Testing Hyd motor using a 2stage pump

   / Testing Hyd motor using a 2stage pump #1  

muddstopper

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Joined
Apr 11, 2006
Messages
2,303
Location
western NC
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Ventrac, Steiner
I have been gathering parts for my firewood processor and am about to build the saw. The only pump I have available to test the saw motor with is my 28gpm 2stage on my current splitter. I eventually plan on purchasing a 30gpm pump just for the saw motor, but for now what I have is what I have. Since these 2stage pumps have a low and high, flow/pressure I am just wondering if it is possible to turn up the highflow/low pressure to where it would produce high flow and high pressure.(1500psi) The pump is new and I dont want to screw it up by turning the pressure up to high on the high flow side of the pump.

My current plans are to use a pulley ratio to get the chain to turn the rpms I am looking for, but thought I would try the motor directly hooked the the saw to see if it might possibly turn fast enough to give me the cutting speed I am looking for. I dont think it will, but would like to just try it before I start a lot of time consuming and expensive fabricating to build the pulley system.
 

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   / Testing Hyd motor using a 2stage pump #2  
The pump will try and run the motor, and when the pressure gets to about 600 or 700 psi, it will shift to the high pressure and low GPM's.

You may have to put a load on the motor to develop the high psi.
 
   / Testing Hyd motor using a 2stage pump #3  
The pump will try and run the motor, and when the pressure gets to about 600 or 700 psi, it will shift to the high pressure and low GPM's.

You may have to put a load on the motor to develop the high psi.


Specs for: 28 GPM DYNAMIC 2-STAGE PUMPMore Photos for: 28 GPM DYNAMIC 2-STAGE PUMP


28 GPM 2 STAGE HYD PUMP
Brand new, DYNAMIC two stage HI/LO pressure hydraulic gear pump. Ideal for applications such as log splitters, presses and other equipment where rapid movement of the cylinder at low pressure is required prior to automatically switching to the high pressure mode to meet load requirements. The change from LO to HI pressure is automatic with the LO stage pressure preset from 400-900 PSI. Minimum of 16 HP required for gas engine use.

SPECIFICATIONS
Displacement:
0.465 cu. in. / rev. HI press. stage
1.860 cu. in. / rev. LO press. stage
Pump Type Gear
Rotation CW
Pressure: 3000 PSI max.
Speed: 3600 RPM max.
Flow:
7 GPM HI press. stage
28 GPM LO press. stage
Unloading Pressure 400-900 PSI
Mount 2 bolt SAE A
Shaft 5/8" dia. x 1-1/2" long keyed
Rqd. Filtration 25 micron
Inlet Port 1" NPT
Outlet Port 3/4" NPT
Size 6-9/16" x 6-1/4" x 4-5/8"
Shpg. 23 lbs.
 
   / Testing Hyd motor using a 2stage pump
  • Thread Starter
#4  
JJ, When I got this motor, it was supposed to be something else and the specs would have been close for what I was wanting. Turns out, it aint what its supposed to be and I dont have any specs to go by. No tags or numbers. I know it will turn 3200rpms at 18.5gpm, but dont know where it will top out at with more flow before it blows aparts. I figure on hooking up fluid and turning it loose, come, bleed or blister. I need about 1500psi to really test cutting power of the saw and dont know if its possible to turn the pump up to that kind of pressure since its rated at only 900psi. Dont want to ruin the pump acting stupid. Basicly, I am trying to not buy parts I dont need or cant use. If it will work with the 2stage, I dont mind buying a pump of proper capacity to run the motor. If it wont do what it needs to do, then I am looking at also buying a different motor for direct mount, or building a pulley jackshaft system and using this motor to run it with. I have a couple of spare motor if I blow this one up, but only one pump. I really need to know if I can turn up the pressure on the high flow side without damaging the 2stage pump. This is only for testing and not for long term usuage.
 
   / Testing Hyd motor using a 2stage pump #5  
The motor will have a pressure and GPM rating which you should not exceed.

The unload pressure on the pump can be set to 400 to 900 psi.

The load determines the pressure developed.

When the load gets to say 900 psi, the pump switches to low GPM and high pressure.
 
   / Testing Hyd motor using a 2stage pump #6  
Muddstopper,
I presume the orange motor in the picture is the motor you are asking about. This appears to be a piston motor so I would suspect the pressure to around 3000 PSi and RPM is the unknown. It looks like there is a Silver name plate on the top of the motor. I presume this mangled beyond recognition. Are there any numbers stamped in the front mounting flange.
 
   / Testing Hyd motor using a 2stage pump #7  
You just don't see a lot of two stage pumps running hyd motors.

At the 18.5 GPM and 3200 rpm you stated, that puts the displacement at about 1.3 cu in and if you use 3000 psi for the pressure, that gives you about 621 in lbs or 51.75 ft lbs.

You can try and put the full 28 GPM to the motor, as the motor will turn at low pressure.

If you put a load on the motor and it gets above the low stage pressure preset, it will shift to the high pressure mode and the motor will slow.

So the motor can run fast up to the low pressure cut off of say 900 psi. That provides about 186 in lbs or 15.5 ft lbs.

If we knew the real displacement, we could get some better figures.

We know the pump can develop 3000 psi.
 
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   / Testing Hyd motor using a 2stage pump #8  
Muddstopper,
BEFORE you run this motor, remove the plug in top center of the housing and fill the housing with oil. Then connect a hose to this port and run it directly to tank. axial piston motors rely on the oil in the case to lubricate the bearings and also must have a case drain line directly to tank that routed as to keep the motor housing full of oil. Not filling the case with oil can (will) cause the bearings to seize and not connecting a case drain will either blow the shaft seal or crack the motor housing.
 
   / Testing Hyd motor using a 2stage pump
  • Thread Starter
#9  
I think I am going to try and comeup with a different plan. I mounted the 2stage pump on my splitter this wkend. Might connect a few lines just to see what the motor will do, but dont think I want to go fooling around with the pressure settings just for testing. The case drain is connected to a return to tank line in the original intended purpose, and is how I intend to connect the motor as well. I bought another 25hp Kholer engine and Have a double pump I think might do for my testing and if it works out, I will just use the combination as is. I got the pump off a large ditchwitch backhoe attachment. I also got some sort of valve that combines both sections of the pump to work together. Not sure how this works. I'll take a pic and maybe some of you can tell me what I need to know, or answer some questions I dont know to ask.
 

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