a tractor question.

unclehan · Feb 24, 2005

it true that a tractor engine makes much greater use of its power than a car engine? We all know that a car engine only uses its a lot of horsepower when accelerating only. This means most of the time the power demand is way below the capacity of the engine for car. This is not true for a tractor right?

Let's say a 150 HP car only uses that much HP when it's floored, but most of the time during cruising, it may only require less than 20 HP, which is way below 150HP.

But what about a 50HP tractor? I think a tractor will make much better use of the power than a car.

Right?

beenthere · Feb 24, 2005

Seems related to the load in both cases.

So, you are thinking the tractor is 'loaded' more than a car?

Bob_Skurka · Feb 25, 2005

it true that a tractor engine makes much greater use of its power than a car engine? 

The engines generate the horsepower, but the transmissions USE the horsepower and apply it to the task at hand. The two machines are geared for totally different purposes. A tractor simply cannot accelerate like a car due to its gearing. A car, conversely, cannot apply the power to the ground the way a tractor can. To effectively compare the two, you'd need to find a car and a tractor that had equal HP and equal weight. The car would be geared totally differently and apply the power differently than the tractor.

chrisjbell · Feb 25, 2005

IMHO, a tractor is a more specific use vehicle than the average car. Cars have to do stop and go, creeping driving. They also have to do high speed, up hill, down hill, and slow and fast curvies. Therefore, I think you are correct that a tractor is more efficient in applying horsepower because it is doing so in a very limited range - slow, strong, and steady. That is what it does and that is about all it does (in terms of translating power to action).

Kind of an interesting question, really...but I'm not sure I needed to get this into my brain. ("Honey, did you take out the trash?" - "Uh, no, I was thinking, uh, about, oh, never mind, I've gotta take out the trash") /forums/images/graemlins/grin.gif

rdbrumfield · Feb 25, 2005

The concept of hp is lost in rpm. The tractor is more likely to out torque an engine in a car with the same hp. Think of what you tractor would do if it's engine was able to turn 5-7000 rpm. Keeping the plow in the ground probably wouldn't be too bad, it would be keeping the soil in the same field that would be difficult.

KiotiJohn · Feb 25, 2005

Bob Shurka pretty well has it. The tractor has a transmission and a different gearing that makes it pull and use HP differently than a car. Of course, a tractor is not using all it's rated HP either unless you have the RPM up to rated speed, but the gearing allows the tractor to use the HP/torque for pulling heavy weights where the gearing and transmission of the car would not allow that. The HP would be wasted in spinning tires on the car. John

Bob_Young · Feb 25, 2005

Yes, the tractor uses much more of its 'rated' horsepower than a car. A tractor rated at 45HP @ 2600 RPM may also be rated at 37 PTO HP @ 2400 engine RPM. When running a PTO implement, the tractor engine is intended to be run continuously at that 2400 RPM....so, yes it's using a much higher percentage of its 'rated' horsepower. If needed it could operate continuously at 2600RPM without durability issues; though PTO operation at this higher RPM would probably cause issues with the implement.

But notice; the so-called redline is much lower than you commonly find in an auto. In the tractor, the 45HP is being delivered by a 2.2 liter engine 'redlined' at 2600RPM. A 2.2 liter auto engine will commonly deliver around 140HP at 6000 RPM; which is at or close to it's own redline. The auto engine could easily run continuously at 2600RPM, probably delivering around 50HP, without any wear or durability issues; but not at 6000RPM. However the additional power that's available above 2600 RPM in an auto is available for intermittant use during acceleration.

Power that's available from a tractor engine tends to be used continuously. Therefore, to keep it in one piece (among other reasons) it's rated at a much lower RPM/HP and governed to operate at or below the rated RPM.

Piston aircraft engines are handled in much the same fashion because on takeoff and climbout the engine must deliver full power continuously for an extended period. Once at cruise altitude, only a modest power reduction is made and the remainder of the flight is conducted at 65 to 75 percent of maximum rated power.
Bob

vtdiesel · Feb 25, 2005

There is also the issue of torque. Remember HP is just torque X time.
A diesel produces much more torque at 2600 rpm then the equal size gas engine. This is how they get fairly good HP ratings at low RPM. I have a VW TDI and it red lines at 4300 rpm, very high for a diesel, but max torque is at 1900. You can feel the engine nose over above about 3300. My F350 red lines at 3300 and pulls all the way.

Henro · Feb 25, 2005

unclehan,

I think they are the same.

A tractor transporting itself quickly across a field is like a car running down the highway, it is using a lot less than its maximum HP available while moving relatively fast.

A car with a trailer that is heavily loaded, that is climbing a steep mountain grade, having to shift down to make it up, is similar to a tractor plowing a field, geared down and grunting to get the work done.

I think the root, unanswered question is:

At what point does a car become a tractor?

/forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif

unclehan · Feb 25, 2005

( unclehan,

I think they are the same.

A tractor transporting itself quickly across a field is like a car running down the highway, it is using a lot less than its maximum HP available while moving relatively fast.

A car with a trailer that is heavily loaded, that is climbing a steep mountain grade, having to shift down to make it up, is similar to a tractor plowing a field, geared down and grunting to get the work done.
)

But I don't think tractors spend most of its operating life transporting itself acrossing fields. I think most of its time it's under load, doing some kind of task. But a car spend the great majority of time cruising. Only rarely do car have to tow a trailer or go up a steep hill.

So yes while they both will encounter the same operating environment, the frequency is completely opposite.

So I guess my orginal question is whether tractor tend to use a higher PERCENTAGE of its rated HP than a car.

Let's say a 200 HP car only uses 200 HP when it's floored, but most of the time during cruising, it may only require less than 20 HP, which is way below 200HP. Say, it uses 10 seconds to accelerate up to speed (uses 200HP), then it spend the next 10 minutes cruising (uses 20HP). This means most of the time the engine is merely using 20 HP out of its available 200 HP. That's only 10%.

But what about a 50HP tractor? I think a tractor will make much better use of the power than a car. It could possibily using only 10% of its rated power (which is 5HP in this case) like a car. I think the percentage will be much higher.

slowrev · Feb 25, 2005

"At what point does a car become a tractor"

At what point does a tractor become a car ? Since I work from home I spend almost as much time on my tractor as my car, also drive it to the country store just down the road. A takn of gas in my scooby roo will last me about 2 months. The wifes car... well...it seems to have a 500 gallon tank /forums/images/graemlins/frown.gif
Well I don't go to wally world on it yet, so I guess it is still a tractor /forums/images/graemlins/smile.gif

Ben

rpeter · Feb 25, 2005

Henro, I think you got your posts mixed up /forums/images/graemlins/confused.gif The “What makes it a tractor" post is the next line down in the forum

Just kidding /forums/images/graemlins/grin.gif

Indydirtfarmer · Feb 25, 2005

Just for laughs, try taking a short trip around town on the ol' tractor! /forums/images/graemlins/grin.gif I have a hooters Restaraunt with-in a few hundred yards of the property. I wait until they're at "full song", and go driving by the window on the John Deere. /forums/images/graemlins/crazy.gif You should see the looks I get! /forums/images/graemlins/confused.gif

Just across the highway from the Hooters, is a car wash belonging to a good friend. I keep the snow shoved off his lot. In return, he gives me a "maint. code" that allows me to wash anything for FREE /forums/images/graemlins/grin.gif I've drove any or all of my tractors across the highway for a quick bath. Consider that I'm actually with-in the city limits of Louisville, Kentucky, and that highway is one of the main commuter arteries. /forums/images/graemlins/smirk.gif

SO.... On a typical saturday afternoon, you're likely to find me in my bibs and John Deere hat, mounted upon my favorite farm tractor, cruising past the Hooters, on my way to town! /forums/images/graemlins/laugh.gif

And I'm doing it with all the efficientcy of my favorite car. /forums/images/graemlins/smirk.gif

Henro · Feb 25, 2005

So I guess my orginal question is whether tractor tend to use a higher PERCENTAGE of its rated HP than a car. 

At first thought one might tend to expect that the tractor does use a higher percentage of its HP rating than a car does. But I wonder if it does. It really all depends on the application. A tractor used only for plowing would probably use a higher percetage of its rated power than a tractor used for mowing grass that is kept well under control, like a golf course fairway, for example.

I would not assume that a car running down a highway at 70 mph, especially in hilly country, is not using a fair amount of HP pushing air out of the way either.

I don't think a general answer is easy to come by...

I would like to think that if we compared a car and a tractor that were running at the same % power output over time, that the tractor would last a lot longer than the car would.

Sure seems that way, anyway...

unclehan · Feb 25, 2005

( 
At first thought one might tend to expect that the tractor does use a higher percentage of its HP rating than a car does. But I wonder if it does. It really all depends on the application. A tractor used only for plowing would probably use a higher percetage of its rated power than a tractor used for mowing grass that is kept well under control, like a golf course fairway, for example.

I would not assume that a car running down a highway at 70 mph, especially in hilly country, is not using a fair amount of HP pushing air out of the way either.

)

Actually, basic calculation shows that a Porsche Boxter crusing at 80mph only uses around 20 HP to overcome the air resistance and rolling friction. (let's neglict hill here since they are rare relative to level road).

But to acceleration from 0 to 60mph in 6 seconds, the Boxter would require 100 HP.

Therefore, the reason why so much cars are SO overpowered is because people care a lot about acceleration. Take the hybrid for example, it can uses a MUCH smaller engine (for greater idling efficiency) because it depends on a motor for acceleration (using energy that was stored previously). That's why it saves so much gas.

But for a regular car, you are using a WAY oversized engine just to accelerate fast while most of time it's not being very efficient (for cruising).

Those tractors that are used for plowing I think would use more HP than a lawn tractor that's used for mowing. But then again, a tractor that's solely used for mowing lawn probably have a much weaker engine than a tractor that's used on the fields. Therefore, the percentage shouldn't be that different, and both of them should be much higher than the cars.

Soundguy · Feb 25, 2005

( Just for laughs, try taking a short trip around town on the ol' tractor! I have )

Luckilly.. the city I live in is still somewhat peopled by farmers. It is not uncommon to see tractors running down the road from field to field. I drive my NH 7610 down the road to the fuel station.. or to mow a pasture.. etc.

I also frequently take 'joy' rides in my neighborhood on my antique tractors.

And 1 time I even drove my tractor to work ( true! )

Soundguy

WVBartMan · Feb 26, 2005

The car to tractor comparison reminds me of my nephew and his misconception as to his understanding of horsepower. Last summer we had a family reunion up on the farm. My nephew brought his new F350 pickup fitted with a lift kit and big mudder tires.

Somewhere in the afternoon he and his father got into a discussion concerning his new pickup verses my Kubota 50 hp tractor. My father informed me I may want to go outside and see what my brother was doing with my tractor. Upon exiting the house I heard the familiar sound of the Kubota heading into the field. Going around the house to get a view of what was going on I could see my nephew in his new F350 being pulled around by the Kubota. The F350 had all four wheels spinning but the Kubota acted like nothing was behind it and just dragging it around in circles in front of a growing number of spectators.

When it was all said and done a 50 horsepower tractor was able to get all 50 horsepower applied to the ground in the proper horsepower to weight ratio (145 lbs per pto horsepower, static) or in this case (6.5 mph = 120 lbs per pto hp).

My poor nephew had the look of disappointment wrapped in embarrassment. He asked me what I thought the problem was and I told him his father cheated. The nephew asked how and I said his father had a 24 year head start in knowing the outcome of that contest.

Soundguy · Feb 26, 2005

I did that with my yanmar 1700 and the neighbors new huskey 24 hp lawn 'tractor'. He swore up and down that his 24 hp 'tractor' would pull my 17/20 hp tractor. Well.. lets just say he was very surprised and very disappointed all at the same time about 1 second after each of us let our clutches out... /forums/images/graemlins/grin.gif

Soundguy

unclehan · Feb 26, 2005

( The car to tractor comparison reminds me of my nephew and his misconception as to his understanding of horsepower. Last summer we had a family reunion up on the farm. My nephew brought his new F350 pickup fitted with a lift kit and big mudder tires.

Somewhere in the afternoon he and his father got into a discussion concerning his new pickup verses my Kubota 50 hp tractor. My father informed me I may want to go outside and see what my brother was doing with my tractor. Upon exiting the house I heard the familiar sound of the Kubota heading into the field. Going around the house to get a view of what was going on I could see my nephew in his new F350 being pulled around by the Kubota. The F350 had all four wheels spinning but the Kubota acted like nothing was behind it and just dragging it around in circles in front of a growing number of spectators.

When it was all said and done a 50 horsepower tractor was able to get all 50 horsepower applied to the ground in the proper horsepower to weight ratio (145 lbs per pto horsepower, static) or in this case (6.5 mph = 120 lbs per pto hp).

My poor nephew had the look of disappointment wrapped in embarrassment. He asked me what I thought the problem was and I told him his father cheated. The nephew asked how and I said his father had a 24 year head start in knowing the outcome of that contest. )

So. what's the point? I don't understand. Are you talking about different gearing (more/less torque). Or are you talking about the original question on which tend to use a higher percentage of the rated horsepower?

Mith · Feb 26, 2005

( And 1 time I even drove my tractor to work )
did you arrive late or start off early?
/forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif