Rotary Cutter Blade tip speed

[Brads 1715]

So I'm looking to buy a rotary cutter/ bush hog. There is all kinds of brands and options out there. I have a ford 1715 that has 27hp and 23pto horsepower. I'm being informed(by the salesperson) that a 5 foot cutter is the largest size this tractor can handle. Im good with a 5 footer. My question is about tip speed. Does a cutter with 16000 tip speed have more cutting ability vs a cutter with 13000 tip speed? I'm not worried about the quality of the cut, im not using it for my yard. Its going to be used in brush, and tall grass. I want a cutter that does its job without overworking the tractor. So maybe what I'm asking is which cutter has the most torque to power through some hard cutting? A high tip speed or a low tip speed?

 

[number9L]

I am a new tractor owner, but when I was asking questions on the forums I was told to get over 15K tip speed for both rotary cutter and finish mower.

I'd think that with the higher tip speeds, the inertia of the blades spinning that fast would have a less tendency to bog down and power on through when you hit larger things.

...

 

[Hollow]

Higher blade tip speed means more contact times per second. Which when cutting brush that means the blade will be cutting through less vegetation for each rotation. And when mowing fields you might not have to run the tractor at such high rpm's. I run a Bushhog 286 behind my tractor and unless I'm in really thick grass I usually run it 400 rpm's under the 540 mark. It uses much less diesel that way!

 

[MHarryE]

Higher tip speeds result in more energy but also give a sharper cut. Think of a blade of grass, piece of brush, etc. whack it slowly and the piece being cut will bend over slightly as its being sheared off. Hit it fast and there is little bending as the blade slices through. Lower engine speed may reduce your fuel consumption depending on your tractor and its power plus ability to hold that speed, but the cutters are rated at PTO speed for a reason - ability to do the cutting job most customers want.

 

[leonz]

I dont have my hand on your wallet BUT.


I think your way underpowered for a five footer for sure.

The not so golden rule is 5 horsepower per foot with a rotary cutter
or flail mower.

With a four footer you may have 7 horse power to run the tractor.

I would ask if you could test mow with a five footer they
can give you to use.

You do know that the rotary cutter blades are ment to be ground with a dull edge dont you?

A rotary cutter only presents half its cutting width to the brush to be mowed with the
following blade always trailing BTW.

ANY rotary cutter or brush/grass flail mower will over work your tractor unless its a four footer.

 

[PandDLong]

I ran a 5 foot cutter with my JD 850, which had a little less HP than the OP's tractor, and I was satisfied with the performance. There are a few factors that help determine how many HP you need for the cutter. For me, I was only cutting grass and weeds - no bushes or saplings, I'm on the prairie - no hills to climb, and I was willing to slow down and take narrower cuts when the grass got thick and heavy. For me, the extra foot practically covered my tracks so I could mow close to a fence line and I could cover ground faster when the grass was thinner and/or dry - which was most of the time.

The specifics of,your needs will either fit a 5 footer or you'll need to drop down a size.

 

[TomSeller]

My opinion is that it depends on how thick the grass is and how thick the brush stems are. If this is tall but not thick grass and not big stems on the brush, you should do fine. Otherwise you might be in low, low gear on your first pass. The next year it will be easier, particularly if you don't let the grass grow full height before you mow. The brush should be less of a concern.

 

[dirt ditch]

My JD is 27hp / 24pto and it runs a 5' just fine. I also run it 400-500rpm lower than the 540 mark. Does not matter, 540 or slower I mow in L3 of a 2 range gear box with the same results.

 

[RoyJackson]

I dont have my hand on your wallet BUT.


I think your way underpowered for a five footer for sure.

Not really...the 5 HP per foot of width is a very tenuous guideline. My first tractor was a Deere 670 with 17 PTO HP. I ran a 60" Landpride cutter behind that. Slow going and some partial width passes, but it did a fine job. My second tractor, a Deere 790 with 24 PTO HP and the same cutter did great...very little bogging through heavy brush and quite a few saplings.

 

[Creamer]

My Ford 1710 amazes me at how well it handles the 60" Bushhog Squealer I have. I cruise through grass, clover, and weeds taller than the tractor with not much problem. It is a good load for the tractor but it is not overworking it. When I get into saplings that I use the loader to knock over I slow down a bit but part of that is just so i make sure I can see and don't get into rocks, mounds, etc.

Your 1715 should handle it fine. Tip speed - definitely agree with the above 15,000 recommendation.

 

[TomSeller]

One thing I like about bigger brush hogs is you can get the same tip speed at lower mower rpm. They run smoother back there and the blades typically have more mass because they are longer to power their way through heavy grass and brush. So smaller isn't always better.

 

[Brads 1715]

Thanks for all the reply's. This is the kind of feed back I was looking for. I had a guy tell me that the faster tip speeds requires more pto horsepower. Verses the slower tip speed(say 12 to 14 thousand) do not require as much pto horsepower. Perhaps the gear ratio on the slower tip speed cutters have more torque than a faster tip speed. Thus making it easier on the tractor. I'm so confused about which one to get. Maybe I'm over analyzing the issue.

 

[LD1]

I would get the higher tip speed ones for reasons already mentioned. HP is a wash. You wont notice one "needs" more power than the other.

And you should be okay with the 5' cutter. May just have to go a bit slower. About everyone uses 5' cutters behind the old N fords, and they were similar on power. And brush/weeds do mow easier than dense grass. Dense grass would bog a 5' cutter behind a 50hp tractor. Just the way it is.

 

[Kioti Tom]

I had a custom brush hogging business for several years and I did it with a Ford 8N (about 23 HP and 19 PTO)
I used a 5 ft KK brush hog. I had no problems with it. Get into really heavy growth, Just I just up the engine
speed. As mentioned do not have a sharp blade. I would sharpen it to about a 1/8th in radius or a bit duller
and it would work great. The sharpening was to mainly take out the nicks in the blade to prevent cracking from
that point and breaking off a piece. ( We do that on Aircraft Propellers) You should be good with what you have
and a 5 foot hog...
Tom

 

[Hollow]

Higher tip speeds result in more energy but also give a sharper cut. Think of a blade of grass, piece of brush, etc. whack it slowly and the piece being cut will bend over slightly as its being sheared off. Hit it fast and there is little bending as the blade slices through. Lower engine speed may reduce your fuel consumption depending on your tractor and its power plus ability to hold that speed, but the cutters are rated at PTO speed for a reason - ability to do the cutting job most customers want.

It all depends on the grass being cut, and the time of year as well. It doesn't take high tip speeds to give a clean cut on many grasses right now. Later on in the summer though stims get harder an don't pop back up after being run over by the tractor wheels as easily, it will take a higher tip speed to suck the grass upright again for cutting. (Assuming the cutter has up draft blades)

 

[Hollow]

Thanks for all the reply's. This is the kind of feed back I was looking for. I had a guy tell me that the faster tip speeds requires more pto horsepower. Verses the slower tip speed(say 12 to 14 thousand) do not require as much pto horsepower. Perhaps the gear ratio on the slower tip speed cutters have more torque than a faster tip speed. Thus making it easier on the tractor. I'm so confused about which one to get. Maybe I'm over analyzing the issue.

I don't see how a higher speeded cutter is going to load the tractor more. Sure it is leveraging more with the gear ratios but the cutter is also cutting through less vegetation per rotation. If I were you I would go with the higher speeded cutter and if you think it is over loading your tractor in areas you can always slow down or increase your overlap. You can always make a 4' pass with a 5' cutter but not the other way around.

 

[Midniteoyl]

Dont know about size vs hp, but as far as tip speed, faster is better. I have a Zero Turn with 19k!

 

[leonz]

Thanks for all the reply's. This is the kind of feed back I was looking for. I had a guy tell me that the faster tip speeds requires more pto horsepower. Verses the slower tip speed(say 12 to 14 thousand) do not require as much pto horsepower. Perhaps the gear ratio on the slower tip speed cutters have more torque than a faster tip speed. Thus making it easier on the tractor. I'm so confused about which one to get. Maybe I'm over analyzing the issue.

OH FOR................


Its a one to one gearbox for goodness sake!! SO your transmitting 540 rpm ASSUMING your going
to use 540 rpm to the gear box which is transmitting the 540 rpm to the stub shaft/stump jumper and then the
two blades ares simply reacting to the centrifugal force generated by one of the blades. wait til you see one
break off and see how far they flywith the 15000 FPM-and safety chains will not stop a launched brush mower blade by the way-there are several threads with news accounts of accidents and fatalities with rotary brush mowers here on the forum.

 

[LD1]

They are not all 1:1 gearboxes....

 

[joshuabardwell]

I think your way underpowered for a five footer for sure.

I have a tractor with 19 PTO HP, if memory serves. I got a 5 ft. rotary cutter because I wanted to cover my tracks, even if I was a little under-powered for it. I didn't have much trouble using it. Did I have to go slower with a 5 ft than I would have with a 4 ft? Absolutely. But, frankly, I don't go very fast when brush cutting anyway, because of the possibility of driving into a hidden ditch or rolling over a piece of debris. Since I'm going to be going slow anyway, may as well get as wide a cut as possible.

I think the difference between a 4 and a 5 ft cutter on a tractor this size is basically cancelled out by the travel speed vs. cut width. With the 5 ft, you go slower, but cut 25% wider. With the 4 ft. you cut narrower but can go faster--if you want to, which you often won't, in which case may as well get the 5 ft.