PTO Pump

[Dougster]

Don't know if this would be helpful or not but there is a new group for hydraulics on this site. Can't wait to see what people dream up in there.

Well Tim, the funny thing is that the MadReferee, God rest his soul, answered and pretty much resolved all of my most basic tractor hydraulics questions long ago. Other than brand-specific stuff... such as this thread... I'm wondering what more can be covered there that hasn't already been discussed a hundred times?

Mad pretty much had everything and everyone in need pretty much covered!

Dougster

 

[bindian]

Seems that is the case... 11.4 GPM at 2,500 engine RPM by spec (with RPM basis also confirmed by Larry's tests).

The bad news is that you didn't get a free 7520 pump upgrade. The good news is that your 511 is operating flawlessly and entirely as one should expect.

At 1,700 engine RPM, using spec or values derived from Larry's observed test results, you were running somewhere between 7.1 and 7.8 GPM... well below the Bradco specified 9 to 12 GPM range. When you increased up to 2,000 engine RPM, you were running somewhere between 8.1 and 9.1 GPM... at best just barely breaking into the Bradco specified range.

Time for either more engine RPMs... or a carefully selected PTO pump that would allow full backhoe flow... up to the 14 GPM bypass valve setpoint... at your desired lower engine RPM point.

Of course, you could always backfit in a 7520 pump!

Dougster

Unless I find a rather large reservoir to fit around the PTO pump, Frame mount and BH, I would default to a 7520 pump if and when I need a new pump.
I can't wait to rev up to 2500 rpm. About 8 more hours!
hugs, Brandi

 

[Dougster]

Unless I find a rather large reservoir to fit around the PTO pump, Frame mount and BH, I would default to a 7520 pump if and when I need a new pump. I can't wait to rev up to 2500 rpm. About 8 more hours!
hugs, Brandi

Of course, I would *kill* to have 11.4 GPM at 2,500 RPM... but that's just me!

I do understand your distaste for running at sustained high RPM. It's awfully noisy, generates a lot more heat... and is wasteful in the sense that you are only *using* a small portion of all that fuel being consumed and power being generated. It will be interesting once you do increase RPM (after 100 hours?) to see where you end up settling... i.e., will 9 or 10 GPM be enough to make that 511 hum? Or will you want to give it everything its got to give???

Upgrading to the 7520 pump would probably neither be a cheap nor a simple drop-in. The suction and discharge ports will have moved enough so that your 4 lines will have to be "adjusted" as well. Could take some reworked or 7520 parts. Still, one would think it would add more overall tractor value and be a lot more user friendly than a PTO pump. I'll bet it would cost a lot less from an Eaton Pump dealer than from a Mahindra dealer. And naturally, you would have to consider the tractor warranty issue. That one issue alone could drive you to a PTO pump if more flow at a lower RPM level is still desired. Or could a 7520 pump be installed by a Mahindra dealer and still leave the warranty intact? Hmmmmm...

Of course, as an aircraft mechanic, you probably have access to all sorts of contacts & resources and could probably relocate those hydraulic lines faster than I can check my oil! Very cool.

Dougster

 

[bindian]

Of course, I would *kill* to have 11.4 GPM at 2,500 RPM... but that's just me!

I do understand your distaste for running at sustained high RPM. It's awfully noisy, generates a lot more heat... and is wasteful in the sense that you are only *using* a small portion of all that fuel being consumed and power being generated. It will be interesting once you do increase RPM (after 100 hours?) to see where you end up settling... i.e., will 9 or 10 GPM be enough to make that 511 hum? Or will you want to give it everything its got to give???

Upgrading to the 7520 pump would probably neither be a cheap nor a simple drop-in. The suction and discharge ports will have moved enough so that your 4 lines will have to be "adjusted" as well. Could take some reworked or 7520 parts. Still, one would think it would add more overall tractor value and be a lot more user friendly than a PTO pump. I'll bet it would cost a lot less from an Eaton Pump dealer than from a Mahindra dealer. And naturally, you would have to consider the tractor warranty issue. That one issue alone could drive you to a PTO pump if more flow at a lower RPM level is still desired. Or could a 7520 pump be installed by a Mahindra dealer and still leave the warranty intact? Hmmmmm...

Of course, as an aircraft mechanic, you probably have access to all sorts of contacts & resources and could probably relocate those hydraulic lines faster than I can check my oil! Very cool.

Dougster

They are called braided stainless steel flex lines. We use them for temporary lines until hard lines can be installed. Just need a few adapters to plumb a longer pump. I would hope my current pump outlives my 3 year warranty. While waiting on my son's car cylinder head to get pressure tested yesterday, I got to dig some dirt up for a new culvert........no stumps and roots. At 2000 rpm I had the BH dancing, hoeing up large heaping buckets of sandy loamy clay. I dug till dark and hope to contnue the dance practice tomorrow afternoon. For digging in dirt not near a stump.........I would love a 36 inch bucket.
hugs, Brandi

 

[Dougster]

They are called braided stainless steel flex lines. We use them for temporary lines until hard lines can be installed. Just need a few adapters to plumb a longer pump. I would hope my current pump outlives my 3 year warranty. While waiting on my son's car cylinder head to get pressure tested yesterday, I got to dig some dirt up for a new culvert........no stumps and roots. At 2000 rpm I had the BH dancing, hoeing up large heaping buckets of sandy loamy clay. I dug till dark and hope to contnue the dance practice tomorrow afternoon. For digging in dirt not near a stump.........I would love a 36 inch bucket.
hugs, Brandi

See, I knew you had some sneaky way to make it work... ...but can those braided lines be used on the suction side too?

And if you are satisfied at 2,000 RPM with the 36 inch bucket... running somewhere between 8.1 and 9.1 GPM I figure... imagine how well you will do at full RPM and 11.4 GPM with that 12 inch bucket! Those stumps better run for cover!

Dougster

 

[SPYDERLK]

See, I knew you had some sneaky way to make it work... ...but can those braided lines be used on the suction side too?

And if you are satisfied at 2,000 RPM with the 36 inch bucket... running somewhere between 8.1 and 9.1 GPM I figure... imagine how well you will do at full RPM and 11.4 GPM with that 12 inch bucket! Those stumps better run for cover!

Dougster

Not sure where you get the 9gpm flow figure at 2krpm. The ML275 uses 10.327 Gpm to raise in 8sec, which is the time Brandi reported.
larry

 

[Dougster]

Not sure where you get the 9gpm flow figure at 2krpm. The ML275 uses 10.327 Gpm to raise in 8sec, which is the time Brandi reported.
larry

A very good point Larry... but entirely inconsistant with the "11.4 GPM at 2,500 RPM" specification for the 6520 and adjusting using either your experience or generic gear pump curves. Something is fishy somewhere. Look at your own results at 2,000 RPM (i.e., 7 seconds, 11.9 gpm) and tell me with a straight face that her pump is putting out just 13.2% less than yours when your pump is 49.1% bigger. Remember, these are essentially identical pumps (on near identical tractors) except for gear length/displacement.

Incidentally, I tried doing my own quicky FEL flow tests yesterday on my ML112. All your numbers had gotten me interested. I could not resist! But all I can say is that without a second person holding a stopwatch, I was screwed. So many variables and no repeatability. No way I could measure accurately with a sweep second hand while running the loader myself. I was searching for a difference of just 0.72 seconds... and it was impossible.

Fully acknowledging that I am old and fuzzy... I *still* can't tell whether I've got a 7.87 or 9.5 GPM pump. Tach bias error aside, I am just not that good.

Dougster

 

[dfkrug]

Incidentally, I tried doing my own quicky FEL flow tests yesterday on my ML112. All your numbers had gotten me interested. I could not resist! But all I can say is that without a second person holding a stopwatch, I was screwed. So many variables and no repeatability. No way I could measure accurately with a sweep second hand while running the loader myself. I was searching for a difference of just 0.72 seconds... and it was impossible.

I agree it is hard to make an accurate speed measurement of the FEL
rising or the hoe dipper extending. I made this measurement at several
engine speeds for my hoe.

Furthermore, as was pointed out, the wall thicknesses of hyd cyls
vary a lot and without a measured ID, you don't know what it is. The
most common size I have measured is about 0.2". If the walls are
even 10% thicker, the cyl volume drops significantly.

 

[SPYDERLK]

Dougster Yes, there are too many variables. Thats why I have been asking for the specs on the pump. It started back when I noticed mine took 8-9 sec to go up at full rpm- my hi idle indicates a hair over 2500 and holds 2500 during lift. Now, after meticulously rebuilding the suction line, I am satisfied that I am pumping real close to 17GPM at full RPM. This doesnt mean I dont want the pump specs, because with MAHINDRAS unreliable knowledge of the product, shown thru their misspeced ads and lack of authoritative information that can be proven correct, I could easily with a straight face think Brandis was putting out closer than expected to what mine is. Since I saw mine being rebuilt after the cam gear broke due to thrust loading from the helical tooth profile driving the heavy pump load, I know that pump speed on the 7520 is 1.09 engine speed. On the 6520 it may not be the same. The 6520 pump may not be as much smaller as we expect. The pumps may be rated by the pump manufacturer at a different rpm and quoted by Mahindra without strict regard for its driven speed. Tachs may be off in different directions, as may timed cycles as you noted - especially with different people. I believe reaction time on the stopwatch button can be a problem. I would prefer using a large sweephand clock and just having someone observe the start and stop time. Sight sense is almost instant. Alternately, finding a way to mark the stop point when using a stopwatch would allow a good predictive button press as opposed to a reactive one that is always late.
In any case, accurate specs are what we need so we can know what the system is capable of.
larry

 

[Dougster]

In any case, accurate specs are what we need so we can know what the system is capable of.
larry

On that fact, we are in total agreement.

You saw Brandi's pump pix. Other than length, do they appear to be the same pump as yours? By the same manufacturer: Eaton (or one of its subsidiaries)? Eaton swears they mark all of their pumps externally with an easily decodable number. If lacking an obvious label, check the engine mounting flange. They are ALL supposed to be permanently marked there no matter what. Once we have that pump number, we will know it all. If these are the same basic pump model (or series), I think we can assume that the gearing is similar and that the pump ratings are specified at the same RPM. It would be rare that they would change the flow rating basis (RPMs, etc.) for the same model or series of pump.

I am not saying Brandi's pump isn't putting out more than spec. Maybe it is. And Lord knows that Mahindra has made mistakes... unintentional or otherwise... in its printed specs before. The rating basis (RPM, volumetric efficiency, oil temperature, operating pressure, load, etc.) could have changed as well. Until we know actual pump numbers, all of this is just twisted fun and wild speculation.

Dougster