What if I don't run PTO speed?

[Flatheadyoungin]

I got this flail up and running, and man, let me tell ya.....it's a VERY humbling experience watching those flails come around at about half PTO speed.....made the hair stand up on the back of my neck...

Anyway, I've always "babied" my equipment. I try not to run it hard, labor it too much, etc. Now, don't get me wrong, I certainly push things to their limits when I feel I need to. However, my PTO is at speed at about 2400, I think. Well, at about 1500 it seems to be spinning VERY fast and I don't like to run my engine that hard.

Other than decreasing my cutting capacity/power, will it hurt anything to run it a bit easier? It seems like I read somewhere about you should always run your implements at speed.

 

[Ductape]

I've run several of my impliments at well under rated PTO speed. I'd say try cutting at 1500...... if you are satisfied with the cut, no harm done.

 

[Glowplug]

You must be talking about engine RPMs when stating 1500 and 2400. I'd say 99% of CUTs have a PTO rated at 540 RPMs. The other 1% are 1000 RPMs. That being said, I usually run my rotary cutter at about 510 PTO RPMs which occurs at about 2200 engine RPMs. Many will say that there's nothing wrong with going slower. But you very well may get some responses from those with the philosophy that by running at a slower rated speed you are actually causing the implement to work harder because it's not working at its greatest efficiency. Kind of counterintuitive. I don't believe that myself. But maybe the guys with more experience will know better.

 

[Ridgewalker]

Interesting topic, one I have wondered about myself. If your brush hogging in an unknown area or cutting small trees 2 to 3 inches in diameter I think you should run at the recommended RPM. The velocity has to help the hog cut with less wear on the drive train. If you're cutting an open/clear pasture I don't see any issues with running slower.

Let's see what the experts have to say...

 

[ihookem]

The engine will let you know if the implement needs more power or slow down. Sometimes I'm just above idle when it's just a few weeds, sometimes i'm 2600 rpm full blast when cutting tall alfalfa. Later, ihookem.

 

[RalphVa]

Running at 2500-2700 rpm typical engine rpm for 540 PTO rpm is certainly not putting much stress on your engine. It'll be stressed less running at its designed speed, with enough oil and coolant circulation, etc. to properly lubricate and to cool it.

My 1983 Benz diesel regularly gets revved to its red line of about 4300 rpm in 1st and 2nd gears because you need all its 65 hp to get around on hills using AC, etc. It still starts and runs almost like new. A new timing chain would restore its designed timing and probably give it a boost in hp and performance. May get around to changing it if a replacement isn't made for it soon (e.g. stick shift diesel, quality made). Still gets almost exactly 30 mpg every tankful.

In my mind any of you gramps out there who are so afraid of running your engines that you keep them at 1500 rpm under load are plain that: old gramps. My father bought my grandfather's 1959 Plymouth V8 sedan with stick shift. Grandpa was forever driving it like most Bombay taxi drivers, e.g. shifting into high gear at around 15 mph. The car had main bearing failure right after Dad bought it. It just couldn't run normally after the bearings had been put under such high loads at such low oil flows.

Ralph

 

[Eagleview]

The centrifigal force is what holds the knives out . Just keep an ear out for clattering and an eye out for marks on the rotor as too slow a speed will have the knives hit the rotor . Other than that its just common sense , appearance of cut , engine sound , temp etc . Use your 1000rpm speed setting if you have one . Good luck with your new toy .

 

[Soundguy]

Flat head.. remember.. it's likely that your engine power band is near it's rated pto speed.. You are likely 'working' the tractor more by loading it down at an rpm out of it's power band, vs letting it run where it is making plenty of power.. some mowers don't clean well at lower rpms.. etc.

Your tractor is a tool meant to run continously at pto speed and load.

soundguy

 

[Farmwithjunk]

Mowers vary. Conditions vary. Engines vary. There is no carved in stone rule that says EVERY mower HAS to run at 540 rpm input speed. Some variation is acceptable. It's a matter of finding that "sweet spot" where the engine runs easy, the mower cuts smooth and efficiently, and the quality of cut is satisfactory.

Here's what I've found with my mowing rigs;

Until a couple years ago, I had a Woods MD172 mower that I used quite frequently on the back of a Ford 3000 (gas) To get a decent cut in almost all conditions, it needed to be ran ABOVE 540 pto rpm's. (issue with the mower mainly)

My MF150 and the Bush Hog 286 seem to cut best in MOST conditions with the engine spinning along as much as 250 rpm under "rated pto speed". It gets incredable fuel economy at that pace too.

Deere 2440 w/Bush Hog 297 mower works best EXACTLY at rated pto speed. Same tractor w/Bush Hog 406 heavy duty cutter likes slightly lower rpms for smoothest operation. The tractor, typical of most older Deere's, is a fuel hog at ANY rpm's.

Deere 6430 w/ Bush Hog 2715L batwing likes a few rpm below rated speed. Runs smoother, cuts better, easier on fuel.

MF583's w/2715L batwings need to run at or slightly above rated speed for best performance.

Engines are meant to operate at a wide rpm range. It's a myth that they only oil well, or won't last long if operated at any speed other than rated speed. You need to keep them operating at a speed where they don't lug down or blast wide open, but variable speed engines will function at any rpm's with-in normal range, and do well.

The best running, most efficient tractors I've ever been around seem to have a peak torque at rpms slightly below peak hp, w/ peak hp at or slightly above rated pto speed. as the engine pulls down SLIGHTLY when under a load, it finds that sweet spot where it's producing peak torque. As an example, the Perkins AD 152-3 diesels (ie MF135/150's) have a rated pto engine rpm of 1750. Peak hp is at 1900 rpm. Peak torque is @ 1600. PTO speed is approx. in the middle. With those rpm's in mind, you have a fairly broad range of acceptable engine speeds at which to operate efficiently with regards to a pto load. Note the "old school" operating range. Newer engines tend to have rated speeds at much higher rpm's. These little Perkins diesels have been known to last well into the 10,000 hour range with little trouble. You think that's coincidental?

 

[davitk]

I run my flail in the high 400's when mowing the "lawn", any faster doesn't improve the cut but uses more fuel. When I hit the heavier stuff I run it at 540 or the engine bogs down. Stop being a little old lady