A question of Horse Power

[dknarnd]

</font><font color="blueclass=small">( Bob,
I agree with everything that you said except:
<font color="blue"> PTO horsepower is the net horsepower minus the horsepower lost to the transmission at a specified RPM.
</font>
When the PTO hp is tested, it is tested with the tractor stationary. I don't how much hp lose a hydro would have when the tractor is stationary because of the transmission, but a manual doesn't lose any hp to the trans. if the tractor is not moving. )</font>

I would think that even when the tractor is stationary it is still turning some components of the transmission/clutch combo therefore loosing some HP. Plus the HP required to turn the gearing in the PTO. Every movement eats away at HP.

What I would like to know is if it uses more available HP to run a Hydro transmission as speed or load increases than it does to run a geared transmission. It would be an interesting curve to see what happens to both PTO HP's as load increases.

 

[cchoate]

Thanks Hobbyfarm / Bob, that clears it up. Next question:
Manufactures that give one HP rating would probably be gross (engine only, nothing else attached) correct?

 

[Bob_Skurka]

Jerry, Regarding the disagreement in terms, I think we might be splitting hairs, I could have been more precise in my wording, when I referred to the HP loss due to the transmission, I was implying that the operation of the PTO itself is run through some sort of a transmission. Just as there are many different types of gear transmissions, of various levels of sophistication, PTOs can be designed/powered in many different ways. On some tractors the design is such that the PTO operates independantly and effectively has its own transmission (a set of gears, etc) that create some loss of HP as it moves from the engine to the implement. On other tractors the design is such that the PTO operates with or through the tractor transmission, it loses power and efficiency in a similar fashion.

Again, I think we actually agree, in a effort to not be too technical (largely because I can't explain technical things too well) and in an effort to be brief and clear (or at least fairly clear) I thought my explaination was, at least, pretty good. I will, however, always concede to your greater technical knowledge, when it comes to technical things, I usually turn to your posts for my answers!

Heck if you want we could get into the concept of two tractors of equal NET HP but dissimilar weight and then really start to split hairs about how much HP is useable when Tractor A weighs 1900# and Tractor B weighs 3000# . . . or using the same two tractors question which is the most efficient. But then no matter how you replied I could probably counter with an example to prove the opposite because useable power and effieciency often are dependant on the job being done. Now if the tractor is designed for a specific job, and it is doing that job, then we could actually figure something out, but I'm not sure it would be practical /forums/images/graemlins/grin.gif


<font color="red"> What I would like to know is if it uses more available HP to run a Hydro transmission as speed or load increases than it does to run a geared transmission. It would be an interesting curve to see what happens to both PTO HP's as load increases. </font>

I dunno. Never seen a curve of an ACTUAL tractor's power, only thing they ever publish is the engine data. One of the moderators, cowboydoc, who doesn't post too often any more, used to post information on HST vs GEAR data that was pretty convincing that the GEAR was perhaps even more efficient than many would believe as compared to HST, however I won't give up on any of my HST tractors (currently have 4 of them).


<font color="green"> Manufactures that give one HP rating would probably be gross (engine only, nothing else attached) correct? </font>

I would strongly suspect that they would post the GROSS hp, simply because we are often swayed by marketing that more is better. Who wants to own a wimpy tractor when you can get MORE???

 

[To20Chris]

I wouldn't think there would be any more loss in PTO hp when the wheels are driven with HST or gear. The main loss with HST will be in diving the wheels period, as this is the hydrualic link. So power that is sent to the wheels is not available to drive the PTO, same for gear and HST, it's just that with HST less of it actually gets to the wheels.

 

[JerryG]

Bob,
You are more than likely right, that we do agree. The way that it was stated, it appeared that there was a large HP loss due to the transmission, as in the previous examples. There is no more loss than the turning of gears to transmit the power to the rear. The transmission is not doing any actually work as in moving the tractor. I in no way meant anything about the hydro vs gear thing. I don't know how much if any HP is lost to a hydro by just running the PTO with the tractor stationary.

 

[normde2001]

I don't know about tractors, but on cars, net HP is what is produced at the rear wheels as shown on a wheel-driven dynomometer.

 

[slowrev]

Just to further confuse things, a 20 HP old steam tractor might dyno out as high as 80 HP!

All HP is not created equal, It's all about torque /forums/images/graemlins/smile.gif

Ben

 

[Bob_Skurka]

Oh Ben, you know darn well those old engines are double rated! An old Nichols-Shepard, Rumsley or Case thresher would have been called a 20-70 or 25-60 or something like that. I think the numbers referred to the dual HP ratings they could put out. I don't understand the steam engines, but they sure are facinating to see.

 

[Soundguy]

I've seen some numbering schemes that used that dual number.. one for engine hp.. and the other for drawbar hp..

Engine hp was plentifull.. but by the time it got thru the gears and cogs and bushings, to the metal wheels on the ground with only brads or cleats or ridges to provide traction in the soft dirt.. it only pulled like half it's power.. etc...

Soundguy

 

[Bob_Skurka]

<font color="red">
I've seen some numbering schemes that used that dual number.. one for engine hp.. and the other for drawbar hp..

Engine hp was plentifull.. but by the time it got thru the gears and cogs and bushings, to the metal wheels on the ground with only brads or cleats or ridges to provide traction in the soft dirt.. it only pulled like half it's power.. etc...
</font>


Chris, you certainly more about the old iron than I do, but I think with the old steam threshers I might be correct (this time). The numbering system they used had the lower number first, for example 20-65. The engines were very low hp, often in the upper teens and lower 20's. The second number, from what I gather, was also hp, but I can't imagine the engine hp would triple through the gears? Heck just last night I was watching the 60th Anniversary Steam Thresher Show video and the 50 Years of Progress Farm Equipment video (Father's day so I got to control the remote /forums/images/graemlins/grin.gif) Anyway, from what I can tell, some of the old steam engines had a dual power configuration.


BTW, there will be another 50 years of progress show in Illinios at the end of August, anyone going???