Gear or Hydrostatic Transmissions for Compact Utility Tractors?

[houstonscott]

My son has a Yanmar. It's a geared tractor, with a hydraulic clutch. You have to put clutch in first time you put it in gear, after that you can change gears without clutch, I really like that. You can speed up in turn a rounds during mowing and slow when necessary. HS

 

[Deere Dude]

I was thinking same thing, cut it up with a chain saw and throw pieces in the bucket. HS

I would rather spend 15 minutes fiddling around with a tractor to do a job even though I could do it manually a lot quicker in five minutes.

Now that the log was pulled out he can lift it up and cut it in lengths at chest high right over his pile.

I just pulled about 10 oaks 18-20" in diameter that were blown over and aiming down a hill in a woods, a scary steep hill. This is one job where a hydro is a godsend, as long as it doesn't slip into neutral. I just drove down frontwards in 4wd, hooked up to a big chunk and dragged it up the hill. A gear tractor would have worked but in this situation a gear would be a lot more dangerous and my guess is a lot harder on the clutch and the pacemaker.

I don't know if gear tractors still can get the front end jumping up and down out of control by not having a good control of the clutch. Seen it happen in older models.

I am thinking that if a person has to stop right away it would be a lot more difficult to step on the clutch and then the brake, than it would be to just back off the hydro pedal to stop.

 

[MultiMow]

Drive the one you like the best. I havent figured out the constant desire on here to try to prove one over the other. The waters will get even muddier as cvt's start coming into play.

Especially given the different approaches to the CVT. Some are simply intelligent hydrostats with an ECU, while others are gear trannys with automatic hydro-controlled torque amplifier circuits. Some manufacturers are even experimenting with automotive style CVTs on light duty applications (friction belts on conical drive pulleys).

To be honest, the only market that will benefit from CVTs are high capacity row croppers... as they are the only ones to spend enough in fuel to see a profit.

Diesel engines don't benefit much from CVTs in terms of fuel efficiency, aside from row cropping or other continuous duty applications.

If I'm not mistaken, John Deere already has a hybrid CVT in production, which centers on a positive geared main drive. It simply used a hydraulically controlled helical gear differential to sync with the engine RPM.

A couple high capacity turbine driven European tractors already use CVTs, as it's the only way to feasibly sync output speed to an engine that idles at 90,000rpm, doesn't produce taxable torque until 95k, makes peak torque at 100k, and peak power at just below maximum RPM of 110,000.

Another example, and my personal favorite, is the "D-drive" and "CDB"... which is (to my knowledge) the world's only constant-positive engagement continuously variable drive. It uses one or two (depending on configuration) planetary differentials to transmit power, which are positively and constantly connected to both the input (engine) and output (drive) shafts. The "D-drive" uses two differentials, and an auxiliary drive to control the bias. As power is added to the auxiliary, ouput shaft RPM increases. When the auxiliary drive is zero RPM, the transmission is in "powered stop", which eliminates both coupling (clutch) and parking brake requirements. The "CDB drive" uses a single differential to achieve the same results... however, the function of the auxiliary drive is reversed. In the CDB, the auxiliary drive power is used to relieve output RPM, as opposed to inducing it. In both of these designs, the auxiliary drive can also serve as the starter motor, if independently powered.

In all actuality, a hydrostatic transmission is a type of CVT... as it allows independently variable control of the output RPM.

There are many other designs as well, including toroidal, multi-toroidal (including "gang", "series", and "parallel"), and multi-disc clutch.

 

[Texasmark]

Drive the one you like the best. I havent figured out the constant desire on here to try to prove one over the other. The waters will get even muddier as cvt's start coming into play.

I think that's about the size of it. Your money, your usage, your likes and dislikes, your choice. I bought a Branson 2400 in January with manual shifter because that's the way I was going to use it. Had I been going to use it in the shuttle mode, or belly mowing around a bunch of obstacles I would have bought the HST version. My lawn mowers are all hydros and 2 are ZTs because that's the way I use them.

 

[holeycow]

I would rather spend 15 minutes fiddling around with a tractor to do a job even though I could do it manually a lot quicker in five minutes.

Now that the log was pulled out he can lift it up and cut it in lengths at chest high right over his pile.

I just pulled about 10 oaks 18-20" in diameter that were blown over and aiming down a hill in a woods, a scary steep hill. This is one job where a hydro is a godsend, as long as it doesn't slip into neutral. I just drove down frontwards in 4wd, hooked up to a big chunk and dragged it up the hill. A gear tractor would have worked but in this situation a gear would be a lot more dangerous and my guess is a lot harder on the clutch and the pacemaker.

I don't know if gear tractors still can get the front end jumping up and down out of control by not having a good control of the clutch. Seen it happen in older models.

I am thinking that if a person has to stop right away it would be a lot more difficult to step on the clutch and then the brake, than it would be to just back off the hydro pedal to stop.

No. If you have decent brakes and you apply the clutch and brake nearly simultaneously
(the timing is learned and somewhat unique with each vehicle depending on engagement and disengagement of the controls) then you can stop quickly or slowly where you want. Push on two pedals instead of release one, that is all.

Never seen a tractor hopping the front end, except crazy people on youtube. Only seen a hopping back end (or the whole tractor in the case of big 4wd units, ouch!). Certain old tractors could flip over backwards onto the operator, but those were light in the front 2wd units. I doubt a modern fwa tractor would do that as they have more weight in the front end and on the front end...

You don't need to be at all hard on the clutch to back up a steep hill (or go forward), you just have to select the right gear and know how to drive a clutch. A good parking brake is a must if you have to get off the machine on the hill.

 

[jk96]

Especially given the different approaches to the CVT. Some are simply intelligent hydrostats with an ECU, while others are gear trannys with automatic hydro-controlled torque amplifier circuits. Some manufacturers are even experimenting with automotive style CVTs on light duty applications (friction belts on conical drive pulleys).

To be honest, the only market that will benefit from CVTs are high capacity row croppers... as they are the only ones to spend enough in fuel to see a profit.

Diesel engines don't benefit much from CVTs in terms of fuel efficiency, aside from row cropping or other continuous duty applications.

If I'm not mistaken, John Deere already has a hybrid CVT in production, which centers on a positive geared main drive. It simply used a hydraulically controlled helical gear differential to sync with the engine RPM.

A couple high capacity turbine driven European tractors already use CVTs, as it's the only way to feasibly sync output speed to an engine that idles at 90,000rpm, doesn't produce taxable torque until 95k, makes peak torque at 100k, and peak power at just below maximum RPM of 110,000.

Another example, and my personal favorite, is the "D-drive" and "CDB"... which is (to my knowledge) the world's only constant-positive engagement continuously variable drive. It uses one or two (depending on configuration) planetary differentials to transmit power, which are positively and constantly connected to both the input (engine) and output (drive) shafts. The "D-drive" uses two differentials, and an auxiliary drive to control the bias. As power is added to the auxiliary, ouput shaft RPM increases. When the auxiliary drive is zero RPM, the transmission is in "powered stop", which eliminates both coupling (clutch) and parking brake requirements. The "CDB drive" uses a single differential to achieve the same results... however, the function of the auxiliary drive is reversed. In the CDB, the auxiliary drive power is used to relieve output RPM, as opposed to inducing it. In both of these designs, the auxiliary drive can also serve as the starter motor, if independently powered.

In all actuality, a hydrostatic transmission is a type of CVT... as it allows independently variable control of the output RPM.

There are many other designs as well, including toroidal, multi-toroidal (including "gang", "series", and "parallel"), and multi-disc clutch.

The Case 55C I just purchased is a CVT and replaced a Case 45 with HST. I couldn't tell you much about the inner workings or design and will have to do some research. I am really impressed with it so far.

 

[Kubota 2350]

You sure do things the hard way.
Why couldn't it be simply pulled out ??

I was thinking same thing, cut it up with a chain saw and throw pieces in the bucket. HS

Beat me to it.

 

[oldpilgrim]

I can think of nothing that an HST can't do better or easier than a gear or shuttle. The little bit more fuel or slightly less PTO HP is little concern to 99 pct of the users of compact tractors . This opinion is coming from someone with 25 years and thousands of hours on a gear machine .

 

[MossRoad]

Yes, a hydro uses more fuel, and yes it whines.... almost as much as gear tractor owners with the argument about loss of PTO power on a hydro.

Why it seems true?

You do need more engine power to make XXPTO HP from a hydro tranny than a gear tranny.

Why it seems false?

If you have a tractor rated at XXPTO HP, gear or hydro, it doesn't matter.... its still XXPTO HP on both tractors.

Now, what's the torque curve on the PTO of both? I've never seen a torque curve for a PTO. Maybe someone can find one.

Anyhow, buy a tractor that meets your PTO HP requirements and put that argument to rest.

As for calling hydro operators less-skilled than gear operators... I'd say its more like you can do the hokey pokey and turn yourself around, or you can just turn yourself around. That's what its all about. What's easier and safer to do the task you need to do.

I can't think of any task that I do where a geared tractor would be better or even equal for me. So in doing what tasks does a compact geared tractor outshine a compact hydro tractor? :confused3:

 

[California]

My son has a Yanmar. It's a geared tractor, with a hydraulic clutch. You have to put clutch in first time you put it in gear, after that you can change gears without clutch, I really like that. You can speed up in turn a rounds during mowing and slow when necessary. HS

That sounds like my smaller Yanmar. (See sig photo below). Powershift, an '80's design, is essentially an ordinary clutch linked directly, no torque converter, to the input of an automotive A/T. Get moving then shift up/down among 3 speeds with a dash lever. The hydraulic clutches inside take a moment to engage which softens full-power shifts, then after engagement its a direct mechanical path from flywheel to output. There's also three mechanical gear ranges for rototill / ground engagement / road, you choose one then shift on the go within that range. Push in the clutch when you need to make a full stop.

This Powershift is the best, most productive form of geared transmission, it sure beats the stop-to-shift crashbox in my larger Yanmar which is now semi retired to occasional heavier loader and backhoe work - because the little one can outperform it on the sloping areas I traverse every time I go into the orchard. I have most of the advantages of a hydrostatic without the whine, heat, high rpm.