PTO Horsepower

[Woodsman30350]

I have checked every spec I can find on my 3040 and cannot find any reference to the PTO horsepower. I states the PTO runs at 540 rpm but not the horsepower. Is it the same at the tractor H.P. rating?

 

[texasjohn]

Nope, every PTO horsepower rating I've ever seen is a few horses less than the engine hp. But, I don't know what the PTO hp is for your tractor. Am sure that somebody will, however.

 

[chh]

Somebody dropped the ball on the Montana website the 2840 is the only one with a full set of specs in the compact tractor line. It is listed as 28 gross engine hp and 23 pto hp. The amount of drop would be very close to the same for your 30 gross engine hp and is a fairly common amount for that size tractor. 25 pto would most likely be a safe bet.

 

[Sackett2]

My 4344HST looses a bit of HP on the pto, due to the HST- 43hp rated, I believe about 35 at the pto

 

[J_J]

Here is some data from a test about efficiencies of engine and PTO. Of course, logic will tell you that a gear transmission will have less loss than a hydrostatic transmission.

Another interesting comparison can be made using the maximum available drawbar hp at 100 percent load and the maximum PTO hp. A ratio of the drawbar hp to the maximum PTO hp is an indicator of the efficiency of the drive train of the tractor. Consider Test Nos. 1255 and 1257 for an IH 986 diesel with 16-speed transmission and IH hydrostatic diesel 186. These tractors have identical engines, producing approximately 105 PTO hp. However, the standard transmission 986 produces 90 drawbar hp, while the hydrodrive produces 80 drawbar hp.

The comparison of drive train efficiencies is as follows. IH 986: 90/105 = 86 percent; IH 186 hydro: 80/105 = 76 percent. The tractor with the standard transmission has less loss in the drive train and is able to transmit more power to the drawbar. The overall fuel efficiency with the standard transmission is obviously better. In this case, the potential buyer would have to decide whether the advantages of the hydrostatic transmission were worth the increase in fuel consumption and efficiency.

 

[Woodsman30350]

Just spoke to Montana in Arkansas and they quoted the PTO horsepower for my 3040 as being 22. Seems a little low to me but I guess I will have to go with a 5 footer cutter.

Thanks for the inputs.

 

[jas67]

I don't know if Kubota is overly conservative with PTO ratings, but, I find it a bit odd that when you have several models that are essentially the same tractor, but with different HP engines, that the higher HP models seem to loose more PTO power to the hydrostatic. I can see the drawbar power being a % of engine power, and thus the model with the larger engine will lose more HP getting that power to the wheels, but the PTO doesn't use the HST.

Case in point:
B7610 - engine=24HP, PTO=18HP
B7510 - engine=21HP, PTO = 16HP.

The B7610 has 3 more engine HP, but only 2 more PTO HP. The B2920, B2620, and B2310 have similar differnces (there is like 3 engine HP between each of these three models, but 2 PTO HP).

I would think that because the tractors weight about the same, the the power required to move the tractor with the HST would be about the same, regardless of available engine HP, and that the full difference in engine HP would be available at the PTO. Also, would more than this PTO HP spec be available for stationary use (such a chipper or generator), since the HST isn't being used?

 

[J_J]

Here is some more stuff about PTO hp.

Tractor engine power can be used in several ways. The most common uses are the PTO shaft and the drawbar. PTO power is easy to accurately measured, and is the most common way of describing tractor power. PTO power is about 96 to 98 percent of engine power

Appendix

 

[shakin]

what engine does the 3040 have that might explain the pto hp difference. my 2840 has the mitsubishi engine.

 

[J_J]

jas67 ,

Anytime that gears are used to increase of decrease rpm, there will be some HP losses.

I believe the HST is always pumping fluid when the tractor is running, and fluid is moving, with very little pressure, and taking up some HP, therefore the difference between a gear tractor PTO HP, and one with HST.

 

[Jerry/MT]

I have checked every spec I can find on my 3040 and cannot find any reference to the PTO horsepower. I states the PTO runs at 540 rpm but not the horsepower. Is it the same at the tractor H.P. rating?

I'll take a stab at this. It may not be exact because different rating philosophies may be used by different manufacturers. But it's illustrative of the process.

The pto only runs at 540 rpm at a certain engine speed. The engine is rated at some max horspower at some speed ( for example 62 hp at 2200 rpm). If the engine rated there, as a rule of thumb, the pto hp will ~ 10 % less due to transmission losses.

For this example ,that means that the pto hp would be 55.8 hp( 62 -6.2 =55.8). But 2200 rpm will provide lets say 660 rpm at the pto. So you have to slow the engine down to get the pto to run at the design limit of the implement, which is 540 rpm. That may mean an engine rpm of 1800 rpm. At 1800 engine rpm or 540 pto rpm, the engine hp may be 51 hp. So that at the pto, the available hp is 55.9 hp ( 51-5.1 =45.9), again due to transmission losses.
A well written tractor spec will provide the correct HP available at the pto at the 540 pto speed or the manufacturer should be able to provide this info.

Hope this helps you.

 

[Jerry/MT]

Just spoke to Montana in Arkansas and they quoted the PTO horsepower for my 3040 as being 22. Seems a little low to me but I guess I will have to go with a 5 footer cutter.

Thanks for the inputs.

Was that 22 hp at 540 pto speed? If so you might get a 6 footer if you are not planning on mowing waist high grass and brush. How does 5 foot compare to the track(width of the rear wheels) of the tractor?

 

[Dallas_Lilly]

A 5 footer will not cover the tire tracks if it has R4 tires.

Interesting thing I found is that the manufacturer (Mitsubishi) sticker that was on my valve cover stated that the engine was only rated for 28.5HP. I do not know where montana came up the extra 1.5 engine HP.

One other thing to consider when answering a HP to cutter question is the elevation that the machine is running at.

I run a 6 foot medium duty cutter on my 3040 and I am at 7,000 feet elevation. It cuts light and medium grass very well in third gear medium range. If I get into thicker thistle and it is more than about 2 feet tall it can really struggle and I have to gear down to first, even then it can kill the engine.

 

[jas67]

jas67 ,

Anytime that gears are used to increase of decrease rpm, there will be some HP losses.

I believe the HST is always pumping fluid when the tractor is running, and fluid is moving, with very little pressure, and taking up some HP, therefore the difference between a gear tractor PTO HP, and one with HST.

J_J,

I understand that there are drivetrain losses in gears, due to friction, and also that the HST is always pumping. I was only wondering why, for example the HP less for a B2920 is 2HP more than that of a B2320. The B2920, B2620, and B2320 are all basically the same tractor with the same transmission, just with different engines. The specs are (engine HP,PTO HP, loss between the two):

B2920 29,21,8
B2620 26,19,7
B2320 23,17,6

Similarly, the B7610 and B7510:

B7610 24,18,6
B7510 21,16,5

 

[LD1]

The HP can be whatever you want it to be. We have no way of knowing how accurate the various manufactures are anyway. With what you are doing a HP or two aint going to make a bit of difference. Get a cutter that will cover your track width and if it is too much in tall grass, SLOW down or take smaller bites.

 

[SPYDERLK]

J_J,

I understand that there are drivetrain losses in gears, due to friction, and also that the HST is always pumping. I was only wondering why, for example the HP less for a B2920 is 2HP more than that of a B2320. The B2920, B2620, and B2320 are all basically the same tractor with the same transmission, just with different engines. The specs are (engine HP,PTO HP, loss between the two):

B2920 29,21,8
B2620 26,19,7
B2320 23,17,6

Similarly, the B7610 and B7510:

B7610 24,18,6
B7510 21,16,5

Those are huge losses from the engine HP. Makes me think they are quoting gross engine HP rather than the net HP available after driving the fan, water pump, and alternator.
larry

 

[BrentD]

I don't know if this holds true for the newer Montanas, but the guy we bought our 4340C from said he sold one of the older Romanian made (re-badged Long) tractors that was rated 65HP to a guy that had a rather cool experience with it. The guy's neighbor had a big implement (can't remember if it was a big hay baler or a large bat-wing cutter) that he was struggling to pull with an 80hp John Deer. The guy takes his 65hp Montana over, hooks up to the implement and takes off with no problems whatsoever. The neighbor says that shouldn't be possible so he hops on the Montana and give it a try and sure enough it pulls the implement just fine. With both guys scratching their heads at this point unsure how a 65hp Montana could out-pull an 80hp John Deer they loaded up both tractors and too them to a dyno. Turns out the 80hp John Deer was only putting out around 73hp to the draw bar, but the 65hp Montana was putting out 85hp!!!

After a little investigating and testing a second Romanina made Montana and getting similar results they decided that either there was a mistake in translation that caused the engine to only be rated 65hp or the enings are seriously underrated due to poor fuel quality in the county of manufacture.

I know that most of the Mitsubishi S4 series engines are slightly under-rated as well. A 45hp Mitsubishi S4E or S4Q engine may actually give you 50hp or over. (Our dozer is an S4E and our 2008 4340C is an S4Q and the engines are almost identical)

 

[Jerry/MT]

I don't know if this holds true for the newer With both guys scratching their heads at this point unsure how a 65hp Montana could out-pull an 80hp John Deer they loaded up both tractors and too them to a dyno. Turns out the 80hp John Deer was only putting out around 73hp to the draw bar, but the 65hp Montana was putting out 85hp!!! QUOTE]

If they put them on a dyno, they didn't measure drawbar horsepower! They measured PTO horsepower. The only question I would have is what rpm thye measured the power at because that makes a difference. If they were both measured at the same pto rpm (540 or 1000 rpm), that's a fair test.

One of the major poblems with quoting power ratings is that they are generally quoted as maximum shaft horsepower at rated engine speed. Then somebody will quote a tractor horsepower as pto horsepower. If you're making a comparison, you have to read the sales brochure and make sure that the horsepower is quoted is the same horsepower for each machine.Maybe the Deere was quoted as engine shaft horsepower and the Montana was quoted as PTO horsepower. you have to really watch out for the marketeers!

 

[LD1]

If they were on a chassis dyno how is that not drawbar HP??

Regardless of the RPM at witch a tractor is rated for their spec sheet, if the tested them the same way on a dyno (either both at max rpm or both at PTO rpm) that is a fair real world test IMO

 

[Jerry/MT]

If they were on a chassis dyno how is that not drawbar HP??

Regardless of the RPM at which a tractor is rated for their spec sheet, if the tested them the same way on a dyno (either both at max rpm or both at PTO rpm) that is a fair real world test IMO

Drawbar power is the force ( in lbs) exerted on the drawbar times the velocity( in ft per sec) of the tractor divided by 550. It's a measure of what a tractor will pull. Generally that was done during the Nebraska test series for a new tractor at the Nebraska Tractor Test Lab.

Pto horsepower is the shaft power measured by the dyno connected to the pto shaft.

The two are not the same.

My other point was that running the engine at max rated rpm and measuring the output at the pto is interesting but if you can't operate your implement at that higher rpm it's kinda' meaningless.