Brush Hog conversion from PTO to Hydraulic

cnat · Jun 14, 2017

I am currently converting a PTO 5 King Kutter Brush Hog (agri gear box) to hydraulic to run off my T200 Bobcat skid steer. The problem I am experiencing is attempting to identify the torque necessary to turn the brush hog at a certain RPM. I called Supply Surplus and this is the only answer I cannot provide to them so they can match a hydro motor for my application. I have read numerous threads referencing GPM, PSI, and PTO RPM, but nothing specific to torque. Any help would be greatly appreciated.

Thank you

DuckSlayer1017 · Jun 14, 2017

Here is a torque to hp converter. Take the hp rating for the cutter and get the torque from the calculator.

Horsepower & Torque Calculator | Spicer Parts

cnat · Jun 15, 2017

Thanks for the reply. I believe I have a 40hp gear box for the cutter. Should the engine RPM be the standard 540? Again, thanks for the help!

DuckSlayer1017 · Jun 15, 2017

If you are adding a hydraulic motor to the input shaft on the gear box then try to get one that is around 540. A little variation will probably be ok.

Farmerford · Jun 16, 2017

I have done the same thing and found that the controlling factor is the need to turn the mower gearbox input shaft at the 540 rpm (or thereabouts) it was designed for. Once you determine the gallons per minute that will flow to the motor you can then easily determine the size of the motor (cubic inches per revolution) that will turn at 540 rpm. The torque and horsepower transmitted to the gear box in put shaft are a function of pressure (which I assume is practically unchangeable-at least it is not increasable) and gpm, which is determined by your loader pump.

Rustyiron · Jun 16, 2017

Don't expect to have tractor driveshaft performance, I have an "ambusher" mower, (factory) built for a SS. It's works well but just not the same "umpff" that you get mechanically coupled to a tractor. I'd hate to try to mow a field with it but for beating back tall brush & saplings, dropping it down from 4-5' up is very effective. I'm sure you've seen it but Surplus center has a motor with a std 6 spline pto shaft that I would think would work providing it will handle the pretty high psi that SS's deliver. My ss is above 3500psi and iirc about 28 gpm on the low/std flow side.