Flail Mower Skid Steer conversion?

PRCWI · Jul 28, 2017

I have seen several different instances of people converting 3pt bush hogs/rotary mowers to be powered by a hydraulic motor run from a skid steer. Wondering if anyone has tried it with a flail mower? Seems like it wouldn't be too complicated if a guy had a center mount flail. I've been considering it but my skid steer only has enough flow to generate about 25hp from the hydraulic motor. Still I like the idea of front mounted mower and being able to operate in tight spaces.

Here is are a couple of examples I found for rotary mower conversions. The motors are easily sources from surplus supply along with the bypass and pressure control valves.
Homemade skid steer brush hog - YouTube

Converting Brush Hog For Skid Steer - YouTube

PRCWI · Jul 28, 2017

I should add I realize a guy can buy flails for skid steers but it seems like you could convert one far cheaper if you have the skills to do some fab work

leonz · Jul 28, 2017

NOPE, NOPE, NOPE. To much depends on the fluid power available for the skid steer attachment circuit and whether you have a quick hitch and a SSQA with a hydraulic gear motor that will deliver the torque needed to create 540 RPM for the flail mowers needed minimum horsepower requirements.

If you were thinking along the lines of attaching a hydraulic motor to the flail mower rotor that would eliminate any efficiency versus the gearbox driven belt drive and you would need a hydraulic motor vane motor that would create 2,200 RPM under load and a vane pump that would push 35 gallons per minute from a hydraulic power pack on the back of the skid steer.

PRCWI · Jul 28, 2017

I agree you need to be very specific in how you match your hydraulic motor to match your flow capabilities for your skid steer but that part seems to be fairly straight forward once you understand it if you have the right calculators to do it. Surplus center carries a range of Hydraulic AG PTO shaft motors.
Ag PTO Output Hydraulic Motors | Hydraulic Motors | Hydraulics | www.surpluscenter.com

They also have a couple of very helpful pages to assist in figuring out what motor to match with your skid steer. This one is great for figuring out the HP, Torque and RPM that would be produced by a specific flow rate:
Surplus Center

I was thinking just replacing it the "PTO" shaft with a Hydraulic motor properly sized for my skid steer.
One for my skid steer properly sized for my flow would generate 21 hp, 2447 in. lbs or 204 ft. lbs of torque, and 537 rpm on the PTO at full throttle with a flow rate of 14.3gpm which is what my skid can do. This would be with a 6.15 cubic inch motor.

6.15 CU IN PTO DRIVE MOTOR | Low Speed High Torque Hydraulic Motors | Hydraulic Motors | Hydraulics | www.surpluscenter.com

Since my skid steer can push up to 3000psi I would also need a regulating valve to limit the PSI going to the motor to 2500 so that the motor would not be damaged by over pressure. SAE 12 3 GPM HYD MOTOR RELIEF BYPASS VALVE | Relief & Cushion Valves | Hydraulic Valves | Hydraulics | www.surpluscenter.com
and a simple one way check valve to allow for run out of the energy in the machine when the Hydraulics were stopped so as not to damage the machine.

There are several 60" flails that have a min HP requirement of 20hp so it seems like even my skid would run one but not sure if there are things I am not thinking off that I should be?

I would think the main things needed would be fabricating a frame to mount the hydraulic motor in line with the Gear box assembly in place of the PTO shaft and fabricating a quicktach to the back of the flail for connecting to the skid steer.

My skidsteer has a relatively low flow as it's older, so it won't generate much above 20 hp through hydraulic power but if I ever replaced it I would think it would be a real possibility to do a conversion like this and get into a front mounted flail far cheaper than it would otherwise cost and even at the specs of my skid it would still seem possible to have it run a 60" flail.

vvanders · Jul 28, 2017

PRCWI said:
I agree you need to be very specific in how you match your hydraulic motor to match your flow capabilities for your skid steer but that part seems to be fairly straight forward once you understand it if you have the right calculators to do it. Surplus center carries a range of Hydraulic AG PTO shaft motors.
Ag PTO Output Hydraulic Motors | Hydraulic Motors | Hydraulics | www.surpluscenter.com

They also have a couple of very helpful pages to assist in figuring out what motor to match with your skid steer. This one is great for figuring out the HP, Torque and RPM that would be produced by a specific flow rate:
Surplus Center

I was thinking just replacing it the "PTO" shaft with a Hydraulic motor properly sized for my skid steer.
One for my skid steer properly sized for my flow would generate 21 hp, 2447 in. lbs or 204 ft. lbs of torque, and 537 rpm on the PTO at full throttle with a flow rate of 14.3gpm which is what my skid can do. This would be with a 6.15 cubic inch motor.

6.15 CU IN PTO DRIVE MOTOR | Low Speed High Torque Hydraulic Motors | Hydraulic Motors | Hydraulics | www.surpluscenter.com

Since my skid steer can push up to 3000psi I would also need a regulating valve to limit the PSI going to the motor to 2500 so that the motor would not be damaged by over pressure. SAE 12 3 GPM HYD MOTOR RELIEF BYPASS VALVE | Relief & Cushion Valves | Hydraulic Valves | Hydraulics | www.surpluscenter.com
and a simple one way check valve to allow for run out of the energy in the machine when the Hydraulics were stopped so as not to damage the machine.

There are several 60" flails that have a min HP requirement of 20hp so it seems like even my skid would run one but not sure if there are things I am not thinking off that I should be?

I would think the main things needed would be fabricating a frame to mount the hydraulic motor in line with the Gear box assembly in place of the PTO shaft and fabricating a quicktach to the back of the flail for connecting to the skid steer.

My skidsteer has a relatively low flow as it's older, so it won't generate much above 20 hp through hydraulic power but if I ever replaced it I would think it would be a real possibility to do a conversion like this and get into a front mounted flail far cheaper than it would otherwise cost and even at the specs of my skid it would still seem possible to have it run a 60" flail.

Just because they list a 60" flail at 20HP doesn't mean it'll run well. Our ford is about 19HP at the PTO but I can easily bog down our 54" flail if I'm heading uphill in heavy grass or going too fast.

PRCWI · Jul 28, 2017

vvanders said:
Just because they list a 60" flail at 20HP doesn't mean it'll run well. Our ford is about 19HP at the PTO but I can easily bog down our 54" flail if I'm heading uphill in heavy grass or going too fast.

Good point.

oldnslo · Jul 28, 2017

The big variable is the inefficiency of hydraulics Vs mechanical drive. It takes very good hydraulic components to provide an over all system efficiency in the 80% range. Geroler / Geroter style Low Speed High torque motors are typically not considered high efficiency components.