Hydraulic Motor Displacement question

[SPYDERLK]

WOOD, I would say that first you need to find a motor series that can make
full use of the pressure you have (3100). MITH suggests the Charlynn 104
series, but that only handles 3000psi continuous pressure. You DO need
to protect from side loads as he points out, and that means you prob want
belt-drive or a gearbox, or another way to protect it.

The pressure only rises to the point required to drive the load, or at which the relief cracks-whichever comes first. The pressure would only rise to max system pressure if you really push the grinder. A motor rated even for 3100 intermittent would be quite safe unless you insisted on running it as hard as you could. A 3000 continuous motor would stand a good chance of wearing out around the same time as the pump.
larry

 

[skidsteer.ca]

Wow guys, now I am starting to get it..

The engine in my tractor is rated at 65HP. For that amount of HP I have always felt as it is a full hydraulic tractor that the fluid flow is a bit under its potential, but I am not the designer so...QUOTE]

With that much hp I'd recommend getting more flow from your tractor if there is anyway possible to mount a second pump, then combine the flow when running the grinder, would also be good for snow blowing or brush mowing.

I have a Erskine grinder and there is a huge difference between running it at 15 gpm (my std flow) and 24 gpm (my hi flow) at 2700 psi.
You do need to design for the max pressure possible if you go with 18 gpm. Here again more flow would let the ginder do the same work at a lower pressure and result in a longer system life.
I can tell you Erskine uses the same motor regardless of flow and lets the rpm fluctuate. (not certain this is the best design or not, but thats how they do it. As a side note the snow blower fan motors are resized every few gpm difference to keep the fan near optimum rpm) They list minimum flow of 15 gpm at 590 rpm and maximum 32 gpm at 1100rpm on a 24" wheel.
Hope that help a bit
Ken

 

[dfkrug]

The pressure only rises to the point required to drive the load, or at which the relief cracks-whichever comes first. The pressure would only rise to max system pressure if you really push the grinder. A motor rated even for 3100 intermittent would be quite safe unless you insisted on running it as hard as you could. A 3000 continuous motor would stand a good chance of wearing out around the same time as the pump.

I have never had a stump grinder, but I have seen them used. Often the
operator is using the full output of his machine. Whether you would
classify that as "intermittant use" or not is the question. My White
motors are specced at 3000psi continuous and they even come with a
3000psi relief valve (with a PHD application) to avoid going over that
pressure. I would go for a motor that was rated at the full pressure of
the pump (continuous) to avoid breakage (not wearing out).

 

[FarmallAok]

Woolandfarms thanks for starting with my similar question for my own 'copy' build of the Wiko Stumper 220. I love stump grinders that throw the chip sideways away from the operator as 95% of them throw to the operator and the machine must climb over the chip!!
JGRREED many thanks for the Surplus centre calc page.. greatest help.

Self build to save approx. 60% of retail.:laughing:

 

[woodlandfarms]

You are required now to share pictures and stories of your build.

 

[SPYDERLK]

I have never had a stump grinder, but I have seen them used. Often the
operator is using the full output of his machine. Whether you would
classify that as "intermittant use" or not is the question. My White
motors are specced at 3000psi continuous and they even come with a
3000psi relief valve (with a PHD application) to avoid going over that
pressure. I would go for a motor that was rated at the full pressure of
the pump (continuous) to avoid breakage (not wearing out).

Unless the pressure is gauged you dont know how close to max you are til it stalls w/o warning. Running close to max results in more stalls. Better to gauge it and run a few hundred below relief setting to support quick momentary increased loads without stalling.
larry

 

[J_J]

You guys are answering to some old post. 2009

 

[dfkrug]

Unless the pressure is gauged you dont know how close to max you are til it stalls w/o warning. Running close to max results in more stalls. Better to gauge it and run a few hundred below relief setting to support quick momentary increased loads without stalling.

Yeah, old post.

You would operate these motors to relief (stall) quite often. With the
PHD, I stall it every few seconds as I hit my many rocks. Of course, the
upstream relief valve opens, since it is set lower (2500 psi).

Same with my backhoe....I hit full force limits (stall) quite often while
digging. Nothing wrong with that, and unavoidable.