A question of Horse Power

Soundguy · Jun 20, 2005

I wasn't indicating that hp was multiplied.. that's faulty physics... if your source hp is x.. it can't become xx or xxx thru a gear system... in fact.. it becomes x-(fractional loss) due to friction.. etc.

Soundguy

Bob_Skurka · Jun 20, 2005

I wasn't indicating that hp was multiplied.. that's faulty physics... if your source hp is x.. it can't become xx or xxx thru a gear system... in fact.. it becomes x-(fractional loss) due to friction.. etc. 

Exactly, that is what I thought.

But it still doesn't explain the dual hp ratings on the old steam engines. And as Ben wrote, (a 20 HP old steam tractor might dyno out as high as 80 HP!) the old steam engines could dyno out at some high numbers; yet they were rated at very low hp. And if I understand it, their numerical designation on the model numbers were the dual hp ratings.

Maybe we need to move this part of the discussion over to the Antique forum?

Soundguy · Jun 20, 2005

well.. like I said before.. a high hp engine.. that has a very lossy drivetrain and is inefficient about getting hp to the ground may dyno out at 100hp at the engine belt.. but only deliver 60 to the ground du to bad traction and in-efficiencies.. etc.

So far everyone I have asked about this claim it is a drawbar / belt hp measurement. the belt number is highest as it is almost engine hp.. can be considered pto hp as the belt was the power coupling.. etc.

Good examples o fthe dual rated machines are the hart-parr

12-27 15-30 17-30 18-30 20-40 22-40 22-45 28-50 30-60 40-80 and 60-100

Twin city was another.. notice the similarities..

16-30, 17-28 20-35 21-32 27-44

Cockshutt had a 18-28 and a 22-44.. but I can't find much info on them.

Nuffield also used a dual number scheme. from what I can find on them.. the higher number was the engine hp rating.. for instance the 10/42 was 42 eng hp and the 10/60 was 60 eng hp. same with the 3/45 and 4/25.. higher number is eng hp. I'm not sure what the lower numbers refer to.. but doubt that it is a hp rating.. got to be a cyl.. or model designator or something...

Soundguy

Bob_Skurka · Jun 20, 2005

That explains a lot.

FWIW, Cockshutt and Hart-Parr are both Oliver companies, in later years Oliver sold the same machines under different brand labels for a while, Cockshutt was sold mostly in Canada from what I can tell. I am not sure if the Cockshutt machines were duplicates of the H-P machines but I know they were duplicates of the Oliver brand, only painted in the Cockshutt color scheme.

slowrev · Jun 20, 2005

Yep, the 20 HP number might be for drawbar, but I saw one pulling a 3 gang plow last night on TV. 20 HP pullling 3 plows ??
Ben

cchoate · Jun 21, 2005

My head is spinning... /forums/images/graemlins/tongue.gif

Spiffy · Jun 21, 2005

In answer to your actual question, its just don't assume anything. If power is your concern, just make sure the numbers are apples to apples.

But for many tractor applications you really do need to go one step further as stated earlier and compare the torque charts: essentially whether the engine will "lug" into the sweet spot and keep up with the demand or get "pulled down" and just kill. For ground engaging you should also compare things like drawbar force [don't know that this is widely advertised in smaller machines, but it may be] at XX ground speed. Of course, depending upon application you may have more power than can be usefully transmitted to the ground anyway!

Hope that helps clarify rather than further muddy the water! /forums/images/graemlins/crazy.gif

JoshJ · Jun 21, 2005

( My head is spinning... /forums/images/graemlins/tongue.gif )
Mighta hafta chalk that up as a horsepower loss as well! /forums/images/graemlins/grin.gif /forums/images/graemlins/tongue.gif

Spiffy · Jun 21, 2005

Yep, the 20 HP number might be for drawbar, but I saw one pulling a 3 gang plow last night on TV. 20 HP pullling 3 plows ?? 

Going to the litteral definition of HorsePower [550lb 1ft/second]; thats 11,000lb drawbar pull (@ 1ft/second)....3 plows, no problem!

Actually, most of the earlier machines I know of follow the nomenclature that Soundguy previously mentioned: HP drawbar - HP belt (or PTO). I think the ones with very small numbers were plow designators not cylinder numbers; but I may be way off on that.

As stated in other threads, you also have to consider the fact that rated HP was developed at what now would be considered very low RPM [excellant lugging power].

Early on, most farmers still knew about what a horse could pull, so tractor manufactures had to be fairly literal with HP ratings. Also, I think some mfgs didn't even test; they just calculated "HP" from bore and stroke and assumed 50% losses to the drawbar. As time when on [someone may correct my history here], I think creative HP marketing is what drove the popularity [I think the creation for that matter] of the Nebraska tests.

By the way, they do have test reports on some of the larger machines often discussed on TBN Nebraska Test but I don't think they do the same "field tests" they did on the tractors of yester-year, so it's still hard to compare [not to mention the torque curve again].

How ironic, that roughly 100 years latter, creative marketing has again rendered advertised HP meaningless in everything from lawn mowers to power tools!

slowrev · Jun 22, 2005

How ironic, that roughly 100 years latter, creative marketing has again rendered advertised HP meaningless in everything from lawn mowers to power tools!

//
Yep pretty much /forums/images/graemlins/smile.gif

Ben