Hydraulic motor question

[SJBegin]

I'm in the design phase for building a combination Harley power rake and forestry mulcher. I'm having many challenges with this project, one being the hydraulic motor choices. I believe a typical Harley rake operates at 540 drum RPM, where as the mulcher is between 1200-1800 RPM. This implement will be built for a skid steer 65hp, 17.1 gpm, 3100psi. I understand that the overall diameter, width, and tooth depth of the drum all play a role in operating capacity. I'm thinking of gearing it to around 1500 RPM at max capacity, and using a flow control valve to slow it down if needed.

My question is: is it more powerful to use a single hydraulic motor, or to run two motors in series or parallel?

With a given amount of potential energy, I understand by adding a second motor reduces the psi and gpm flow per motor and would have to account for this. I maybe wrong, but it may also help it run cooler and more efficient. I have noticed that almost every implement built uses only one motor to turn a typical drum. I use to run a ski trail groomer and on this particular machine it did use 2 motors for the rear tiller.

I'm ultimately looking to get as much power to the drum as possible to minimize the lag in drum RPM as you work the machine in dense brush, stumps ect.
Any input is much appreciated, Thanx

 

[yarg]

I just did much of this for my project and can say, it is not the easiest info for a layman to get.
The 17.1 gpm at 3000 psi I think translates to about 30 HP.
A chain reduction or gear reduction would be best on one motor because they are generally more efficient.
A motor with maybe 1500 rpm and a reduction of about 3 to 1 would get the Harley rake speed?
With that HP you would need some major gear box or a 100 pitch chain to handle it.
Two seperate motors would mean twice the cost for motors and valves? That could very easily out do any gears or chains.
No, I am no expert, just sharing my thoughts. Good luck and you will not get any cut downs from me for trying This is sometimes what those of us who are not experts can get

 

[J_J]

I'm in the design phase for building a combination Harley power rake and forestry mulcher. I'm having many challenges with this project, one being the hydraulic motor choices. I believe a typical Harley rake operates at 540 drum RPM, where as the mulcher is between 1200-1800 RPM. This implement will be built for a skid steer 65hp, 17.1 gpm, 3100psi. I understand that the overall diameter, width, and tooth depth of the drum all play a role in operating capacity. I'm thinking of gearing it to around 1500 RPM at max capacity, and using a flow control valve to slow it down if needed.

My question is: is it more powerful to use a single hydraulic motor, or to run two motors in series or parallel?

With a given amount of potential energy, I understand by adding a second motor reduces the psi and gpm flow per motor and would have to account for this. I maybe wrong, but it may also help it run cooler and more efficient. I have noticed that almost every implement built uses only one motor to turn a typical drum. I use to run a ski trail groomer and on this particular machine it did use 2 motors for the rear tiller.

I'm ultimately looking to get as much power to the drum as possible to minimize the lag in drum RPM as you work the machine in dense brush, stumps ect.
Any input is much appreciated, Thanx

Each hyd motor has a pressure rating, and will develop a certain amount of torque and develop a certain HP.

You need to figure the rpm and torque need to turn the drum with X numbers of carbide teeth.

Maybe copy someones design or design one. yourself.

You might consider direct couple, or chain drive, or even belt drive.

If you use two hyd motors in series, the pump pressure of say 3000 psi will divide across the two motors, each one developing 1500 psi and the same GPM will pass through both motors.

If using hyd motors in parrallel, each will develop pump pressure of say 3000, but the GPM will divide between the two motors. GPM's determins the rpm of a hyd motor.

My Power-Trac uses hyd wheel motors direct coupled, in a series /parrallel configuration. The front hyd motors are parrallel with the rear hyd motors.

The pump is a Variable Speed Pump, with a working pressure of 3000 psi. This 3000 psi is dropped across the two 1500 psi hyd motors in series , using the pump flow of X GPM's

This combination gives a certain rpm for tire rotation/vehicle speed, and enough torque to move a 3900 lbs machine at about 10 MPH.

Two small hyd motors may equal one large hyd motor , but the rpm's will not be the same.

Look at the specs on this hyd motor.

Surplus Center - 18.3 cu in WHITE 430300W3131CAAAA HYD WHEEL MOTOR

18.3 cu in /rev

It can develop up to 3000 psi.

Continuous torque of 7100 lbs.

Continuous rpm of 250.

Flow required for continuous operation 20 GPM

 

[oldnslo]

You can purchase motors with variable volume controls to provide different speeds.
Some mulchers run two motors direct drive while others only use one. Others use Cog belt drives. I think you will find that the most common motors used on mulcher heads are Rexroth A6V or A2FM bent axis motors. When using these or any motor on a skid steer pay close attention to the back pressure in return line. Any back pressure reduces the amount of work you can do.

 

[J_J]

If you build your machine as a Harley Rake and a mulcher, you are messing with the concept for each one.

The Harley Rake stays in the dirt and rocks, and you expect the points to be rounded.

The forestry mulcher is designed to cut and tear and you try to keep it out of the dirt and rocks. I am thinking a sharp mulcher is better.

I don't think I would want to keep this in the dirt as much as the drum and teeth cost.

Second picture is mulcher teeth.

Third picture is a Harley Rake, and it has little carbide nubs on the drum, and never intended to be sharpened.

 

[SJBegin]

Thanx for all the input, to get an idea of the machine I would like to build here's a link Penn State Demo 3 - YouTube , if it doesn't open just go to youtube and search for FAE STC/SSL or Penn State demo FAE. A great deal of hp and Hi-Flow hydraulics is required to run this particular one, given the skid steer I own I'll need to account for this, but this is the general idea. My skid steer is just like my garage... not big enough!!!

I believe these units go for $20-30K, way to much $$$ to justify spending with what the market is willing to pay. Maybe I'm just dreaming, but if there's a will, there's a way.