Rotary Cutter Brush Hog gearbox ratio

[Brumm]

Has anyone replaced a 1:1.47 ratio brush hog gearbox with a higher ratio 1:1.93 or 1:2.83 ratio. Would this setup help the brush hog to operate under reduced acceleration contributing to fuel economy and more efficiency? Would the 1:2.83 ratio gearbox perform well using the ground speed PTO? The tractor used for this implement would be a Massey Ferguson 135 with a Perkins diesel to maintain pasture, small shrubs and tall grass of 2' in height.

My sincere thanks to all who can provide information. With this knowledge I hope to make an efficient easy to handle Rotary Cutter.

 

[loggin]

Has anyone replaced a 1:1.47 ratio brush hog gearbox with a higher ratio 1:1.93 or 1:2.83 ratio. Would this setup help the brush hog to operate under reduced acceleration contributing to fuel economy and more efficiency? Would the 1:2.83 ratio gearbox perform well using the ground speed PTO? The tractor used for this implement would be a Massey Ferguson 135 with a Perkins diesel to maintain pasture, small shrubs and tall grass of 2' in height.

My sincere thanks to all who can provide information. With this knowledge I hope to make an efficient easy to handle Rotary Cutter.

I would think there are a few things to consider here.

To begin with, how big is the brush cutter?

The higher the ratio, the less power you have to cut the brush.

I would think the 1:2.83 is likely too high, that is almost twice the speed of the original.

It will be interesting to see what others have to say!

 

[MTGreen]

Are you running a chain or the standard blade arms?
I would imagine speeding it up would potentially be advantageous if running chains.

Changing the ratio has nothing to do with acceleration, just the rotational speed of input PTO shaft vs output shaft

 

[Brumm]

Thank you for your kind response. I was thinking of a 5' or 6' size brush hog using blade arms.
Yes I agree with you that 1:2.83 is very fast to run on engine PTO operation (A). May I know your opinion on using the 1:2.83 on a rotary cutter using the Ground Speed PTO option (B) to operate.

 

[loggin]

Thank you for your kind response. I was thinking of a 5' or 6' size brush hog using blade arms.
Yes I agree with you that 1:2.83 is very fast to run on engine PTO operation (A). May I know your opinion on using the 1:2.83 on a rotary cutter using the Ground Speed PTO option (B) to operate. View attachment 863577

I believe using ground speed pto operation it is hard to get the balance right between forward speed and pto rotation. Much easier to get the balance right if you can vary the engine rpm and change gears when the grass/brush become thicker or more dense.

Just my 2 cents.

 

[Brumm]

I believe using ground speed pto operation it is hard to get the balance right between forward speed and pto rotation. Much easier to get the balance right if you can vary the engine rpm and change gears when the grass/brush become thicker or more dense.

Just my 2 cents.

Thank you for your good advice. I'm very grateful to your input on this topic. I shall continue to do more research and learn more. Thank you very much.

 

[BigGG]

Thank you for your good advice. I'm very grateful to your input on this topic. I shall continue to do more research and learn more. Thank you very much.

I agree with Loggin. Assuming your ground speed setting is like our old MF50, it is not good for bush hogging, I've never figured out what it would be useful for.

You want the independent PTO drive so the blade can be spinning while you are still, or nearly so.

I'd stick with the original ratio. Blade tip speed is controlled by the ratio, and is designed for a certain speed.. Speeding it up too much could create a danger from objects being discharged at excessive speed.

 

[Brumm]

I agree with Loggin. Assuming your ground speed setting is like our old MF50, it is not good for bush hogging, I've never figured out what it would be useful for.

You want the independent PTO drive so the blade can be spinning while you are still, or nearly so.

I'd stick with the original ratio. Blade tip speed is controlled by the ratio, and is designed for a certain speed.. Speeding it up too much could create a danger from objects being discharged at excessive speed.

Yes, you are correct as safety must always come first. I am planning to fabricate my own rotary cutter. The 5' rotary cutter doesn't cover the entire tyre tracks so I plan on building a 6' rotary cutter to cover the entire rear tyre track width. I was planning on something like the Medium Duty Kodiak design but a little more lighter in weight to prevent the front of the Massey Ferguson tipping up (see-saw effect). I came across a brush hog gearbox with the ratio of 1:1.69 any opinions on this ratio for performance compared with the common 1:1.47 gearbox.

 

[Brumm]

One more question Gentleman,
The Massey Ferguson 135 Perkins Diesel has a tested PTO of around 35hp what horse power gearbox is suitable? 40hp or 60hp ? My utmost thanks to all who contributed to make this topic educational. Hope this helps others in need. Thank you.

 

[HybridVigor]

I agree with Loggin. Assuming your ground speed setting is like our old MF50, it is not good for bush hogging, I've never figured out what it would be useful for.

You want the independent PTO drive so the blade can be spinning while you are still, or nearly so.

I'd stick with the original ratio. Blade tip speed is controlled by the ratio, and is designed for a certain speed.. Speeding it up too much could create a danger from objects being discharged at excessive speed.

You hardly ever see them anymore but I imagine the primary advantage for a ground speed PTO was for a wagon or trailer with a powered axle. A PTO shaft would connect to the tractor and drive the wheels on the trailer. This was a feature for things like forage wagons and would effectively give the operator another driven axle to get though muddy conditions.

In your scenario BRUMM I would be afraid that your MF135 wouldn't have enough horsepower to spin a 6ft cutter in heavy grass at less than full engine speed. My understanding is that engine speed required to hit 540 RPM on the PTO is typically at the peak of the powerband for the engine. While spinning the engine slower with the higher ratio gear box would be more efficient in light cutting applications, if you have heavy grass to cut it may stall out the tractor. I have a slightly smaller tractor I use with a 5 ft. cutter and 2 ft. grass is sometimes more than I can handle if it is very lush.