PTO Pump

[bindian]

Wow....this is too much after spending all night in a wheel well changing out a chafed Skydrol hydraulic line. Let me see if I got it right. More pressure gives us more digging power. More rpm up to point (when the pressure relief valve opens), gives us more pressure. So all we need to do is put a pressure guage just in front of the system relief valve to make sure we are hitting max pressure at different rpm settings. Right?
hugs, Brandi

 

[Dougster]

Wow....this is too much after spending all night in a wheel well changing out a chafed Skydrol hydraulic line. Let me see if I got it right. More pressure gives us more digging power. More rpm up to point (when the pressure relief valve opens), gives us more pressure. So all we need to do is put a pressure guage just in front of the system relief valve to make sure we are hitting max pressure at different rpm settings. Right?
hugs, Brandi

Time for you to go get some sleep. It will all make more sense on a clear head.

Dave is right that more deliverable system pressure will increase digging force (i.e., actual pounds force applied at any point by the BH). Larry is right that more RPM's... and therefore more hydraulic flow... and therefore more backhoe working speed... together with full hydraulic system operating pressure will increase digging power (total power/energy output by your backhoe inputted into your work task). Remember that digging force all by itself doesn't do any work. There must be motion/movement to produce work and get your project completed!

But beyond that, things get complicated by the nature and controls of an open center hydraulic system wherein system flow remains essentially constant at a given pump RPM but system pressure varies with load from system backpressure only up to the full relief valve setpoint. Things get even more complicated when you add in system relief valve crack setpoint (which is usually somewhat lower than the full flow relief setpoint) and integral spool relief setpoints and backhoe relief and bypass valve setpoints.

Essentially what you want is to assure that your backhoe is realizing full tractor (or PTO) hydraulic system operating pressure (or full backhoe subsystem design pressure, if lower) and the optimum or maximum flow possible to the backhoe before the backhoe's bypass valve opens and starts dumping flow.

A PTO pump could not only deliver more hydraulic flow... but could also deliver more pressure if the tractor hydraulic system's operating pressure is somewhat below the design pressure of the backhoe. The 509/511 backhoe's design pressure (relief valve setpoint) is 2,500 PSIG. By comparison, the published operating pressure of my 4110 is 2,400 PSIG and I'm sure the relief valve crack setpoint is somewhat lower.

Dougster

 

[Tim_in_IA]

Wow....this is too much after spending all night in a wheel well changing out a chafed Skydrol hydraulic line. Let me see if I got it right. More pressure gives us more digging power. More rpm up to point (when the pressure relief valve opens), gives us more pressure. So all we need to do is put a pressure guage just in front of the system relief valve to make sure we are hitting max pressure at different rpm settings. Right?
hugs, Brandi

I think a pressure gauge is a great idea. Now I need to install one on the tractor side and on the pto pump side. Might help me troubleshoot my loader controls and 3pt as well.

 

[SPYDERLK]

I think a pressure gauge is a great idea. Now I need to install one on the tractor side and on the pto pump side. Might help me troubleshoot my loader controls and 3pt as well.

ihave mine gauged. its plumbed directly from the output fitting at the pump using 1/4 hose with a critical orifice installed at the pump end of the hose. Always tells me what pressure the pump is working against. The 7520 tractor relief is set at 2690. Loader and BH are at 2500. Worth 10x the $25 investment to be able to view these specs in action.
larry

 

[bindian]

I should be asleep now, but I want Dougster to exhale that breath he has been holding. Besides, my weekend started at 0700 this morning. I went to see my parts guys today and got the number for a 6520 4WD hydraulic pump. It is 007202366D91. While he was looking up the number for the 7520, I was telling him why I needed both numbers. Well, the computer heard me talking and well, it wasn't pretty.....................it locked up. So we had to go to another computer and the hydraulic pump number for a 7520 4Wd came up as 000013797P04.
I will try to take photos tomorrow, but might be overruled as I brought home a 20 foot length of black plastic corrigated culvert in the 24 inch roundness that wants to get buried and it might make me forget the photo session.
niteynitehugs, Brandi

 

[Dougster]

I should be asleep now, but I want Dougster to exhale that breath he has been holding. Besides, my weekend started at 0700 this morning. I went to see my parts guys today and got the number for a 6520 4WD hydraulic pump. It is 007202366D91. While he was looking up the number for the 7520, I was telling him why I needed both numbers. Well, the computer heard me talking and well, it wasn't pretty.....................it locked up. So we had to go to another computer and the hydraulic pump number for a 7520 4Wd came up as 000013797P04. I will try to take photos tomorrow, but might be overruled as I brought home a 20 foot length of black plastic corrigated culvert in the 24 inch roundness that wants to get buried and it might make me forget the photo session.
niteynitehugs, Brandi

Thanks Brandi! Please go get some sleep! In the end, I'm convinced that only photos and information read right off the pump will tell us the real story.

Dougster

 

[bindian]

I'm convinced that only photos and information read right off the pump will tell us the real story.

Dougster

Dougster,
I didn't see any markings or numbers or even letters on the pump. Until I looked at the photos and saw photo 6. I even got my inspection mirror and flashlight to look. I might have to take the bracket off to see if any more markings are on it.
I noticed a grease fitting just behind the pulley. You can see it in photo 2 real good. My Ops Manual doesn't say anything about putting grease there. Can anyone tell me if and when we need to grease it? Photos 7 & 8 shows the bottom of the pump with a plug. Is this another port?
hugs, Brandi

 

[bindian]

Okay...........here are photos 1, 2, & 3
hugs, Brandi

 

[Dougster]

Dougster, I didn't see any markings or numbers or even letters on the pump. Until I looked at the photos and saw photo 6. I even got my inspection mirror and flashlight to look. I might have to take the bracket off to see if any more markings are on it.

Thanks Brandi! Well, it is clearly an Eaton brand hydraulic pump. Now the question is... Which One???

If there are no other external markings, I may need a few key dimensions to match it up... unless someone here with a 7520 can confirm or deny that this is a 7520 pump.

Dougster

 

[SPYDERLK]

Brandi, it appears to be an identical cross section but shorter pump than the one on my 7520. Mine is 9.5" from boltface to the outside surface of the cover on the PS end. Yours looks to be about an inch less, all in the 1st section. I will post pictures soon.

That grease fitting services a set of tapered roller bearings supporting the shaft that couples to the pump and to the output pulley. They are sealed so wont need much grease. Due seal orientation, overgreasing will push past the inner seal w/o damage, into the engine oil. Id say give it 3strokes to make sure its greased - then 1 stroke whenever you feel like its been awhile.
larry