gbritnell
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Offline awake

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Re: Excavator side project
« Reply #13 on: March 27, 2020, 12:05:10 AM »
Very nice! A slick way to recreate the look of the hydraulics without the mess.
After seeing one with the real hydraulics at a show that sprung a hose, it was an easy decision! That and the cost of the hydraulics - wow. Amazing how small they can make them and how much power they get, though. This way wont be as strong, but should be fun to play in the sandbox with. Burying misbehaving shop elves....  :LittleDevil:

Hmm ... now that you mention it, a leaking hydraulic hose would be slick, too ... in a different and quite unpleasant way!
Andy

Offline JC54

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Re: Excavator side project
« Reply #14 on: March 27, 2020, 01:53:29 PM »
Thanks for putting this thread together Chris. I had tried to access the other site with no joy at all. Keep it coming.    John  :old: :DrinkPint:
When the Fun Stops,, Stop!