Hydraulic Pump Sizing Question

Charles84 · Apr 2, 2020

EDITED TO TRY TO CLARIFY BETTER:
What i'm trying to accomplish is to run 2 variable speed piston pumps off of the Flywheel of a 35hp Briggs Vanguard to power 2, or possibly 4 hydraulic wheel motors. I am trying to understand whether putting the second pump in Tandem on the Flywheel shaft will create significant extra resistance, thus requiring a significant amount of extra torque from the engine.

The Surplus Center 'Horsepower to Drive Hydraulic Pump' calculator states that a 34hp Gas engine (17 hp Electric) will drive a pump at 13gpm @2000 psi. I am trying to figure out how these calculations relate to driving 2 of the same pumps in tandem. Would you require a 68hp Gas engine to drive (2) 13gpm variable displacement pumps @ 2000 psi in Tandem? Or could you drive 2 of them off of the same 34hp engine? I don't understand the torque requirements or the resistance that is occurring inside the pumps, and for some reason I'm having really hard time trying to grasp these concepts.

4570Man · Apr 2, 2020

I’m lost at what you’re trying to accomplish.

Charles84 · Apr 2, 2020

Please refer to my edited post at the beginning of the Thread.

RickB · Apr 2, 2020

Using the Surplus Center calculator it requires a 33.8 hp gas engine to power a single 13 gpm pump @2000 psi. If that info is accepted at face value you would indeed need 67.6 hp to run two of the same pumps at 2000 psi.

rScotty · Apr 2, 2020

RickB said:
Using the Surplus Center calculator it requires a 33.8 hp gas engine to power a single 13 gpm pump @2000 psi. If that info is accepted at face value you would indeed need 67.6 hp to run two of the same pumps at 2000 psi.

That's right. you need to supply twice the HP to do this. No matter how you hook up the two pumps, you are asking them to do twice the work of one pump. So you will have to supply twice the hp. into them to get that much flow out.
rScotty

oldnslo · Apr 2, 2020

Charles,
Do you mean two variable volume piston pumps vs saying variable speed?

If yes, are these manually controlled for displacement like HST drive on lawn mowers. If Manual displacement control you can reduce displacement which will let pressure increase with a smaller engine. I.e. yes you can run two pumps of this style on your 35 HP Briggs.

Charles84 · Apr 3, 2020

oldnslo said:
Charles,
Do you mean two variable volume piston pumps vs saying variable speed?

If yes, are these manually controlled for displacement like HST drive on lawn mowers. If Manual displacement control you can reduce displacement which will let pressure increase with a smaller engine. I.e. yes you can run two pumps of this style on your 35 HP Briggs.

I meant to say variable displacement. Thanks for catching that. I'm assuming variable volume is the same. Yes, this would be a manually controlled displacement HST drive.

Looking to run two Hydro-gear PR pumps in tandem off the flywheel shaft of the Briggs Vanguard 35hp (and one gear pump on a stub shaft from the other side of the engine) Will be powering 2 hydraulic wheel motors with the piston pumps and a FEL/Backhoe with the gear pump. Gear pump won't be in use when maxing the piston pumps. I was initially concerned about not having enough torque at the wheel sprockets,(This is a track vehicle) but it appears with 35hp there will be plenty, and a modest top speed of 6.82mph. I'll start a Build thread once I have finalized the schematics and I'm ready to actually start building. I have a stripped down JD420 that i will be using as the core. The 35hp will barely fit under the hood, with some minor modifications to the exhaust. I want to keep this looking as much like a Regular John Deere, minus the tracks of course.