PTO Pump

[Dougster]

I timed my 6520 this morning after a quick warm up and at 1700 rpm, it rasied the bucket right at 9 seconds. At 2000 rpm, it raised the bucket right at 8 seconds. I did this 3 times and got the same results. I used my watch. I didn't look at the bucket at all, but felt the bucket hitting the top "stop".

Oh Lordy Lordy! This just adds to the mystery! It still could be either pump! I give up until we get some photos!!!

Dougster

 

[bindian]

Brandi, is there any initial jerkiness as you raise your loader the 1st time after sitting overnite. if so you have a suction side air leak. If not you have the 11.9 pump or, much less likely, a pressure side leak to the sump return or PB line when you are raising the loader.
larry

Larry,
I don't remember any jerkiness. I will see in the morning. Remember I do have the 6520. According to my Ops Manual loader times, everything is fine.
hugs, Brandi

 

[bindian]

Oh Lordy Lordy! This just adds to the mystery! It still could be either pump! I give up until we get some photos!!!

Dougster

Dougster,
You want photos??? I have a lot oif photos of my dog. How many do you want?
I guess I can take the side panels off and see about a photo session. But not Wednesday. It will have to be sometime Friday.
hugs, Brandi

 

[Dougster]

Dougster, You want photos??? I have a lot oif photos of my dog. How many do you want? I guess I can take the side panels off and see about a photo session. But not Wednesday. It will have to be sometime Friday.
hugs, Brandi

Doggies are great!!! Let's see them!

Seriously, I guess I shouldn't assume that you can see the hydraulic pump on other tractors from the outside like you can on mine:

Admittedly, for my own selfish reasons relating to this backhoe performance issue, I'd just like to see this 7520 vs. 6520 pump mystery solved once and for all.

Dougster

 

[Willman]

Just to put my 2 cents in this pump conversation....
Last week I was discussing with my local dealer about what pump is in my 2004 4110 and if the newer pump would be a direct replacment.
He had no idea.
I too would like that 10-15 % more power for the 509 BH.
It just seems to have a slight lack of power now that I really know how to use the BH.

 

[DavesTractor]

Just to put my 2 cents in this pump conversation....
Last week I was discussing with my local dealer about what pump is in my 2004 4110 and if the newer pump would be a direct replacment.
He had no idea.
I too would like that 10-15 % more power for the 509 BH.
It just seems to have a slight lack of power now that I really know how to use the BH.

More volume gives you more speed, but not more power. Higher pressure gives more power.

 

[Dougster]

Just to put my 2 cents in this pump conversation.... Last week I was discussing with my local dealer about what pump is in my 2004 4110 and if the newer pump would be a direct replacment. He had no idea. I too would like that 10-15 % more power for the 509 BH. It just seems to have a slight lack of power now that I really know how to use the BH.

Hi Will - As mentioned earlier, I am not entirely sure that we don't already have the alleged "larger" pump. The fact is that I think they are playing games... perhaps unintentionally and even unknowningly... with the advertised flow hydraulic rating of the 4110.

Here is what I know and don't know. Perhaps someone can fill in some of the gaps: The pump on my October 2004 production Model 4110 is a Joyang Hydrotech Co., Ltd. Model F21 Double Type Pump (feeds hydraulic system and steering through different sections). The hydraulic system feed section is rated at 14.0 cc/pump revolution while the steering is rated at 6.5 cc/pump revolution. Those are theoretical ratings at 100% volumetric efficiency. The pump is good up to 3,000 pump RPM. That much is clear.

Beyond that, things get murky. At various times, Mahindra has rated the 4110's hydraulic system flow at 2,700 engine RPM and at 2,500 engine RPM. At times they have used a conservatively assumed 91% volumetric efficiency and at other times... perhaps now? ...something higher. According to Joyang, the volumetric efficiency of my main pump section, apparently brand new, varies between about 96.5% and 99.0% depending mainly on oil temperature. The volumetric efficiency of the steering pump section, brand new, is slightly lower at between about 92.0% and 99.0%. It is unclear if there is a drive ratio... engine RPM vs. pump RPM... although one can make a good case based on the numbers that it is 1:1. Still, I have been unable to confirm this critical piece of data so far.

Historically, the 3510 appears to have always had one pump size down (in both sections) from the 4110 to save a little power... or at least that appears to have been the original design intent. It is unclear if this design criteria changed over the years intentionally or simply by accident... either physically or just on paper. For years, the published ratings were the same for the main hydraulic pump section for both machines... but different for the steering pump... a very unlikely real world situation if Mahindra had chosen to standardize on one pump. Now, of course, both main and steering section published flow ratings are different for the two machines.

There is other evidence and I could go on, but you get the idea. Based on the actual pump I've got and different operating assumptions and roundoffs, you can make a very good case that my late-2004 already has a 9.5 GPM pump. Or not.

I forgot to check the pumps on the new 2006 and 2007 4110's that I found down at different dealerships in MA and CT. My aging mind was on other tasks those days and I didn't have my camera with me anyway. Never did find a new 3510 to check... and that input is critical to my theory.

This backhoe performance & PTO pump discussion has sparked my interest again... so next time I promise not to be so forgetful. When I learn more, I will publish my results!

Dougster

 

[Dougster]

More volume gives you more speed, but not more power. Higher pressure gives more power.

Hi Dave - Certainly in a static, controls-free, hydraulic model that would be the case... but do we really have a true static model here? I remember asking the original selling dealer (i.e., the owner) about this in regard to possibly buying the PTO pump and he talked about the big increase in speed but also talked about a roughly 10% increase in effective digging power.

I doubt he was an MIT hydraulics professor, but he certainly had plenty of BH seat time & PTO pump-installing experience, so I took that to mean a bit more seat of the pants power... or maybe just more useful power. Even on my 4110 (without a PTO pump)... it seems to me that I can exert a helluva lot more force on an object with the RPMs at 2500 than at 2000. It seems like it's more than just speed. It seems like there's more digging power.

Is there anything to this? Or are we just wishing or imagining it?

Dougster

 

[SPYDERLK]

More volume gives you more speed, but not more power. Higher pressure gives more power.

power is speed times force. So it will have more power even tho no more force at same P with higher flow.

larry

 

[Dougster]

power is speed times force. So it will have more power even tho no more force at same P with higher flow.
larry

A good point. Dave probably meant: More volume gives you more speed, but not more digging force. Higher pressure gives more digging force.

I should have been more careful with terms as well.

Dougster

 

[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