Does HST Transmission Rob Horsepower??

   #51  

4570Man

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To continue splitting hairs that don't make much difference; the PTO drive does not go through the HST, so there is no power to be lost to the PTO because of a HST. So if the tractor is stationary the PTO HP on a HST or shuttle will be identical. If the tractor is being driven, engine hp is being used to both power the PTO and to move the tractor. The HST does use more of the engine hp to drive the tractor, making less available to the PTO. But in a situation such as mowing heavy brush where PTO hp is an important consideration, the PTO is usually consuming the bulk of the engine HP while moving the tractor isn't using much power at all, so the real world difference is quite negligible. However in the extremely rare instances you are mowing thick brush while going up a steep hill at maximum speed in high range, you would likely see a noticeable difference.

Exactly. In the more reasonable comparison of mowing heavy grass on mostly flat ground there would be very little difference.
 
   #52  

Cougsfan

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One more note; If you are indeed concerned that a HST might leave you short of PTO horsepower, you should really consider buying a larger tractor, regardless of the transmission type you prefer.
 
   #53  

ericm979

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I'm certainly not in the anti HST camp as that's what works for me. But I think that HSTs do lose a little power vs the same model gear trans even when stationary and running a PTO implement like a chipper. I base that off of manufacturer's specs where the PTO HP is usually a little lower for the HST trans.

Remember that an HST is basically a pump and a motor. One or both can be variable displacement. I think that in most modern CUTs it's the motor that is variable and the pump is fixed displacement. Which means that even when stationary and the range trans is in neutral, the HST pump is pumping fluid. Even though the motor side is not doing any work, that fluid has to go somewhere. The engineers most likely make it go somewhere with a low resistance to flow but it's not zero. Thus some power, like ~1hp on a 40hp machine, is being used by the HST even when stationary.
 
   #54  

dieselscout80

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While it is just one Hydro tractor note the Max Pull numbers for all of these IH 544 variants.

I would not have guess which on had the highest Max Pull rating of 6,579 lbs.


What does it prove not much.

What IH said was that the tractors with Hydros excelled at PTO work due to no gear splits to limit the operation, so the perfect speed could be obtained.

I know that when mowing or baling sometime you need to slowdown, but the next lower gear is way to slow.
 
   #55  

4570Man

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While it is just one Hydro tractor note the Max Pull numbers for all of these IH 544 variants.

I would not have guess which on had the highest Max Pull rating of 6,579 lbs.


What does it prove not much.

What IH said was that the tractors with Hydros excelled at PTO work due to no gear splits to limit the operation, so the perfect speed could be obtained.

I know that when mowing or baling sometime you need to slowdown, but the next lower gear is way to slow.

I’ve been saying that for a long time about a HST tractor. If you had a bunch of gears you wouldn’t have that problem but a compact tractor practically never does.
 
   #56  

ptsg

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I’ve been saying that for a long time about a HST tractor. If you had a bunch of gears you wouldn’t have that problem but a compact tractor practically never does.
Most tractors these days offer at least 12 speeds forward and 12 reverse, you're saying that in 12 gears you can't find one that suits the job? That's impressive.

On my end, I can have at least three different gears all the time that I could use for the same job, and if I'm doing PTO work, I can still "split" those gears by using 540E.

Even a 9x3 transmission will still have plenty of gears.
 
   #57  

dieselscout80

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Sometimes it is not the lack of gears, but rather the gear splits.

If you need to use/go one gear below a range or use/go to one gear above a range you have to completely stop.

I look at this when I am look for a newer tractor.

I like to mow my pastures at 3.5 MPH and having the ability to down shift if the grass is thick its important to me as I do that shift often in places.

I think if I had a tractor with range of four synchronized gears with nice even 1 MPH splits starting say 1.5 MPH (e.g., 2.5, 3.5 & 4.5 MPH), then I may never have to switch ranges for most work on our property.

I guess what I am saying its the correct gear combinations that is important. With some tractors I have looked at the 2.5 MPH and 3.5 MPH gears are in different ranges.

That said I make do with a gear drive tractor with 8 unsynchronized gears.

All the upgrades to tractors just make them nicer to operate and to each his own.

What tractor/transmission you chose is simply your choice and it not right or wrong it just yours and I hope you enjoy operating it.
 
   #58  

Hay Dude

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Most tractors these days offer at least 12 speeds forward and 12 reverse, you're saying that in 12 gears you can't find one that suits the job? That's impressive.

On my end, I can have at least three different gears all the time that I could use for the same job, and if I'm doing PTO work, I can still "split" those gears by using 540E.

Even a 9x3 transmission will still have plenty of gears.
I cant get the correct gear sometimes even with 16 speeds!
Especially with hay work.
Sometimes the difference between 5 high and 6 high is raking too slow or too fast.
The newer version of my tractor has 24 speeds (3x8). My older version is a 16 speed (2x8). I find myself looking for those “in between” gears sometimes.
 
   #59  

Hay Dude

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Wow, this thread is really getting a little tribal! I grow weary of reading "if anyone who doesn't agree with my particular choice of transmission, they are obviously mistaken." Having owned and/or operated HST, geared tractor with dry clutch or shuttle for many years, I can understand how someone could prefer one over the others, either way. None can claim absolute superiority for all conditions, and each have advantages in certain conditions. And if one has any ability at all to adapt, one could easily live with any of them under most any condition.
Good point. I also have observed that although this is “Tractor by Net” it is mostly “[small, under 75HP] Tractor by Net”. Hydrostatic is going to be disproportionately more popular HERE because larger tractors are unavailable with hydro.
The last 20 years in bigger tractors has seen the emergence of IVT/CVT transmissions. Drives like a finger-touch hydro.....
I thought it couldn’t get better when the push button powersfhift transmissions came out. The IVT/CVT is even better. Extremely nice to operate.
 
   #60  

aczlan

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To continue splitting hairs that don't make much difference; the PTO drive does not go through the HST, so there is no power to be lost to the PTO because of a HST. So if the tractor is stationary the PTO HP on a HST or shuttle will be identical. If the tractor is being driven, engine hp is being used to both power the PTO and to move the tractor. The HST does use more of the engine hp to drive the tractor, making less available to the PTO. But in a situation such as mowing heavy brush where PTO hp is an important consideration, the PTO is usually consuming the bulk of the engine HP while moving the tractor isn't using much power at all, so the real world difference is quite negligible. However in the extremely rare instances you are mowing thick brush while going up a steep hill at maximum speed in high range, you would likely see a noticeable difference.
The HST still has the charge pump running even if you aren't moving, so that constant load is the difference between the PTO HP of a HST and a gear tractor.

That said, for brush hogging I would much prefer a HST over a geared tractor and slightly over a shuttle shift with torque converter such as Kubota's GST. It is much more convenient to be able to bump forward or backwards a couple inches with just your foot and not have to change a lever or move otherwise.

So, for anything besides heavy dirt work (such as plowing/disking a field) I would go with HST or possibly a GST transmission

Aaron Z
 
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