540 rpm?

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bird dog
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540 rpm?

Postby bird dog » Thu Sep 06, 2018 3:15 pm

Question. Most shredders say to operate at a pto speed of 540. What happens if you don't? It seems that if what you are cutting is thin, why run at full speed if it is working correctly at say 470?

Thanks
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Re: 540 rpm?

Postby M-5 » Thu Sep 06, 2018 3:36 pm

Momentum, When the 'Mower" is running at operating speed it is most efficient , slower speeds can be harder on the tractor. If your using a shredder like it supposed to be used the cheese does not care how fast you go.
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Re: 540 rpm?

Postby ddd75 » Thu Sep 06, 2018 3:47 pm

just depends on your tractor, implement and conditions.

thin hay i usually run around 1900 and heavy hay is 2100 .. i have never operated at full 540.
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Re: 540 rpm?

Postby Texasmark » Sat Sep 08, 2018 1:52 pm

Depends. The faster the PTO RPMS, the higher the tip speed, the more kinetic energy stored in the blades and the nicer the cut. I usually run 540 on the PTO for that reason but I have tractors that have different PTO ratios that I can select so on light cutting I can cut the tractor RPMS down and still get 540 on the PTO.
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Re: 540 rpm?

Postby ddd75 » Sat Sep 08, 2018 3:04 pm

i was just reading my vermeer baler manual and it says to run the baler at 75% PTO speed.
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Re: 540 rpm?

Postby greybeard » Sat Sep 08, 2018 4:13 pm

Texasmark wrote:Depends. The faster the PTO RPMS, the higher the tip speed, the more kinetic energy stored in the blades and the nicer the cut. I usually run 540 on the PTO for that reason but I have tractors that have different PTO ratios that I can select so on light cutting I can cut the tractor RPMS down and still get 540 on the PTO.


This.
Newton's First Law. 'An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.'

The rotating mass of the blades and hub turns into a de facto flywheel that stores the energy, instead of relying on a second to second timeline dependence of the pto shaft's HP. Some mowers are better at it than others. As Dash said, the pto rpm too low really puts a load on the tractor, AND, is also hard on the gearbox(es). You really want to use the torque and energy that is built up in the rotating mass below the gearbox, instead of having the gearbox take the brunt of every thing the forage or brush throws at it.

I had to explain to one of my neighbors, the importance of keeping his 6' mower rpm up just last week, after he sheared his 3rd shear pin in as many hours, cutting thick grass and some goatweed. It was a chore to get his pto shaft off the gearbox the 3rd time, as the ujoint hub had galled the shaft badly. He actually thought it a case of his 50hp tractor being 'too powerful' for his 6' mower.
operator error.

50 rpm can make a LOT of difference to those blades. The difference between trying to push the edge of a machete thru a cornstalk and raring back and hitting the stalk with a good swing.


Do you 'have' to run it 540? No, but that depends on travel speed, what you're cutting, and how good your mower is designed and the gear ratio of the gearbox. Well designed mowers are designed to take advantage and use the kinetic energy as part of the hp/torque equation.
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Re: 540 rpm?

Postby farmerjan » Sat Sep 08, 2018 8:17 pm

I'm no mechanic, nor do I know alot about all that greybeard was saying.... but the first farmer that taught me to run a tractor and haybine, said that you had to run it at the rpm it called for, if that is what type of equipment you were running, and that if you needed to go faster, then the tractor gear could be changed and the rpm should be run where it needed to be. And if I was in very heavy thick stuff, then I needed to keep my rpm up and SLOW my ground speed by shifting down a gear. I don't know if that is right, but I do what I am told and if it is 540 rpm for the bush hog, then I try to run it at that and if it needs more fuel to get there, and is "too fast" traveling, then I drop a gear, and keep the rpm up and travel a little slower.
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Re: 540 rpm?

Postby Son of Butch » Sat Sep 08, 2018 9:07 pm

thin stand or thick... shift gears to adjust ground speed
look at your lawn, if your rpms are too slow for your ground speed you get a raggedy cut, same with large equipment
if your stand is so thin, why waste time by slowing machine and staying in low gear?
Only reason would be safety on hills or bad terrain.
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Re: 540 rpm?

Postby Brute 23 » Sat Sep 08, 2018 9:35 pm

What is the benefit of not running 540?

There is no way of knowing with out having the run sheets on that motor. Most motors have an area of use then based on the load they can really dial in the sweet spot for peak efficiency.

One thing to consider is potential cooling issues even though with a pretty light load it shouldn't be.

I don't really see the benefit of running a lower RPM. I doubt the fuel consumption or wear and tear really amount to much. You probably have more to risk going against the recommended RPM than to gain trying to do it differently.
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Re: 540 rpm?

Postby bird dog » Sat Sep 08, 2018 10:00 pm

Thanks for the replies. Reasons I asked are many but Butch mentioned one. The terrain is rough and and hilly and to get the speed correct sometimes is difficult. Two ranges and four gears is not quite enough to hit the sweet spot. Fourth gear in turtle is to slow. First gear in rabbit is to fast.

Fuel consumption is another issue. The extra 500 RPM's needed to get to 540 uses quite a bit of fuel over days usage. I would like to have a tractor that would turn the 540 at a less RPM when it is okay to do so but there s not one in my future.

I don't shred enough for it really to matter, just curious more than anything. I mowed some the ditches this morning before the rains came. Second gear turtle because it was rough and on a side slope. I needed every bit of the 540 rpm's power for this. Its a wonder how good a crop of Johnson grass I can grow in areas that are unavailable to graze.
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Re: 540 rpm?

Postby True Grit Farms » Sat Sep 08, 2018 10:20 pm

I rotary mow and cut hay at 540 rpm or more. I bale oats at 250 rpm or less and as fast of a ground speed as I can handle. Every thing is different and finding the sweet spot is the secret to success.
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Re: 540 rpm?

Postby Brute 23 » Sat Sep 08, 2018 11:14 pm

bird dog wrote:Thanks for the replies. Reasons I asked are many but Butch mentioned one. The terrain is rough and and hilly and to get the speed correct sometimes is difficult. Two ranges and four gears is not quite enough to hit the sweet spot. Fourth gear in turtle is to slow. First gear in rabbit is to fast.

Fuel consumption is another issue. The extra 500 RPM's needed to get to 540 uses quite a bit of fuel over days usage. I would like to have a tractor that would turn the 540 at a less RPM when it is okay to do so but there s not one in my future.

I don't shred enough for it really to matter, just curious more than anything. I mowed some the ditches this morning before the rains came. Second gear turtle because it was rough and on a side slope. I needed every bit of the 540 rpm's power for this. Its a wonder how good a crop of Johnson grass I can grow in areas that are unavailable to graze.


Got ya. Ive always like that our JD has 2 ranges, 4 gears in each, then a little shifter for another gear in between the main ones. So you can run 3rd and flip that deal and its faster than 3rd but not as fast as forth. Some one can probably explain it better but its handy as be nice. I find myself using it a lot. Not sure how common that is.
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Re: 540 rpm?

Postby ddd75 » Sun Sep 09, 2018 6:42 am

Brute 23 wrote:What is the benefit of not running 540?

There is no way of knowing with out having the run sheets on that motor. Most motors have an area of use then based on the load they can really dial in the sweet spot for peak efficiency.

One thing to consider is potential cooling issues even though with a pretty light load it shouldn't be.

I don't really see the benefit of running a lower RPM. I doubt the fuel consumption or wear and tear really amount to much. You probably have more to risk going against the recommended RPM than to gain trying to do it differently.


no benefit.. most equipment likes to be run at full speed, super high rpm for long duration's..

I know some people who even engage equipment at full 540.. :lol2:
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Re: 540 rpm?

Postby greybeard » Sun Sep 09, 2018 8:07 am

Brute 23 wrote:Got ya. Ive always like that our JD has 2 ranges, 4 gears in each, then a little shifter for another gear in between the main ones. So you can run 3rd and flip that deal and its faster than 3rd but not as fast as forth. Some one can probably explain it better but its handy as be nice. I find myself using it a lot. Not sure how common that is.

I don't know much about the Green ones.
Is that what they call a creeper gear?
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Re: 540 rpm?

Postby Texasmark » Sun Sep 09, 2018 8:19 am

greybeard wrote:
Brute 23 wrote:Got ya. Ive always like that our JD has 2 ranges, 4 gears in each, then a little shifter for another gear in between the main ones. So you can run 3rd and flip that deal and its faster than 3rd but not as fast as forth. Some one can probably explain it better but its handy as be nice. I find myself using it a lot. Not sure how common that is.

I don't know much about the Green ones.
Is that what they call a creeper gear?


My Branson 6530 has shuttle 24/24. I have 4 ranges with 3 gears per. Then I have a creep lever that cuts everything in half. If you want to know what creeping is, A1/2 is a snail pace. Believe it or not I used it once. Helping a neighbor position a lid on his 300 gallon septic tank. He had adhesive around the rim to seal it and the lid had to come down perfectly centered. Creep did the trick.

On PTO speeds, On my JD 4230 I had a 1000 rpm spline that I'd use when mowing with my 8' Mohawk twin blade so that I could halve my rpms and still get my 540 mower drive. On the Branson I have 3 PTO speeds, 540, 1000, and halfway between selected with a 3 position lever in the console.
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