PTO PUMP

[J_J]

My 1445 , 13 gal pto pump is connected piggyback to the wheel motor pump. This would make the pump run anytime the engine is running. This seems like poor engineering. In my opinion, the only time the pto pump should be runing, is when you are using an implement that requires a pto supply. What I am getting to, is the fluid that the pto pump is pumping is being relieved back to the tank if it's not being used by a motor. This builds up heat, and puts unnecessary wear and tear on the pump.
What is your opinion?

J.J.

 

[Bob999]

A clutch system on the drive for the PTO pump would have benefits--reduced wear and tear on the pump and reduced heat build up as you note. Additionally it would presumably reduce fuel consumption.

Conversely a clutch system would add weight and complexity, increase initial cost, increase maintenance, and take space--with the possibility that the machine would have to be bigger and heavier.

This appears to me to be a classic engineering trade off.

I would note that other manufacturers of other equipment make the same choice--tractors and skid steers for example--and perhaps others.

 

[Taylortractornut]

Your right with the clutch complexity on a pump. most loaders have 3 oupms one for steering and brakes, one for the boom and one for the bucket and auxhilary hydralics. The only way to remedy that on a PT would be to use a charge pump and a Variable displacement pump. but the charge pump has to circulate a little and the valves will be closed center to. But like you said it takes space costs more and is more complicated.

 

[MossRoad]

In my PT425, the variable volume pump is on the front of the engine and there are two pumps piggy backed on the rear of the engine. As far as I know, all three pumps are always running. The PTO and steering pump provides power to the hydraulic PTO from the front half of this pump and power to the steering rams, lift/tilt mechanism and auxiliary PTO from the back half of the pump.The variable volume pump provides power to the drive wheel motors.

From what I can tell, the front section of the rear pump that provides hydraulic PTO power just re-circulates continuosly under little pressure. But when you flip the electric switch on the dash to turn on the PTO, a solenoid kicks in and the fluid is diverted through the PTO circuit. You can really tell when that dude comes on, as the mighty Kohler lets you know it is now under load /forums/images/graemlins/shocked.gif /forums/images/graemlins/tongue.gif If you forget to hook up the hydraulic hoses to the implement and turn on the PTO, it will stall the engine after a few seconds of bypass noise. So this makes me think that even though it is circulating all the time, it isn't under much pressure at all until it's show time. If it had some type of clutch assembly, it would have to be a more complicated and costly machine.

 

[Schultz]

What you describe MR is an open center hydraulic circuit. Also, if it wasn't and it was relieving it self by a relief valve the engine would be under full load all the time and you would hear that squealing relief valve as soon as you start it up. The only pressure or work the fluid is doing when the PTO isn't engaged is the amount of pressure it takes it to pump it through the circuit and maybe a return filter. This should be less than 20psi, which would cause very little heat build up or power loss. Although if the PTO pump were clutched it would reduce some whirrrring pump noise you likely hear with all that hydraulic stuff going.

 

[J_J]

Now that I think about it, my pto is activated by a lever which must be an on/ off valve with free flow back to the tank in the off position.

I still think that the pto pump should have been mounted to the engine with a clutch and 12 volt activation like an aircondition pump so that the pump is at rest until it's needed.

Does anyone have a hyd diagram for a pt-1445 about ten years old. My engine is a 45hp gas engine with the tram pump at the main end, piggybacked by the pto pump. The steering/lift pump is mounted to the front of the engine with a v belt .


J.J.