PTO Pump

[Dougster]

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.

This, of course is typical. The first section is the main hydraulics section while the second (back) section is steering. If there is any difference in main hydraulics flow rating on essentially identical tractors, you'd expect the back section to be near or exactly the same length while the front section length will vary almost directly in proportion to rated pump flow. Diameter will remain exactly the same for the same manufacturer & model series of pump.

From your assessment Larry, it sounds right now like Brandi does have the advertised 6520 pump and not the 7520 pump. If true, this explains a lot about her earlier lack of performance with the 511.

By the way, all Eaton pumps are externally marked. If not on the body, check the mounting flange.

Dougster

 

[bindian]

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

Larry & Dougster,
My pump is 8 inches from the mounting flange to the aft end. So that makes it smaller then Larry's 17 gpm pump. So I have a 11 gpm pump.
hugs, Brandi

 

[Dougster]

Larry & Dougster, My pump is 8 inches from the mounting flange to the aft end. So that makes it smaller then Larry's 17 gpm pump. So I have a 11 gpm pump.
hugs, Brandi

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

 

[SPYDERLK]

Previous reported info:OK, here are some 7520 pump times for full extension of the 275 loader. They are timed HOT ~ about 160F -I was clearing land at the edge of a field for a couple hours - then took readings. Full extension is 5.5 quarts.
* 2500rpm -- 5sec -- 16.7gpm
* 2250 -- 6sec -- 13.9gpm
* 2000 -- 7sec -- 11.9gpm
* 1750 -- 8sec -- 10.4gpm
There are some small rounding errors in the gpm figures.

Dougster, I know your good at this so I wish you would check my figures. The ML275 has 3" cylinders with 22.5" stroke. For me that takes 5.516quarts to raise. Pumping this amount in 6 sec is extremely close to 13.75 GPM. By proportional extension of these figures for 17gpm I get 4.853sec to deliver 5.5qt. I rounded this time off to 4.9 when I did the previous GPM calcs based on my times - hence the small errors. Now corrected, for Brandis and mine, at 8s rise time, we have (4.853/8) X 17 = 10.31GPM. If I have not made a mistake that means Brandis delivers enuf at 2Krpm and will probably do very well at 2250. For some reason my delivery seems to spike above 2250. Could be a non linearity in the tach? If the same behavior holds true on Brandis, I predict a near 6s rise time on hers at 2500rpm --well above 12gpm. Above spec. We really need pump specifics. My pump has numbers. Main section 4085 and 60121609. P/S section 4028 and 50121509. Do you know how to get specs?
Larry

 

[Dougster]

Dougster, I know your good at this so I wish you would check my figures. The ML275 has 3" cylinders with 22.5" stroke. For me that takes 5.516 quarts to raise. Pumping this amount in 6 sec is extremely close to 13.75 GPM. By proportional extension of these figures for 17gpm I get 4.853sec to deliver 5.5qt. I rounded this time off to 4.9 when I did the previous GPM calcs based on my times - hence the small errors. Now corrected, for Brandis and mine, at 8s rise time, we have (4.853/8) X 17 = 10.31GPM. If I have not made a mistake that means Brandis delivers enuf at 2Krpm and will probably do very well at 2250. For some reason my delivery seems to spike above 2250. Could be a non linearity in the tach? If the same behavior holds true on Brandis, I predict a near 6s rise time on hers at 2500rpm.
Larry

Hi Larry - First I would ask if you are using the exact "ID" of your cylinders. I'm guessing your cylinders are either 3/16" or 1/4" thick. Secondly, be sure to use the exact measured stroke of the cylinders (check both sides and average). Next, you really do need a stopwatch and to measure down to 1/10 second or better because 1 whole second is a lot of flow here (relatively speaking). Your results imply that you used the nearest whole second.

Obviously, the tach could be off. Not much you can do about a fixed (or varying) bias error there unless you want to bring in calibrated equipment. Repeating the test multiple times will only reduce the smaller "random error" component of test measurement uncertainty... although multiple tests are always a help. Be sure to watch your oil temperature as that will directly affect pump performance (albeit in a relatively small way). Likewise, while very minor, make sure your FEL load is consistent between tests.

I question the fact that you feel you found noticeably lower volumetric efficiency at lower speeds. Your speed was not varied so much that this should change markedly. It tends to suggest tachometer error more than anything else.

Get me your cylinder "ID" and I will gladly recheck your numbers.

Dougster

 

[SPYDERLK]

OK, here are some 7520 pump times for full extension of the 275 loader. They are timed HOT ~ about 160F -I was clearing land at the edge of a field for a couple hours - then took readings. Full extension is 5.5 quarts.
* 2500rpm -- 5sec -- 16.7gpm
* 2250 -- 6sec -- 13.9gpm
* 2000 -- 7sec -- 11.9gpm
* 1750 -- 8sec -- 10.4gpm
There are some small rounding errors in the gpm figures.

The times were done with a sweep hand stopwatch with 0.2sec resolution, were quite repeatable, and I believe slightly conservative since I pressed the button as I operated the handle and again as I saw loader stop. Rpm was as indicated on tach while servicing the raise load. Pump rpm is 36/33 engine rpm.

If you plot those numbers you see that the pump is more efficient at higher speed. Less time per revolution for internal leakage.
larry

Dougster, they are 3" ID - -specd in the manual and confirmed by measurement of OD and subtracting as you said. Stroke is 22.510. Times are to nearest 0.2sec because that is the resolution of my sweephand stopwatch. The times for those rpms just happened to come out on the whole seconds. I believe they may be a tick conservative due to slight anticipatory start and reactive stop factors. YES - the oil was hot and getting hotter during the 30 or so loader lifts for time trials.
larry

 

[Dougster]

Dougster, they are 3" ID - -specd in the manual and confirmed by measurement of OD and subtracting as you said. Stroke is 22.510. Times are to nearest 0.2sec because that is the resolution of my sweephand stopwatch. The times for those rpms just happened to come out on the whole seconds. I believe they may be a tick conservative due to slight anticipatory start and reactive stop factors. YES - the oil was hot and getting hotter during the 30 or so loader lifts for time trials.
larry

Larry, I come up with exactly 5.508 quarts or 1.377 gallons per lift based on your 22.5 inch stroke (assumed actual/measured average for two cylinders). All conversion constants used were at least to 8 significant figures. That yield's the following table:

Time to Lift --------Calculated Flow Rate
5 Seconds.................. 16.524 GPM
6 Seconds.................. 13.770 GPM
7 Seconds.................. 11.803 GPM
8 Seconds.................. 10.327 GPM

Time for exactly 17.0 GPM delivered flow rate: 4.860 Seconds

These are the corrected values!!!

Dougster

 

[SPYDERLK]

Quote Dougster: Larry, I come up with exactly 5.880 quarts or 1.470 gallons per lift based on your 22.5 inch stroke

I keep coming up with 5.509 qts for the volume. Otherwise, our proportions match.
larry

 

[Dougster]

I keep coming up with 5.509 qts for the volume. Otherwise, our proportions match.
larry

Opps... you are correct - Excel data entry error!!! I'll go back and edit the table.

Dougster

 

[Tim_in_IA]

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.

 

[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