Advice on Hydrostatic Transmission vs Gears

[Too many Kubotas]

Hmm. Looks like I've been using my tractors wrong, always doing my very best not to spin tires. Maybe that's why their tires last so long?

If I want to spin tires I drive the Challenger. Although it's an automatic, not an HST, so not a great comparison.

 

[SPYDERLK]

On an HST the high pressure work port reliefs relieve the flow to the opposite work port not the reservoir. They also keep the system at full torque as long as the relief is active. Not sure why you think they dump energy unless you are referring to inertia of moving vehicle.

eek. That sounds like a like a quick fluid fry, circulating the oil straight back to the pump. The energy dump is across the relief valve. The fluid going back to the pump is then re energized as it is pulled through and forced out to whatever will take it. When the wheels wont turn a small amt leaks past the working elements in the hyd motor that drives the wheels leaving the remainder deadheaded and relieved continually at the relief. That isolated circuit will heat very quickly.

 

[oldnslo]

eek. That sounds like a like a quick fluid fry, circulating the oil straight back to the pump. The energy dump is across the relief valve. The fluid going back to the pump is then re energized as it is pulled through and forced out to whatever will take it. When the wheels wont turn a small amt leaks past the working elements in the hyd motor that drives the wheels leaving the remainder deadheaded and relieved continually at the relief. That isolated circuit will heat very quickly.

You are 110% correct that an HST in a stall going over the work port relief will get hot very quickly. That is why the more expensive system will have another pressure limiting valve on the control part of the circuit so the pump destrokes before work port relief setting. This again keeps system at max pressure but not create near as much heat at stall condition.

Some of the newer “E” style HST. Trannies may have this feature but I know my Branson with mechanical control swashplate does not.

 

[Shawn T. W.]

With a loader you can always make the tractor heavy. Iv never found an HST tractor that will spin wheels pushing and lifting with differential locked. Iv never found a gear tractor that wouldnt, at half throttle, even fully ballasted and counterweighted.
Maybe a 4 range trans on the hst would do it.

Well ... my Mighty Massey, which I call "My Little Baby Fergie"! Is Amazing then!!! A SCUT sized GC 1725 MB with a whole whopping 25 HP, and 2 range HST!

Here you can see she came to a tire spinning stop from a full 6' wide rear blade full of gravel ... Rear tires are filled, 4X4 with rear axle locked ... Bucket was only filled about 3/4 full as once I drop the blade on the ground, there is not much counter weight (ballast) on the back ...

So ... I believed if tires are spinning ... I needed more weight ... So, I added 70 Lb steel wheel weights to each of the rear wheels, and rigged up a way to add another 200 Lbs of steel weight lifting plates to the backhoe frame (since have added another 75 Lbs) ... Better, but still spun the tires to a stop on damp clay this time!

Even added 50 pounds to the floorboard, and made sure the fuel tank was full!!

If you can't spin a tire with a HST, either you aren't trying very hard, or doing it wrong! Sure I can "stall out" a HST, but can easily do that with a 535 HP semi-truck trying to be stupid starting out in high range with a full load pointed up hill ... Most tractors and semi-trucks aren't usually out doing smoke shows, but I've spun the tires on both!

-------------------------------------

But to the OP - for the intended purposes you've listed, I'd say a HST would be the "better" choice. If you're doing a lot of ground engaging like dragging a plow to turn over ground for days/weeks on ended every year, a geared transmission would be a better choice ... For full disclosure I own two HST tractors, and much prefer a standard geared transmission in a semi-truck!

 

[SPYDERLK]

Well ... my Mighty Massey, which I call "My Little Baby Fergie"! Is Amazing then!!! A SCUT sized GC 1725 MB with a whole whopping 25 HP, and 2 range HST!

Here you can see she came to a tire spinning stop from a full 6' wide rear blade full of gravel ... Rear tires are filled, 4X4 with rear axle locked ... Bucket was only filled about 3/4 full as once I drop the blade on the ground, there is not much counter weight (ballast) on the back ...

View attachment 4091293

So ... I believed if tires are spinning ... I needed more weight ... So, I added 70 Lb steel wheel weights to each of the rear wheels, and rigged up a way to add another 200 Lbs of steel weight lifting plates to the backhoe frame (since have added another 75 Lbs) ... Better, but still spun the tires to a stop on damp clay this time!

View attachment 4091493

Even added 50 pounds to the floorboard, and made sure the fuel tank was full!!

View attachment 4091494

View attachment 4091495

View attachment 4091496

If you can't spin a tire with a HST, either you aren't trying very hard, or doing it wrong! Sure I can "stall out" a HST, but can easily do that with a 535 HP semi-truck trying to be stupid starting out in high range with a full load pointed up hill ... Most tractors and semi-trucks aren't usually out doing smoke shows, but I've spun the tires on both!

-------------------------------------

But to the OP - for the intended purposes you've listed, I'd say a HST would be the "better" choice. If you're doing a lot of ground engaging like dragging a plow to turn over ground for days/weeks on ended every year, a geared transmission would be a better choice ... For full disclosure I own two HST tractors, and much prefer a standard geared transmission in a semi-truck!

Be Happy! I know I am when using the application complimenting features of HST. The precision of movement without having to clutch or brake is ideal for work on wooded slopes. Many different forcing situations arise, mostly pushing uphill. HST works great, 'til it hits its abrupt limit and just wont go.

 

[TMGT]

Be Happy! I know I am when using the application complimenting features of HST. The precision of movement without having to clutch or brake is ideal for work on wooded slopes. Many different forcing situations arise, mostly pushing uphill. HST works great, 'til it hits its abrupt limit and just wont go.

What hst tractor are you using for this comparison?

 

[IXLR8]

Be Happy! I know I am when using the application complimenting features of HST. The precision of movement without having to clutch or brake is ideal for work on wooded slopes. Many different forcing situations arise, mostly pushing uphill. HST works great, 'til it hits its abrupt limit and just wont go.

What HST are you using? I have been using HST tractors since 2006 and I have never hit any limit like you have been talking about. Spun the rear tires yes, stalled it out due to running at too low of a rpm yes.

 

[SPYDERLK]

Be Happy! I know I am when using the application complimenting features of HST. The precision of movement without having to clutch or brake is ideal for work on wooded slopes. Many different forcing situations arise, mostly pushing uphill. HST works great, 'til it hits its abrupt limit and just wont go.

What hst tractor are you using for this comparison?

What HST are you using? I have been using HST tractors since 2006 and I have never hit any limit like you have been talking about. Spun the rear tires yes, stalled it out due to running at too low of a rpm yes.

NH Boomer 35 w loader, grapple, ballasted R4s, and 5 foot bushog as counterweight. Working on 15 to ~ 20 degree hillside. Plenty of power/motive force 'til it throws it all away across the relief valve.

 

[TMGT]

NH Boomer 35 w loader, grapple, ballasted R4s, and 5 foot bushog as counterweight. Working on 15 to ~ 20 degree hillside. Plenty of power/motive force 'til it throws it all away across the relief valve.

What range? What rpm? Are you just pushing the hst pedal farther when it loads up?

Not familiar with the Boomer 35 operation, but if you're operating the HST properly it shouldn't do that.

 

[SPYDERLK]

What range? What rpm? Are you just pushing the hst pedal farther when it loads up?

Not familiar with the Boomer 35 operation, but if you're operating the HST properly it shouldn't do that.

1st range of course, at or near full rpm. 4wd. If wheels spin I lock the diff. If wheels wont turn I push the pedal a little farther til it spins, moves, or the engine bogs w/o wheels turning. Theres the force limit.

- - What do you mean "shouldnt do that"? - I explained the inherent absolute necessity of a relief valve earlier in post #19. The variable displacement pump, controlled with the pedal, is capable of producing system destructive pressures without enough engine load apparent to cue the operator of the strain developing.

 

[hayden]

Good advice for someone who does not fully understand the issue. It will not solve the problem I stated. The issue, mainly, is that the HST - at relief - will dump all energy stored in the rotating mass of the engine, and the energy it is producing while running, into the hyd sump. The relief is absolutely necessary due to the zero to max speed control. Right there at 0+ you have infinite "mechanical advantage" to provide very low hyd flow at "infinite" pressure, enabling infinite torque - even with a small engine. You wouldnt even know it til it broke. This situation cannot be allowed.
A gear trans positively dumps its energy to the wheels, or the clutch slips, or it breaks. The mechanical advantage is always finite and constant in accordance with the gear ratio. HIGH overload transients can be supported because a good safety factor must be built in to survive even normal use in such a "direct" drive system. All bets are off with creeper gear ranges tho. Mechanical advantage there is astronomical.

I guess I'm not seeing what you describe in all my years running various HSTs. In my experience, if the tires don't spin, the engine stalls. There is no relief valve function like in lifting hydraulics. Now I haven't looked closely at my HST design to see what actual relief valves exist to protect the internals, but functionally it works just the same as a gear transmission in that it either spins the tires are stalls the engine depending on the selected gear and load. I think if you are hitting some sort of relief valve, you are just operating in too high a gear. I run into that all the time with loader work where I can't push hard enough into a pile of material. Selecting a lower gear lets me push until the wheels spin, which is my cue to stop pushing.

 

[hayden]

eek. That sounds like a like a quick fluid fry, circulating the oil straight back to the pump. The energy dump is across the relief valve. The fluid going back to the pump is then re energized as it is pulled through and forced out to whatever will take it. When the wheels wont turn a small amt leaks past the working elements in the hyd motor that drives the wheels leaving the remainder deadheaded and relieved continually at the relief. That isolated circuit will heat very quickly.

OK, but so what? This is why HSTs have oil coolers. I guess I don't see what teh big deal is, other than an inconsequential downside. HSTs consume more energy - that's well know. In their typical applications, that's a welcome tradeoff for the operational convenience and performance.

 

[hayden]

1st range of course, at or near full rpm. 4wd. If wheels spin I lock the diff. If wheels wont turn I push the pedal a little farther til it spins, moves, or the engine bogs w/o wheels turning. Theres the force limit.

- - What do you mean "shouldnt do that"? - I explained the inherent absolute necessity of a relief valve earlier in post #19. The variable displacement pump, controlled with the pedal, is capable of producing system destructive pressures without enough engine load apparent to cue the operator of the strain developing.

Sounds like the gearing in the NH may not go low enough. I've never run one, so no personal experience with them.

 

[walnutman]

Hydrostatics are extremely controllable, but hugely force limited compared to gear tractors. In my experience based on more than 10 gear or hydro tractors, you will always encounter situations where you cannot apply enough "go" in any range to spin the wheels on an HST. Up to that point you are happy. After it you feel betrayed -- and maybe stuck.

There's a new kid on the block in the Yanmar IHMT hybrid hydrostat transmission. It basically switches between hydo and full coupling depending on usage. Trust me, my YT359C with 59hp has no problem grunting into a pile with the loader and spinning tires... in 4x4.
and with 59hp the trans put 52 into the PTO. That's efficient.

Read up Yanmar YT3 series (YT347/YT359) IHMT/I-HMT Transmission workings

 

[SPYDERLK]

There's a new kid on the block in the Yanmar IHMT hybrid hydrostat transmission. It basically switches between hydo and full coupling depending on usage. Trust me, my YT359C with 59hp has no problem grunting into a pile with the loader and spinning tires... in 4x4.
and with 59hp the trans put 52 into the PTO. That's efficient.

Read up Yanmar YT3 series (YT347/YT359) IHMT/I-HMT Transmission workings

Thats an interesting "new kid". If I were in the market ...

My Boomer 35 has no trouble with pile work either. I often use 2nd range to minimize accidental spinning divots. Its easy to over force the situation in lo range.

 

[Little Red Tractor]

It's more a matter of application and preference. For some jobs, gears are likely the best; for others, hydro gives a lot of advantages. I've used both, as well as power shift types, and for my application--mostly mowing--the hydrostatic is the best option because of the maneuverability. It also is hand with FEL use.

Another comment on cabs: small tractors=small (often cramped) cabs. Bigger tractors give you a lot more creature comfort in the cabs.

 

[fidowanttobe]

For the op's stated concerns, the choice is HST.

Yup.

 

[Fxfymn413]

Had both and my vote (and my last 3 tractors after I had a gear tractor) is HST. Easy to operate and very reliable.

Going away the best HST I have ever owned is my Grand L 4060 HSTC with the high range/low range shift on the fly capability that gives you 6 speeds.

My experience is that the HST will quickly slow when going over the road as you climb hills. The range shift allows you to drop a gear with the range lever without stopping so you do not bog the machine down. It is also handy when you need to operate at very slow speeds such as when you are rototilling.

You do not need to keep the pedal pressed when using cruise mode which I do when moving over the road or doing tasks that require a constant speed such as tilling.

 

[rmburrow]

I’ve seen a lot more threads with seized or burned out clutches vs HST problems. HST transmissions are for the most part very reliable.

May not apply to full size tractor, but I have a John Deere X320 where the hydrostatic transaxle failed at 400 hours and is not serviceable. At least $1600 to replace. Neighbor has 4 John Deere X300 series tractors with the K58 transaxle at his shop unserviceable. My mechanic has several more in the junk yard. Motor on the X320 fine, mower deck fine, but the transaxle is junk built by Tuff Tork and unsupported!!

 

[oldnslo]

May not apply to full size tractor, but I have a John Deere X320 where the hydrostatic transaxle failed at 400 hours and is not serviceable. At least $1600 to replace. Neighbor has 4 John Deere X300 series tractors with the K58 transaxle at his shop unserviceable. My mechanic has several more in the junk yard. Motor on the X320 fine, mower deck fine, but the transaxle is junk built by Tuff Tork and unsupported!!

The HST used in X320 is not in the same class or category as HST used in tractors. They are considered a sealed unit with no provisions for oil changes, may or may not have work port reliefs(might count on wheels spinning). The Tuff Torq K46 is known problem, K58 maybe similar but I am not sure.