Just something I’m curious about and I’m sure somewhere there is a mathematical formula to figure it out. An example I’ll use is this. We have an Oliver 1650 gas tractor we moldboard plow with. Tractor is rated at 65-66 hp. Growing up we were always told by dad to run the tractor at around 1700-1800 rpm. I believe the the engine has an operating rpm of around 2400 rpm at wide open throttle . How much of that 65 hp are we using at say 1700 rpm ? We never ever use any tractor at full rpm even for pto work where 540 pto rpm is. Usually around 2000 for pto work like making hay ect. I do realize pto equipment is designed to run at 540, but that’s not how I was taught. I do however run my 300 wide open when blowing snow.
- Thread starter 300jk
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fastfarmall
Well-known Member
The reason your dad told you to run at the run at that RPM, was to save fuel,and it works, my 806 Diesel,I throttle back to 2100, that's a sweet spot for that engine! It burns less fuel! You ever look up tractor on the Nebraska Test results, and see what the horse powerhour per Gallon is at different RPM's. One of the leaders of the industry was the 720 John Deere Diesel ! I would say 85% power was used, but the load pulls easier,because your going slower so u need less power!
MarkB_MI
Well-known Member
- Location
- Motown USA
The authoritative source of that information is the Nebraska tractor test. However, it has no horsepower data for engine speeds below 2200 rpm. At 2200 they were able to get 67 horsepower at the PTO.
If the Oliver's torque curve is flat from 1700 to 2200 rpm, it would produce 77 percent of 67 horsepower at 1700 rpm. Which would be 52 hp.
Oliver 1650 gas Nebraska test
If the Oliver's torque curve is flat from 1700 to 2200 rpm, it would produce 77 percent of 67 horsepower at 1700 rpm. Which would be 52 hp.
Oliver 1650 gas Nebraska test
Steve@Advance
Well-known Member
Interesting question!
It's beyond my thinking to understand it. To me, horsepower is a convenient smoke and mirror way for manufacturers to misrepresent their product. Torque is what does the actual work.
This link explains a lot, but most is way over my head.
The last 3 paragraphs put in better in prospective, especially the part about a car going down the drag strip, extending out the RPM capabilities allowing higher speeds in a lower gear, something totally useless in an enduring torque application such as a tractor, marine, or stationary engine. Just because the engine is not running at redline doesn't mean it's lacking in it's potential output, it's applying what it needs to get the job done.
HP and Torque
It's beyond my thinking to understand it. To me, horsepower is a convenient smoke and mirror way for manufacturers to misrepresent their product. Torque is what does the actual work.
This link explains a lot, but most is way over my head.
The last 3 paragraphs put in better in prospective, especially the part about a car going down the drag strip, extending out the RPM capabilities allowing higher speeds in a lower gear, something totally useless in an enduring torque application such as a tractor, marine, or stationary engine. Just because the engine is not running at redline doesn't mean it's lacking in it's potential output, it's applying what it needs to get the job done.
HP and Torque
Ronnie Budd
Member
Sure. It's simple. Horsepower is a theoretical number that is derived by measuring torque, then multiplying it by RPM, and then dividing by 5252. So all you need to do is find the torque of the engine at whatever RPM you are interested in and you can calculate the horsepower.
For example, 144 Ft/Lb s of torque multiplied time 2400 RPM and divided by 5252 yields a horsepower number of 65.80 HP.
Assuming that the engine is still making 144 Ft/Lbs of torque at 1700 RPM yields a horsepower number of 46.61 HP. But you have to realize, it's torque that is turning the shaft and turning the wheels. Horsepower is a theoretical number derived from a formula devised by James Watt back when he was selling steam engines and people wanted to know how many horses his engine would replace.
Because Horsepower is a theoretical number derived from a calculated formula, gearing can be (and is) used to multiply torque, but not horsepower.
For example, 144 Ft/Lb s of torque multiplied time 2400 RPM and divided by 5252 yields a horsepower number of 65.80 HP.
Assuming that the engine is still making 144 Ft/Lbs of torque at 1700 RPM yields a horsepower number of 46.61 HP. But you have to realize, it's torque that is turning the shaft and turning the wheels. Horsepower is a theoretical number derived from a formula devised by James Watt back when he was selling steam engines and people wanted to know how many horses his engine would replace.
Because Horsepower is a theoretical number derived from a calculated formula, gearing can be (and is) used to multiply torque, but not horsepower.
john in la
Well-known Member
Torque is how big of a load you can pull.
H.P. is how fast you can pull the load.
And the torque curve equates to the rpm needed.
That is like trucks from years ago were screaming at highway speeds in the range of 1900 to 2100 rpm.
Today with our different torque curve a truck can pull that same load humming along just above a idle at 1200 rpm.
So a more important question is how does your tractors torque curve change over the rpm range.
H.P. is how fast you can pull the load.
And the torque curve equates to the rpm needed.
That is like trucks from years ago were screaming at highway speeds in the range of 1900 to 2100 rpm.
Today with our different torque curve a truck can pull that same load humming along just above a idle at 1200 rpm.
So a more important question is how does your tractors torque curve change over the rpm range.
MarkB_MI
Well-known Member
- Location
- Motown USA
Folks seem to be confused about horsepower. Horsepower is simply the rate at which work may be done. More horsepower means more work gets done per hour. And horsepower is calculated by multiplying torque times speed. Torque, in itself, does NOT mean work is done. You can hold 40 ft-lbs of torque on a wrench indefinitely and no work will be done. Only by MOVING the wrench under torque is work done.
If we had an engine that put out constant torque from zero to 5000 rpm, its horsepower curve would be a straight line starting at zero rpm/zero hp and ending at 5000 rpm and whatever its maximum horsepower might be. But internal combustion engines don't behave that way; they typically have curved torque curves and consequently curved horsepower curves. And they may or may not put out maximum horsepower at maximum rpm.
If we had an engine that put out constant torque from zero to 5000 rpm, its horsepower curve would be a straight line starting at zero rpm/zero hp and ending at 5000 rpm and whatever its maximum horsepower might be. But internal combustion engines don't behave that way; they typically have curved torque curves and consequently curved horsepower curves. And they may or may not put out maximum horsepower at maximum rpm.
MarkB_MI
Well-known Member
- Location
- Motown USA
> There are drawbar horsepower figures for various rpm on that test.....1700 rpm shows 51 drawbar hp, vs 59 at full rpm, with 66 pto hp at that rpm...just look a bit further down.
Thank you, Ben.
Thank you, Ben.
Goose
Well-known Member
One thing that always frustrated me was my dad would never run a tractor over about 2/3 throttle, no matter what he was doing. Even after I showed him a line in the owner's manual for a 44 Massey that said not to run the tractor under load at anything less than full throttle.
As far as the original question goes, it's mostly determined by the torque curve that's built into the engine. It reminds me of when we quit racing stock cars. Someone put one of our stock car engines in a drag car, thinking he would clean house. As it turned out, he got wiped out at the starting line. Why? Because the engine wasn't built for low end torque, it was built to "turn on" between 5,000 and 8,000 rpm.
As far as the original question goes, it's mostly determined by the torque curve that's built into the engine. It reminds me of when we quit racing stock cars. Someone put one of our stock car engines in a drag car, thinking he would clean house. As it turned out, he got wiped out at the starting line. Why? Because the engine wasn't built for low end torque, it was built to "turn on" between 5,000 and 8,000 rpm.
Russ from MN
Well-known Member
- Location
- Bemidji MN
A few years ago I was at the big show at Rollag MN, and they have a prony brake there for testing horsepower. A very simple device, along with a tachometer, and a formula can calculate real horsepower. I'm sure a modern dyno does it just as well, but with the prony brake it's all so visible, and they explained it all. It was really neat to watch the big old steamers go well beyond their rated HP after they got steamed up!
Brendon-KS
Well-known Member
- Location
- Goessel, KS
You are 100% correct. An engine produces two "things", torque and revs. Without BOTH present no work can be done. That's where power comes in - it is the combination (by means of multiplication) of torque and speed. Power alone tells you how much work an engine can do in a given amount of time.
super99
Well-known Member
I don't know about the HP, but it depends on how big of a load you are pulling. If the motor isn't lugging and you can shift up a gear and throttle back and run the same speed you will save on fuel and your hearing. I always figured that when doing this, if you could advance the throttle and response was instant you were OK. If you hit the throttle and it smokes and takes a while to open up, better drop a gear and run wide open.
Bruce from Can.
Well-known Member
- Location
- Woodville, Ontario, Canada
I am a simple guy, and have a simple answer. The tractor engine is governed, there for delivers maximum hp at full throttle. Running full throttle will not hurt the engine because the governor will not allow it to rev higher than the manufacturer had intended. Naturally running the tractor at the correct rpm to achieve 540 pto speed many require something less that maximum rpm.
fastfarmall
Well-known Member
So 59 is the drawbar maximum horse power,85% of 59 is 56.1
fastfarmall
Well-known Member
I was here too, i was standing next to Donny Duffner from Climax,and that G John Deere was on after the steamer,,He said to me boy that G doesn't have much does it, i agreed he's got G's a lot stronger than that!!
Janicholson
Well-known Member
Mechanisms designed for a specific PTO or belt speed are not going to fly apart at full throttle. But the engine will never reach full Horse power when throttled back to the specific "Book" rpm unless the operator became a secondary (and busy) governor that watched a tach more than the windrow, or furrow, or mower swath, juggling the throttle to keep it at that speed does work with a cruse control and digital processors. but that "aint" happening on our old tractors. Run it Wide open and get done. when pulling hard it will get to that sweet spot. and if it satys above it yippee, we got done faster. I stick to that! My uncle taught me to hook the Farmall 400's throttle hand lever below the bottom ov the serrated notches. I believe and how. Jim
MarkB_MI
Well-known Member
- Location
- Motown USA
One more thought. For the most part, it's torque, not speed, that creates wear and tear on the engine and drive train. More torque means more pressure on parts that wear, such as bearings and gears. If a tractor's engine is operated at a lower speed than rated rpm, horsepower is reduced but not necessarily torque. So engine life might not be increased all that much by operating at a lower power setting.
Another reason often given for operating at reduced power is improved fuel consumption. But if we go back to the <a href="https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1562&context=tractormuseumlit">Nebraska test</a> and check out the section "Varying Drawbar Power and Fuel Consumption with Ballast", we see that specific fuel consumption at 100 percent power is 0.618 lb/hp-hr, but at 75 percent power it increases to 0.669 and at 50 percent it's up to a whopping 0.778 lb/hp-hr. Even though fuel consumption is much less at reduced power settings, less work is getting done so the tractor burns more fuel and takes longer to do the same work as it would at 100 percent power. One might think this behavior is peculiar to the gas tractor, but a check of the <a href="https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1561&context=tractormuseumlit">diesel tractor test</a> shows the same thing.
Another reason often given for operating at reduced power is improved fuel consumption. But if we go back to the <a href="https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1562&context=tractormuseumlit">Nebraska test</a> and check out the section "Varying Drawbar Power and Fuel Consumption with Ballast", we see that specific fuel consumption at 100 percent power is 0.618 lb/hp-hr, but at 75 percent power it increases to 0.669 and at 50 percent it's up to a whopping 0.778 lb/hp-hr. Even though fuel consumption is much less at reduced power settings, less work is getting done so the tractor burns more fuel and takes longer to do the same work as it would at 100 percent power. One might think this behavior is peculiar to the gas tractor, but a check of the <a href="https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1561&context=tractormuseumlit">diesel tractor test</a> shows the same thing.
Traditional Farmer
Well-known Member
- Location
- Virginia
As a practical matter having run a lot of different tractors over the years there can be a big difference over how much HP different tractors loose at reduced throttle.In general the older tractors still have pretty decent HP at 1/2 throttle but these newer tractors are like the old Detroits once they loose a little
RPM the HP or ability to keep pulling drops quickly.I've never liked to lug an engine down a lot when pulling a heavy load just go to the next gear,same thing when crossing a mountain with a truck just shift gears and make it easy on the motor.
RPM the HP or ability to keep pulling drops quickly.I've never liked to lug an engine down a lot when pulling a heavy load just go to the next gear,same thing when crossing a mountain with a truck just shift gears and make it easy on the motor.
Brendon-KS
Well-known Member
- Location
- Goessel, KS
The author of the article you link to is still falling for the typical myths that many folks do who don't fully understand these concepts. This is particularly evident with statements like "Gasoline engines may exhibit horsepower ratings that are lower, equal to, or greater than the respective peak torque rating" - this makes absolutely no sense at all. You can't refer to having "more torque than power" or vice versa because they aren't the same "things" - one is power and one is torque. The fact that the NUMBERS associated with torque and power when using typical USA units happen to be close to each other and are "the same" at 5252 rpm doesn't mean anything. If we used inch-pounds for the unit of torque we could say that an engine always has "more torque than power" but nothing changes. If we referred to the power in watts we could say that the engine always has "more power than torque". It's like if I said that my height equals my weight because I'm 175 cm tall and weigh 175 lbs. Well, yeah, the numbers are the same but that doesn't mean anything - its just the result of the units of measure that I picked. Comparing power and torque NUMBERS in the same manner is equally meaningless and for an author to do this in an article throws up a definite red flag.
At the end of the day it is engine torque combined with engine speed that accomplishes work. Further, torque combined with speed is the very definition of power so it follows that by definition it is power that accomplishes work. It doesn't matter what the engine speed is or how much torque is being produced at the crankshaft as long as the combination of the two provides enough power to do the job. Things like duty cycle, service life, and efficiency obviously play into which engine is more suitable for a particular task but the above facts still hold true.
At the end of the day it is engine torque combined with engine speed that accomplishes work. Further, torque combined with speed is the very definition of power so it follows that by definition it is power that accomplishes work. It doesn't matter what the engine speed is or how much torque is being produced at the crankshaft as long as the combination of the two provides enough power to do the job. Things like duty cycle, service life, and efficiency obviously play into which engine is more suitable for a particular task but the above facts still hold true.
495man
Well-known Member
Oh, likely heard to do that from "old so and so" who is a local "expert" with no tangible credentials but knows way more than the engineers who designed. You pointing out the correct thing in the BOOK is meaningless because people who wrote that "never drove a tractor". Sound right?
My favorite? Don't run the 540 RPM machine at 540 RPM because it isn't made to go that fast.
Traditional Farmer
Well-known Member
- Location
- Virginia
If you ever used a Twin Wheel Drive Allis Chalmers sickle bar mower you'd learn,or should learn, after about the 3rd total rebuild that yea maybe the pin heads were wrong about this thing being run at 540 RPM.About 2/3 throttle they'd give great service.
Traditional Farmer
Well-known Member
- Location
- Virginia
A lot of times,probably most time,the full HP of a tractor isn't needed.I rake hay with a 45 HP David Brown tractor,probably needs only about 20 or so HP
so I go up a gear and cut back to about 1/2 throttle to get the desired ground speed. Because the tractor has some lower RPM power it pulls the rake a long just fine and gets great fuel
economy.
so I go up a gear and cut back to about 1/2 throttle to get the desired ground speed. Because the tractor has some lower RPM power it pulls the rake a long just fine and gets great fuel
economy.
Some good facts in this thread, some not so much. Horse power is NOT "just a theoretical number"......James Watt found that an average draft horse could exert a force of 150 pounds while walking at 2.5 miles/hour, thus the 'horse power ' was defined & still in use today. Stood the test of time for a hundred years.
Ronnie Budd
Member
Now , go back and read the rest of the history on how James Watt came up with the "formula" that we have been using for a hundred years. The measurements he did resulted in odd numbers that wouldn't easily convert. So, they rounded them off to come up with the constant of 5252 that is used as the divisor in our modern horsepower formula. So yes, it is "theoretical".
MarkB_MI
Well-known Member
- Location
- Motown USA
> Now , go back and read the rest of the history on how James Watt came up with the "formula" that we have been using for a hundred years. The measurements he did resulted in odd numbers that wouldn't easily convert. So, they rounded them off to come up with the constant of 5252 that is used as the divisor in our modern horsepower formula. So yes, it is "theoretical".
The formula for power has not changed since Watt's time. It is P = fv, where P is power, f is force and v is velocity. When dealing with rotational rather than linear work, the formula becomes P = 2πTn, where T is torque and n is the rotational speed. That "constant" of 5252 is not really a constant but rather a conversion factor. Working in the metric system, there is no need for a conversion factor. But using English units, one horsepower equals 33,000 ft-lb/min. 33,000 divided by 2π is 5252.
Power is not a "theoretical" value. It is a [i:654c4848f0]derived[/i:654c4848f0] value, meaning it is calculated from other values (torque and speed) as it cannot be directly measured. To say power is theoretical would be like saying electrical resistance is theoretical, just because it has to be calculated from voltage and current.
The formula for power has not changed since Watt's time. It is P = fv, where P is power, f is force and v is velocity. When dealing with rotational rather than linear work, the formula becomes P = 2πTn, where T is torque and n is the rotational speed. That "constant" of 5252 is not really a constant but rather a conversion factor. Working in the metric system, there is no need for a conversion factor. But using English units, one horsepower equals 33,000 ft-lb/min. 33,000 divided by 2π is 5252.
Power is not a "theoretical" value. It is a [i:654c4848f0]derived[/i:654c4848f0] value, meaning it is calculated from other values (torque and speed) as it cannot be directly measured. To say power is theoretical would be like saying electrical resistance is theoretical, just because it has to be calculated from voltage and current.
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