mj007
Silver Member
- Joined
- Mar 13, 2010
- Messages
- 247
- Location
- Western Colorado
- Tractor
- 2009 Kioti CK20S HST, 1937 Oliver 60 RC, 4 Case VA Series tractors.
Gotcha!
Hydraulic Flow question
- Thread starter blucoondawg
- Start date
- Views: 13907
Gotcha!
the old grind
Elite Member
- Joined
- Jul 21, 2012
- Messages
- 4,412
- Location
- Mid-Michigan
- Tractor
- NH T-1520 HST, NH TC33DA HST, Case DX26 HST, .Terramite T5C, . NH L785
PTO speed/eng rpm seems to be a simple matter of internal gearing, so the two can be all over the place.
My old FNH (1.3L) 1520's 540rpm PTO speed was @2250 and its redline 2600, per tach markings.
The new (1.7L) T-1520's 'PTO speed' is @2450, with "high idle" @2840 and "rated" @2600, per factory manual.
Not all engines make max torque at 'max' rpm and the rare one's torque at highest rpm can fall off such that max hp isn't there either. That said, whatever the 'pto rpm' of the engine is it should be at or near torque peak and 'rated' PTO hp must be taken with a grain of salt, esp with a 'light duty' CUT such as mine.
Anyway, I expect my hydro pump to put out max pressure at most speeds (say 1500rpm & up) with excesses controlled/diverted, but it's logical that flow is so nearly proportional to rpm.
This is way better than centrifugal water pumps that'll give you so many feet of head OR so many gpm (pick one) but would be darn lucky to give half their rated max for both at the same time. (Guess that's why hydro Q answers are so definitive and water-moving ones more like "try this & see what you get".
)
Oh, and thanks, guys for the depth of info. I haven't had so much fun with this topic since "Hydraulics #whatever" in college.
My old FNH (1.3L) 1520's 540rpm PTO speed was @2250 and its redline 2600, per tach markings.
The new (1.7L) T-1520's 'PTO speed' is @2450, with "high idle" @2840 and "rated" @2600, per factory manual.
Not all engines make max torque at 'max' rpm and the rare one's torque at highest rpm can fall off such that max hp isn't there either. That said, whatever the 'pto rpm' of the engine is it should be at or near torque peak and 'rated' PTO hp must be taken with a grain of salt, esp with a 'light duty' CUT such as mine.
Anyway, I expect my hydro pump to put out max pressure at most speeds (say 1500rpm & up) with excesses controlled/diverted, but it's logical that flow is so nearly proportional to rpm.
This is way better than centrifugal water pumps that'll give you so many feet of head OR so many gpm (pick one) but would be darn lucky to give half their rated max for both at the same time. (Guess that's why hydro Q answers are so definitive and water-moving ones more like "try this & see what you get".
)Oh, and thanks, guys for the depth of info. I haven't had so much fun with this topic since "Hydraulics #whatever" in college.
grsthegreat
Super Star Member
Also, most skid steer equipment is designed to run at 3,000 PSI. not the 2200-2500 that most farm tractors supply.
I had to add a 3 point hydraulic pump and reservoir for my loader mounted blower for this reason. My system also stores 25 gal of low viscosity oil so it can cool off as it operates. If the hydraulic oil gets too hot it could fry your hyd pump.
I had to add a 3 point hydraulic pump and reservoir for my loader mounted blower for this reason. My system also stores 25 gal of low viscosity oil so it can cool off as it operates. If the hydraulic oil gets too hot it could fry your hyd pump.
J_J
Super Star Member
- Joined
- Sep 6, 2003
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- 18,952
- Location
- JACKSONVILLE, FL
- Tractor
- Power-Trac 1445, KUBOTA B-9200HST
Just playing with numbers.
engine:
3000 rpm - .9 cu in pump - 12 GPM
2500 rpm - .9 cu in pump - 10 GPM
1300 rpm - .9 cu in pump - 5 GPM
There is a difference.
PTO rpm is that rpm that the engine has to turn to turn the PTO shaft at 540, or one of the other PTO speeds.
Max engine rpm is usually higher in all cases.
engine:
3000 rpm - .9 cu in pump - 12 GPM
2500 rpm - .9 cu in pump - 10 GPM
1300 rpm - .9 cu in pump - 5 GPM
There is a difference.
PTO rpm is that rpm that the engine has to turn to turn the PTO shaft at 540, or one of the other PTO speeds.
Max engine rpm is usually higher in all cases.
