ROTARY CUTTER SPEED

[flINTLOCK]

Most posts I've seen refer to running RC about 540 rpm. A farmer bushogs the brushy areas around my development and his tractor is so quiet while running, I know he's running at less than 540. Any harm in that??

 

[RoyJackson]

Most posts I've seen refer to running RC about 540 rpm. A farmer bushogs the brushy areas around my development and his tractor is so quiet while running, I know he's running at less than 540. Any harm in that??

You won't get a clean cut..that's about it. Maybe a bit more vibration.

As far as the farmer...you ought to ask him. I'm guessing he may be running his tractor at a lower RPM, but the PTO is still doing 540 RPM.

My cutter is pretty quiet once it's spun up to operating speed and if I'm not going through any heavy stuff...but I know "quiet" is a relative term.

 

[Z-Michigan]

My tractor is quieter at 2200 rpm (which equates to 540 PTO) than it is at 1400-1800 rpm which I use for non-PTO tasks. And the cutter doesn't make much noise unless it's chewing on something. I would not be surprised if the farmer is operating at 540 PTO RPM (or 1000rpm if he has a big setup made to work at that speed). Many JD models include an "economy" PTO that allows 540 PTO rpm at a lower engine rpm for lighter tasks, while allowing the same 540 PTO rpm at higher engine rpm for max hp.

I agree that there shouldn't be an issue with running below recommended rpm, but the cut quality will suffer pretty badly.

 

[flINTLOCK]

Thanks. I'll ask him next time through.

 

[riptides]

Most posts I've seen refer to running RC about 540 rpm. A farmer bushogs the brushy areas around my development and his tractor is so quiet while running, I know he's running at less than 540. Any harm in that??

Depends on the cutter and the cuttie. With various type of grasses I vary the RPM speeds dramatically on the go. I have a mixture of weed, fescue, orchard grasses and what not. Some of the weeds go up to four feet, they may get the 540rpm. Some of the grass areas may get conciderably less rpms.

You'll have to operate and figure out what is best for you. I rarely operate at full rated rpms 100 percent of the time.

Blade, terrain and material type all factor in to the rpms needed for a "good" cut.

-Mike Z.

 

[Soundguy]

At proper pto /eng speed.. i can't hear my batwing mower unless it is really eating woody stuff.

Soundguy

 

[flusher]

Most posts I've seen refer to running RC about 540 rpm. A farmer bushogs the brushy areas around my development and his tractor is so quiet while running, I know he's running at less than 540. Any harm in that??

My neighbor has a Ford 8N that generates 545 rpm at the pto at 1500 rpm engine (gas). My 2005 Kubota B7510HST generates 540 rpm pto at 2600 rpm engine (diesel) for my KK brush hog. The 8N purrs along when he brush hogs. My Bota screams.

 

[JerryG]

This question has come up many time over the years. I have never seen a cutter damaged by running a slower RPM, but thought it would be interesting to see what a manufacture would say. So, I emailed Woods about this and here is what they said.

No damage will be done to your 5' rotary cutter if operated at slower than 540 RPM. The cut quality may not look as nice, because the blades are rotating slower. Operating at a slower RPM will require more HP from your tractor.
Let us know how we can be of assistance.
Xxxxx Xxxxx
Special Accounts Coordinator
Woods Equipment Co.

 

[Farmwithjunk]

It's obvious that some folks feel very passionate about this subject. It's equally apparent that the results are varied from person to person, mower to mower and tractor to tractor.... and let's not forget grass and weeds to grass and weeds.

I just walked in from 3 hours of mowing. I cut for about an hour with my Massey 150 and the 6' Bush Hog 286. 540 rpm on the pto is @ 1750 engine rpm. I cut a while at that speed. I cut for a while at 1500 rpm. I cut a while @ 1400 rpm. And I'd bet NO ONE, maybe not even I could walk out in the field and tell where the slower or faster engine speed was used. Then I fired up the Deere 6430 and 15' batwing. I varied rpms as much as 800 revs from slow to fast. Same deal. You can't tell the difference..... EXCEPT..... on the fuel gauge. The Massey will run all day on aprox. 2-1/2 gallons less fuel by holding at 1500 rpm as opposed to 1750. Not sure on the Deere, as I've never really checked the "milage". The Massey has been with me for 36 years. If using it "easy" was going to hurt it, I believe it would have by now.

But... By the adament beliefs of a few, there must be some tractor/mower/grass/rpm combo's that DO see a difference. All I can say is, try it and see for yourself. If you CAN'T run at a slower rpm and save fuel while still getting great results, DON'T. If you can, go for it. It works for me and has for quite a few years. That doesn't guarantee the next guy will have the same results. But to say it's yes OR no, but no MAYBE is just plain ol' wrong.

 

[RoyJackson]

My neighbor has a Ford 8N that generates 545 rpm at the pto at 1500 rpm engine (gas). My 2005 Kubota B7510HST generates 540 rpm pto at 2600 rpm engine (diesel) for my KK brush hog. The 8N purrs along when he brush hogs. My Bota screams.

That old Ford has a lot more cubic inches..probably more then double. As far as max torque...well, a lot more then your B7510.

 

[RoyJackson]

It's obvious that some folks feel very passionate about this subject. It's equally apparent that the results are varied from person to person, mower to mower and tractor to tractor.... and let's not forget grass and weeds to grass and weeds.

I didn't see too much excitment on this topic...
Now, is it better to brush cut with a hydro or gears...??

That'll bring a response!

 

[Farmwithjunk]

I didn't see too much excitment on this topic...
Now, is it better to brush cut with a hydro or gears...??

That'll bring a response!

Hydro or gear?
Cal/clor or Rim Gaurd?
R4's or R1's?
Which mows the best?

Answer; Which ever you have in your barn at the time.

 

[Varmintmist]

Most of my mowing is 1200 rpm. It cuts fine at that speed, I did the lawn once with the brushhog and it looked ok, except I cant get real close to the house

If you run into thick heavy clumped grasses you will probably have to kick it up a few and slow down some. Same if you are mowing over multiflora rose. For avg spring weeds, gear up and rmps down a little. If it looks like you need to go faster, then give her a kick.

 

[Z-Michigan]

Hydro or gear?
Cal/clor or Rim Gaurd?
R4's or R1's?
Which mows the best?

The one and only way to mow is with a sickle-whip mower pulled by a tractor with R18 tires filled with plutonium and using a turbo-electric transmission. Anything else kills the grass and spreads rabies.

 

[flINTLOCK]

I figured that I'd inch up the rpm's till the initial vibration smooths out and try it at that speed. Not sure what that is right now, but I know it's substantially less than the 2500 rpm's I need for 540 at PTO. Should be able to save some fuel since I'm cutting grass and light weeds.

 

[john_bud]

I didn't see too much excitment on this topic...
Now, is it better to brush cut with a hydro or gears...??

That'll bring a response!

I tried cutting with hydro (fluid), but it just made a mess and didn't cut anything. Then I tried a gear. It wasn't too sharp, so it didn't do much cutting either, but was a lot less messy.

I think sticking with a mower blade will be the best for my cutting needs.

jb

 

[Z-Michigan]

I just walked in from 3 hours of mowing. I cut for about an hour with my Massey 150 and the 6' Bush Hog 286. 540 rpm on the pto is @ 1750 engine rpm. I cut a while at that speed. I cut for a while at 1500 rpm. I cut a while @ 1400 rpm. And I'd bet NO ONE, maybe not even I could walk out in the field and tell where the slower or faster engine speed was used. Then I fired up the Deere 6430 and 15' batwing. I varied rpms as much as 800 revs from slow to fast. Same deal. You can't tell the difference..... EXCEPT..... on the fuel gauge. The Massey will run all day on aprox. 2-1/2 gallons less fuel by holding at 1500 rpm as opposed to 1750. Not sure on the Deere, as I've never really checked the "milage". The Massey has been with me for 36 years. If using it "easy" was going to hurt it, I believe it would have by now.

Back to serious posts now... I read the above last week and have to say I was skeptical, but instead of questioning it I figured I would just give it a try. I did, and got a surprise. On my tractor 540 PTO is at 2200 engine rpm. I tried 1800 and 2000 engine rpm (the lower equating to about 445 PTO) and found the results were about the same as at 540 PTO rpm. Big surprise to me. Also found out a few other things in the process:

1) I'm not getting really good cut quality on grass at any ground speed much over 3.0mph, even at 540 PTO rpm. This is a big disappointment as I sized the tractor vs. mower to allow for cutting at higher speeds (and on power alone I could cut at 6-8mph, maybe even more). I can cut various weeds and woody plants at higher speeds than 3mph with perfectly good cut quality, though.

2) This is probably old news to those with experience, but cut quality seems a lot better on really tall grass (12" or more, especially if 20" or more) than on grass that is just on the tall end of lawn grass (6-8"). I figure that the taller grass provides more resistance to being just knocked over and therefore gets cut more evenly.

3) With my setup I'm not getting good cut quality on anything when I go significantly below 1800 engine rpm. Not saying that this will hold true for everyone else's setup, but that's what I find on mine.

 

[pat32rf]

Hydro or gears- You gotta be kidding! Gears may be OK for someone with a big flat field of grass but when you wanna cut thick or thin, up or down, its real nice to just let up on your pedal a bit to ease into things instead of trying to slip a clutch or grab a lower gear half way up a hill.
I just wish that my JD had a clutch pedal that would disconnect the PTO like my old Bota did.( It had hydro and a clutch)

 

[3RRL]

I just cut about 2 acres of wooded meadow and surroundings last weekend at my remote property. The grass and weeds were about 3 to 4 feet high. I checked out the blades and bolts on the 6' Howse rotary cutter before I started and also the gear oil level. Then sharpened the blades a tad and hooked it up.
Here's a picture before:



And one after I got done.



I had to cut between the trees on the perimeter of the meadow, going forward and backwards at times. I have a 55 hp gear tranny Kama 554 with 540 PTO rpm at 2300 engine rpm in the 540 PTO speed. I have 2 PTO speeds, 540 and 720 rpm.
Here's another view:



I can't go too fast because the terrain is not flat. In fact, it is my food plot, so there are several natural swells and gullies and a steep bank on one side. I mow in 2nd or 3rd low, and using 1 low reverse to cut up the steep bank.



I cut all this terrain at 1725 engine rpm with my PTO in the 720 range. That means the PTO is spinning at 540 rpm, which is perfect for my rotary cutter. This engine rpm range also just happens to fall in the engine's peak torque range (or very very close to it). So when it feels a strain, it pulls through it with very little bog down at all. Additionally, I get much better fuel economy. It took me about 4 hours to finish everything, going around the trees, gullies and banks.

To give you an idea of what it looked like when still green, check this out.



I had cut a part of it a month ago when it was still green to generate some interest for the wildlife.



IMO, there is nothing wrong with using lower rpm when mowing. In fact, I would go as far to say the lower rpm you can get away with, the better for a number of reasons. Fuel economy and wear and tear on the tractor AND your rotary cutter are a couple of them. The flip side is how fast you want to get it done , of course.

I could have used lower engine rpm on the down hill passes, but although it does not look very sloped, it is. So going uphill I needed to keep the engine rpm at a reasonable point to generate enough hp to keep her going. I would say your limiters are the kind of terrain and what you are cutting determines the hp needed, and the outcome of the cut. That is, is it desirable and acceptable to you. That in turn will tell you if the PTO rpm is correct for YOUR job.

 

[riptides]

...pictures...

No see them. See them in the edit/quote though. Hmmmmm....

-Mike Z.