Does HST Transmission Rob Horsepower??

   #61  

5030

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I'm the opposite because of the inherent heat of operation. Why large ag tractors never have Hydrostatic transmissions and modern ones are now CVT instead of gear drive.

The most efficient and the least parasitic power loss will always be a gear drive.
 
   #62  

Hay Dude

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Just had the MF7495 out today. Runs like a dream with the CVT.
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MHarryE

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Modern large CVT’s are part hydrostatic. They het their CVT by rotating the ring gear on the planet Aries with a hydro motor. Rotate it one way and the result will be near zero, rotate the other way to get max. Many have a second planetary that comes into play part way. But the hydrostatic motor controls the ring gear.
 

LD1

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Tractor PTO is mechanical/gear all the way through.

Engine power transfer to the PTO will be the same whether tractor has a gear transmission or an HST transmission as PTO does not interface with the wheel transmission.


Engine power transferred to tractor wheels will be higher with a gear transmission.

HST is easier to use and speed choice infinite but it is pump/hydraulically driven, which is less efficient transferring energy than mechanical/gear drive.

Only a few tractor brands offer an HST transmission on tractors generating more than 60 engine horsepower. Over 60 engine horsepower most new tractors are available only with gear + shuttle shift.

HST and Gear/Shuttle are equally reliable.

HST and Gear/Shuttle are more reliable than traditional Gear/Clutch .

VIDEO:

Neal Messick, Messick's Tractor, ( five stores in Pennsylvania )
relates that Messick's sales are 90% HST in tractors of 60 horsepower or less.
Im surprised no one has commented on this.

Am I the only one that found this video a little off in that the gear tractor pulled harder?

Maybe I missed him say....but what range was that hydro in? No wheel slip at all.....

IF I put my MX in Low range, I can spin the tires. I fail to see how a gear tractor, under the same circumstances, also spinning the wheels....can pull any harder than that. IF anything, the HST being 154 pounds heavier, should pull harder???

When comparing PTO HP between HST and gear....maybe saying "rob" as in HST rob's more power is the incorrect term....but its an easy way to explain it. Take my MX5100 for example. Same engine HP between gear and hydro. Gear puts 44HP out the PTO, the HST puts 42.5 to the PTO. Meaning it takes takes the HST tractor an extra 1.5HP just to operate the drivetrain compared to the gear. So its easy to just say the HST (as in the transmission/drivetrain) "robs" power from the pto.

Arguing on verbiage is just semantics at this point. We all get the concept.

I went from a gear L3400 to a HST MX5100. There is no comparison to the convivence of a HST for 90% of the work done. For mowing/brushhogging which comprises a good 50% of my work....its like comparing a zero turn to a garden tractor. Ease of speed changes to slow down for dense areas...or to take it easy around obstacles, or ease up for rough areas, and speed back up for smooth areas is beyond compare. Same for loader work.

MY old gear tractor I felt like there was never a perfect gear/speed. I either wanted to go a little slower.....or I wanted to go a little faster. But with a gear....down shifting might me a huge step down in speed, or up shifting might be too fast. The HST is always the perfect speed.

Now where the HST has its downfalls is hard ground engaging stuff. Like plowing and discing. I have a JD210 transport disc. and a 3-14 plow. Low range max speed is 3.7MPH. Medium is like 7.5. Low range just seems too slow for plowing or discing. I'd like 4.5-5 mph. But shifting to medium It simply lacks the power to pull it any faster than low range can. Hence the inefficiency of HST. A gear tractor with a few gear selections between 3.5 and 7.5MPH would solve this. But for no more plowing/discing than I do (just a couple of large gardens and 2 acres of field corn) the sacrifice is worth it for the other 90% of the things I do that a HST really shines at.
 

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-I heard from guys at work that the new tractors with HST transmissions rob the PTO of HP? What is the difference between HST and Shuttle Shift? Would like to buy a tractor to bush hog about 20+ years of brush overgrowth on 70 acres. I'm a fan of the FORD 10 series tractors but the new tractors seem inviting.
Personally I would look for a good 10 series ford mainly because of their simplicity. 70 ac of brush mowing is going to offer a lot of opportunities for things to go wrong. With these newer tractors all it takes is one stick to catch a wire and all the sudden you have an engine shutdown because some sensor or safety circuit is disconnected.

An older gear tractor with split brakes can offer almost a zero turn radius once you get the hang of stab braking and just a whole lot less to go wrong. I do all my brush hogging with my oldest tractor which is an old Oliver Super 55. It works great and even if I had a catastrophic failure, It would still be cheaper for me to buy another and replace it the whole thing then to have my JD sent to the shop to replace the PTO clutch packs or something similar.
 

crazyal

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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.
Actually it's the pump that's variable. Most CUTs have a single speed motor. In the case of the Kubota Grand L tractors (and a couple others) they have a two speed motor. When not moving the only loss vs a geared tractor in HP is the pump that supplies oil to the HST pump. It's not much but it does use some HP.
 

4570Man

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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’ve never seen a small tractor like 5,000 pounds or less on this side of the pond with 12 gears. 4 with a hi/low would be a more common package. Admittedly I haven’t spent much time looking at small geared tractor transmissions because I don’t have any desire to have one.
 

ptsg

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I’ve never seen a small tractor like 5,000 pounds or less on this side of the pond with 12 gears. 4 with a hi/low would be a more common package. Admittedly I haven’t spent much time looking at small geared tractor transmissions because I don’t have any desire to have one.
Over here, most 30+ HP tractors will have at least 12 gears, some will have more. Some 25 to 30HP will have a 9x9 Shuttle shift transmission, like the Kubota B2650. Anything smaller will have the common 9x3 transmission.

The Kubota L2501 over here, is actually a 50HP tractor with mid mounted ROPS, draft control and some other stuff.

I've found that manufacturers will offer a lot more "farming related features" in Europe, like position and draft control, wider range of gears, R1 radial tires, quick attach hooks, front weights, front 3 pt, 540E/1000 PTO, etc. While in the US, they know most <50HP tractors are usual just to move snow around or mow the lawn and they seem to focus more on how easy is to connect the mid mounted mower or how many cup holders it has.
 

Hay Dude

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Over here, most 30+ HP tractors will have at least 12 gears, some will have more. Some 25 to 30HP will have a 9x9 Shuttle shift transmission, like the Kubota B2650. Anything smaller will have the common 9x3 transmission.

The Kubota L2501 over here, is actually a 50HP tractor with mid mounted ROPS, draft control and some other stuff.

I've found that manufacturers will offer a lot more "farming related features" in Europe, like position and draft control, wider range of gears, R1 radial tires, quick attach hooks, front weights, front 3 pt, 540E/1000 PTO, etc. While in the US, they know most <50HP tractors are usual just to move snow around or mow the lawn and they seem to focus more on how easy is to connect the mid mounted mower or how many cup holders it has.
Probably because farms in Europe tend to be much smaller. When we visited in times past, it was common to see 10 acre farms. I bet youll see those features more and more on small tractors.
As the years go by in the US, so many Americans are fleeing the corruption of cities for lower taxed, simpler, less violent areas and go back to gardening & small time farming...
 

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HST loose quite a bit more HP than gear transmissions do but how much, depends on where the transmission is being operating at in its power curve. That is if you're trying to go fast, then its loses are quite high. The losses vary from something over 8% to over 15 while at high speeds. This is why slower machines tend to use HST systems since they don't need to go high speeds anyway. Gear transmissions loose less than 2%.

I should add that HST tractors rock at certain jobs, like loader work. (y)
 
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