Skid steer brush cutter

[Damato]

I have a case 1845c. It produces 16 GPM at 2,300 PSI. I have an old land pride bush hog. It's 72" wide. It has a 90 H.P. gear box. I would like to convert it to run off the skid steer. I know I need a check valve and a relief valve. I'm just not sure what size hydraulic motor to get. Will my case be able to handle a 90 H.P. gear box? What is the best way to connect the gear box and motor? Thanks for any help

 

[oldnslo]

With that flow and pressure you will get approx 25 HP from the motor and probably less so I suspect you will be very disappointed in the cutting performance

 

[Damato]

With that flow and pressure you will get approx 25 HP from the motor and probably less so I suspect you will be very disappointed in the cutting performance

**** that sucks. So there's no point in using this bush hog. Even if I put a suitable gear box on the bush hog that matches the skid steer it probably wouldn't be able to turn the blades. Is that right?

 

[oldnslo]

Your existing gear box would work just connect the motor to the input shat.

Yes I suspect you would have limited performance for any serious cutting.

Others that have a hydraulic driven cutter may chime in with real world experience.

 

[4570Man]

The gear box is fine. There’s no need to change it. The performance will be similar to a 25 pto hp tractor.

 

[Fallon]

With that flow and pressure you will get approx 25 HP from the motor and probably less so I suspect you will be very disappointed in the cutting performance

My 40hp L4060 does about 10gpm @ 2,500psi... 14hp or so. Noticably less than the 25hp PTO my old 32hp machine had. It will spin the 12" auger on the PHD ok, but not great at all. I'd want over double that flow for a 5' mower. The hydraulic PHD is a usability upgrade but very noticably less power. That 25ph PTO was a decent match for a 5' rotary cutter. And hydraulics are less efficient than a PTO.

 

[Damato]

What size hydraulic motor do I get? What size can I expect it to cut? I rented a bradco 60" bush hog for my case. I was cutting at least 3" diameter saplings.

 

[oldnslo]

16 GPM x 231 = 3696 cubic inches/ min

3696 / 600 = 6.16

At 100% efficiency a 6.16 cubic inch / rev motor would provide 600 RPM with 16 GPM flow

Find a motor rated for greater than 2300 PSI and you would not need a relief just a run down check valve.

Larger motor will run slower with more torque

 

[Xfaxman]

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What is the best way to connect the gear box and motor? Thanks for any help

Ours uses a coupler and the shear bolt. The cushion valve is built in to the motor:

Note the 3/4" hoses:

 

[Joe Malovich]

A concept that was missed here is that Hydraulic Horsepower = Pressure * Flow / 1714 with units in PSI and GPM. So OP 2300*16/1714=21.47HP but actually less because there will be some return pressure so the pressure in the equation would actually be (pressure in-pressure out).

 

[4570Man]

A concept that was missed here is that Hydraulic Horsepower = Pressure * Flow / 1714 with units in PSI and GPM. So OP 2300*16/1714=21.47HP but actually less because there will be some return pressure so the pressure in the equation would actually be (pressure in-pressure out).

The biggest concept that was missed is momentum does most of the work in brush cutting.

 

[Fallon]

The biggest concept that was missed is momentum does most of the work in brush cutting.

It depends on what you are cutting. Cutting thick grass actually uses a fair bit more HP than brush or small trees most of the times. Grass is a constant drain on power where the brush or thicker stuff is only intermittent. Momentum we I'll carry you through brief heavy bits, but if your sustained HP applied to the cutter isnt higher than the average requirements it's just going to keep slowing down the cutter until you stop feeding material.

 

[Damato]

So if I put a 6.15 CI hydraulic motor on this 90 HP gear box what thickness can I expect it to cut?

 

[SilentJ]

A concept that was missed here is that Hydraulic Horsepower = Pressure * Flow / 1714 with units in PSI and GPM. So OP 2300*16/1714=21.47HP but actually less because there will be some return pressure so the pressure in the equation would actually be (pressure in-pressure out).

Exactly right, plus some efficiency loss in the motor

The skid loader output is 21 HP (hydraulic). If you think you can Magically make 21 Hp behave like 90, then you致e learned a new law of physics.