Tractor classification — HP vs torque

   / Tractor classification — HP vs torque #21  
HP may get you to speed but torque or more properly torque rise will keep you going.
My Branson 8050 is rated at 2500 rpm to have 78 Engine HP or 65 PTO HP.
When I am roading it in high gear many hills will pull it down,
I can hit the bottom of many hills in high gear at 24-2500 rpm as we go up the hill gradually the speed will
start to slow as will the engine rpm this downward trend will continue till the engine rpm have gotten down to 14-1600
rpm and she can hold that engine speed for a considerable time. We will eventually make the grade and the engine rpm will increase again back to the governor set point. If the hill is enough to pull the tractor under 1400 it goes under the torque peak and will rapidly continue to drop untill I clutch and drop a gear.
 
   / Tractor classification — HP vs torque #22  
If the hill is enough to pull the tractor under 1400 it goes under the torque peak and will rapidly continue to drop untill I clutch and drop a gear.
Aren't gears wonderful? There's why we call them torque mulitpliers. You can count the torque advantage on fingers plus toes, and feel it in the seat of your pants.
The HST world is a bit more of a challenge, but comfortable.
 
   / Tractor classification — HP vs torque #24  
The relationship between engine torque, rpm, and hp are well defined. If you know two of the three the other is easily calculated.
 
   / Tractor classification — HP vs torque #25  
You can go to the Nebraska Tractor test site and read many of their reports.
 
   / Tractor classification — HP vs torque
  • Thread Starter
#26  
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Well, that's a good example of the difference between "Internet lookup" versus "education".

Where did you get those calculators? …
Yes… you can find anything on the internet…🤓

This calculator is supplied by Spicer…Spicer Horsepower and Torque Calculator

It’s like dad always told me: “No sense talking to the monkey when you can talk to the organ grinder…” I figured Spicer knows a thing or two about multiply and handling Torque…

I don’t make my living on a tractor, I do hope to make my life easier with my purchase though.. That being said…

I come from a motorcycle background… each and every magazine road test I read comes with a dyno chart in the spec section of the report… observing the torque curve on various engines (in various states of tune) is revealing… the “torque spike“ (read: high HP) engine that’ll push a bike to over 180 mph on the banks of the Daytona Super Speedway will be utterly useless in a motorcycle that’s buried up to its skid plate in mud in the Tennessee outback… a “tabletop flat” torque curve would come in handy there… which is where, I believe, a tractors torque measurement might be a pertinent selling point…

of course there’s always the exception…
 
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   / Tractor classification — HP vs torque #27  
As others mentioned, drawbar HP for pulling and PTO HP for powering implements.

You can spin an implement all day with big PTO HP, but it won't do you any good if you can't move it effectively.

With that said, I don't see CUTS with drawbar HP listed. Haven't looked in a long time, maybe it's changed, but I can't recall seeing that spec on anything but AG tractors.
 
   / Tractor classification — HP vs torque #28  
Yes… you can find anything on the internet…🤓

This calculator is supplied by Spicer…Spicer Horsepower and Torque Calculator

It’s like dad always told me: “No sense talking to the monkey when you can talk to the organ grinder…” I figured Spicer knows a thing or two about multiply and handling Torque…

I don’t make my living on a tractor, I do hope to make my life easier with my purchase though.. That being said…

I come from a motorcycle background… each and every magazine road test I read comes with a dyno chart in the spec section of the report… observing the torque curve on various engines (in various states of tune) is revealing… the “torque spike“ (read: high HP) engine that’ll push a bike to over 180 mph on the banks of the Daytona Super Speedway will be utterly useless in a motorcycle that’s buried up to its skid plate in mud in the Tennessee outback… a “tabletop flat” torque curve would come in handy there… which is where, I believe, a tractors torque measurement might be a pertinent selling point…
That's the point I hoped I was making - Apologies if my explanation was confusing.

I thought those calculators might be for something else than engines. So they are gear shaft torque calculators. They work well for calculating gear or shaft stress or any other place where you treat input torque as a constant and want output torque calculated.

For engines, where we are more interested in how we get torque as an input in the first place, it is the shape of the torque curve that matters. It can't be treated as a constant and give any useful info.

The formula is the same either way, but how it is used makes a difference.
rScotty
 
   / Tractor classification — HP vs torque #29  
I was alway told, there is no substitute for displacement when it comes to power, torque or horsepower. The ck2510 has a 85 cubic inch engine and the MT225s has a 77 cubic inch engine. In the automobile world, there is still meat on the bone(aka detuned)for the ck2510. Which would make the torque curve a little higher and a little more flat.
 
   / Tractor classification — HP vs torque #30  
Back in the mid seventies, one of my first jobs out of college was developing master pump settings for various engine applications on the dyno. What I recall is that a relatively high power turbocharged tractor would have a torque rise of 15% at the time. NA engines had less torque rise, as they would quickly run out of air and be smoke limited as to the shape of the torque curve.Torque rise is the difference between torque at rated engine speed and torque peak. Fifteen percent allows the all speed governors to maintain constant engine speed when the plow or implement encounters difficult going in the field.

combines had no need for much torque rise between rated and peak torque , just based on the nature of operation, ie running on what is called the overrun curve between high idle and rated.
Some fuel systems didn’t have much sontrol of delivery at different engine speed, so you were essentially hardware limited as to the shape of the curve. The drivetrain and cooling system guys were also pretty much in control of what the final shape of the power curve looked like. Putting out a tractor that wouldn’t cool, or blew up geartrain wasn’t a financially viable option from a warranty or customer satisfaction perspective.

Torque rise today is usually a lot more than 15%. Nebraska changed their testing some in the early 1990s and started to publish engine torque numbers and torque rise between rated speed and peak torque. I'll pick on some tractors I've run that have been tested at Nebraska and have figures available for peak torque and torque rise. They are definitely not high power by modern standards but the New Holland would have been a pretty potent tractor back in those days and the others' size would have put them right in the middle of the ag market back then, so not completely inappropriate.

- Deere 5075E (Final Tier 4, common-rail turbocharged and intercooled): Rated speed 2100 RPM. Peak torque 209 ft-lb at 1249 RPM, torque rise 31.6%
- Deere 5083E: (Tier 3, mechanical injection, turbocharged): Rated speed 2400 RPM. Peak torque 204 ft-lb at 1499 RPM, torque rise 41.3%
- Deere 5410: (Tier 1, mechanical injection, naturally aspirated): Rated speed 2400 RPM. Peak torque 204 ft-lb at 1094 RPM, torque rise 42.5%
- New Holland T6030 (Tier 3, mechanical injection, turbocharged and intercooled): Rated speed 2200 RPM. Peak torque 422 ft-lb at 905 RPM, torque rise 63.6%.


Going back to the original question as to why engines are rated according to HP rather than torque is because horsepower is what accomplishes work. You can have a high-torque engine that turns slowly or a low-torque engine spinning fast and both will do the same amount of work. For example, CNH's Workmaster 70/Farmall 70A are competitors to the Deere 5075E above and they take the opposite strategy with engines:

- Deere 5075E (FT4): 179 cid turbocharged (17.7 PSI), intercooled, common-rail three-cylinder. Rated speed 2100 RPM, redlines at 2200 RPM. Produced 64.2 PTO HP at 540 PTO RPM (2083 engine RPM), 209 ft-lb torque at 1249 RPM, torque rise of 31.6%. Fuel efficiency 14.2 HP-hr/gallon.
- CIH Farmall 70A (2019): 136 cid turbocharged (18.2 PSI), intercooled, common-rail three-cylinder. Rated speed 2600 RPM, redlines at 2800 RPM. Produced 63.5 PTO HP at 540 PTO RPM (2575 engine RPM), 167 ft-lb peak torque at 1798 RPM, torque rise of 29.2%. Fuel efficiency 13.8 HP-hr/gallon.

The much smaller engine with a much higher operating speed has noticeably less torque but makes almost exactly the same PTO power, has a similar torque rise, uses about the same turbocharger boost, and even has very similar fuel efficiency. I would thus expect very little difference in performance between the two engines despite the torque difference.
 
 
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