3 pt brush mower question about slip clutch?

[kirkmcquest]

Hello,

I am in the market for a 3pt brush mower for a 31 hp Kobuta. I notice all the brushmowers have gearbox HP ratings. Most seem to be 40hp or higher. Does that mean 40 is the HIGHEST HP that can run that mower or the LOWEST required?

Thanks

Kirk

 

[tman1020]

Generally horsepower ratings for gear boxes are maximum horsepower that they can handle. The width of the cut will determine the minimum horsepower required. Also the weight of the unit will come into play in relationship to what your three-point and tractor can handle.

 

[MESSMAKER]

Generally horsepower ratings for gear boxes are maximum horsepower that they can handle. The width of the cut will determine the minimum horsepower required. Also the weight of the unit will come into play in relationship to what your three-point and tractor can handle.

That is not always true. Some mowers will come with a hp rated box as well as a min. hp for the unit. A 31 hp tractor will probably run most any 5 foot cutter. You can run a smaller cutter on a more powerful tractor, but you will strain the components on your cutter unless you are careful.

 

[tman1020]

That is not always true. Some mowers will come with a hp rated box as well as a min. hp for the unit. A 31 hp tractor will probably run most any 5 foot cutter. You can run a smaller cutter on a more powerful tractor, but you will strain the components on your cutter unless you are careful.

The minimum horsepower rating is usually due to width of cut not capacity of gearbox. please use caution 31 hp does not necessarily mean you can run a 5 foot bush hog. 5 foot bush hogs are very heavy even light duty ones. There are 31 hp tractors that may not have the hitch capacity or counterweight for that large of an implement on a three point.

 

[CobyRupert]

Interesting question: Say mower is rated for 40 Hp.
If run with a 70 hp tractor:
-If it hits something, gearbox doesn't care what the tractor hp is? Gearboxes' life (and tractors PTO)depends on slip clutch.
- However, if just normally mowing, and traveling at a speed where the mower is consuming (and gearbox is transferring) >40 hp, one could make an argument that gearbox is being strained. However, one would hope that the gearbox is built to take some shock/impact loads and this safety factor easily accommodates the extra horsepower. In fact, wouldn't the shock load be reduced when you hit something since you're running the slip clutch closer to it's break away threshold at the higher horsepower? (Hmm?-Not sure about that)

Now take the opposite case: Running 40 hp mower with 25 hp tractor (Assuming tractor has the capacity to handle it- another sign that hp ratings are just a recommendation):

No problem as horsepower required is just a function of speed. A mower that requires 40 hp at 3 mph only requires 20 hp at 1.5 mph.

Here's an interesting question: From the gearboxes' view, is a 40 hp gasoline engine equal to 40 hp diesel? I believe the answer is No. Thus reaffirming that horsepower ratings are just suggestions.