PTO Speed.....can I run less without harm?

[Fordiesel69]

At 540rpm PTO that places my engine at 2450 RPM. With a woods 72" rear finish mower, can I run at 2000RPM to 2200RPM without harming the tractor? It is a new holland boomer 30. I get just as good of cut at the slower RPM, but not sure if this is harmful.

Grass does not get terribly long either so engine does not have to work hard.

 

[k0ua]

At 540rpm PTO that places my engine at 2450 RPM. With a woods 72" rear finish mower, can I run at 2000RPM to 2200RPM without harming the tractor? It is a new holland boomer 30. I get just as good of cut at the slower RPM, but not sure if this is harmful.

Grass does not get terribly long either so engine does not have to work hard.

Thats fine, you are not going to hurt anything.. typically the cut is not quite as good at lower speeds, but if you are happy with it I don't see any harm. Just less noise, probably less fuel used, and as long as the tractor is not lugging down, which it does not seem to be, then I think you are fine. Obviously if the grass was higher or wetter you might have a problem then. I often bushhog. (trimming not mowing a field) at much lower RPM's mainly as a safeguard to not throw rocks so far if I hit any. I have some rough areas to trim with the rotary cutter.

James K0UA

 

[MHarryE]

Classical energy formula E=1/2 mass x velocity squared. If you increase the speed to rated speed, the blades will carry more energy to carry them through the cut, and that energy increases with the square so for example increasing from 400 rpm to 540 rpm increases the energy at the blades by 1.8 times. It allows them to carry through the cut and throw the cut material out of the way better. So there are advantages to running at rated speed but if the slower works for you... Mine doesn't. At lower speeds there is more hammering and banging going on, but I am often cutting tall, heavy grass with some brush where blade momentum is most important.

 

[Combustix]

Depending on grass height I will run from 1800 to 2200. 540 is about the same rpm on my b2710

 

[bigbull338]

youll be fine running at 2000 to 2200rpms.i have yet to run the pto at 2450rpms for 540 pto.when i shredd i run at 2000rpms give or take.

 

[foreman Etexas]

youll be fine running at 2000 to 2200rpms.i have yet to run the pto at 2450rpms for 540 pto.when i shredd i run at 2000rpms give or take.

Same here even pulling my 15ft batwing I dont run but 2,000rpm's

 

[TripleR]

I run mine at or near full 540, but as you can see, this varies. I seem to remember an old really long thread on this.

Some of our older tractors lost gauges long ago, so on those my brothers guesstimate just like I always did and they are still running; no problems.

 

[bigbull338]

I run mine at or near full 540, but as you can see, this varies. I seem to remember an old really long thread on this.

Some of our older tractors lost gauges long ago, so on those my brothers guesstimate just like I always did and they are still running; no problems.

on those tractors that the rpm meters no longer work.you can tell just about what the rpms are just by listening to the moter.

 

[TripleR]

on those tractors that the rpm meters no longer work.you can tell just about what the rpms are just by listening to the moter.

You sure can; one of them I have driven since dad bought it new in 1955; Massey Ferguson since new in 86, Case 995 was well used when we bought it, but you can just "feel" it.

My brother has put aftermarket oil pressure and temp gauges, but the rest is by instinct. We use a stick for a fuel gauge.:laughing:

 

[Jay4200]

Classical energy formula E=1/2 mass x velocity squared. If you increase the speed to rated speed, the blades will carry more energy to carry them through the cut, and that energy increases with the square so for example increasing from 400 rpm to 540 rpm increases the energy at the blades by 1.8 times. It allows them to carry through the cut and throw the cut material out of the way better. So there are advantages to running at rated speed but if the slower works for you... Mine doesn't. At lower speeds there is more hammering and banging going on, but I am often cutting tall, heavy grass with some brush where blade momentum is most important.

I think mower blade cutting ability is more of a momentum thing then an energy thing. If so, linear with velocity, not squared.

JayC

 

[bucktaker]

My old MF35 ran at pto speed around 1500 rpm with a gas z134 motor most work was around 1200-1500 rpm i am having trouble getting used to the kubotoa needing to be above 2000 rpm to get any work done. The power curve is not as flat as the old motor.

I did some bushhogging of my pastures and some of it I ran @ 2000 rpm the rest at 2500rpm with is real close to 520 pto speed the cut was much better at higher rpm. once I turn the tunes up on my Ipod inside my headphones it was ok just takes some getting used to the vibration of the motor turning 2500 rpm.

 

[boggen]

i normally do not max the gas pedal out. when mowing but operate around 75% to 80% gas pedal. and could care less about RPMs. but focus on ground speed and changing gears. so i can mow as fast as i can, without having to make a 2nd or third past. and use the extra room on the gas pedal. when i hit a thick patch of grass or need to go up a hill i will put gas pedal to the floor for that temporary doing.

as other said, you need high enough RPM's so grass shoots out of the deck. and more RPMs you have the better the grass gets cut and shoots out.

but with mowing, you have areas that grow faster, and/or thicker. and more areas that are dryer while other areas that will stay wet / damp. then you have leaves and/or pine needles. that can get rather thick. as i noted above i like leaving some room on the gas peddle. so i have little extra power for when i need it. vs needing to change gears or like to get through stuff.

 

[Jerry/MT]

At 540rpm PTO that places my engine at 2450 RPM. With a woods 72" rear finish mower, can I run at 2000RPM to 2200RPM without harming the tractor? It is a new holland boomer 30. I get just as good of cut at the slower RPM, but not sure if this is harmful.

Grass does not get terribly long either so engine does not have to work hard.

You won't hurt a thing by cutting at a slower rpm.

 

[strum456]

This is one of my pet pieves. All the dealers and operator manuals say to run everything at PTO speed. For some equipment and conditions, PTO speed is definitely required. BUT, there are so many conditions where PTO speed is not required, but people who where never told otherwise continue to run at full speed because they are lead to believe that it is harmful to do otherwise (definitely no offense meant toward the OP).

With many machines, you can just tell by the sound if it is running efficiently. I have seen a number of square balers that just do not sound good at PTO speed. They rock up and down on the draw bar, the plunger is hammering, and you end up replacing a shear pin somewhere every few rounds.

Even wose yet, I see people crank the tractor up to PTO speed, then throw the equipment in gear. It's bad enough when people do this with lawn mowers, but when I see this done on farm equipment I just go



Take it easy on your equipment, use a little common sense, and it will thank you.

 

[rambler]

Won't be any problem.

You don't want to 'lug' your tractor, or make it struggle to keep up RPMs, but what you suggest won't be anywhere near any sort of problem at all to your tractor or mower. Might slightly affect your cut quality as others say, but....

Won't be any problem at all that you'll ever notice, and not harmful to anything.

--->Paul

 

[MHarryE]

There is a lot of misinformation in this thread. Contrary to some things that have been stated, we engineers do not tell people to speed things up so they wear faster and we sell more stuff.

Using a square baler as an example, the flywheel is important in smoothing out the driveline loading. Energy for cutting off the incoming windrow and compressing the hay occurs in about 90ｰ of the 360ｰ stroke and the majority of the energy needed in this 90ｰ comes from the flywheel - if the baler is running at the correct speed. Slow it down and the energy needs to come directly from the driveline which increases loads on the u-joints, shafts, gears, all the way to the engine.

The blades on a rotary cutter have the flywheel effect of the flywheel on a square baler. Running at a slow speed can result in increased slip clutch slipping and resultant wear, plus it will not have the capability of cutting through the kind of brush for which the mower is intended.

 

[Soundguy]

might be running it slightly out of power band.. and sucking action might be less.. but as long as not lugging or laying grass down.. shouldn't 'hurt' the tractor. quality of the cut maybee.


that said.. I'm continually amazed by those concerned about running their tractor at rated pto speed.. like the engineers designed it to be ran and worked at.

kind alike running your rider mower at 1/3 down from the lil notch they give you on the throttle quadrant.. we know how good that works..

 

[strum456]

The flywheel on a baler does not have the ability to change weight with the load conditions. That is what the throttle is for. Every JD IH OR NH baler I have ever run has a sweet spot where I can tell the flywheel has the right amount of momentum to cycle the punger without loading the driveline or shaking the machine apart. This sweet spot is generally below PTO speed for most hay conditions.

 

[Redneck in training]

Tractor engines are way derated. The could produce about three times as much power if you would let them. That is why they last forever even when run at rated speed. If you examine power, torque and specific fuel consumption curves you will see that PTO speed is somewhat past maximum torque so when the load increases causing engine to slow down torque goes somewhat up. Therefore it is much harder to bog down the engine. Also specific fuel consumption is the lowest around peak torque. So for the best efficiency it is advisable to run at rated speed. There are exception to the rule though. In example PHD could (should) be run just above idle speed.
Mower power consumption is more or less proportional to mass of grass mowed over particular period of time. It you cover the same area at lower speed it will not give you any fuel saving. In fact you might use more fuel because you will operate away from the best efficiency speed.

 

[Soundguy]

yep.. and if mowing at lower rpm.. that = slower.. and might take less of a bit.. that increases mowing time.. and unless you are getting a huge fuel savings.. you might have a fuel net loss due to extended mowing times. all depends on specific machine..