Splitter question

[triptester]

Log splitter pumps do not have a built-in pressure relief. The relief is usually in the control valve.

 

[LD1]

Not familiar with the name for a gear pump when the output is blocked and it's locked to a driving motor with adequate hp.

What you describe just don't happen and is not how hydraulics work. No such thing as a locked rotor. If flow sees resistance, and the motor and pump are still running, it will continue to build pressure. Pump and motor are coupled so if one stops, both stop. That's a motor stall.
The scenerio you describe, system will build pressure until one of only 2 things happen

1. You run out of power to keep building pressure...motor stalls.

2. Pressure is relieved. This can be busted parts or hoses, or a prv opening, or finally splitting the wood.

No idea what you are talking about dealing with motor HP ratings. All the motors I deal with, locked rotor amps is far more than. Fla. So the motor is actually capable of more Hp than rated, just not for long. Only motors I see fudged are things like fan motors or air compressor motors on low end stuff.

 

[Texasmark]

#1 is my locked rotor senario......the motor has put out all it can and it's rotor aka rotation, have stopped......locked....pump with it like you said since they are locked together essentially.....good v belt.

Well time to move on to something else.

 

[LD1]

If that's what you were calling locked rotor rating for a pump, it has nothing to do with the pump. Only the motor HP.

 

[Texasmark]

If that's what you were calling locked rotor rating for a pump, it has nothing to do with the pump. Only the motor HP.

Since the pump is driven and not driving then yes even if the pump and drive mechanism were contained in the same housing as an integral unit. However, when it can get no more drive from the motor due to the torque required to spin/attempt to spin the shaft in the process of attempting to pump harder (pressure increase) while attempting to "move fluid" into a blockage (no PRV) then it acts like a locked rotor on a motor.................it stops turning....aka locked rotor....the drive shaft. I thought we finished this yesterday?

 

[LD1]

Since the pump is driven and not driving then yes even if the pump and drive mechanism were contained in the same housing as an integral unit. However, when it can get no more drive from the motor due to the torque required to spin/attempt to spin the shaft in the process of attempting to pump harder (pressure increase) while attempting to "move fluid" into a blockage (no PRV) then it acts like a locked rotor on a motor.................it stops turning....aka locked rotor....the drive shaft. I thought we finished this yesterday?

Apparently not, cause either you

1. dont understand
2. understand but using incorrect terms that may confuse others

There is no such thing as a locked rotor rating for a hydraulic pump. It is called a motor stall.

Pumps DO have a max pressure rating. Using the max pressure rating and flow you can calculate the size of the motor needed to drive the pump. But it is still possible to stall. Just because the pump has a max pressure rating, doesnt mean the pump automatically stops trying to make pressure once that is reached. IF you dont have (or have an incorrectly set) PRV, than you can make more pressure. But you may twist off the input shaft of the pump, crack the housing, bust gears, etc.

I think you understand all of this. But I dont think we will be "finished" until you stop using the term "locked rotor" with a hydraulic pump.

I think the only time I would even consider using that term when talking about a pump is if there was a catastrophic failure of the pump and the shaft was actually seized. Then I might say something like "Pump is toast...The rotor is locked up"

 

[Texasmark]

Ok. I told you I am not a pump guy. How about an electrical engineer. Sparkey! If the shaft isn't turning and can't then it's locked just as if it were rusted in place or you had a pin through it locking it in place or drove an axe between the gears locking it in place. It's trying to move fluid by rotating two meshed gears but the fluid path is blocked and fluid doesn't compress so it can't move any more fluid and it can't cavitate as there is no mechanism for onset so it locks up. If it's locked up and it's shaft is locked to the armature shaft of the driving force...motor, then it and the motor have a locked rotor, locked shaft, stuck shaft, immovable shaft, brain fart or whatever you want to call it. Grin.

So if pump jargon says a locked rotor is a "motor stall", so be it. If the motor is stalled the rotor is essentially locked and that term defines, asymptotic increase in current and collapse of voltage across the windings which occurs the second the shaft (armature) ceases to turn generating counter electromotive force which keeps the current in check when rotating as designed.

So you use motor stall and I'll use locked rotor!

 

[LD1]

So you use motor stall and I'll use locked rotor!

Or you could take this as an opportunity to learn something and use the correct terms, so next time we have a hydraulic discussion people will be able to understand you instead of having no idea what you are talking about.

When the motor stalls, it isnt because:

the shaft isn't turning and can't then it's locked just as if it were rusted in place or you had a pin through it locking it in place or drove an axe between the gears locking it in place

Its because the motor just dont have enough power.

Thats why there is no such thing as the term "locked rotor". For a given pump, stall pressure would solely be based on motor HP.

Lets say you have a pump that makes 10gpm at 3600RPM and is 85% efficient.

Formula is HP= (GPM x PSI)/(1714 x eff) If you know what HP motor you got, you can re-arrange and solve for max pressure.
max pressure = (HP x 1714 x eff)/GPM

So, you have a 20 hp motor. You could make 2913psi before you stall. But you would incorrectly use the term locked rotor.
Throw a 30HP motor on there and now you can make 4370psi before the motor stalls.

So clearly, with the 20hp motor, the rotor wasnt "locked as if it were rusted in place", it just didnt have enough HP to continue turning.

 

[handirifle]

LD1
At least some of us are learning. Quite educational actually, for me anyway.

I see Central Ohio in your location, Columbus? My younger brother and older sister live near Ashville. In fact my sister and her husband own/run Renick's Market, on hwy 33.

 

[LD1]

Bout 30-40 minutes north of Columbus.

Assume you mean ashville just south of Columbus? Off 23, not 33? I've only been by there once. Never really venture south of Columbus unless I am going WAY south out of state on vacation or something