I was curious about the effect, which the HST goes into bypass, and the tractor fails to spin the tires. I have a the largest engine in the tractor class. It has been observed(causing annoyance)by some that in low gear, you can't make the engine stall on my tractor leading to the conclusion that it has a weak HST.
I would not have drawn that conclusion anyway. I would just assume that its designed to bypass before a stall. That seems like a reasonable design feature and does not indicate how much hp the tractor can apply in dynamic situations (i.e. not up against a hill).
If my observations are true, the HST can put the same torque to the ground that a gear transmission(with the corresponding gear ratio, or ground speed).
I don't see how those observations lead you to that conclusion. I'm not saying you are wrong, I just don't understand your reasoning. My reasoning that suggests that HST does rob you of some HP (draw bar) compared to a gear tranny might be wrong also but is based on several things. First, it has been mentioned that the HST generates a good bit of heat. That means less HP. How much? I have no idea. But I also remember reading, and experiencing, that an automatic tranny in a car or truck puts significantly less of the flywheel HP to the ground than a gear tranny. I'm assuming that loss is in both heat and in spinning/pushing transmission fluid, etc. I may be wrong about the reason but countless dyno tests published in magazines suggest that the effect is true. But that was during the days where a straight drive always got better mileage than an auto and that has obviously changed so the HP loss may be a thing of the past and it might not translate to an HST anyway.
But so far, two important facts remain. 1) No one has produced any test results to suggest that the drawbar HP would be the same or different yet....so we just don't know for sure and 2) If a Kubota L4400DT and a Kubota L4400HST (and comparable machines) cost the same thing, this would not be a big issue and would be a non-issue if someone could prove that drawbar HP was the same. But, they don't cost the same, and likely never will....and I'm not holding my breath regarding drawbar HP comparisons either. (Although there were some posts regarding some Ag based tests of some domestic CUTs but I don't know if there were any incidental gear vs HST reports).
And I suspect that if a dealer told me the DT and the HST put the same torque on the ground and cost the same, I'd give the HST a serious look. But I still wouldn't buy it because I want to be able to work on this thing in the future.
I guess I will jump a little into the debate. For me, the ability to precisely position the tractor, make small incremental and predictable movements, hold a position on a hill, and safely start movement on steep slopes is critical to my safety and activities (I do most things without helpers). An HST is an order of magnitude better than a gear for these things.
I will be told, and fairly so, that I have no basis for disagreeing with this statement since I have never spent any quality time with an HST, but I feel safe in challenging your 'order of magnitude'. I have never been in any situation, no matter how tight or precarious that I have been unable to make precise and predictable position changes, movements, and adjustments. I can start on any hill (on my hilly property), up or down, wet or dry, and hold position on same, with little or no effort and rarely even have to think about it. I spend lots of quality times on wet, muddy and rocky hills, in the woods, around the cabin often with loader full and or implements on the back. and So it just seems a bit preposterous so think that HST is that much better. How can this be? Either, I'm delusional, which is possible and in which case you guys should just humor me or I'm some sort of Zen master with a clutch and a gear shift, or maybe, just maybe, that when you spend enough time with manual transmission you just learn to make it do the things it can and is supposed to do. I think that's probably it, because I've never been a master of anything and having that insight proves I'm not delusional.(I hope!)
So, is HST
any better at these things? I can't say since 1) No experience 2) zero problems with my gear tractor (which has no synch or shuttle shift). But I trust you guys that it might be some better, maybe even a lot (I don't know about a magnitude
), but if given the rather extreme positions I get my tractor into and out of with relative ease, it still seems unlikely to be worth the money to me.
With a gear, you have to develop the art of transistioning between the brake and the clutch in order to do the things I would need to do safely and effectively.
I guess when you've spent your entire life driving nothing but manuals, that art becomes second nature. I very honestly am almost never even aware of doing these things. The main time I do become aware is when my left knee begins to ache and that would undeniably be less of a problem with an HST!
I don't mow or pull ground engaging equipment, so my observation don't apply there.
Well, even if you had, some of these guys wouldn't accept your observations unless you'd been doing it for 15 years on both types, every day, uphill, in the snow, with no cab.
