Green Tractor Talk banner

1 - 20 of 30 Posts

·
Registered
Joined
·
2,587 Posts
Discussion Starter #1 (Edited)
I stopped at my dealer today and grabbed a 3series brochure for my brother in law and got a quote. I’ve been having 2 series and 1 series brochure since I bought mine. So I was just comparing them And that’s when I noticed it.

1023e = 22.4hp and 15.3PTO
1025r = 24.2HP and 18PTO
2025r = 24.2HP and 17.2PTO
3025e = 24.7HP and 17.4PTO
 

Attachments

·
Super Moderator
Joined
·
4,886 Posts
Huh. Typical Deere weirdness.

If you go look at the Deere web site and look at each model they say:


1025R Eng HP 23.9 PTO HP 13.4 kW/18 hp
2025R Eng HP 23.9 PTO HP 13.4 kW/18 hp
3025E Eng HP 24.4 PTO HP 14.4 kW/19.4 hp

Pick any 2 Deere documents and they can't seem to agree on much. :laugh:
 

·
Registered
Joined
·
3,235 Posts
I stopped at my dealer today and grabbed a 3series brochure for my brother in law and got a quote. I’ve been having 2 series and 1 series brochure since I bought mine. So I was just comparing them And that’s when I noticed it.

1023e = 22.4hp and 15.3PTO
1025r = 24.2HP and 18PTO
2025r = 24.2HP and 17.2PTO
3025e = 24.7HP and 17.4PTO
If I had to hazard a guess, I would say that it’s due to more of a parasitic load in a bigger, heavier tranny and maybe larger hydraulic pumps. I know the 1025 has only 1 pump for both implement and steering systems, what about the other 2?
 

·
Super Moderator
Joined
·
4,886 Posts
Oh, another difference I just noticed in looking at the brochures. The 1023E, 1025R and 2025R ratings are at an engine speed of 3,200 RPM. The 3025E rating is at 2,400 RPM.
 

·
Registered
Joined
·
2,587 Posts
Discussion Starter #5
I added pictures to the original post.

I also noticed the PTO’s KW match on the 2025 17.2(13.4kw) and the 1025 18(13.4kw) and the 3025 17.4(12.9kw) is the lowest KW.
Man this is confusing
 

·
Premium Member
Joined
·
1,651 Posts
I stopped at my dealer today and grabbed a 3series brochure for my brother in law and got a quote. I’ve been having 2 series and 1 series brochure since I bought mine. So I was just comparing them And that’s when I noticed it.

1023e = 22.4hp and 15.3PTO
1025r = 24.2HP and 18PTO
2025r = 24.2HP and 17.2PTO
3025e = 24.7HP and 17.4PTO
Always Look In the Manuals There Product Literature can be all over the Place John Deere Operator Manual | Parts & Services | John Deere US But 99% of the time the Manual will be accurate
 

·
Registered
Joined
·
131 Posts
I added pictures to the original post.

I also noticed the PTO’s KW match on the 2025 17.2(13.4kw) and the 1025 18(13.4kw) and the 3025 17.4(12.9kw) is the lowest KW.
Man this is confusing
The reason that it is confusing is that consumers like to think in terms of horsepower so that is what is marketed to them. HP however is a derived number which comes from torque and torque is what matters. HP = (torque * RPM)/5252 .. the magic being that number 5252 which itself is the byproduct of a number of conversions to convert the easily measurable (torque) to the definition of horsepower. Horsepower is defined as effort over time, specifically 550 foot pounds per second which, is a non-intuitive thing to measure. Torque on the other hand is very measurable, it is a twisting force and the units of expression (ft lb or NM or whatever) dictates how the measurement was arrived. We typically think in ft lb so that is 1 pound at 1 foot or 1 ft lb. If someone tells you that a particular 'thing' has x amount of torque you can intuitively figure out how useful it is. All that being said;

The reason that the table you provided is confusing is that one of the factors in the equation (RPM) can change dramatically while HP only changes a little.

Here is the same information but converted to torque. You can see that the 2025 loses a little bit of usable power over the 1025, probably due to increase in mass but otherwise the engine and PTO outputs make more sense than just looking at HP alone. The 3025, despite having the same HP as the 1025 is more powerful because it is making that HP at a lower RPM (so more torque).

Conversion to Torqu.JPG

(the PTO output is dependent on the recommended PTO shaft speed, either way, the 3025 has greater potential output even at the same rated horsepower of the other units simply because it won't bog down due to the increase in available torque)
 

·
Registered
Joined
·
322 Posts
Many years ago, I went with my neighbor to Sears where he was picking up a new air compressor. Whilst he was busy with the salesman, I was BSing with another salesman, an older wiser type. I asked him, regarding the air compressor, "How is a 5 horsepower motor supposed to run on a 15 Amp 120 Volt circuit?" He gave me a knowing grin and replied, "Them's Madison Avenue horsepower." 'nough said.
 

·
Registered
Joined
·
519 Posts
Oh, another difference I just noticed in looking at the brochures. The 1023E, 1025R and 2025R ratings are at an engine speed of 3,200 RPM. The 3025E rating is at 2,400 RPM.
Believe it’s a different engine for the 3025E. It’s a lower revving larger displacement engine that is why it produces the same torque and horsepower at lower rpm.


Sent from my iPhone using Tapatalk
 

·
Super Moderator
Joined
·
4,886 Posts
Believe it’s a different engine for the 3025E. It’s a lower revving larger displacement engine that is why it produces the same torque and horsepower at lower rpm.
I think it's all Deere doing the Hokie-Pokie for regulatory purposes. :laugh:

The 3TNV80 in the 1025R develops max HP at 3200 RPM and that's the specs Deere advertises.
The 3TVN88 in the 3025E develops it's max HP at 3,000 RPM. But Deere doesn't advertise those numbers. They use the 2,400 RPM specs instead. Why?

By advertising the 3025E at 14.4 Kw/24.7 HP they are bound by the Tier 4 emissions standards for engines that are less than 25 HP.

But Yanmar's charts show that the engine used in the 3025E produces just over 27.1 Kw/36.3 HP when you crank it up to 3,000 RPM. If Deere used the 3000 RPM numbers they'd have to apply the > 25HP Tier 4 standards and they would have been forced to outfit the 3025E with a DPF setup.

They down-rated the 3TVN88 engine so they could keep the cost down on the 3025E.

It's kinda funny. The 3025E, 3032E and 3033R all use the 3TVN88 engine. But if you look at Deere's specs for them:

3025E = 24.7 HP @ 2,400 RPM
3032E = 31.1 HP @ 2,500 RPM
3033R = 32.2 HP @ 2,600 RPM

Increase the RPM to dial in the HP you want to advertise....
 

·
Registered
Joined
·
22 Posts
I added pictures to the original post.

I also noticed the PTO’s KW match on the 2025 17.2(13.4kw) and the 1025 18(13.4kw) and the 3025 17.4(12.9kw) is the lowest KW.
Man this is confusing
John Deere info is all over the place usually.

Look at your brochure info for the 2025r.

24.2HP / 17.8kW. It's already messed up right there with that, they can't convert HP to kW properly.

Most likely they took the old HP from the 2025R Gen1 and used the current metric info for the engine power of 17.8kW and the folks editing the brochure didn't bother to find out what the equiv HP is for that.

24.2 hp= 18.05 kW
17.8 kW = 23.87 hp

So Gen 2 engine probably has 23.9 hp vs Gen 1 of 24.2. RPM may also be different for reporting, for gen1 vs gen2 also but that woudln't affect simple conversion of hp to kW.

Just me guessing and the marketing folks that edit the brochures getting incomplete data from another group and reusing last model info in the already created templates...
 

·
Registered
Joined
·
596 Posts
I think it's all Deere doing the Hokie-Pokie for regulatory purposes. :laugh:

The 3TNV80 in the 1025R develops max HP at 3200 RPM and that's the specs Deere advertises.
The 3TVN88 in the 3025E develops it's max HP at 3,000 RPM. But Deere doesn't advertise those numbers. They use the 2,400 RPM specs instead. Why?

By advertising the 3025E at 14.4 Kw/24.7 HP they are bound by the Tier 4 emissions standards for engines that are less than 25 HP.

But Yanmar's charts show that the engine used in the 3025E produces just over 27.1 Kw/36.3 HP when you crank it up to 3,000 RPM. If Deere used the 3000 RPM numbers they'd have to apply the > 25HP Tier 4 standards and they would have been forced to outfit the 3025E with a DPF setup.

They down-rated the 3TVN88 engine so they could keep the cost down on the 3025E.

It's kinda funny. The 3025E, 3032E and 3033R all use the 3TVN88 engine. But if you look at Deere's specs for them:

3025E = 24.7 HP @ 2,400 RPM
3032E = 31.1 HP @ 2,500 RPM
3033R = 32.2 HP @ 2,600 RPM

Increase the RPM to dial in the HP you want to advertise....
What RPMs will a 3025E allow you to run it? Did they limit the RPMs to match the specs or did they just throttle down and measure it then?


Sent from my iPhone using Tapatalk
2017 2038r 72” MMM Command Cut 220r loader
 

·
Super Moderator
Joined
·
4,886 Posts
What RPMs will a 3025E allow you to run it? Did they limit the RPMs to match the specs or did they just throttle down and measure it then?
The question on how high RPM you can run a 3025E is a good one. The Operator's Manual shows the PTO marker on the tach at 2500 RPM so it must go at least that fast. I don't own a 3025E but maybe we can get someone that does to look at what the max RPM they can get to is.

Deere doesn't actually do any testing for the engine specs. All of their engine specs come straight from Yanmar. If you look at any of the CUT brochures there is a little note at the bottom of the specs page that all engine specs are from the engine manufacturer. If you look at the Yanmar specs they chart out engine HP starting at 1,800 RPM and work their way up to 3,200 PM in 100 RPM increments. (which makes for some really pretty power curve graphs! :laugh: )

Any given Yanmar engine can get used for a ton of different purposes so they do static tests and then the builder can tune their machine around the engine. There's no telling what Deere does with these things once they get a hold of them. Tweak the fuel systems, tweak the exhaust, tweak the software, on some machines they add a turbocharger...
 

·
Registered
Joined
·
2,587 Posts
Discussion Starter #14
How can they advertise less to bypass emission even though it will produce more? Seems illegal lol.
So you are also saying that the 3 series are all the same power?
 

·
Registered
Joined
·
1,336 Posts
I always hear people say that torque is what actually matters, but that isn't really true. Especially in tractors. Here is why.

The way you measure horsepower is you take an engine and you apply a load to it. For ease of visualizing, say that the engine is trying to lift a weight using a pulley with the PTO as a spindle (a makeshift dynamometer). Say you have two tractors, Tractor 1 and Tractor 2, and you want to measure HP. The numbers I'm going to use are made up for the purpose of explaining. So say we measure both tractors at 1500 rpm (engine rpm, so the PTO RPM would be a lot less), and Tractor 1 can lift 500lbs before the engine runs out of steam (however that happens...maybe stalls, maybe it just can't lift anymore, whatever, it doesn't matter). Tractor 2 can lift 800 lbs. So Tractor 2 has a lot more torque.

Now we crank up the engine RPMs to try to lift the weights faster. The faster you try to spin it, the harder it is on the engine...it is trying to do more work over a shorter period of time. Tractor 1 can spin all the way up to 3500 RPM before its torque output drops to the point at which it can no longer lift that weight. It can lift it really fast! So the numbers are crunched, and based on how much work it does over time ((RPM * torque) / 5252=HP), we conclude that it has 20 HP (PTO or engine, it really doesn’t matter, this is just a thought experiment).

Tractor 2, on the other hand, can only lift that 800lbs up to 2300 RPM, then it runs out of steam. It is working a lot slower than Tractor 1, but it is lifting a lot more weight. Say we crunch the HP formula and we conclude that it is putting out 15 HP.

So since HP is work over time, Tractor 1 actually has more power than Tractor 2, because it can do more work over a set period of time. But Tractor 1 still can't lift an 800lb weight, while Tractor 2 can. So Tractor 2 still has more torque.

Now...that makes it sound like torque matters, but...

Torque can be multiplied almost infinitely with gearing (within reason). Increasing torque reduces output speed (e.g. final drive). So you can take an engine that produces 10 ft lbs of torque and multiply it to 10,000 ft lbs. But while it can make 10 ft lbs at a really high speed, it would make 10,000 at a very very very slow speed. So you trade speed for torque. This is what tractors do...they take the torque output of the engine and amplify it massively by the time it gets to the wheels. That's why a dinky little 25hp engine in your tractor gives it much more pulling power than your 300hp car, and why your tractor is so slow and your car is so fast.

While you can amplify torque with gearing, you cannot change HP. HP always stays the same (for the most part…some power is always lost in any complex system). Since HP is work over time, HP is the thing that really matters when evaluating engine power, not torque. You can take that engine in Tractor 1 and change the gearing until it can lift 800lbs on its PTO spindle (which in this example acts as our dynamometer), or even 8,000 lbs. It will just do it very slowly...but it will still have 20 PTO HP, whether it's lifting 500lbs, 800lbs or 8,000lbs. If you geared it down so that it could lift 800 lbs, the same as Tractor 2, then it would lift that 800 lbs faster than Tractor 2 would, because it has more HP. Likewise, you can gear Tractor 2 up until it can only lift 500lbs, and it would lift that 500lbs faster than it lifted 800lbs, but still slower than Tractor 1 can lift 500lbs, because tractor 1 has more HP.

This assumes that the torque @ RPM of both engines is tested the same way. This is not always the case, which is why lawn tractor can sometimes appear to have more HP than a CUT. Also, some engines are designed differently, optimized for higher RPMs, for example. But we are talking about tractor engines here, which are all similar enough that this generalization works.

This is why tractors are marketed using HP. Given tractors of similar size and weight, the one with more HP will do the same work as one with less HP, but it will do it faster. How much faster depends on how much more power. But the 1025 and the 3025 are not of similar size and weight, so comparing HP between the two isn't particularly useful. If you compare the 3033R, the 3039R and the 3046R, they will each do the same things, but the higher HP models will do those things a little faster than the lower HP models. But not as faster as you may think, which is why HP is part super useful measurement and part marketing gimmick.

PTO HP is a little bit different, and comparisons here are much more useful. A higher HP engine will put more torque into that PTO at the same PTO RPM as a lower HP engine. Though things don't always need as much PTO HP as we sometimes think they do, unless you're on the clock.

Please keep in mind that the above is just an example created for the purpose of understanding the relationship between horsepower and torque and how they are measured and applied. It's not meant to be an accurate representation of any specific tractors, engines, etc.
 

·
Super Moderator
Joined
·
4,886 Posts
So you are also saying that the 3 series are all the same power?
Not at all. What I'm saying is that when Deere gets a boatload of 3TVN88 engines from Yanmar, all of those raw engines are capable of producing the same HP output.

Deere then takes those engines and puts them in various machines. As they do that, they bolt on different components (fuel systems, exhaust systems, turbos, etc...) and program different software to tune each engine differently by tractor model.

But the specs Deere lists in their brochures are the manufacturer's specs. Deere doesn't tell us the rated outputs after all their tuning is done. I'm sure there are engineers at Deere that have measured actual output for each configuration but they don't give us that info in their advertising brochures.

GM does the reverse of this. I'm sure they have/had a default "rated output" for the 5.7L LS1 engine but they advertise the actual HP as the engine is configured for each car model they put it in instead of advertising the the default.
 

·
Registered
Joined
·
131 Posts
I always hear people say that torque is what actually matters, but that isn't really true. Especially in tractors. Here is why.

The way you measure horsepower is you take an engine and you apply a load to it. For ease of visualizing, say that the engine is trying to lift a weight using a pulley with the PTO as a spindle (a makeshift dynamometer). Say you have two tractors, Tractor 1 and Tractor 2, and you want to measure HP. The numbers I'm going to use are made up for the purpose of explaining. So say we measure both tractors at 1500 rpm (engine rpm, so the PTO RPM would be a lot less), and Tractor 1 can lift 500lbs before the engine runs out of steam (however that happens...maybe stalls, maybe it just can't lift anymore, whatever, it doesn't matter). Tractor 2 can lift 800 lbs. So Tractor 2 has a lot more torque.

Now we crank up the engine RPMs to try to lift the weights faster. The faster you try to spin it, the harder it is on the engine...it is trying to do more work over a shorter period of time. Tractor 1 can spin all the way up to 3500 RPM before its torque output drops to the point at which it can no longer lift that weight. It can lift it really fast! So the numbers are crunched, and based on how much work it does over time ((RPM * time) / 5252=HP), we conclude that it has 20 HP (PTO or engine, it really doesn’t matter, this is just a thought experiment).

Tractor 2, on the other hand, can only lift that 800lbs up to 2300 RPM, then it runs out of steam. It is working a lot slower than Tractor 1, but it is lifting a lot more weight. Say we crunch the HP formula and we conclude that it is putting out 15 HP.

So since HP is work over time, Tractor 1 actually has more power than Tractor 2, because it can do more work over a set period of time. But Tractor 1 still can't lift an 800lb weight, while Tractor 2 can. So Tractor 2 still has more torque.

Now...that makes it sound like torque matters, but...

Torque can be multiplied almost infinitely with gearing (within reason). Increasing torque reduces output speed (e.g. final drive). So you can take an engine that produces 10 ft lbs of torque and multiply it to 10,000 ft lbs. But while it can make 10 ft lbs at a really high speed, it would make 10,000 at a very very very slow speed. So you trade speed for torque. This is what tractors do...they take the torque output of the engine and amplify it massively by the time it gets to the wheels. That's why a dinky little 25hp engine in your tractor gives it much more pulling power than your 300hp car, and why your tractor is so slow and your car is so fast.

While you can amplify torque with gearing, you cannot change HP. HP always stays the same (for the most part…some power is always lost in any complex system). Since HP is work over time, HP is the thing that really matters when evaluating engine power, not torque. You can take that engine in Tractor 1 and change the gearing until it can lift 800lbs on its PTO spindle (which in this example acts as our dynamometer), or even 8,000 lbs. It will just do it very slowly...but it will still have 20 PTO HP, whether it's lifting 500lbs, 800lbs or 8,000lbs. If you geared it down so that it could lift 800 lbs, the same as Tractor 2, then it would lift that 800 lbs faster than Tractor 2 would, because it has more HP. Likewise, you can gear Tractor 2 up until it can only lift 500lbs, and it would lift that 500lbs faster than it lifted 800lbs, but still slower than Tractor 1 can lift 500lbs, because tractor 1 has more HP.

This assumes that the torque @ RPM of both engines is tested the same way. This is not always the case, which is why lawn tractor can sometimes appear to have more HP than a CUT. Also, some engines are designed differently, optimized for higher RPMs, for example. But we are talking about tractor engines here, which are all similar enough that this generalization works.

This is why tractors are marketed using HP. Given tractors of similar size and weight, the one with more HP will do the same work as one with less HP, but it will do it faster. How much faster depends on how much more power. But the 1025 and the 3025 are not of similar size and weight, so comparing HP between the two isn't particularly useful. If you compare the 3033R, the 3039R and the 3046R, they will each do the same things, but the higher HP models will do those things a little faster than the lower HP models. But not as faster as you may think, which is why HP is part super useful measurement and part marketing gimmick.

PTO HP is a little bit different, and comparisons here are much more useful. A higher HP engine will put more torque into that PTO at the same PTO RPM as a lower HP engine. Though things don't always need as much PTO HP as we sometimes think they do, unless you're on the clock.

Please keep in mind that the above is just an example created for the purpose of understanding the relationship between horsepower and torque and how they are measured and applied. It's not meant to be an accurate representation of any specific tractors, engines, etc.
Except that doesn't apply to tractors :)

The way you measure horsepower is you take an engine and you apply a load to it.
No, the way you measure horsepower is you take an engine, and you measure its ability to apply a force and the RPM at which the force is applied, then you have to convert that to HP. In other words, you measure torque, and RPM, and you multiply those together and divide by 5252 to derive HP. All dynos whether engine or chassis work this way BTW.

The formula you shared is incorrect
(RPM * time) / 5252=HP)
(probably a typo) Its (RPM*Torque)/5252=HP --- RPM *is* time (revs per minute).

You cannot practically measure HP, the definition of one horsepower is a unit of power equivalent to 550 ft lbs per second (or 550 pounds lifted 1 foot in 1 second). Its a fully linear measurement (lifting). In pragmatic terms that is almost impossible to measure repeatedly across engines and basically impossible to measure accurately in a car since an engine or a car cannot create linear motion without translating the rotational motion of the engine through a drivetrain, and then you have to deal with traction/friction. So we don't even try to measure HP, we simply do the conversion and that's where that magic number of 5252 comes in. That number comes from the conversion of HP (defined as linear motion) into an equivalent in rotational force that we can measure repeatedly and accurately. We then have to go through several steps to come up with a constant that represents that rotation, trust me that it comes down to 5252. (RPM).

For tractors and diesel trucks and anything else that values doing work 'easier', torque is all that matters. If you want a long life engine, if you want a more simple engine, and you want an engine that can do more pragmatic work moving big loads, you want torque.. period.. If you want to move a small load fast, then HP matters.

The reason that 5252 is important is that is where the conversion in total available power (work output) crosses over from torque to horsepower.

Look at any engine power curve, the work output (total available power) cannot come from horsepower until you cross that line (or thereabouts), up and until that point, the work output is coming from torque. No amount of torque amplification through gearing (converting HP into torque) will save you as you simply;

Increase inertia/parasitic loads beyond practicality
Drastically shorten the life of the engine and/or drivetrain
Or both

Torque can be multiplied almost infinitely with gearing (within reason).
Not really, the way you would get there is to figure out how to get the engine into its horsepower sweet spot (high RPM) and dump that into the driveline to overcome your 'infinite' gearing inertia. That is why top fuel dragsters blow through clutches (and sometimes engines) every race, its the conversion of 5000 horsepower at ridiculous RPMs that have to be suddenly converted into forward motion through a limited drivetrain. (all while not losing traction).

But we don't have to make up theoretical examples as the table I previously provided shows that for a tractor, only torque matters. Its not about how much horsepower you have, its about how you go about making it. (HP being a derivation of torque and RPM).

View attachment 668996

You can see from the above (JD marketing and emissions gamesmanship aside for a second) that the 3025 makes more engine and PTO torque because it can create the required torque at lower RPM (its a bigger engine). It will produce greater work product meaning more available torque to feed into the driveline, be less susceptible to stalling by a wide margin. Bottom line is that it has 25% greater torque because it can make the same HP at 25% lower RPM but for all practical purposes the HP rating is the same. That is why HP doesn't matter when evaluating tractors unless of course you want to start making 5000 RPM tractors. The table shows also why you cannot use HP as a comparison except *within* the same tractor family but if you really want to get a feel for the difference between one model and the next within the family, figure out how much torque they can create.
 

·
Registered
Joined
·
1,336 Posts
Except that doesn't apply to tractors :).
It applies perfectly to tractors. Yes, the formula/time thing was just a typo/brain fart, I fixed it, thanks for pointing it out.

As for the rest, yes, HP is a calculation, which is what I said. You only measure torque under load and convert it. HP is typically measured at the engine crank, and the torque multiplication happens after that. So the engine output is separate from what you end up with in your final drive, which is up to the transmission and axles (or PTO gears).

You ever notice how a torque curve is usually pretty flat but the HP curve starts low, climbs and then drops off?

This is a HP and torque curve for an International DT466:

dumfuk.jpg

Note that the torque output is almost constant through most of the RPM range, except very low idle and towards the end when the engine can no longer keep up.

If you check JD engine specs for a 2032R (gen 2), you will see that its max HP is 30.7 at 2500 RPM. At this RPM, the rated engine speed, it produces 64.2 lb ft of torque.

But...its maximum torque is 77.4 lb ft, and that is produced at 1625 RPM.

What that tells you, based on what I said in my original comment, is that this engine produces a certain amount of torque, which increases slightly as the RPMs go up and then starts to taper off as the revs continue to climb. At some point, you reach the point at which the engine produces the most power, which is not always or usually the most torque. In fact, as evidenced by the 2032R (and 38R and I think most or even all other tractors), the torque the engine produces actually drops off after a certain RMP, but the power continues to climb (e.g. 2032R, torque tops out at 1625 RPM, then drops steadily until 2500 RPM, past which point it drops off rapidly). So even though the engine is making less torque at higher RPMs, it is producing more HP because it is applying that torque faster (higher RPM). That's how you get HP, which is work over time.

Or to put it another way...

What happens when you measure is that the dyno applies a load (resistance) that the engine has to overcome. Then you increase RPMs. The result is the torque curve, which represents the maximum torque produced at every point throughout the rev range. At some point, that torque curve takes a dive because the engine doesn't have enough power to apply torque much beyond this speed. So what you have with the torque curve is a measure of the engine's ability to overcome resistance (do work) at various RPMs. Since RPMs are a measure of how fast that work is being done, that gets converted into horsepower with the above mentioned formula.

That's it. It's that simple. AFTER that, you can apply gearing (transmission) to change the final output torque at the wheels and the PTO.

Let's look at the PTO. Let's pretend for a moment that there is no parasitic loss from the hydro. With the engine spinning at its rated RPM (say the 2032R at 2500 RPM), the PTO spins at 540 RPM (or thereabouts). The engine is spinning 4.6 times faster than the PTO. This means that the PTO gearing reduces speed and amplifies torque. So you take 64.2 ft lbs of torque at 2500 RPM and reduce that to 540, which gives you almost 300 ft lbs @ 540 RPM at the PTO, which, when we run it through the formula, gives us the same HP as 64 ft lbs at 2500 RPM. Now we know PTOs don't work that way, that there is a lot of loss in the hydro, but it should serve to explain how the torque amplification works. If there were no parasitic loss from the hydro at all (which is impossible) that is what you would see at the PTO.

Hope that makes sense.
 

·
Registered
Joined
·
131 Posts
It applies perfectly to tractors. Yes, the formula/time thing was just a typo/brain fart, I fixed it, thanks for pointing it out.

As for the rest, yes, HP is a calculation, which is what I said. You only measure torque under load and convert it. HP is typically measured at the engine crank, and the torque multiplication happens after that. So the engine output is separate from what you end up with in your final drive, which is up to the transmission and axles (or PTO gears).
You do not measure horsepower (*ever*). You measure torque and RPM and you convert that to horsepower (*always*). Unless you know of a very different kind of engine, you cannot measure HP at the crankshaft. When people say wheel horsepower, crank horsepower (brake horsepower) they are always talking about measuring torque, and RPM, and converting to HP. HP is a linear force, torque is a rotational one. The power curves you see are a poor attempt at trying to illustrate the relationship between power derived from turning force and power derived from how much force you can apply in a given amount of time. The right hand side of the graphs show you the meaningful number which is HP whether it comes from that turning force or work accomplished (in this case work or Revolutions per minute).

You ever notice how a torque curve is usually pretty flat but the HP curve starts low, climbs and then drops off?
Yes, and I understand why. If the engine could handle more RPM the HP curve would continue to climb and cross over at ~5252 RPM. Torque creates the initial power, horsepower keeps it going, the crossover point is what it is.

This is a HP and torque curve for an International DT466:

View attachment 669018
That graph exactly explains my point. All of its usable power comes from its ability to produce a lot of torque. An engine with otherwise equal horsepower at the same RPM (lets say the right hand side reads 275 in both cases) but less torque would not be nearly as usable. That is why, for all practical purposes we would be far better off if tractors were marketed with torque and RPM alone. That is math everyone can intuitively understand. If I told you I could apply 1000 pounds of twisting force at 1000 RPM you would know that the object being moved would be only affected by 100 pounds of force at 10 feet. You would also know that if I reduce RPM, I reduce torque. etc.. simple, simple, simple. It is why evaluating tractors on HP is misleading and why it doesn't matter. E.G if I tell you that I have 4 tractors that are only differentiated by a couple of HP (as they are from 1023 to 3025) how would you know which one could produce the most usable work output. Thank you JD and every other manufacturer for your helpful information.

Note that the torque output is almost constant through most of the RPM range, except very low idle and towards the end when the engine can no longer keep up.

If you check JD engine specs for a 2032R (gen 2), you will see that its max HP is 30.7 at 2500 RPM. At this RPM, the rated engine speed, it produces 64.2 lb ft of torque.

But...its maximum torque is 77.4 lb ft, and that is produced at 1625 RPM.

What that tells you, based on what I said in my original comment, is that this engine produces a certain amount of torque, which increases slightly as the RPMs go up and then starts to taper off as the revs continue to climb. At some point, you reach the point at which the engine produces the most power, which is not always or usually the most torque. In fact, as evidenced by the 2032R (and 38R and I think most or even all other tractors), the torque the engine produces actually drops off after a certain RMP, but the power continues to climb (e.g. 2032R, torque tops out at 1625 RPM, then drops steadily until 2500 RPM, past which point it drops off rapidly). So even though the engine is making less torque at higher RPMs, it is producing more HP because it is applying that torque faster (higher RPM). That's how you get HP, which is work over time.
Ignore the JD marketing/environmental games. Focus on the real world we live in. Tractors are low RPM machines designed to do a lot of work over long periods of time. The useful byproduct of those design constraints (maximum work output, longevity, efficiency, etc) is that you want a high-torque, low RPM engine. That is why HP *in the evaluation of the tractor* doesn't matter. The gear amplification you keep talking about isn't going to suddenly change because you decided to run much faster RPM, you will only lose efficiency in the important part of the power band (low RPM), it will gain or lose some efficiency depending on implementation but the reality is that it has a fixed operating window and torque is the only useful measure of how much work you can get done.

Or to put it another way...

What happens when you measure is that the dyno applies a load (resistance) that the engine has to overcome. Then you increase RPMs. The result is the torque curve, which represents the maximum torque produced at every point throughout the rev range. At some point, that torque curve takes a dive because the engine doesn't have enough power to apply torque much beyond this speed. So what you have with the torque curve is a measure of the engine's ability to overcome resistance (do work) at various RPMs. Since RPMs are a measure of how fast that work is being done, that gets converted into horsepower with the above mentioned formula.

That's it. It's that simple. AFTER that, you can apply gearing (transmission) to change the final output torque at the wheels and the PTO.
Actually no. You are correct that the torque measurement is a measurement of the engines ability to overcome resistance but the torque curve is expressed and mapped on the right hand side of every graph to HP. Its all HP. What matters is how you get there.

Lets start with something we can agree on. You cannot have HP without torque. You cannot measure HP without measuring Torque. Torque is a measure of the twisting force required to turn something. That something happens to be connected to wheels or in this case a PTO. The speed at which you can do that work is expressed as HP but measured as Torque. Given that the HP rating on the machines is not really changing much but the capabilities of the tractors in question are then what must be changing is torque and RPM. Make sense? This means, that the only effective way to think about comparing two tractors in the real world is torque. Yes, a higher HP, bigger motor will naturally produce more torque but if the horsepower is changing by 10% and torque is changing by 25% which is the more meaningful number for comparison.

Let's look at the PTO. Let's pretend for a moment that there is no parasitic loss from the hydro. With the engine spinning at its rated RPM (say the 2032R at 2500 RPM), the PTO spins at 540 RPM (or thereabouts). The engine is spinning 4.6 times faster than the PTO. This means that the PTO gearing reduces speed and amplifies torque. So you take 64.2 ft lbs of torque at 2500 RPM and reduce that to 540, which gives you almost 300 ft lbs @ 540 RPM at the PTO, which, when we run it through the formula, gives us the same HP as 64 ft lbs at 2500 RPM. Now we know PTOs don't work that way, that there is a lot of loss in the hydro, but it should serve to explain how the torque amplification works. If there were no parasitic loss from the hydro at all (which is impossible) that is what you would see at the PTO.

Hope that makes sense.
Again, same thing. If you have to spin at 2500 RPM and produce 540RPM you are going through a 4.6:1 gear ratio whereas if you can produce the same HP at 1800 RPM you are producing significantly more torque at 540RPM while using a much smaller gear ratio. Hence, more usable power is being transferred to the PTO, the engine is capable of producing more torque (pay attention to yanmar specs, not JD) and the bigger tractor becomes a much more usable instrument.

Take three tractors of the same or similar horsepower, for easy math lets say all 3 make 10 horsepower. The first one does so at 1000 RPM, the second at 80RPM, the third at 50RPM. Torque is HP*5252/RPM . You tell me which you would buy? (they make 52, 65, 97 ft lbs of torque respectively). Standing in the showroom looking at three 10 horse machines would be confusing. Looking at nearly double the torque is not. Lets turn that around, lets raise the horsepower to 50 horse, and spin the motor at 5000 RPM, all of a sudden I am only making 50 pounds of torque and I am going to have to go through a big gear/hydro translation (torque amplification) to get back to usable work output all while losing low end capabilities, engine longevity, power manageability, and risking reliability.

I am not saying that HP doesn't matter, but in the tractor world it matters less than you think, that's why we don't have or need 500HP tractors and while a motor that would laughable in the automotive world in terms of HP is a killer machine in the tractor world. I am still impressed by the sweet spot the 1025 hits.
 
1 - 20 of 30 Posts
Top