Parasitic drag of hydraulic motor question

[ParkerFly]

Do you care to explain the difference between a motor spool valve and a regular valve that has a float position? This is a new one for me.
I had my eye on an electric valve earlier that I thought might work for controlling this motor. Here is a link if you don't care to take a look and see what you think:
Northman Fluid Power Hydraulic Directional Control Valve – 26.4 GPM, 4500 PSI, 3-Position, Double Solenoid, Open Center Spool, 12 Volt DC Solenoids, Model# SWH-G03-C3-D12-10 | Power Solenoid | Northern Tool + Equipment
Thanks again,

 

[kennyd]

I have limited wireless access where I am at now, I can link and explain later if you not get an answer before I can get to my desktop-sorry for the delay.

 

[hayden]

I think the answer to your question is Yes, running the pump creates a parasitic load. With your value in float, the motor is circulating fluid in a circle to itself as long as it continues to rotate, and the pump is pumping fluid in a circle to itself as long as the pump is running. Both are parasitic loads, one creating drag on the motor, and the other creating load on whatever is driving the pump. It's not a huge load, but it does take work/energy to pump fluid around in circles.

 

[oldnslo]

Do you care to explain the difference between a motor spool valve and a regular valve that has a float position? This is a new one for me.
I had my eye on an electric valve earlier that I thought might work for controlling this motor. Here is a link if you don't care to take a look and see what you think:
Northman Fluid Power Hydraulic Directional Control Valve 26.4 GPM, 4500 PSI, 3-Position, Double Solenoid, Open Center Spool, 12 Volt DC Solenoids, Model# SWH-G03-C3-D12-10 | Power Solenoid | Northern Tool + Equipment
Thanks again,

Yes this valve will allow the motor to free wheel in the home position. In the home or center position all ports are common just like a "Float" spool.

 

[J_J]

ParkerFly,

You do realize when using a solenoid valve, the hyd motor speed jumps to it's max speed as dictated by the pumps GPM's . You can vary the hyd motor speed by regulating the pumps rpm.

A lever hyd valve can feather and control the speed, fwd or rev if manual operation is needed to vary the motor rpm. If you let it free wheel, there will be more wear and tear on the hyd motor, and perhaps more heat.

There are other ways to control the speed of the motor such as a flow control valve from 1 - 8 GPM's. This is used for one direction only, and has relief.

Surplus Center - 3/8 NPT HYD FLOW CONTROL VALVE W/RELIEF RDRS137-08

There are larger GPM valves available.

 

[SSdoxie]

What do you have this motor connected too that causes it to rotate from the mechanical force? With what I will call a laoder valve with float, when in float the fluid from the pump goes through the open center portion of the valve and back to tank. Both ports on the valve to the motor are open (connected) to each other and also to tank which allows the motor to rotate. To measure pump load on the engine at this point you need to know the pump flow GPM and pressure at the pump. GPM X PSI/1714 = required HP.

 

[ParkerFly]

I think the answer to your question is Yes, running the pump creates a parasitic load. With your value in float, the motor is circulating fluid in a circle to itself as long as it continues to rotate, and the pump is pumping fluid in a circle to itself as long as the pump is running. Both are parasitic loads, one creating drag on the motor, and the other creating load on whatever is driving the pump. It's not a huge load, but it does take work/energy to pump fluid around in circles.

Does running the pump increase the parasitic load on the motor though when it's in float, vs. when the pump is off?

ParkerFly,

You do realize when using a solenoid valve, the hyd motor speed jumps to it's max speed as dictated by the pumps GPM's . You can vary the hyd motor speed by regulating the pumps rpm.

A lever hyd valve can feather and control the speed, fwd or rev if manual operation is needed to vary the motor rpm. If you let it free wheel, there will be more wear and tear on the hyd motor, and perhaps more heat.

Yes, but max speed will be a good thing with my setup. Currently I have lever hyd valve controlling it and it works well, I just have every other hydraulic function on an electric valve and like the simplicity of it. I currently never feather my lever valve, it's always all or nothing. I am able to feather it by varying the RPM of my pump.

What do you have this motor connected too that causes it to rotate from the mechanical force? With what I will call a laoder valve with float, when in float the fluid from the pump goes through the open center portion of the valve and back to tank. Both ports on the valve to the motor are open (connected) to each other and also to tank which allows the motor to rotate. To measure pump load on the engine at this point you need to know the pump flow GPM and pressure at the pump. GPM X PSI/1714 = required HP.

The motor has a sprocket on it and is hooked into the driveline of a large weight. The weight is pulled forward by an axle, and the hydraulic motor is used to pull it back into place. My current pump is 12 GPM @ 2000 RPM - here is a link to the pump I use: https://www.surpluscenter.com/Item.asp?item=9-1737-S
The valve is regulated at 2000 psi. Thanks for all the help and sorry it took me a few days to get back on here and caught up.

 

[SSdoxie]

In answer to question of parasitic load on the hydraulic motor while in float. No, the open center flow from gear pump is not connected to the work ports when in float. Load on the engine at free flow should be less than 1 hp unless it takes more than 150 psi. just to flow the oil. It is rare to see free flowing/non-working pressure over 25 psi. If you do not have an oil cooler in system after the control valve I would suggest you install one. The hydraulic motor, when in float is cycling a small amount of oil through that motor which creates heat. Best to cool that oil down to help seals in the motor last longer.

 

[J_J]

He is using a clutch type hyd pump, and is only working part time to do a specific job, and then he probably shuts off the motor, The hyd motor with the weight attached, is acting as a pump for the time it takes to reel out the weight. The rpm on the hyd motor is probably not that great, and would be dictated by the amount of the weight.

The pump only uses 16 HP to run it.

This setup almost sounds like a system to pull a cover over a dump truck to cover the contenrs.

I am not even sure that parasitic drag has any affect in a short time operation..

 

[DRL]

Sounds more like a tractor pull sled to me. The axle pulls the weight forward during the run and the hydraulics pull it back to the start position.

DRL