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.