Mowing What size Brush hog

   / What size Brush hog #1  

DAonly

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May 7, 2011
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Tractor
McCormick CT36HST/105 Loader
Hi fellas---- Don't believe I've ever posted here before.

I have a 2010 McCormick CT36HST tractor .......38.5 hp Mitsubishi 4 cyl. diesel. In case you missed the model its a Hydrostatic tranny. Bought it new. I'm wanting to buy a brush hog, but because it's a hydro tranny and I lose a good bit of pto hp because of it, what size brush hog will it handle ..... a 5' or a 6'? Not wanting to cut down big saplings and such but more of high weeds and such in old hayfields.
One dealer says it'll handle a 6 footer, but from what I read the pto only puts out 29 hp.

Thanks in advance for any input!
 
   / What size Brush hog #2  
My 5 ft rotary cutter manual states 25 hp minimum at the PTO.
 
   / What size Brush hog #3  
I run a 5'on our 30 h.p tractor and a 6' on a 44 h.p tractor ;both medium duty cutters.With the bigger tractor and BH in very thick heavy grass(6'+) it will bog down the tractor.I would stay with a 5' in your case.
 
   / What size Brush hog #4  
All other things being equal (and keeping it simple)

A 6 footer traveling at 5/6 the speed of a 5 footer uses the same power as the 5 footer.

A 5 footer traveling at 6/5th (120%) the speed of a 6 footer uses the same power as the 6 footer.

That is, it takes "x" amount of energy to cut an acre. How quickly you do it (either by ground speed or width of cut, or both) determines how much power is required.

Can tractor physically handle (lift, not get tippy, etc..) both cutters?
 
   / What size Brush hog #5  
Better a five foot 900-1,000 pound heavy duty model than a 600 pound light-medium duty model.

I put 300 engine hours on my tractor annually. I needed a five foot medium duty (Category 3 drive line) Rotary Cutter overhauled annually at $600 per.

My current five foot 1,006 pound (Category 4 drive line) Land Pride (brand) RCR2660 (model) Rotary Cutter cuts everything to 2" without slowing. Blades are 1" thick by 4" broad = tremendous strength and inertia.

My tractor has 37-gross horsepower.


LINK: https://www.landpride.com/ari/attach/lp/public/specs/312-783s.pdf
 
   / What size Brush hog #6  
All other things being equal (and keeping it simple)

A 6 footer traveling at 5/6 the speed of a 5 footer uses the same power as the 5 footer.

A 5 footer traveling at 6/5th (120%) the speed of a 6 footer uses the same power as the 6 footer.

Can tractor physically handle (lift, not get tippy, etc..) both cutters?

Coby, curious how you are calculating this. Simple ratio of cutting width to traveled speed, with all other variables remaining identical? If so, I hadn't thought of it that way. Not sure about that approach. Won't other factors change with the increase in cutting width, e.g. implement weight, maybe gearbox size, friction coefficients... :scratchchin:
 
   / What size Brush hog
  • Thread Starter
#7  
For what it's worth, I forgot to mention that the rear tires are almost 6 foot from one to the other......if I get a 5 footer I'd have to overlap my cuts which isn't any big deal I guess......I'd hate to buy a 6 footer and find the pto hp is underpowered.
I've had a 6' Bush Hog finish mower that I've used for 15 years that's done a decent job but not good for real high or too thick of growth. Had to give up my Old '56 Ford 640 series tractor that I restored as the body couldn't take any more abuse. Much easier operating this McCormick Hydro with power steering no less! Plus it's got a front end loader and 4wd.
Some good information here from what I've read.
 
   / What size Brush hog #8  
Coby, curious how you are calculating this. Simple ratio of cutting width to traveled speed, with all other variables remaining identical? If so, I hadn't thought of it that way. Not sure about that approach. Won't other factors change with the increase in cutting width, e.g. implement weight, maybe gearbox size, friction coefficients... :scratchchin:

Within limits, (keeping it simple)
It takes a certain amount of total energy to cut a given area. No matter if you do it quickly or slowly.
Power is a measure of how fast you can apply that energy (to reach that total).

So at a constant (horse) power output over a set amount of time the energy you can apply (and area you can cut) is fixed/limited (it is what it is). (That is, it doesn't matter if your going faster with a narrow cutter, or slower with a wide cutter, at the same constant horsepower output, the area cut (i.e. the total energy output) will be the same).

You can think of it in a lot of different ways, but horsepower required is a function of how quickly do you want to cut a given area.

Just like riding a 10 speed bike up a hill. It will take double the (horse) power to do it in 2 minutes versus 4 minutes, but both riders spent the same amount of total energy to get to the top of the hill.

(As an aside: If you do it in 2 minutes in low gear you need a lot of rpms and a little torque, if you also do it in 2 minutes, but in high gear you need a lot of torque, little rpms. Here, there's the same amount of energy and power output in both cases. (but now we're into torque curves, optimum rpm's, and engine's limits on rpm and torque, etc...))

Yes, in reality, implement weight, and gearbox differences, gearing of the tractor, even the torque of a 5' blade versus a 6' blade comes into play, but these variables are probably insignificant compared to the variables of the grass/brush your cutting and the speed you're traveling.
 
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   / What size Brush hog #9  
A 5' wide cutter behind a 6' wide tractor is mowing 1 knocked down tire track of grass (from the previous pass).
A 6' wide cutter behind a 6' wide tractor is mowing 2 knocked down tire tracks.
Other differences is when you want to mow next to a fence or building.
 
   / What size Brush hog #10  
Your tractor has a 65" wheel base and weighs 2711#. I had a 1720 New Holland that had the exact same wheel base and weighed 2800#. With the rears loaded she was around 3300#. The AG rear tires were set to 60". Your tractor will handle a light 6 foot cutter but you will need ballast on the front. Keep the weight of the cutter under 800#. Anything over that and you will get light in the front. I know from experience.
 
 
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