Old Hydraulic Gear Pump

[NJ Toolnut]

Hi All,

Since I've never ran a hydraulic log splitter and because I'm an absolute noob when it comes to hydraulics, please go easy on me (I learn fast)!

My neighbor gave me an old Commercial Shearing cast iron hydraulic gear pump from a dump truck. The only numbers on its data plate are 110356 and 2/86. The numbers GB1685 appear on the main casting. The inlet and outlet ports are located opposite each other. Inlet diameter appears to be 1.25" or so, outlet diameter is about 1" with 12 threads per inch. Splined shaft diameter is about 7/8", splines are ANSI 22-4/SAE B, 13 tooth, 16/32 diametrical pitch. The splined shaft sticks out from the 2-bolt mounting flange by about 1.25". I have not yet determined the mounting bolt circle size. Is anyone familiar with these gear pumps or able to suggest a resource from which I can information about them? I'd like to know displacement per revolution, max RPM, direction of rotation and max pressure. Regarding a potential application, I'm exploring the possibility of using this pump to power a log splitter from my Ford 1910 Compact Tractor PTO. I have about 20 hp available at the 540 RPM PTO shaft. I know I will need a gearbox to obtain required pump RPM, but I have a milling machine and a lathe, as well as access to a welder. Since this is not a two stage hydraulic pump cycle times may be relatively slow, but on the other hand this seems like a fairly large pump with a relatively high flow rate for a splitter application. Getting it free was huge for me, since I could never justify the price of a commercial splitter.

Thanks in advance for your comments!

Stan

 

[Farmerford]

Stan: Its Friday afternoon, I don’t want to start the next project (and don’t have too since I am both chief and sole worker), so here are some rambling thoughts on your project.

1. You can calculate the displacement per revolution of a gear pump with a formula on the Bailey’s hydraulics site once you pull the end plate and measure the gears. That formula is probably in many places on the internet.
2. RPM is harder to pin down. If the pump was driven by a typical truck transmission bolt on PTO it is still not narrowed much. It has been a while, but most of those PTO’s were stamped with a ratio on the side expressed as a percentage or multiple of engine rpm; i.e., an 80% or 0.80 means the PTO output shaft turns 80% of crankshaft speed. The problem is that the range of ratios I recall was very wide: perhaps from ¼ crankshaft speed to an overdrive of 2:1. If you have access to the parent truck you might find the ratio indicated on the manufacturer’s plates.
I would think a large tandem dump would need 15 gpm to move the ram at a reasonable speed. That number and the displacement of the pump would let you back into an rpm. I also think the 1.25” inlet is consistent with up to 20 gpm, but probably no more than that.
I think maximum rpms for gear pumps are limited primarily by the inflow of fluid; if the pump turns too fast the fluid will not enter fast enough to prevent cavitation, which of course is both inefficient and harmful. Cavitation will show up in vibration/noise at the pump and probably bubbles in the hydraulic fluid. I have two Prince PTO gear pumps; one for a 540 rpm PTO and one for a 1,000 rpm PTO; I note that they are exactly the same pump, only the pto coupling sizes differ. If it were me I would assume your pump could turn 2,000 rpm without cavitation.
I realize there are other limitations on rpm, including the bearings and side wear plates (or the side plates themselves if there are no replaceable wear plates). But my gut feeling is that 2,000 rpm is not too fast for them.
3. I think the most likely limitation on your pump’s output is pressure. Pressure affects the torque on the input shaft, leakage past the gear teeth and the end seals, and the load on the shaft bearings because the difference in pressure between the input and output creates the bearing load. It is probably an older pump and on a system that might have operated at a lower pressure to reduce leaks, hose blowouts, etc. I would certainly limit pressure to 2,000 psig, and perhaps even lower.

4. So here are some completely off the cuff, totally unsupportable, SWAG’s:
2 cubic inch per revolution pump
PTO on dump truck had 1:1 ratio, so the pump turned at crankshaft speed
Owner operator who is paid by the load would hold the engine at 2,000 rpm to speed up dump, so we assume the pump can tolerate 2,000 rpm
2,000 rpm at 2 ci/r= 4,000ci/min, or 4,000 divided by 231 = 17 gpm
7” diameter cylinder on dump truck takes 2 gallon per foot of extension
So it takes 10 gallons to extend cylinder 5’, which requires about 35 seconds for a full dump. Seems slow, but I won’t rethink at this point. Maybe pump is 3 ci/rev.
You drive pump 2,000 rpm with 4:1 gearbox from 540 rpm pto.
17 gpm at 2,000 psi is 19 hp pump output, so considering losses your 20hp pto will probably bog a bit.
4” logsplitter cylinder requires 2.5 quarts per foot to extend, so to move the typical 2’ stroke will take 5 quarts, which till take the pump 3.5 seconds to produce.

All this is worth exactly what it cost.

PS: I am rebuilding a 1931 Lodge & Shipley 14 x 30. It is in pretty good shape except for the bevel gear on the back of the apron that is turned by the carriage drive rod; somebody crashed it somehow and messed up the gear selector.

Send pictures.

 

[Leejohn]

I had a pump, just about what you guys are talking about, on my log splitter and run it at 540. The speed was good and it had good pressure. I would try it that way 1st, but run the pressure line the size it is now all the way to the valve then reduce. I only ran about 1500 to 2000 rpm on the tractor, the pump lasted around 15 year. The gears in mine were about 2" long and about 1 1/2" dia.

 

[NJ Toolnut]

Farmerford,

Thanks for your thoughts!

I'll look up the formula for calculating pump displacement from gear dimensions. I don't have access to the dump truck the pump came from, my neighbor told me the pump was attached to the front of the engine, not the transmission. I don't know if it ran the cylinder for the dump or only the plow that was attached to the front of the truck. Based on the diameters of the inlet and outlet ports and the research I've done, my best guess for flow is also somewhere between 15-20 GPM. I'm also going to assume the pump can tolerate 2000 psig and 2000 RPM unless I hear otherwise (I've emailed what is left of Commercial Shearing in S. Africa). I was considering a 4:1 chain drive, perhaps using #40 chain.

My lathe is a 1945 Monarch CY, 16.5" x 54" catalog size--actual swing is 18". It is in mint condition, and I've held <0.001 on diameter over 36 inches. Lodge & Shipley also made superb lathes. Is yours a Model B? You can probably have a replacement bevel gear machined, but you will need deep pockets. I'll post some images of the lathe and the pump.

Leejohn,

Thanks for your post! I think my pump gears are smaller than 2" long by 1.5" in diameter, but I will measure them. If I could run at PTO speed it would eliminate the chain drive design, machining and fabrication effort. One particular design concern is avoiding radial load on the pump shaft.

Stan

 

[oldnslo]

NJ,
A word of caution on taking the Commercial pump apart. Some if not all of them where pressure side loaded and the seals for the side loading feature can be a real PITA to reinstall especially when they fall out before you get a chance to look at them. I believe Commercial shearing was purchased by another company but don't remember who it was. Possibly Parker or called Commercial Intertech today?? They where used a lot on construction and commercial machinery. Possibly try calling places like Attica hydraulic exchange in Michigan or Hydraulic parts source in Michigan. Both of these companies rebuild hydraulic components and they may be able to provide you with some specs for your pump.

If your fluid level in the reservoir will be above the pump inlet you can run these at 540 RPM with no problem. If oil level is below the pump inlet at 540 RPM you may have trouble getting the pump to prime.

I would guess farmer ford is close on his sizing SWAG.

Mounting I would suspect is a standard SAE-B 2-bolt mount. Measure the mounting pilot diameter to determine which one.
SAE-A has 3 1/4" dia pilot
SAE-B has a 4" dia pilot,
SAE-C has a 5" dia pilot

 

[NJ Toolnut]

Oldnslo,

Thanks for sharing, and especially for the words of caution!

Regarding dissassembly (potentially avoiding it) someone on another forum suggested setting the pump up with some reducers and small diameter hoses for the inlet and outlet ports, priming it with fluid from a clean bucket and then measuring the volume delivered per revolution (while turning the shaft by hand) as a way to estimate displacement. The obvious advantage of this procedure would be that dissassembly would not be necessary. I wonder how accurate the result would be. In the absence of information from the manufacturer or elsewhere, I need to determine the relationship between RPM and flow rate.

Yes, Commercial Shearing became Commercial Intertech and was subsequently purchased by Parker. My experience has been that companies typically do not retain information about old models of equipment beyond ten years, but there are exceptions. When I called what is left of Monarch Machine Tool Company seeking information about my lathe, they were able to tell me who the original purchaser was, and were even able to provide the list of accessories ordered as part of the original purchase in May, 1945! I will try calling Attica and Hydraulic Parts to see what I can learn.

I currently plan on mounting the reservoir on the splitter above the pump, so no worries getting it to prime. I wonder whether flow would be adequate at 540 RPM to result in a reasonable cycle time. I won't be sure until I learn or estimate the displacement.

I measured the diameter of the mounting pilot and it is 4". SAE B confirmed.

Stan

 

[CNC Dan]

then measuring the volume delivered per revolution (while turning the shaft by hand) as a way to estimate displacement....
I wonder how accurate the result would be.

Make 10 turns and divide the result by 10. That should be more accurate.

 

[NJ Toolnut]

CNC Dan,

Thanks, good suggestion!

Stan

 

[NJ Toolnut]

Hi All,

I received a response Monday morning from Commercial Shearing in S. Africa, who forwarded my message to a US distributor (Swanson Industries in Morgantown West Virginia). The Swanson contact replied almost immediately to inform me that he could determine my pump model from a couple of external casting dimension measurements. I made the measurements last night and emailed them, then received his response this morning. The pump is identical to a Parker Hannifin Model P30. The nice guy at Swanson even provided a brochure for it. Rotation is CCW, displacement is 1.97 cubic inches per revolution, maximum pressure is 2500 psi and maximum RPM is 2400. The brochure has tables showing required HP as a function of RPM at 2500 psi and flow as a function of RPM. From these tables, required HP ranges from 14 at 900 RPM to 36 at 2400 RPM, and flow ranges from 6.5 GPM at 900 RPM to 19 GPM at 2400 RPM. From the data in these two tables, I was able to graph flow vs. HP. Basically, at my max PTO HP (20) the pump will flow about 9.8 GPM, and this occurs at around 1300 pump RPM. I extrapolated flow to PTO RPM (540--the tables did not go that low) and obtained about 3.5-4.0 GPM. My conclusion is that this pump could definitely be used to run a splitter if I gear up the pump from PTO RPM to 1300 RPM to obtain reasonable cycle times, but cycle times will not be fast even then.

I would appreciate any comments you may have in view of this new information.

Stan

 

[NJ Toolnut]

Hi All,

It gets even better: I checked the rotation direction of my PTO shaft and it is CW as viewed from the back of the tractor. This is the correct direction of rotation to mate up with the hydraulic pump through a chain drive, since the pump shaft turns CCW as viewed from the shaft end of the pump. In addition, I checked the owner's manual for my tractor and found out I have 28.5 PTO HP. I could use all of this available HP by driving the pump at about 1900 RPM, getting about 15 GPM flow at 2500 psi.