Why is Gross HP used?

[hbaird]

I am new to tractors. I know Horsepower is work done over time. I understand Flywheel Horsepower and Rear wheel Horsepower. The former is the work that can be accomplished at the flywheel, IE, before drive train loses. The latter is the work applied to the load after all transmission loses. Most engines have fuel to pump, oil to pump, and many have an alternator / generator load, and water to pump, this load is normally subtracted from the maximum production of the engine before computing HP because most engines won't run long without these accessories. Transmission loses are low,1% to 3%, for mechanical gearboxes and higher for hydraulic drive train systems. The US, some time ago, sold autos using a, somewhat imaginary, marketing based rating for HP. Now the convention is real Flywheel HP. So where does Gross fit in all of this and why is it used for some tractors? I expect there must be a reason some Tractor vendors, but not many in the world, use Gross HP. I can't find any practical Industrial use for the term. Any reply would be helpfull.
Harold

 

[Bob_Skurka]

Harold, Gross HP is simply a marketing ploy. Every tractor company seems to have settled on using Gross HP to describe the HP of their tractors, at least that is true with compact tractors. When you wrote that there is no practical use for it, you are absolutely correct. A more effective real world measurement would be HP after deducting for loads.

What is even more troubling is the capacity measurement points. Some manufactures measure their 3pt lift capacity at the ball eyes at the end of the 3pt arms. But a much more practical, real life capacity measurement is actually 24" behind the ball eyes. Kubota, New Holland and Massey Ferguson measure honestly at 24" behind the ball eyes in their marketing marterials. John Deere provides these measurements in some of their material.

Also some manufacturers seem to measure their FEL lift capacities at the pivot points which are actually behind the buckets. Again a more honest measurement would be at the bucket center. Kubota, New Holland and to a lesser extent Massey Ferugson provide these honest measurements in their marketing material. John Deere provides these measurements in some of their material.

Branson, Century, Kioti, Mahindra provide numbers that are often misleading. John Deere sometimes does. I believe that just like inflated Gross HP number are a marketing ploy (read that as a legal lie) the capacity numbers used in marketing material, while techincally accurate, is at best disingenuous and could be considered to be misleading and deceptive.

 

[depratt_equip]

Bob if you will recheck some of your specs, you will see that Kioti rates all of there 3 pt lift cap @ 24" behind the lift point. So you are incorrect about the Kioti specs being misleading.

As long as a persons compares apples to apples (example 3pt hitch 24" after or at the hitch) Then you can still compare specs. Even though one mfg may not rate there buckets at the center, but rate it at the pins you can still use that number to compare to others as long as they proivde specs at the pins as well. Main thing to do is compare apples to apples.

 

[frank_f15]

Bob: i was wondering if there is a sort of rule of thumb that one could use, , say you wanted to buy a 30hp tractor(hydro) is there a pecentage you could use to be close to the actual HP delivered?

 

[RoyJackson]

"What is even more troubling is the capacity measurement points. Some manufactures measure their 3pt lift capacity at the ball eyes at the end of the 3pt arms. But a much more practical, real life capacity measurement is actually 24" behind the ball eyes. Kubota, New Holland and Massey Ferguson measure honestly at 24" behind the ball eyes in their marketing materials. John Deere provides these measurements in some of their material. "

I went through a handful of the on line Deere manuals. All indicated the 3PH capacity was 24" aft of the links.

Sometime the schematics of the tractor's dimensions, weights and capacities (you've all seen them...a side view of a generic tractor with a multitude of dimensions indicated by upper case letters (A, B, C...)) are confusing to read. I could never understand why a loader would be rated at the bucket pivot pin. However, that number may come in handy if one switches from a bucket to forks or some other implement that can be rigged to the loader arms. Same thing applies to the 3PH, but there may be uses we residential type users would never think of. When Deere puts this data together, I'd wager the same dimensional points and other metrics are used on all their tractors, not just our little ones. Simply put, that schematic would be a template for all tractor type products.

 

[Bob_Skurka]

Jon, you are correct, I went back and even check a prior thread where I posted much more of this data in much greater detail. Kioti does post their 3pt capacity at 24" behind the ball eyes.

So to correct my prior post and clarify

As it appears to me now the following companies list FEL capacity at the bucket center in on-line MARKETING material:
- Century
- Kubota
- Massey Ferguson
- Case-New Holland

As it appears to me now the following companies list 3pt capacity at 24" behind the ball eyes in on-line MARKETING material:
- Kioti
- Kubota
- Case-New Holland
- possibly John Deere

As it appears to me now the following companies list BREAKOUT force in MARKETING material at 500mm ahead of the pivot point and/or the bucket lip:
- Branson
- Century
- Kubota
- Massey-Ferguson
- Case-New Holland


The only 2 companies who meet my "honest marketing test" and make ALL 3 lists are
- Kubota
- Case-New Holland


The companies who do not make all 3 lists are:
- Branson
- Century
- Deere
- Kioti
- Mahindra
- Massey-Ferguson


As for the "Apples to Apples" comparision statement you made, I absolutely agree with you. That is however a huge problem for consumers because it is often very difficult to figure out what number the tractor manufacturer is actually using!!!


EDIT: Roy . . . you are correct that the on-line manuals have the honest numbers for the JD products. What I am critical of are the marketing numbers. Some of the marketing numbers are very vague in where they come from and the FEL numbers are from the pivot points. There is a difference between marketing material and operating manuals.


Also, people my want to refer to this thread that started out questioning one thing and evolving into something completely different. Rated capacity versus bucket capacity thread

I would also point out that I am not bashing any brands here, just posting findings from looking at the MARKETING materials that the companies use. I used my comments to point out an example of my belief that the marketing departments often list things that favor their products even if they don't compare apples to apples with the other brands.


Frank . . . I never looked into that, however I suspect that each manufacturer might have different effeciency losses based on the additions they put on their engines.

 

[MessickFarmEqu]

Frank - Hp loss runs around 80%.

I'm in the same boat with Bob on this one. I get alot of confused customers comming over from the JD dealership thats 5 miles away. The Op manuals may have the proper numbers but the marketing literature often does not. The latest slip of the tonuge is their "3-year" warrenty. You have to read the find print to see that its drivetrain only. I've heard other dealers encouraging other manufacturers to do the same stuff... its dishonest business in my opinion.

 

[MikePA]

<font color="blue">Frank - Hp loss runs around 80%. </font>
80% of the engine hp is lost in the drivetrain?

 

[Bob_Skurka]

Neil, I know you are not bashing John Deere but simply stating your experiences as a dealer with what is confusing customers. Do you agree with my above conclusions about the marketing practices of the other companies as well?

I have figured out, by using the manufacturers data, that a 3pt hitch measured at the ball eyes has roughly 30% to 40% higher capacity ratings than one measured at 24" behind the ball eyes.

Also by using manufacturers data and some simple math, by rating a FEL at the pivot point instead of at the bucket center (roughly 19.5" in front of the pivot) that the capacity is inflated roughly 35%.

Anyone who has been digging around on TBN for any length of time knows I push for "apples to apples" comparisions. Jon DePratt suggested above, and I agreed with him that "apples to apples" comparisons are valid. However, what I have found is that people can NOT figure out what numbers to use to make the proper comparisions based on some of the MARKETING materials that the companies use.

Bringing all this back to the original issue of GROSS HP, I think it all falls into the same bucket of LEGAL DECEPTION. Tell the consumer that the machine is rated for "X amount" of whatever, and then bury the actual data somewhere in the bowels of the operating manual. The fine print may point out that the engine's GROSS HP was measured on a dyno without any loads . . . or it may point out the FEL/3pt hitch capacity is measured at "x position" instead of something that a consumer can actually use. It is all legal. It doesn't mean it is right.



Neil, BTW, I am unclear on what you mean by 80% hp loss.

 

[tjkadar]

Last week we had a company come out and demo their product for us. It was a direct push, track based vehicle, driven via remote control used for groundwater sampling and subsoil sampling. Lucky for us, the president of the company had come along for the ride and to see how things were going with his products.

While talking to the president of the company we got into a discussion of marketing departments and their use of numbers to sell products. Even in his own company, he had problems with the marketing department wanting to use the largest possible numbers they could, even if those figures had no relation to real world operations.

Specifications are like a shell game; they shuffle numbers around hoping you wont catch the slight of hand. Now this does not mean a company makes a poor product or is a bad company. In the marketing game, that is the way it has always been done and will continue to be done by most.

Personally, I don’t put much stock in hp figures. Instead, show me a dynamometer graph. Let me see the area under the curve. Let me see the torque rise and then I can decide which machine might be able to do the most work.

But in the end, the only real way to tell is to drive each machine yourself. One machine might actually have a bit more ‘power’ then another, but the ergonomics might not fit you. You’ll do more real world work in a machine that fits you then in something you can’t get comfortable with.