Run @ 540 PTO RPM or faster when cutting?

Boy, oh boy, oh boy!!

When I swiched from baling square bales with wd45 to using 185 on a 14t baler, I noticed the knotters not moving as fast with the 185 as they did with the wd45. I am sure that my wd and wd45 pto runs faster than 540. 185 at 2000 rpms is suppose to be 540 and it just didn't work as fast as with the wd45. Maybe I am just simple, but that is the way it seemed. Bill

wow how such a simple question can piss some people off. Tractor running slower than designed will do more damage than a tractor running faster. Cut the speed of a spinning shaft in half double its size, is a rule of thumb. A faster spinning shaft has less stress than a slow one. When a manufacturer has a 540 or 1000 pto mark on the tack it means to not pull the tractor's rpms to below that point or be prepared for problems.When a tractor is dynoed its is full throttle pulled down under load to its rated speed, which gives the proper reading on the dyno. This is how the dealers or fools think that a tractor is making tons of power, dyno it at full throttle and not pull it down to rated speed (the 540 mark or 1000 mark depending on the pto) and the dyno reads big numbers. Seen a dealer try and convince a customer his 2-105 white was making 200+hp stock, I told the guy there was no way in hell a stock 105 could do that, I got in a huge argument with the dealer because he had no clue how to properly dyno a tractor. The throttle on any brand tractor goes to the end for a reason and if the company didnt think so it wouldnt go that far. To call people names because they are running a tractor wide open, I hate to say this but you are showing your ignorance of the situation.When I was a kid we use to use a gehl 99 recutter to grind high moisture corn from ear corn to the silo it ran 1000 rpm , my uncle had a xt series 3 we filled silo with that thing for years and it would play with that recutter, loaned it to the neighbor because his Case tractor had broke down and he needed 1000 rpm on his recutter, after a couple of days he was complaining that the XT kept boiling over, we couldnt imagine what the deal was because we never had such a problem, went down to see what the trouble was he was running the XT at 3/4 throttle making it labor and not flowing the water properly opened it wide open like we ran it (for years I might add) the tractor cooled right down and played with his recutter. Thus endth the lesson, to steal a phrase.

Kcgrain has it right. In the Nebraska test the tractor is running at full rated speed and then the PTO is loaded to bring the RPMs down to 540 to simulate field conditions not throttled back till the PTO is running 540 with no load. I guess what pisses us, or at least ME off is when someone who is ignorant about how to operate a tractor starts throwing around words like stupid while spouting opinions which are pure nonsense. If you really can't think of a situation where a tractor should be operated wide open, take it off the trailer and hook it to a tillage tool. Or at least read your owners manual.

PLEASE...

Everybody, go back and read the OP question.

There is no point in arguing horsepower against appropriate speed.  The implement is rated at 540, because the ASME COMPATIBILITY CRITERIA are all based on making equipment interchangeable between machines.  The whole purpose, was to establish design criteria so that IMPLEMENT MANUFACTURERS could make a good implement, that would be used between many different machines.

The machine was built to operate on a given PTO type, it had a given shaft size and spline count, was expected to be operated at the given RPM (1000 or 540 usually), and was expected to be brought no more than a certain amount of torque (the workload) and not more than a given amount of shock (hence, shear-pins).

Tractor manufacturers accomodate ASME PTO categories the same way.  They build a tractor, fit it with tires, gearing, and ballast according to the amount of tractive effort they're trying to provide.  Once that's all done, they set up the engine governor for however they feel will be most successful under those circumstances.  THEN they set up gearing that provides one or more of the common ASME PTO speeds applicable to that category.  They put a demarcation band on the tachometer to give a general indication of what engine speed yields the designed ASME PTO speed.

Then they put the tractor in your hands.

From that point, you pick your implement, and hopefully, you pick something that's a good match... i.e., don't pick a Category II PTO implement requiring 89hp, and put it on a Category II tractor that's only 55hp.  Likewise, don't expect a Category 1 540rpm post-hole digger... or your ground-man operator, to survive with it stub-adapted to a Category III 110hp tractor with a 1000rpm PTO.

Finally, don't swear by the premise that 'faster is better' or 'slower is better', and don't generalize postulation that stress on a given component at one speed is more, or less than speed at another.  Stresses given up in one scenario, are always met, and replaced with stresses from others.

Reason:  The engineers who designed the machine know more about what they were thinking and doing... than anyone else ever will.  As a frequent retrospective engineer, I face challenges left by engineering errors and presumptions, not only from original design, but changes that casually occur in manufacture, but worst, after modification by people who may have had a pretty good grasp for what was happening, but clearly did NOT understand the ramifications of how their modification affected other aspects of the situation.

If you want something to yield the safety, performance, longetivity, and durability intended by the original design, then OPERATE it that way.  That means, if the tractor's book says "Operate at xx for maximum power"... but the PTO device says "Never operate above xx", you'd better take the more conservative route of the two.

Next... Throw fallacy in the trash.  When an industrial or agricultural engine is designed, it is 'curved'.  That means, it is analyzed on a dyno for fuel consumption, torque, and thermal stability.  When they leave the factory, you can rest assured that the Owner's Manual will indicate the acceptable range of operation... and staying within those guidelines will provide the performance indicated in all curves.  They didn't 'design' it to be used to drive implements faster than the IMPLEMENT DESIGNER intended.  NO engineer would even THINK of doing that.

The comment about overheating due to insufficient RPM-  Bunk.  It MAY have happened, and you may swear by it, but I assure you that the reason has NOTHING to do with the engine being designed that way... it's because there's an UNDERLYING PROBLEM that needed resolution.  ALL cause of low-speed overheating on a LIQUID-COOLED engine can be traced to either compression leaks (into the water jacket, typically through cracks, a damaged coolant circulatory pump, a failing gasket, or a missing or stuck thermostat.  First condition, is combustion gases being forced into the jacket, and displacing coolant from the top of the cylinder head.  Remaining conditions cause overheating because draw pressure at the INLET SIDE of the water pump is too low to prevent cavitation... and coolant therefore is not able to absorb waste heat for extraction.  I guarantee that agricultural engine manufacturers DID NOT design and release an engine that would overheat at common ambient ranges when operated below some speed... especially for non-pressurized cooling systems. 

And finally, the speed at which you set the engine speed lever defines GOVERNED SPEED, not THROTTLE.  At just off idle, you can apply a heavy enough brake load to the engine such that the governor will respond by opening the throttle all the way.   You may not get maximum engine rated HP, but this is because of the disadvantage indicated in the TORQUE CURVE.  Peak Torque occurs at the point where the cylinders fill most completely.  Peak horsepower, however, occurs where the coincidence of torque and RPM yield the highest multiplication product.  In reality, calculating PTO horsepower is irrelevant, because abiding by the ASME standard means you only need torque... the other variable is FIXED AT 540.  That means for every ten foot-pounds of torque you can find at the shaft, that equates to a smidgen past one horsepower.  100ft-lbs = 10hp.  500ft-lbs = 50hp.  If your implement is only strong enough to take 350ft-lbs, and you feed it 630, you'll be visiting either the morgue or hospital, and your machine will be in the workshop or scrapyard.

Now, as for running machines that indicate higher acceptable input speeds, the manufacturer rated them as such for good reason.  Machines like silage blowers NEED to run fast, they're designed and built to do that, and simply will not throw adequately if you don't... but they're RATED accordingly.  I suggest, however, that if you have a 1000rpm silage blower, and only a 540rpm-equipped tractor PTO, that you look for some other drive method, as your tractor engine will be hard-pressed to GET there, or if it does, will be screaming bloody murder to swing it's PTO at almost twice it's rated speed... and you'll likely not be able to get the engine to spin there without disabling the engine governor.

Finally, there are some machines that you simply CANNOT run outside rated speed.  First and most obvious- the AC generator.  540rpm = 60hz line frequency.  Try to spin the engine 'faster' to get 'more power', and you'll be burning up electronics, overspeeding electric motors, and generally wrecking stuff.  Likewise, running it too SLOW will generate power at too low frequency, causing motors to drag and overheat.

Laws of Man, when broken, will frequently get you a slap on the wrist.  violating the Laws of Physics and Nature will get you the death penalty, and there ain't no trial-by-jury.

So ignore the factory tachometer and just bury the throttle at all time when using it under a load??

Dave,the engine on the XT wasnt over heating beacuse of insufficient RPM or a design flaw by Allis Chalmers  that wasnt my statement it was over heating because the engine not being at full throttle was  not running at the HP needed to run the recutter, so the engine, laboring was generating more heat than the system was designed to cool. At full throttle the engine was  no longer laboring, wasnt generating the extra heat was flowing more water more air etc to remain cool. Also because this engine is turbo charged it proabably wasnt developing full boost to develop full power, at wide open the engine in its design was devloping the hp, boost, cooling capacity etc to handle the load.There was no internal problem with that tractor, none, not a clogged radiator, bad pump loose belt nothing the only difference was the RPMS and the lack of available HP for the job.I still have the tractor if it had some interanl problem it hasnt showed up since 1981 when this happened.which would pretty much rule out any such problems you stated.

Wow, this topic has taken off. On my 7050 I only pull a 4x18 plow so I usually only run about 1,900 rpm. It has never overheated or poured black smoke or whatnot. I could use the XT but the 7050 is much more comfortable and I like having all that available power. I also have run the XT at less than full rpm pulling a 9 shank Krause chisel plow without problems but the tractor will lug in the tough spots so I normally run at 2,200 rpm. My Dad rarely ever runs a tractor at full throttle unless whatever he's hooked to requires it and he made it through a lifetime of farming without blowing an engine. I tend to run a little faster than Dad and so far after about 30 years of field work never have had any problems either. I think everyone here knows their equipment pretty well so that they know what they can do and can't. Some run fast and some run a little slower.

Dave, you dont have to worry abot me taking it personally, am always willing to learn something new, but I do know the XT has or had no problems in that sitation, other than it was not making full hp on a continuous bassis. If you ever ran a recutter its a heavy pto load like a dyno but it lasts for hours on end, rather than intermitant, like a hard spot in the field etc, so once the load starts its there for as long as you were grinding, which back than we would start it at 7 am shut down for lunch and start back up till about 4  so other than a small breather as the next wagon pulled in it was pretty much full load . The only difference between the 2 setups was one was full throttle and playing with the recutter, and 3/4 throttle and laboring on it. Now the out line you have decribed may have had something to do with it, but we have had no heating problems with that tractor in any situation other than a recutter at lowered rpms. Again not to beat a dead horse here, but I am not saying that every situation requires full rpms, but in a heavy load, the engine and implements were designed for full speed and you are not doing any damage to either by running it there. Nor is the engine or implements being damaged by a slower setting, a little common sence will go along way in this, every condition requires a different approach, but on the recutter full rpm was required . Its much like a semi tractor taking a hill if your pulling the hill in too high a gear the engine begins to labor the heat starts to rise, shift down a gear, bring the rpms up lower the load and the temp goes right back down. By some of your guys comments about full throttle settings hurting engines or being abusive is just so out in left field, if that was so there would be a million dead semis blown up on the side of any grade, becasue every trucker I know is going to have there foot in it for full power to take a hill. My last point here on this matter is again, if damage or abuse was occurring in full RPM the manufacture would not let the throttle go that far. Peace everyone.

ranger42 wrote: Great explanation Dave!....I appreciate the explanation from an enginerring perspective and common sense. From my experience I agree with you on every front. Also, I think we all can agree that there are instances where engines are "de-tuned" for longevity. One I know that has been discussed on this site in the past is the 426 in the N-6 combine. Where RPM's were dropped most often by private owners or AC mechanics who have them in for service and they had much more luck for durabilty stand point.

I don't know what the OEM rpm setting for the N-6 was, but the 426 wasn't happy at the 2550 rpm setting of the 7080.  The engine was much happier at the 2400 rpm setting of the 8070.

In the case of your Loco with a cylinder not producing as much as the others, one dead or low cyl is reducing the maximum output from the engine, the operator then leans on the throttle more for a longer time. Fuel useage is up/economy is down. There again, pushing more fuel into it, more heat developed. Same load, engine not producing full power, RPM's down, more heat, taxing the cooling system....

Always run all my blower  tractors wide open , cause i hate unplugging pipes from an 80 foot silo .. 

I keep seeing all of the discussion and remember 2 things Dad would kick my for (not the only 2 by the way) Running pto equipment over pto speed and not running full throttle on heavy tillage loads.  It worked for him on every tractor from a square back WC to the 8070 and many in between.

D17JIM wrote: I keep seeing all of the discussion and remember 2 things Dad would kick my [IMG]uploads/1/censored.bmp"> for (not the only 2 by the way) Running pto equipment over pto speed and not running full throttle on heavy tillage loads.  It worked for him on every tractor from a square back WC to the 8070 and many in between.

This is the shortest and best advice I've heard.Been doing that for 35 years and haven't any problems.

Well to answer the original question, I run my 175D with the brushhog at the 540 rpm mark on the tach, throttle up as needed in the tough stuff, throttle back going down hills. I have done this for the last 7 years and probably could run the tractor without a tach as I can "feel" the correct range just by the sound and vibration. I've tried running faster, but I think it actually makes the cut worse and my fuel consumption just goes up. In rough conditions (rocks, rough ground) I throttle way back and the quality of cut doesn't change...and I stay more relaxed and in control.  Running wide open is just stressful to me.