HST vs. Gear Trans

[beppington]

HST fan responding again

... The gear wins out towing, ground engagement ...

My 3.5 ton Kubota Grand L3940 HST has no problem spinning all 4 wheels when trying to pull something impossible, so I'm not sure how a geared tractor could tow or engage the ground better?

... and just crusing around.

My Kubota Grand L3940 HST has a sliding cruise control lever which can be set at any infinite speeds (not gear limited) between 0 and ~16 mph, so I'm not sure how a geared tractor would cruise better?

I'm wondering if your HST machine is one of the earlier versions with just a pedal, without the controls & options offered now?

 

[Volfandt]

HST fan .
both points quoted are somewhat related, the gear tractor gets more power to the ground at much lower rpm which makes for a better cruising experience, for me
Lower noise, vibration and the joy of almost being able to count each power stroke are the major contributors IMHO

Of my 2 HST's, one is foot pedal controlled and the other hand lever controlled. I much prefer the foot controlled and it is my primary worker.

I no longer have my old TE20 but it was a gear tractor w/working turning brakes, that was an unbeatable combination when plowing and discing. Once in the proper gear range I rarely clutched and used the turning brakes to help spin at the ends of the rows. Great ol machine.

I primarily finish mow and I much prefer the HST for that duty.
YUMV
Dave

 

[_RaT_]

I have both a Kubota L4850, a 5 cylinder shuttle shift tractor with 8 forward gears and a L3940 HST+. I completely agree with you. When I am ripping with the box scrapper its nice to have the gears, when I'm doing any kind of finesse type work be it loader, loader with grapples, mowing, post holes or tilling, the HST is killer.

HST fan .
both points quoted are somewhat related, the gear tractor gets more power to the ground at much lower rpm which makes for a better cruising experience, for me
Lower noise, vibration and the joy of almost being able to count each power stroke are the major contributors IMHO

Of my 2 HST's, one is foot pedal controlled and the other hand lever controlled. I much prefer the foot controlled and it is my primary worker.

I no longer have my old TE20 but it was a gear tractor w/working turning brakes, that was an unbeatable combination when plowing and discing. Once in the proper gear range I rarely clutched and used the turning brakes to help spin at the ends of the rows. Great ol machine.

I primarily finish mow and I much prefer the HST for that duty.
YUMV
Dave

 

[RoyJackson]

HST fan responding again
My 3.5 ton Kubota Grand L3940 HST has no problem spinning all 4 wheels when trying to pull something impossible, so I'm not sure how a geared tractor could tow or engage the ground better?

Discounting traction, that HST has a fluid coupling rather then metal to metal (as with gears). You'll see slippage and heat buildup.

In the real world, most of us TBNers won't see any difference...we'll run out of traction.
In the real world, HST and gears selection is nothing more then a matter of choice.

 

[Chilly807]

As to shifting on the fly, as long as you double-clutch you can do it with a gear drive (non-synchro) transmission. My Kubota is much happier doing it shifting up, going down isn't as good for some reason. I rarely do it, but I prefer it to lugging the engine starting off in 4th and high range.

Sean

 

[_RaT_]

So what your telling me Roy is that my L4850 with an oil immersed EverClutch is not actually made of a friction lining similar to that like a brake or a car clutch but rather metal to metal. Thats where my coupling takes place from the engine to the drive train. Interesting. In the end, my HST also uses gears, I guess in a similar analogy you could say it is "metal coupled" :laughing:

Discounting traction, that HST has a fluid coupling rather then metal to metal (as with gears). You'll see slippage and heat buildup.

In the real world, most of us TBNers won't see any difference...we'll run out of traction.
In the real world, HST and gears selection is nothing more then a matter of choice.

 

[RoyJackson]

So what your telling me Roy is that my L4850 with an oil immersed EverClutch is not actually made of a friction lining similar to that like a brake or a car clutch but rather metal to metal. Thats where my coupling takes place from the engine to the drive train. Interesting. In the end, my HST also uses gears, I guess in a similar analogy you could say it is "metal coupled" :laughing:

You know...I work in fluid transmission (power generation and such) and I made an assumption that's probably incorrect.
The fluid couplings I've worked with don't use direct metal to metal contact, but a series of rotors and vanes (and the fluid which may be a hydraulic fluid or an ATF) actually connects the mechanical transmission components to the power source (in my case, large electric motors...not engines).
So, since I have never had an HST nor do I expect to own one, can't say I've ever looked at an illustrated breakdown/schematic other then in passing.
The assumption was that HST would use similar principles which it may...or may not.
In our case, the coupling is there to provide a "soft start" and has fusible plugs to vent the system if the fluid gets too hot. Remember, liquids don't compress...just generate heat.

So, if your HST works in the same manner, you'll get a degree of slippage which should ultimately vent out in some way to prevent the mechanical component damage.

That sound about right?

 

[RadarTech]

I have shut my HST tractor off on the hill and never experienced the runaway tractor that you describe. My understanding is that if you do not set the brake and the tractor creeps forward far enough to pump the fluid out of the HST then it will freewheel. But I do not think it is immediate like if you missed a gear or if your foot slipped off of the clutch (both of which I have done with a geared tractor and it was scary and could have been tragic) I operate a HST on the hills and find that the HST is safer because you don't need the brakes while changing directions or when stopping.

I agree with you. Lots of hills and I have shifted down from m til l plenty of times on hills with my hst. I find it to be an attention issue.

 

[SPYDERLK]

HST fan responding again

My 3.5 ton Kubota Grand L3940 HST has no problem spinning all 4 wheels when trying to pull something impossible, so I'm not sure how a geared tractor could tow or engage the ground better?

I see you have added 1-1/2 tons to your tractor. My 6.5T 7520 will spin its 4 loaded Ags at 800 rpm idle in 1st - a 1.7MPH gear. Add a bunch more weight and even bringing the engine up to operating range wont conquer the added traction. Your HST would eventually limit this way by the relief valve popping. The gear would overtorque while slowly stalling. The HST would just stop. I have experienced this on HST and it is extremely frustrating.
Im not saying I dont like em -[a lot]- but that gear puts out more and gives ample warning of impending limit.
larry

 

[_RaT_]

Wait, let me come back and read this after some coffee...:thumbsup:


Two cups of coffee later and I'm still confused, my head hurts. Lets see, which tractor to jump on this morning, my gear or my HST, decisions.

You know...I work in fluid transmission (power generation and such) and I made an assumption that's probably incorrect.
The fluid couplings I've worked with don't use direct metal to metal contact, but a series of rotors and vanes (and the fluid which may be a hydraulic fluid or an ATF) actually connects the mechanical transmission components to the power source (in my case, large electric motors...not engines).
So, since I have never had an HST nor do I expect to own one, can't say I've ever looked at an illustrated breakdown/schematic other then in passing.
The assumption was that HST would use similar principles which it may...or may not.
In our case, the coupling is there to provide a "soft start" and has fusible plugs to vent the system if the fluid gets too hot. Remember, liquids don't compress...just generate heat.

So, if your HST works in the same manner, you'll get a degree of slippage which should ultimately vent out in some way to prevent the mechanical component damage.

That sound about right?