HST ? improved over the years

[lawn_king]

30 years of working tractors here. International gear & kubota hydros. Both have been great! Im about to jump up to a kubota hst + transmission. Its just a marvel of hydro engineering, with the stall gaurd, auto throttle & adjustable hst responce, its like driving the 6 speed in my new pick up. Hydrostats (imho) started out good and just keep getting better!

 

[Yankee Clipper]

This is not intended to be a sales pitch but a response from a tech person.

I can speak for the Kubota Grand L 40 hydro. The new hydros are electronically controlled and they have load sensing, a hydraulic gear splitter and auto throttle. You also can set the response so you get a modulated (smooth) start and stop or immediate response, like the old systems. They are easy to operate, smooth as glass which makes the experience better and you are more productive because the computer is working for you.

The smooth operation found between a Kubota Grand L 30 series and 40 series is considerable. The 30 series is/was a very good system but the 40 series is much nicer in all respects. The cost increase is not that much in the scheme of things and yes, the reliability of the electronics is there. (No one worries about reliable solid state ignition on their cars anymore, do they? The same companies build these electronics.)

The future is here now and you will really appreciate the difference electronics make.

Check it out at your dealer.

 

[JC-jetro]

Hi all,
I understand all the advantages of the Hydro but sometimes shear simplicity is the key. A simple hammer always work as long as you can hit the nail and just about nothing to maintain. It just appears to me the condition of the hyd fluid, cleanness, filtration of the sediment and stuff is of utmost importance for proper operation. It looks to me when time is of essence and every second counts one can not discount HST. Hydraulic driven motor is a marvel of engineering indeed. My question is what kind of service can you get or expect from HST transmission if your total use of tractor maybe in the neighbor hood of 30 hrs a year with long storage time without activity? As the adage goes "use it or loose it". looks to me HST has to be used constantly to have a better life expectancy. I hate the darn thing to "dry rut" in storage.

No flow/no pressure= no go and that bothers me. You can see 60 yr old tractor that still keeps on going.. may not be going fast .. but keeps on going.

Just my 2 cent. I appreciate ya'lls opinion.

JC,

 

[PA hayseed]

Things I would use the CUT for:

Loader work (gravel, dirt, mulch)
backhoe
Roto tilling,
skidding logs
light grading
setting landscaping
shuttling material in the loader

Nick

I have a 45 HP tractor with HST, I do lots of loader work. One hand on steering wheel, one hand on FEL lever, one foot on pedal (Fwd or RV). I drive my tractor down the road some too, and find the HST nice for changing speeds as I slide to the right for the big rigs. I test drove a gear drive and an hst at the dealer before purchasing, and they were kind enough to let me dig into their bank so I could see the difference. The HST is so much faster moving between digging, backing, turning and dropping/spreading.

 

[MossRoad]

Soon to be in the market for a 20-32 HP CUT.
Have not had the time to demo any (work Schedule), just arm chair shopping.
I have this far discounted any HST models do to my preconcived notion that they are loud and "herky-Jerky" (My only CUT experiance is on machines of 20+ years ago, or bob cats)
Talked to a CUB/Yanmar and a Kioti dealer, when I mentioned this, they said, No the new HST machines are smoth as silk ? One guy mentioned something about a "clutch" in the HST drive that smooths it out ?

Can anyone shed some light on this ?
I know I need to get out and try some, but it will be a month or 2 till My time is freed up.

Thanks,
Nick

I ran this late 70's IH2500b pretty regularly for about 10 years between 1990 and 2000 and then occasionally for another 5 before selling it to an IH salvage yard. The HST was smooth and responsive and that was a 25 year old machine.


A couple things I would look for in an HST...

Make sure the forward and reverse pedals are on the opposite foot as the turning brakes. Otherwise the brakes are as good as useless for turning. I cannot figure out for the life of me why anyone would design a tractor with the directional pedals and brakes on the same foot.

The IH had a dampening system so that if you yanked your foot off of the directional pedals it would not jerk to a stop, but stop smoothly. My current tractor stops on a dime if you pull your foot off the directional pedals. It can cause a really hard jolt to the operator.

 

[john_bud]

Hi all,
I understand all the advantages of the Hydro but sometimes shear simplicity is the key. A simple hammer always work as long as you can hit the nail and just about nothing to maintain. It just appears to me the condition of the hyd fluid, cleanness, filtration of the sediment and stuff is of utmost importance for proper operation. It looks to me when time is of essence and every second counts one can not discount HST. Hydraulic driven motor is a marvel of engineering indeed. My question is what kind of service can you get or expect from HST transmission if your total use of tractor maybe in the neighbor hood of 30 hrs a year with long storage time without activity? As the adage goes "use it or loose it". looks to me HST has to be used constantly to have a better life expectancy. I hate the darn thing to "dry rut" in storage.

No flow/no pressure= no go and that bothers me. You can see 60 yr old tractor that still keeps on going.. may not be going fast .. but keeps on going.

Just my 2 cent. I appreciate ya'lls opinion.

JC,

JC, If you like simple then you best ditch the gear tractor and get an HST. After all, they have fewer parts and are just basically a variable displacement pump and a hydraulic motor. It just doesn't get any simpler than that! Now the new "40" series Kubota HST-Plus is a new deal with integrated computers and all that, but the basic transmission is still simple.

As for reliability, it's probably 3-5x higher reliability HST vs Gear.

As for operational cost, you will probably go thru 5 clutches on a gear trans and 2 sets of bearings before you have to open the HST. And by that time, you may as well buy a new tractor as the rest of the HST machine will probably be on it's last legs.

As for abuseability - you can easily abuse a gear tractor. I've seen 1 year / 100 hour gear tractors with broken gear teeth and totally toasted clutches. There are reputable reports of abusive users (normally minors, greenhorns or dumb hourly workers) that have smoked clutches in under 40 hours. All it takes is a bright boy or girl slowing down and creeping into a pile by slipping the clutch rather than down shifting and riding it half depressed. sniff sniff, what that smell? smells like a $2000 clutch job!


To address your question of only 30 hours of use per year. Hmmm. That one is harder. Machinery does not like to run then sit. Tractor are more like a good bird dog, only happy when being run ragged! You may find that with an HST the tractor is so easy to use it gets used more! (Well, it could happen!) As long as you don't contaminate the hydro fluid with water the HST will stay happy. As most tractors (gear and HST) use common sump for trans, hydraulics and differential that's going to be an area of concern no matter what you buy.

All I know is in 20 years when you go to sell that tractor with 600 hours - it will probably be a nice one!

jb

 

[JC-jetro]

JC, If you like simple then you best ditch the gear tractor and get an HST. After all, they have fewer parts and are just basically a variable displacement pump and a hydraulic motor. It just doesn't get any simpler than that! Now the new "40" series Kubota HST-Plus is a new deal with integrated computers and all that, but the basic transmission is still simple.


jb

John,

I could not disagree with anything that you said. I need to get an opportunity to open up a hyd pump and motor. The pump reminds me so much of my first pressure washer with cheesy swash plate made out of pot aluminum and cheaply made components. The piston was solid SS but all the piston seals were nylon with spring loaded intake and exhaust valve on the water side. I got a bit of water passed the seal , got mixed with the oil and soupy mess killed the pump in nothing flat. I know the material are a lot better with hyd pump and motor in tractors and such. I just can not see the pump seal last longer that machined gear. I accept all your argument about the novice, inexperienced, careless or may be a "moron" as an operator but think if the operator is good the gear tractor should last longer with very little maintenance if it kept in storage to keep moisture and condensation at bay.

JC,

 

[john_bud]

(Shhhhh don't let it out -> in reality you have to work pretty hard to find a "bad" technology transmission on a new tractor. Differences between operators makes more of an impact on reliability than the whole HST vs gear thing. - but don't let it out that I told you - I have a reputation as an HST bigot to uphold!)

jb

 

[JC-jetro]

(Shhhhh don't let it out -> in reality you have to work pretty hard to find a "bad" technology transmission on a new tractor. Differences between operators makes more of an impact on reliability than the whole HST vs gear thing. - but don't let it out that I told you - I have a reputation as an HST bigot to uphold!)

jb

John,

Capisch.. That'll be our little secret. Just keep up the reputation at all costs

JC,

 

[dfkrug]

I need to get an opportunity to open up a hyd pump and motor. The pump reminds me so much of my first pressure washer with cheesy swash plate made out of pot aluminum and cheaply made components. The piston was solid SS but all the piston seals were nylon with spring loaded intake and exhaust valve on the water side.

I have not opened up a press washer hyd pump (yet), but it sure sounds
different from an HST setup. Take a look at my pix posted in my B21
rebuild thread. The variable displacement pump pistons have no seals...they
are just a close-tolerance fit into the cylinder block. Also, the HST uses
the same fluid as the gearboxes and rear end, but separate filtration.

As for an HST being simpler than a gear trans setup, even a non-electric
HST like my Kubota and Kioti still have full gearboxes and a dry clutch, like
gear. So it does add some more complexity, though not as much as say
the new Kubota HST-plus, or even NH's dual-displacement motor HST with
electric controls. But I do love HSTs.

 

[frank_f15]

this is just MHO but i would never cosider anothe tractor without HST but this is just for my uses, makes a world of difference on my old legs and arms not having to clutch and shift every time i need to change directions.

 

[art]

Hi all,
I understand all the advantages of the Hydro but sometimes shear simplicity is the key. A simple hammer always work as long as you can hit the nail and just about nothing to maintain. It just appears to me the condition of the hyd fluid, cleanness, filtration of the sediment and stuff is of utmost importance for proper operation. It looks to me when time is of essence and every second counts one can not discount HST. Hydraulic driven motor is a marvel of engineering indeed. My question is what kind of service can you get or expect from HST transmission if your total use of tractor maybe in the neighbor hood of 30 hrs a year with long storage time without activity? As the adage goes "use it or loose it". looks to me HST has to be used constantly to have a better life expectancy. I hate the darn thing to "dry rut" in storage.

No flow/no pressure= no go and that bothers me. You can see 60 yr old tractor that still keeps on going.. may not be going fast .. but keeps on going.

Just my 2 cent. I appreciate ya'lls opinion.

JC,

I can understand your concern for a hydro transmission life. We just had one in our shop and it it was on it's way to tractor heaven. The tach was broke just over 8700 hours. The tractor had pulled a five bottom plow and a 13' disc as well as mowing and chopping I think it has done just about every duty on a farm that it could. It was last on the spreader this winter and the engine was showing some wear but everything showed the same with little work ever having being done to it.. The tractor was a IH 826 model from 1971 or 72.


I know it would have burnt more fuel doing the tillage work, over the gear drive. Put they would have saved on the mowing and chopping or other PTO duties. Probably only had the brakes done twice!

 

[john_bud]

As for an HST being simpler than a gear trans setup, even a non-electric
HST like my Kubota and Kioti still have full gearboxes and a dry clutch, like
gear. So it does add some more complexity, though not as much as say
the new Kubota HST-plus, or even NH's dual-displacement motor HST with
electric controls. But I do love HSTs.

Actually, the gears for the L-M-H range gears are in the mid case housing and are not part of the transmission. Right? At least thats the way it is in the L10 series, don't know for sure on the B's. Also isn't the mid case the same or essentially the same, in the manual trans and HST? Normally only a 2 range in the manual trans, but can be 3 range with creep gears?

Not that it matters greatly - neither are prone to failure....

jb

 

[MossRoad]

I can understand your concern for a hydro transmission life. We just had one in our shop and it it was on it's way to tractor heaven. The tach was broke just over 8700 hours. The tractor had pulled a five bottom plow and a 13' disc as well as mowing and chopping I think it has done just about every duty on a farm that it could. It was last on the spreader this winter and the engine was showing some wear but everything showed the same with little work ever having being done to it.. The tractor was a IH 826 model from 1971 or 72.


I know it would have burnt more fuel doing the tillage work, over the gear drive. Put they would have saved on the mowing and chopping or other PTO duties. Probably only had the brakes done twice!

Was it on its way to tractor heaven because of the HST, engine, other items or a combination of all of the above?

One thing about an HST, at least my late 70's IH2500b, was that you were supposed to run it at PTO throttle all the time for maximum performance. If you tried to run it at slow engine RPM a little light on the dash would light up and indicate low HST system pressure.

 

[art]

Was it on its way to tractor heaven because of the HST, engine, other items or a combination of all of the above?

One thing about an HST, at least my late 70's IH2500b, was that you were supposed to run it at PTO throttle all the time for maximum performance. If you tried to run it at slow engine RPM a little light on the dash would light up and indicate low HST system pressure.

It was a combination, even the tires were in question. If the tractor had a good hydro the value would have been about the 7500 that it would have cost to put the hydro in. The engine of coarse was weak and original and at least needed a good valve job to seal up the head gasket leak but at 9000 hours it would only drive out the rings. Tires were weak, cosmetics were done a few years back but sheet metal was straight. I kind of figured about fifteen to fix completely.

 

[dfkrug]

Actually, the gears for the L-M-H range gears are in the mid case housing and are not part of the transmission. Right? At least thats the way it is in the L10 series, don't know for sure on the B's. Also isn't the mid case the same or essentially the same, in the manual trans and HST? Normally only a 2 range in the manual trans, but can be 3 range with creep gears?

Not that it matters greatly - neither are prone to failure....

In the B21 I had apart, the main gearbox contained all the shafts, gears,
and shifter forks for the 3-ranges as well as the PTO and MFWD. This
tractor had small gearbox on the back of the bell housing to lower the
output shaft too.

There is no equivalent tractor with a gear trans, but I can see that the
HST/charge pump combination is essentially just placed on the front of
the main gearbox. I can imagine a tractor like an L3130 that has 3 trannies
offered (FST, GST, HST) could use the same gearbox for the HST and
FST. The GST uses electrically-operated wet clutches, so I imagine that
gearbox would be different. I have not taken them apart, so I do not
know.

With the FSTs (fully synchro trans) has Kubota dropped all the old fashioned
unsynchro-ed trannies?

 

[dfkrug]

It was a combination, even the tires were in question. If the tractor had a good hydro.....

If the HST was kept full of clean oil, I wonder how it would fail. There are
no gears or internal seals. The bearings, pistons, and cylinders would last
indefinitely unless starved of clean oil. I guess the external seals could
eventually fail, but that hardly constitutes HST failure. Overheating an
HST's oil would be theoretically possible, but that would take some doing.
I guess you could run it on relief until the oil cooked and boiled.

When I was looking for my first used tractor, I was concerned about the
condition and costly repairs that might be necessary with an HST. But I
have since learned that abuse of a used tractor (as usually is the case with
a former rental machine) is much more likely with gear trannies. Worn
clutches were more likely than starved HSTs. Now I believe that the HST
in a used tractor is probably the most reliable part!

 

[JC-jetro]

I have not opened up a press washer hyd pump (yet), but it sure sounds
different from an HST setup. Take a look at my pix posted in my B21
rebuild thread. The variable displacement pump pistons have no seals...they
are just a close-tolerance fit into the cylinder block. Also, the HST uses
the same fluid as the gearboxes and rear end, but separate filtration.

As for an HST being simpler than a gear trans setup, even a non-electric
HST like my Kubota and Kioti still have full gearboxes and a dry clutch, like
gear. So it does add some more complexity, though not as much as say
the new Kubota HST-plus, or even NH's dual-displacement motor HST with
electric controls. But I do love HSTs.

Dave,

Thanks for your reply. I found your posts to be very informative and for a visual person can greatly appreciate the pics. I'll study them. I knew that HST would not eliminate the main dry clutch and the gearing required for low-med-high.

Art and John, Thank for the good info. Bottom line "one shoe does not fit all". For many many applications and variety of reasons personal or need based, HST is the only way to go. For yours truly with an occasional brush hugging (neighbour hays my front field for her cattle's) , garden and food plot tilling a a gear tranny and non-live transmission driven PTO works just fine, poor me ..I have to use the dirt scoop in lieu of fel I call it REL, Rear End Loader)

One other point for most of the work I do, I hardly ever need to rev the engine up beyond 1300-1500 rpm and would think same task with HST requires at least 2000-2200 no matter what to maintain required flow and pressure.

I think, I know what I want to get if I built out there. But don't think I'll ever part with my trusty little mule that asks very little of me.

JC,

PS. Does anyone has a source that explain valving (intake and exhaust) in a hyd pump and motor? It looks to me they are two machined plate with open port that rotation of driven gear in case of pump and action of swash plate in case of motor, causes rotation of valve plates where in turn provide for suction and compression cycle. Am right? Is one of the valve plates stationary always?

 

[dfkrug]

. Does anyone has a source that explain valving (intake and exhaust) in a hyd pump and motor? It looks to me they are two machined plate with open port that rotation of driven gear in case of pump and action of swash plate in case of motor, causes rotation of valve plates where in turn provide for suction and compression cycle. Am right? Is one of the valve plates stationary always?

There is no valving in a HST.

The cylinder block contains multiple pistons, which spin on a central
axis. The pistons are free to move in and out of the cylinder block
according to the angle of the swash plate. When the SP is set at 90
degrees to the axis of the spinning cyl block, each piston is stationary
relative to the block, and no oil is pumped. If you tilt the swash plate
either way, some of the pistons now move into and some move out of
the cyl block. Oil is now pumped. That is for a variable displacement
pump. Either or both pump or motor can have a variable angle swash
plate. Tractors use a variable pump and sometimes a variable motor.
My 2 current CUTs have a fixed displacement motor.

 

[JC-jetro]

There is no valving in a HST.

The cylinder block contains multiple pistons, which spin on a central
axis. The pistons are free to move in and out of the cylinder block
according to the angle of the swash plate. When the SP is set at 90
degrees to the axis of the spinning cyl block, each piston is stationary
relative to the block, and no oil is pumped. If you tilt the swash plate
either way, some of the pistons now move into and some move out of
the cyl block. Oil is now pumped. That is for a variable displacement
pump. Either or both pump or motor can have a variable angle swash
plate. Tractors use a variable pump and sometimes a variable motor.
My 2 current CUTs have a fixed displacement motor.

Dave,

I have a hard time imaging pumping action without an inlet port and outlet port. I have also looked at some axial pump design same as article below suggests. They do mention a valve plate. The rotation of cylinder block against the valve plate seems to me emulate suction and pressure cycle when the cylinder block rotate passed inlet opening(suction) or outlet opening (pressure). You may be able to say there is no valving but I think the function of valving is archived thru rotation of cylinder block against stationary valve plate.

JC,

Axial piston pump - Wikipedia, the free encyclopedia