PUMP and Motor size

[horseman 120247]

I am looking at putting a 21 gpm pto pump (540rpm) on my tractor (27 HP) and using a 7.3 cu in. hydraulic motor to power my snow blower. Can anyone tell me approximately how much power (HP) that motor should deliver to the snowblower.

 

[jbooth]

These are preliminary findings from some web hydraulic calculators.

21 GPM pump @ 2000 PSI will require 28.75 HP.

21 GPM @ 2000 psi is capable of 24.5 hydraulic HP.

Didn't take the time to run your particular pump through the calculator.

 

[kennyd]

These are good resources: Baum Hydraulics Corp :: Spec Calculator

 

[AKKAMAAN]

I am looking at putting a 21 gpm pto pump (540rpm) on my tractor (27 HP) and using a 7.3 cu in. hydraulic motor to power my snow blower. Can anyone tell me approximately how much power (HP) that motor should deliver to the snowblower.

You can run a 21gpm pump at 2200psi with a 27hp motor
Your blower motor will do 21*231/7,3=664rpm minus reduction for volumetric inefficiency in pump and motor, approx 15% of in each, if load pressure stay high.....probably little less at lower pressure....so you can expect about 0.85*0.85*664= 480rpm at highest pressure and higher rpm as pressure decreases....0.95*0.95*664=600rpm is most likely the highest rpm you can expect
Output shaft power on motor at 2200psi will be 27*0.85*0.85=19.5hp...

The efficiency numbers I used have to be taken with a grain of salt, will need manufacturers data to calculate more accurate....also, there will be some minor mechanical friction losses in pump and motor that will reduce output power some more, so call it 19hp per now...
There might also be some minor flow losses in a control valve.....also negligible....

 

[oldnslo]

If the motor you have selected is a LSHT (Low Speed High Torque) geroller or geroter style AKKAMAN is being optimistic on the efficiency. Some of these are in 50- 70 % range.

Roy

 

[AKKAMAAN]

If the motor you have selected is a LSHT (Low Speed High Torque) geroller or geroter style AKKAMAN is being optimistic on the efficiency. Some of these are in 50- 70 % range.

Roy

Thanks Roy! I was talkin in general terms gear pump/motor!!:thumbsup:
Btw I flagged for "the grain of salt" too.....hahhahahahha....my "safety belt and parachute"

 

[jbooth]

After posting earlier with what is probably bogus info, I have looked at quite a few web based hydraulic calculators. The calculators are all over the map.
I had been relying on one to calculate the hydraulic HP to a saw I run on my skid steer. 1 site gave the hp at 24 and another at 36. Well, Dad always told me the best way to ruin a discussion was to have someone in it who knew the subject. Guess I better quit posting and just read.

 

[J_J]

Sorry for your troubles.

If your tractor has 27 HP You can't develop more HP than you have to start with.

Is this not what you are looking for?

hydraulic motor torque (in-lb) = Pressure (Psi) x motor displacement (in3/rev) / (2 x Pi)

Hydraulic motor power (Hp) = Torque (in-lb) x RPM / 63025

https://www.surpluscenter.com/item.asp?item=9-1047-1&catname=hydraulic