Stupid Question of the Day

[Copenhagen]

Ok fellas, I need some help wrapping my brain around this one.

How does the hydraulic fluid get from the pump to the track motors of an excavator?

I had a new guy ask that question today and I had no answer for him. It is something I have never really thought about.

Since you have unlimited 360* swings, there are obviously no hoses. I'm lost on this one.

Thanks

 

[heavylift]

center swivel ..It's in the center with lots of hoses running into it

 

[heavylift]

center swivel

 

[Andy1845c]

I'll admit to wondering the same thing.....

Didn't some of the older machines run out of swing and engage the track motors to keep turning in the desired direction?

 

[[-Agent-]]

I'll admit to wondering the same thing.....

Didn't some of the older machines run out of swing and engage the track motors to keep turning in the desired direction?

That could get dangerous if you were on top of a pile or something and didn't know you were going to run out of swing, track you right off the top.

 

[JimBruce42]

center swivel

Seems like a very good question to me... and after looking at heavylift's photo, I gotta admit... I'm still confused:beatsme

 

[bill onthehill]

Think of it as 4 grooves in a flat plate with seals that slide on the plate. Each drive has fluid passing through 2 grooves to the lower chassis and out to the drive motors. Each groove carries the fluid for one direction of movement. This allows the machine to move it's tracks regardless of the house position or where the dipper is at. They all rotate around a center pivot shaft and the rotation is driven by slew motor turning a gear that turns the house using a ring gear similar to a starter and a flywheel. When they leak at the seals it is a job to repair.

 

[heavylift]

It's like a bar stool ...top spins...bottom stay put..... the hose are attached to the top.. then the are a bunch of oil grooves and o-rings , bearings. it transfers fluid thru the grooves to the bottom stationary part(while it rotates or stationary) with the various ports exiting the bottom, sends the fluid where it goes....

 

[[-Agent-]]

So the valves for the specific directions are in the under carriage, so all this thing is doing is sending pressurized oil down there, not controlling anything?

 

[JimBruce42]

I believe I get it now, and the valves are up in teh housing with the rest of the valves, all that they do is control which direction the oil flows into and out of the final drives... which are basically hydraulic motors.

 

[[-Agent-]]

I believe I get it now, and the valves are up in teh housing with the rest of the valves, all that they do is control which direction the oil flows into and out of the final drives... which are basically hydraulic motors.

But there are two motors, so wouldn't there need to be 4 lines running down? So that each motor can run independently? I'm still confused.

 

[ForsytheBros.]

Does a scenario ever develop in worn out seals where the grooves "short circuit" and erroneous flow pressures develop?

 

[spitzair]

This is how it works as far as I know... You have a rotating and stationary component. The inner upper unit in my example here is attached to the upper structure and rotates with it (Dark grey) while the outer lower unit (light grey) is fixed to the lower structure of the machine. Machined all around the inside diameter of the lower unit are groves that match up with a port from the upper unit. You can have as many circuits as you like going through depending on the size of the rotating assembly... On most excavators it's 5, 2 for each motor and a case drain. On minis you also have the circuit for the blade... Somebody please correct me if I'm wrong but I'm pretty sure this is how it works...
Hope it helps.

 

[[-Agent-]]

Thanks for the drawing, I see how it works now. That is actually a brilliant design.

 

[willie59]

Somebody please correct me if I'm wrong but I'm pretty sure this is how it works...
Hope it helps.

Wow spitzair, helluva good drawing bro! :notworthy

And your spot on man, that's pretty much what it looks like inside.

And yes ForsytheBros., if the seals fail internally, you would get a "short circuit" effect.

 

[John C.]

On a tracked machine there is an extra passage for two speed travel making six the normal swivel. There are swivels with even more passages and some with a hollow center for an air swivel and electrical swivel as well. Rough terrain cranes are an example.

Really nice drawing!

 

[Copenhagen]

Thanks for all of the replies fellas. I was still confused until I saw the drawing. The design of those are surprisingly simple yet extremely complex.

Thanks again!

 

[willie59]

There are swivels with even more passages and some with a hollow center for an air swivel and electrical swivel as well. Rough terrain cranes are an example.

Oh jeezzz, don't remind me of that John C. I once had to pull the swivel out of a P&H T300 hydrocrane which have only a lower engine. Four Vickers Vane pumps up front to deliver oil up 4 BIG lines connect to the swivel directly above the front tandem stump. Electrical collector ring hanging off the bottom of it with a bunch of rings. Outriggers were controlled by toggle switches in the upper cab sending voltage to the valves on the lower frame. Then you had power and ground to upper, ignition, start, shutdown, and all the gauges and warning lights. Lastly an air swivel right up the center for the air throttle. That thing was an absolute PITA to work on. On top of bad seals, it also had electrical issues from years of shadetree electrical repairs, so I basically decided to re-do the connections in the collector ring. Had wires hanging down under the machine, a pile of wires. Was off on a field job, returned to find one of the other mechanics had moved the rig. Yep, u-joint yoke on front of the front tandem got a hold of the pile of wire and made holy hell out of it. Like I needed more work to do on that thing. :Banghead

 

[OCR]

Stupid Question of the Day:

Wow spitzair, helluva good drawing bro! :notworthy

And your spot on man, that's pretty much what it looks like inside.

And yes ForsytheBros., if the seals fail internally, you would get a "short circuit" effect.

Yes, that is a good drawing... :thumbsup

And when the seals start to fail, that can equate to weak travel power...

And, I need to get ours fixed again, thank you very much... lol


OCR...

 

[willie59]

And, I need to get ours fixed again, thank you very much... lol


OCR...

Ok...what's the story with that?