Compact tractor horse power

[professor]

I recently read a book about compact tractors and the impact they have had on different areas of agriculture, industry and suburbia. The book was interesting reading however there were some mistakes. The author stated compact tractors now have more horse power but are lighter in weight thus making them more efficient. Without weight and torque what good is horse power? The first garden tractors were in the 10-12 horse range and they were tanks. It amuses me when I see lawn tractors with 22 horse engines and light duty transmissions and weighing in at 700 lbs. My 9 horse Farmall cub will out pull my 17 horse JD 280 lawn tractor. I feel people are buying horse power that is useless to them. Am I totally wrong?

 

[Don87]

No, you aren't totally wrong, and the way you described the book you read, the author isn't totally right.

But without actually reading the book, it's hard to make much sense of what he was saying.

Case in point is that newer compact tractors(ie: CUTS) are 4wd, which will pull more than a 2wd of similar HP.

And the 2 tractors you listed are in totally different classes........One is a farm tractor, the other is a lawn mower.

 

[bcp]

Higher horsepower on a riding mower/garden tractor mower helps it go through tall, thick grass easily, or power a large tiller. Without more weight, it doesn't help traction.

The same situation applies to compact tractors. A 1500lb 20hp tractor may cut grass almost as well as a 3000lb 20hp tractor, but it won't plow nearly as well.

When 4wd enters the picture, you should probably compare tractor weights based on "weight on drive wheels." Then a lighter weight 4wd tractor is closer to the equal of the same hp heavier 2wd tractor.

Bruce

 

[Midniteoyl]

I recently read a book about compact tractors and the impact they have had on different areas of agriculture, industry and suburbia. The book was interesting reading however there were some mistakes. The author stated compact tractors now have more horse power but are lighter in weight thus making them more efficient. Without weight and torque what good is horse power? The first garden tractors were in the 10-12 horse range and they were tanks. It amuses me when I see lawn tractors with 22 horse engines and light duty transmissions and weighing in at 700 lbs. My 9 horse Farmall cub will out pull my 17 horse JD 280 lawn tractor. I feel people are buying horse power that is useless to them. Am I totally wrong?

Look at the power curves of a lawn tractor engine.. that '22hp' is peak RPM and is no where close to what the max throttle of the tractor is set at. A 22hp tractor is prolly working at 15-16hp maxed. To run a higher RPM and 22hp means you will destroy the engine in short order

 

[Larro Darro]

4WD makes a big difference. When I first got my B7500 I was always breaking though the grass with the rear tires and spinning down if the bush hog dragged at all. After switching to 4WD that never happens. I do tear up the grass with the skids on the mower though. It does a decent job running a 5' tiller also. If it is in solid turf, it tries to push the tractor ahead. But after the second or third pass, it does just fine.

We had to buy tires for my 3930 and we used the lift pole on the B7500 to load them. It was plenty strong to pick it up. The only problem, it picked up the front of the tractor. Me and my BIL had to stand on the front while my sister steered it into the truck.

SCUT's and CUT's are great for what they are good for, but for farming, you need a real tractor.

 

[cisco]

Horsepower tends to be emphasized in the signs on garden tractors sold at big box stores.....but for the even semi-sophisticated such is only 1 part of the equation. So, yup, HP is a number, but at what rpm for both HP and torque? Let's try the Audi 3.0 as an example (cause that's the first example I found via Google). The diesel version is 240 hp at 3750 rpm with 406 lb/ft at 1750 rpm whereas the gas version is 280 hp and 295 lb/ft at much higher rpm levels (4900 for the torque figure). Compression ratio, as in diesel in the 20:1 range while gas engines meant for regular (not premium) are in the 8:1 range, explains much of the difference. So, if you've a gas tractor how high do you intend to wind up the engine for routine work, and when will it blow up (these engines are high tech and carefully machined) - hmm, so most gas tractors are operating lower than the optimal torque range, which is already below diesel. Now, lemme see, how about transmission efficiency and does one expect to use the pto, as in bush hogging? I just returned from a hunt club "work day" (think sweat equity partially reimbursed in cold beer), and bush hogged for hours on end. When I chose a modest sized tractor (Kubota L3400), I paid more attention to pto than HP as the former is always lower than the latter, mostly in a predictable manner as in there is more loss with a hydrostatic than a shift transmission and if one wants the ease of shifting one should consider choosing the next higher HP/torque engine being offered (ain't hard as Deere and Kubota seem to have price points for every few HP increase). If I wanted to use a 6 ft hog in 3-5 foot heavy brush, I was going to need X amount of pto. Now, all the HP/torque in the world ain't going to help if one isn't well connected to the ground - ever spin your tractor tires pulling a box blade through heavy dirt? - so, 4WD vs 2 WD, tractor weight (loaded tires and all), and tire tread (lawn vs. R4 vs R1) factor into the equation at this point.
So, y'all probably well know this stuff already and aren't about to buy a tractor based on an HP advertisement alone. Nuff said - time for another beer.

 

[jenkinsph]

I recently read a book about compact tractors and the impact they have had on different areas of agriculture, industry and suburbia. The book was interesting reading however there were some mistakes. The author stated compact tractors now have more horse power but are lighter in weight thus making them more efficient. Without weight and torque what good is horse power? The first garden tractors were in the 10-12 horse range and they were tanks. It amuses me when I see lawn tractors with 22 horse engines and light duty transmissions and weighing in at 700 lbs. My 9 horse Farmall cub will out pull my 17 horse JD 280 lawn tractor. I feel people are buying horse power that is useless to them. Am I totally wrong?

Don't think you are totally wrong but maybe confused. A well designed mower is better with less weight and higher floatation so that it compacts the ground less but still needs power to keep the blades up to speed. Tractors need weight and the heavier Farmall should easily outpull the lawn mower. The Farmall would have decent pulling ability but at a low ground speed. Recognize that the speed with which you can pull a given load is equally important, a higher hp tractor with the same weight as a lower hp tractor can pull the same load at a higher mph.

 

[sd455dan]

I recently read a book about compact tractors and the impact they have had on different areas of agriculture, industry and suburbia. The book was interesting reading however there were some mistakes. The author stated compact tractors now have more horse power but are lighter in weight thus making them more efficient. Without weight and torque what good is horse power? The first garden tractors were in the 10-12 horse range and they were tanks. It amuses me when I see lawn tractors with 22 horse engines and light duty transmissions and weighing in at 700 lbs. My 9 horse Farmall cub will out pull my 17 horse JD 280 lawn tractor. I feel people are buying horse power that is useless to them. Am I totally wrong?

I think they should list the torque @RPM or better yet a dyno sheet with RPM and torque and horsepower graphed out... I agree that torque is the more important thing to look at first- since horsepower is just a derivative of torque and RPM.
And for mowing more HP can equal more acres mowed per hour

 

[WilliamBos]

I think they should list the torque @RPM or better yet a dyno sheet with RPM and torque and horsepower graphed out... I agree that torque is the more important thing to look at first- since horsepower is just a derivative of torque and RPM.
And for mowing more HP can equal more acres mowed per hour

The HP rating you see listed is PTO hp. Engine HP#'s are meaningless.

You want teal data, get your local dealer to run it on a PTO dyno for you. Most AG tractors will spin more PTO HP than the factory ratings.

 

[sd455dan]

The HP rating you see listed is PTO hp. Engine HP#'s are meaningless.

You want teal data, get your local dealer to run it on a PTO dyno for you. Most AG tractors will spin more PTO HP than the factory ratings.

I see what you are saying, about pto vs. (engine) hp but my point was that a torque curve will tell you a lot, as well as the RPM- peak torque occurs @ -regardless of where it is measured...

Actually all the sales fliers I have seen list both- and I agree that when comparing tractors marketed in the USA to use the PTO HP #s. Since several of the companies are overly optimistic and seem to use a short term (peak) hp # off the crankshaft with no accessories for the advertised HP which on some is FAR higher than the actual PTO HP output.

Also find it kind of interesting that more honest HP #s are from some of the Chinese tractors- which are specified as- (12 hours @ rated power) also If I want serious #s the Nebraska test data is the most revealing -but normally is only available for tractors that are going to be sold in the state of Nebraska...

Taking the tractors in and having them tested sounds fun and educational, but until one of them exhibits a lack of power I'll hold off- also the Ford 3000s independent pto clutch will not hold 100% of the engines power so it would not tell me much.