Proper PTO RPM?? Will too low hurt the tractor?

[sld]

This is a good topic.

My truck with 4.30 gears turns around 2700 rpms at 80 mph. I don't think twice about setting the cruise for hours on end.

When my tractor is turning 2700 rpms it sounds like it is screaming. I tend to bush hog at something less if it is cutting okay.

But really, it is designed to run at that rpm and it will do so all day every day for a long time. As long as you don't lug it, and see a lot smoke, it probably won't hurt it.

Maybe it is because your senses are more attached to an open cab tractor and less in a quite cab of a truck.

 

[Eagleview]

Forgive me if you seen these before , or heard me say it before .

My tractor has an engine speed of around 2700 @ 540 PTO speed .

It also has and a 1000 PTO setting that is achieved at about the same revs .

Because i have peak torque @ 1400 revs , i select the 1000 PTO setting and run the engine @ 1400 revs . The PTO speed runs around 540-580 rpm's as i have a digital PTO speed readout on my dash .

The type of thick scrub in the photos is a daily occurance , the PTO lever has been in the 1000rpm speed setting since the day i bought the tractor in 2006 . If the going gets real tough i may need to shift to a lower gear to slow my ground speed and give a little more twisting torque to the PTO .

My engine runs like a clock , never uses oil , never gets hot and is extremely economical running at these low revs . You guys will probably never venture into scrub like this but the power to weight ratio of your tractors and the light mowing you are doing you will never have a problem using a lower engine RPM .

It's no different to mowing a lawn with a push mower , if it's only an 1" long you would not use full revs when 3/4 will do the task .

We obviously have different opinions on this issue , i suggest you try it yourself and see how it goes in your particular circumstance .

 

[whistlepig]

This is a good topic.

My truck with 4.30 gears turns around 2700 rpms at 80 mph. I don't think twice about setting the cruise for hours on end.

When my tractor is turning 2700 rpms it sounds like it is screaming. I tend to bush hog at something less if it is cutting okay.

But really, it is designed to run at that rpm and it will do so all day every day for a long time. As long as you don't lug it, and see a lot smoke, it probably won't hurt it.

Maybe it is because your senses are more attached to an open cab tractor and less in a quite cab of a truck.

On tractors we don't have a Lug-O-Meter or an exhaust temperature gauge. Exhaust temperature is critical on a diesel. You can fry a diesel engine if exhaust temps are too high. Diesels do that. Lugging is the prime source of high exhaust temp. So to save some fuel and wear and tear on your diesel engine by lugging it at low rpm is not a wise choice.

 

[Soundguy]

Hmm, Your car let say is designed for 100 MPH and odometer says the same. Do you drive 100 MPH at any given time and condition?

JC.

His car may be -capable- of 100mph, and has a max HP rating per the manufacturer. Running a car at max hp output will make it's lifespan drop to minutes or hours.... ever notice that race cars get rebuilt alot.. like every race!! the cooling systems and engine output on these machines have a much lower 'rated' constant HP output than their max... tractor engine are setup differently.. one of the big things is rpm... most tractors make their hp at realitively low rpm compaired to race cars.. etc.



soundguy

 

[sld]

On tractors we don't have a Lug-O-Meter or an exhaust temperature gauge. Exhaust temperature is critical on a diesel. You can fry a diesel engine if exhaust temps are too high. Diesels do that. Lugging is the prime source of high exhaust temp. So to save some fuel and wear and tear on your diesel engine by lugging it at low rpm is not a wise choice.

Point well taken. It sure doesn't hurt a small diesel to run at 2700 rpms.

At the same time, if you are mowing 8 inches of grass down to 4 inches, 2700 rpms may not be needed.

 

[JC-jetro]

His car may be -capable- of 100mph, and has a max HP rating per the manufacturer. Running a car at max hp output will make it's lifespan drop to minutes or hours.... ever notice that race cars get rebuilt alot.. like every race!! the cooling systems and engine output on these machines have a much lower 'rated' constant HP output than their max... tractor engine are setup differently.. one of the big things is rpm... most tractors make their hp at realitively low rpm compaired to race cars.. etc.



soundguy

Chris,

I have no issues with the points you are making as compilation of my comments previously attest to it. All I'm saying one engine rpm and associated PTO revolution may not the most optimal operating point for all different conditions. If I need I'll run my engine at 2500 rpm to give me 540 pto rpm. Considering the torque I need, ground speed that I feel safe, result that I expect to get, topography of my land, and the only time I need to run my brush hog at 540 is when the field grass is thick and is taller than 4'. Any thing else I do is between 1500-1800 rpm and in no time I'm lugging or bogging the engine down and the minute condition dictates it I'll change to oblige. I reckon the original poster is cursing himself for asking the question in the first place.

JC,

 

[sweep]

Ok.. so lets see.. your tractor manual, and implement manual are telling you what to run the pto at.. IE.. the rated speed.

1.I'm assuming you are a mechanical engineer and a mechainic since you are 2nd guessing the directions of the equipment manufacturer and the tractor manufacturer.



2. 540 to much wear? You machine is rated to run that speed..

1. No, neither. Just at times the NH owners manual is vague and just does not make sense. I.e. My OM say's to install an engine heater block if you are starting the tractor below 0 degrees F. Before I installed my heater, my tractor sounded like a rod was going to come out when I started it at 15-25 degrees. I have my heater plugged in anytime the temp goes below 45 degrees because the tractor's engine just sounds so much better on start up.

2. I never said that. I cut my field 3-4 times per year. 540 just seems overkill when I am cutting off the tops of a handful of scraggling weeds in mid summertime

 

[sweep]

I reckon the original poster is cursing himself for asking the question in the first place.

Just about. I also run my geared tractor in 7-8 gear at 1500-1800 rpm and I don't think I am lugging the engine. If I see some higher or thicker grass up ahead I push up the rpm. I wonder if the 540 setting is based upon one of those "Nebraska test" where the grass is 2 feet tall and so many blades per square inch.

I sometimes wonder if we all baby and worry about these tractors a little at times-myself included. Heck when it's 5 degrees outside I start up my cold car and take right off. My tractor no way. First startup, whether hot or cold outside I let it run for a few minutes before upping the rpm....and I'm sure that engine is way more durable than my car's engine.

 

[Soundguy]

Chris,

I have no issues with the points you are making as compilation of my comments previously attest to it. All I'm saying one engine rpm and associated PTO revolution may not the most optimal operating point for all different conditions. If I need I'll run my engine at 2500 rpm to give me 540 pto rpm. Considering the torque I need, ground speed that I feel safe, result that I expect to get, topography of my land, and the only time I need to run my brush hog at 540 is when the field grass is thick and is taller than 4'. Any thing else I do is between 1500-1800 rpm and in no time I'm lugging or bogging the engine down and the minute condition dictates it I'll change to oblige. I reckon the original poster is cursing himself for asking the question in the first place.

JC,

If the OP had to ask about this.. then it's good he got all the opinions posted.

IE.. run a good rpm to keep from lugging the engine, and if in doubt about load.. run at rated rpm and not worry about the wear.

soundguy

 

[JC-jetro]

This is what democracy is all about, But I now declare, this horse is beat to a pulp, has no pulse no more and dead as a doornail: D, Great discussion though.

G'day all,
JC,