N80,
Drawbar HP.
Ok, here's the easy version without the math stuff that doesn't add anything anyway. Imagine a magic engine that makes a million HP and has the same weight as my 34hp kubota engine. (Go with me on this). But it is in a tractor that has totally bald tires. I mean teflon coated slicks. Now we compare that tractor with 1 million hp to my 34 hp kubota. Which one will be able to pull a greater weight the longer distance in the shorter time? Obviously the 34hp tractor, as the other one is only able to spin the tires. So, the million hp tractor would have zero drawbar hp. Right?
Got it. That makes perfect sense.
Now, imagine that the million hp engine in put into a tractor with a 3pt hitch that is 100 ft in the air, but with good tires. (I do have a point, stick with it). Which tractor has more drawbar hp? Well, the million hp tractor is pulled over backwards due to the 3pt hitch being so high and again it results in zero drawbar hp.
Okay.
Now imagine that you put the million hp engine into a normal tractor with good tires. But, you attach a helium blimp to it that removes all but 1 oz of weight. Again, zero drawbar hp and the 34 hp tractor wins.
Again, I get it.
My point (since you stuck with it), is that drawbar hp is only limited on the upper end by engine hp, then parasitic loss like ps pump, hydro pump, transmission etc.
John, I'm listening, and I understand, but I don't think you are listening to me. This is THE VERY REASON that when you want to make fair comparisons you have to limit the variables like tires, weight, set up. That's why we say all-other-things being equal. I understand that less HP can outpull more HP that is not applied properly. NO ONE is arguing that.
Most tractors will give the identical drawbar hp no matter what transmission they use.
I don't think that is correct and I don't think that you can prove it. It does not make sense. At the same time, I cannot prove it is wrong either since I don't have any hard data.
I did state that previously in a clear fashion. The choice of tires, tractor weight, balance and the design geometry of the 3pt coupled with the wheelbase etc make the biggest differences, (greater than the trans type).
Yes, we get that. That is why you compare apples to apples. That's why this argument, this comparison, comes in two flavors:
1) Same
exact tractors. Same tires. Same set up, everything identical except trannies. Due to the losses you described in the pump, etc, it is probable that the HST will deliver less dbhp, but as has been mentioned it will be trivial and maybe even insignificant.
2) This is the important one. I stayed with you, so you stay with me. Now we are talking about what you can buy for 'x' amount of money with dbhp being the issue. Keep brand and tires and all that equal and the primary variable, the primary thing you get less of, is HP. But sure, you could start introducing variables like poorly made, less expensive tractors but that just sets the discussion into a death spiral by introducing red herrings that do not help resolve the issue and have no real practical application. Few of us is going to buy a Belarus over almost anything else, just for moer HP.
And so, the fact remains that for all practical matters and for 'x' amount of dollars you can buy more HP (where ever you want to measure it) with a geared tractor than with an HST.
Why is that so hard to understand? Or more to the heart of the matter, why is it so hard to admit?
