How does horsepower affect performance?

rk246 · Dec 15, 2005

As I have always thought about it,

Torque= ability to get something moving
HP= the ability to keep it moving...

I would think the higher hp tractor would give you more ability to pull the box blade, grade etc.

I don't know if the bigger deer has larger tires on it? But I went from a Kubota 3130 to a 3830 which has larger tires and more hp with pretty much everything else being the same. You definetely see the increase in hp while doing just about anything....

hudr · Dec 15, 2005

I have to agree w/ most of these guys here. We are talking about slow moving pieces of machinery. Torque multiplication is how tractors get things done. Power (HP or Torque) is almost abstract. It is the ability to put that power on the ground.
Example: I have a 50HP 2WD Mahindra. It is at the edge of its TRACTION envelope w/ a 6.5' offset disc. However, I was lent a 40hp 4WD Kubota during a warranty issue w/ my tractor. With all 4 tires pulling, the little Kubota pulled the daylights out of that disc. It wouldn't budge it in 2wd.
So, I would say power is important, but not as important as the application of that power.
In direct answer to the question: I would get the larger HP tractor if possible. It is much easier to add weight and ballast than it is HP.

jcmseven · Dec 16, 2005

Thanks for the replies so far. To me, this is an interesting question, and one I do not know the answer to assuredly. It would seem logical that the two tractors would be equivalent in their pulling of implements. There seems to be a difference between PTO horsepower and drawbar pull. If the two machines listed are equal in weight and have similar tires, they should seem to pull about the same, even though one has more engine power (both torque and horsepower). The only area that I personally see a difference would be with regard to speed. For example, if each machine were pulling a box blade that requires 4 mph at a given point (grade, hill, etc.) to maintain enough momentum not to slow the tractor until it bogs or loses traction then it seems there may be a difference. The more powerful machine seemingly being more likely to keep the speed up such that it does not dip below the point at which the tractor is struggling to keep momentum up against a heavy object. This would seem to be of little benefit when moving very slowly, or in tight quarters. The big question is: in real world usage, would that be enough to merit spending the extra money? My friend is very practical and would shoot me (kidding) if he spent more than he needed to for the type work he will be doing.

John M

rk246 · Dec 16, 2005

Just tell him you did some research and all of it showed that bigger is better, it was very scientific.... /forums/images/graemlins/smile.gif

slowrev · Dec 16, 2005

To me it works like this.

Torque = the ability to do work.
HP= How fast it will do the work.

Totally unscientific, just my opinion

Ben

IslandTractor · Dec 16, 2005

I suppose you could make an argument that higher horsepower would allow you to pull an implement at higher speed. Not that it would be reasonable use of a tractor but you could pull a box blade at road speed in high gear if the tractor was powerful enough. I think the real point here is balance: does the tractor have sufficient power to get the work done in a reasonable amount of time? Any given task is likely to involve much more than just pulling the implement so doubling horsepower/implement size does not halve the time involved. How often would a few extra HP really change the way you get work done or save significant time to justify higher purchase and operating costs?

3RRL · Dec 16, 2005

It doesn't matter which side of the discussion you're on. In order for something to be "justified" to a person, there are a million factors involved, mostly personal reasons that make sense only, personally, to that individual. Facts are weighed and measured to differing (individual) needs...you know what I mean. "Well, that's nice but I don't need that" or "This one is good enough for what I need" or how about this one "Geez, whish I could afford THAT!" etc...

But as far as your example in the comparison, there is a difference, for sure.

( If the two machines listed are equal in weight and have similar tires, they should seem to pull about the same, even though one has more engine power (both torque and horsepower).)
This not completely true nor does it ( "seem logical")... "about" is closer, though.
Let's exaggerate the example to put this HP and torque thing into perspective, accentuating the difference:
Imagine the two with same weight and tires, as you said, only they are semi-trucks and trailer(80,000lbs). One has a 1500cc VW engine (less hp & torque) and the other a 500HP+ Diesel (WAY more HP & torque)...

( The only area that I personally see a difference would be with regard to speed. For example, if each machine were pulling a box blade that requires 4 mph at a given point (grade, hill, etc.) to maintain enough momentum not to slow the tractor until it bogs or loses traction then it seems there may be a difference.)
The BB being the trailers and the grade being the Grapevine (interstate 5 in Ca)...yes, I would say there'd be a difference.

( The more powerful machine seemingly being more likely to keep the speed up such that it does not dip below the point at which the tractor is struggling to keep momentum up against a heavy object.)
Totally agree there.

( This would seem to be of little benefit when moving very slowly, or in tight quarters. The big question is: in real world usage, would that be enough to merit spending the extra money?)
Just tell your friend to ONLY use his tractor for above description (limit his loads and speeds, stay off ANY grades) and NEVER use for anything else and I'm sure he'll be happy. Tell him he can borrow your tractor to do everything else. /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif

Sorry to seem so pushy about this /forums/images/graemlins/confused.gif, but since you brought up the subject, it is important to understand that there really is a difference, and always will be. Now, how much of a difference in the practical, real world...I couldn't put a value on that??? Hope that's alright with you. As I said above, personal prefference and usage...whatever, will play a greater roll in the choice your friend makes anyway.

jcmseven · Dec 16, 2005

Good points on all accounts. I hope this has been a reasonable discussion. I never divulged which side of the discussion I am on, but it has been for more power if the cost is reasonable.In my memory, I can recall no tractor owner, or really owner, who regrets getting a more powerful machine. I have seen many who regretted getting a less powerful machine, and I have been one of those in the past. To me, that difference was worth as much as I could afford, to him maybe not, but we will see.

John M

jmc · Dec 16, 2005

If you only need torque, you can get it by downshifting. You could pull stumps with a squirrel in a rotating cage if you have enough gear reduction, traction, and patience. Two squirrels would pull the stump twice as fast, if they were the of the same sex, straight, and cooperating. You would also need to halve the gear reduction.

John

flwiii · Dec 16, 2005

Horsepower is really a relative term. 1 horsepower, as defined by Mr. Watt is the power required to raise 33,000 pounds 1 foot off the ground in 1 minute. This led to the constant used to measure horsepower (5252). Therefore horsepower is RPM times torque divided by 5252. So horsepower is really an expression of torque at a given RPM.

There are too many variables to determine which tractor would pull better. The biggest variable of couse is putting the power to the ground. This is the same problem that drag racers face. More torque at a given RPM and therefore more horsepower does not necessarily equate to a win. It has always come down to how well you can apply that power to the ground. If you break them loose all the way down the track, you've got too much horsepower. If you can't break them loose at all, then you may well have too little horsepower.