hydraulic pump rpm
- Thread starter brownbagg
- Start date
Motors come in common speeds, nominally 1100, 1700, and 3400 rpm. What are you switching from and to? I also believe that if you double the speed of the pump then your going to have to at least double, or more, the hp of the motor.
lg
no neat sig line
lg
no neat sig line
TheVintonZoo
Member
Brown,
If you have a fixed displacement or "gear pump", the rotating speed of the motor will effect how much flow will come out of the pump directly effecting the speed of ram on your log splitting.
If you matched the HP numbers at a higher RPM your replacement motor has less output torque to deliver to the hydraulic motor which will ultimately decrease the force it can exert on the log.
If you have a fixed displacement or "gear pump", the rotating speed of the motor will effect how much flow will come out of the pump directly effecting the speed of ram on your log splitting.
If you matched the HP numbers at a higher RPM your replacement motor has less output torque to deliver to the hydraulic motor which will ultimately decrease the force it can exert on the log.
Last edited:
Bondo
Well-known member
Ayuh,.... It S u r e Does,...
Goin' faster, ya need more Power to do what it used to do, Faster,...
Goin' slower, ya just loose out all 'round,....
Goin faster can create all kinds of issues, most hydraulic pumps have a maximum RPM of about 2400. I found out the hard way on a bale wagon, exceeded the max RPM blew out the seals and then found out the pump wasn't rebuildable cost me about fifteen hundred to replace the pump and resheave it to match my motor.
Eaton pumps have quite a bit of info on their website another one is Parker.
Eaton pumps have quite a bit of info on their website another one is Parker.rustyjames
Well-known member
For a log splitter you really would want to go with a 2 stage pump.
pancho400cid
Well-known member
What RPM is the original motor, and what RPM is the new motor?
If the new motor is the same voltage, same rated HP, and different by a few RPM that is probably OK. Induction motors vary slightly in RPM from one motor to the next even when they are same mnfr/model #. As said, a fixed displacement pump's flow would vary directly with motor RPM but a small RPM change will not matter.
Example: Motor A drives pump at 1740 RPM and delivers exactly 5 GPM. Motor B drives pump at 1750 RPM. Pump output would be 5 x (1750/1740) = 5.02 GPM. Big deal - Especially in light of the low duty cycle of a log splitter
It's when the motors have a different pole count (example 4 pole would run around 1750 RPM at 60 Hz where a 2 pole motor might run 3450 RPM at 60 Hz). Now you have issues.
If the new motor is the same voltage, same rated HP, and different by a few RPM that is probably OK. Induction motors vary slightly in RPM from one motor to the next even when they are same mnfr/model #. As said, a fixed displacement pump's flow would vary directly with motor RPM but a small RPM change will not matter.
Example: Motor A drives pump at 1740 RPM and delivers exactly 5 GPM. Motor B drives pump at 1750 RPM. Pump output would be 5 x (1750/1740) = 5.02 GPM. Big deal - Especially in light of the low duty cycle of a log splitter
It's when the motors have a different pole count (example 4 pole would run around 1750 RPM at 60 Hz where a 2 pole motor might run 3450 RPM at 60 Hz). Now you have issues.
What happens is that the pump will cavitate if run too fast , can`t **** the oil up fast enough . Cavitation destroys pumps . Now , you say the rpm is a " little higher " . How much higher ? A few rpm ( +/- 50 will only effect flow output ) . You didn`t say what kind of a pump .... gear , gerotor ??? All pumps have a max rpm and definite suction line requirements that must be followed . Some industrial gear pumps can run up to 3000 + rpm , while Ag pumps generally are much lower and the duty cycle isn`t continuous as the industrial stuff is . Why don`t you get the pump model number , manufacturer etc and go to their site and see what they say their specs are .
BTW , I used to work for Parker with the Hydraulics Group and have torn down many pumps over the years . Most pumps are destroyed by only several things ..... cavitation , heat and dirt in the systems . We rarely saw pumps that were overspeeded ( if such a word exists ) .
As far as hp requirements , there are several formulas .... HP = (gpm x psi) divided by (1714 x pump efficiency) . Assume 85% eff and you`ll be safe as most pumps run about 90% overall . Notice I said overall , as pump efficiency consists of volumetric and mechanical efficiency .
A general formula for flow is ( rpm x displacement in cubic inches) divided by 231 ( I assumed 100% volumetric efficiency ) .
Have I confused you now ???
BTW , I used to work for Parker with the Hydraulics Group and have torn down many pumps over the years . Most pumps are destroyed by only several things ..... cavitation , heat and dirt in the systems . We rarely saw pumps that were overspeeded ( if such a word exists ) .
As far as hp requirements , there are several formulas .... HP = (gpm x psi) divided by (1714 x pump efficiency) . Assume 85% eff and you`ll be safe as most pumps run about 90% overall . Notice I said overall , as pump efficiency consists of volumetric and mechanical efficiency .
A general formula for flow is ( rpm x displacement in cubic inches) divided by 231 ( I assumed 100% volumetric efficiency ) .
Have I confused you now ???