Cat 340D Excavator build - Page 2

ddmckee54 · #1 02-20-2020, 05:35 PM

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 · #2 02-20-2020, 09:43 PM

Thanks Don!!

frizzen · #3 02-20-2020, 09:59 PM

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 · #4 02-20-2020, 10:08 PM

Quote:

Originally Posted by 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 · #5 02-24-2020, 05:00 PM

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:

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

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 · #6 02-24-2020, 07:46 PM

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:

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

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 · #7 02-25-2020, 06:24 AM

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

Kerst

crueby · #8 02-25-2020, 08:04 AM

Quote:

Originally Posted by kerst

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 · #9 02-25-2020, 12:55 PM

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

crueby · #10 02-25-2020, 02:17 PM

Quote:

Originally Posted by jack van

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

I had not thought of that, nice idea!!

ddmckee54 · #11 02-25-2020, 03:45 PM

Chris:

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

Don

crueby · #12 02-25-2020, 04:10 PM

Quote:

Originally Posted by ddmckee54

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 · #13 02-26-2020, 06:57 PM

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 · #14 02-27-2020, 02:07 AM

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 · #15 02-27-2020, 10:27 AM

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 · #16 02-27-2020, 02:46 PM

Quote:

Originally Posted by crueby

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 · #17 02-27-2020, 07:56 PM

Quote:

Originally Posted by ddmckee54

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!