Why no hydrostatic transmissions on larger tractors?

[LouNY]

Watch their video. It explains how it works. At full speed, it's gear driven. Anything slower is hydrostatic. No plaetary gear involved like others.

Not quite, it is a dual power feed with some from the hydrostatic side and some from the mechanical side,
Yes, the main drive is a planetary with a brake. The planetary drives the hydro pump while the brake determines the mechanical power side of the transmission.

 

[MinnesotaEric]

Mainly because of the heat generated, the noise, the inefficiency, and short lives.
More horsepower aggravates and increases all of the above.
The new CVT and IVT transmissions do use a small hydrostatic drive incorporated
into the transmissions planetary gearsets and bands to provide the last bit of varible speed in addition to the several clutch packs and gear sets.
It is a very limited hydro in respect to it's speed range to reduce all the above.

I haven't run any large loaders in several years but they did not have hydrostatic transmissions at that time they had multiple speed transmissions with torque converter drives.

Reliability? Hough, the people who invented putting a loader on a tractor, as well as the first articulated payloader, also had hydraulic transmissions as early as 1946, as I recall. Some of these payloaders have tens of thousands of hours.

 

[npalen]

The International 966 is a 1970's vintage hydrostat at about 90 HP. Some are still running today.

 

[Hay Dude]

IH had some pretty big Hydros.
The new Holland TV series articulating tractors were hydros, too.
I have a Fendt CVT in my Massey 7495. Its not really a hydro. It drives like one, but it’s finger touch.
No pedals.

Hopefully have a Challenger coming with a Tech Star CVT in a few weeks. It’s also made by Fendt.

 

[redman135]

Hello Indian Territory, full hydrostatic gearbox large tractors were tried in the 70's and failed.

 

[ArlyA]

hydrostatic transmissions have very poor efficiency so larger HP machines tend not to have them. Its really that simple but machines like pay-laoders still benefit from there use.

 

[LouNY]

IH made several Hydro tractors.
We had a 656 Hydro in 1968, it was a good light duty tractor.
It was handy and "quick" for maneuvering around but not much quicker then the 560 we also had.
It is still on the farm the transmission has been replaced 2 times and is weak again.
It is a gas engined 656 and with the Hydro it simply sucks gas, it's fuel economy is non existent.
I have also worked and ran several other Hydro's the 1026 and the Hydro 100 got the most hours the
Hydro 100 was the nicest one especially after the turbo got bolted on to it. They are good PTO tractors
heavy drawbar work was not, even just hauling heavy loaded wagons made for lots of noise and heat
generation. The Hydro 100 was the nicest tractor I had driven at that point for chopping as long as
you were chopping into a wagon beside you or a truck, start pulling a wagon to chop into and she would fall on her face.
Again transmission noise and heat.
Most of those tractors the transmission was the weak point it was very expensive and did not have the durability
of the geared transmissions which is why so few exist today.
The Versitiles and New Holland TV's are also very nice chore tractors, very handy and nice to work but not for heavy drawbar work.
When subjected to heavy drawbar work the tractors were extremely noisy, ran hot and had transmission issues.

 

[Number15]

Antonio Carraro makes 75hp hydrostatic tractors. I understand people like dealers close so perhaps not an option. I love mine but I am only 20 hours in on owning it. I'll let you know after a couple of hundred hours how I feel . They are not traditional tractors either because they bend in the middle so there's that

 

[Jims1025R]

I opine that the larger power, the more difficult it is to get the engine out through an HST to the wheels. I had a 14HP JD650, manual transmission. It had lots of umpf (for a small tractor), you could certainty stall it pushing or pulling too hard. I replaced it with a 25HP JD1025R. It does not have the [mini] brute force that the JD650 did. When you work it too hard, it makes really unpleasant noises which the engine turns and the wheels don't - so I stop doing that. But the 650 would either have moved the load, spun the wheels, or stalled. So I opine that the tractor manufacturers know this, and don't build bigger tractors which won't pull a heavy load well.

 

[jyoutz]

Reliability? Hough, the people who invented putting a loader on a tractor, as well as the first articulated payloader, also had hydraulic transmissions as early as 1946, as I recall. Some of these payloaders have tens of thousands of hours.

I’m not sure about reliability being a factor. My dealer’s service manager told me they replace far more clutches on gear tractors than they see HST problems.