The advancement of Hydro Transmissions

[Dargo]

Dargo, did I step on your toes or something when I said what I said about my Kubota 3130 HST? .

Nah, I'm more of a different shade of green guy. But, I'm more than happy to point out statements that simply are not good generalities and are misleading. If you've been on here long, you'll see that several guys here are not afraid of calling a spade a spade and are not concerned about being politically correct. From being involved in strip mines, I can tell you that absolutely zero of the largest earth moving pieces of equipment on earth have a clutch and a gear shift. I suppose they are just for show and they need to get out of the way before they get hot and let a gear driven tractor 1/20th of their size do the work, huh?

 

[Ryan03]

my grandfather bought a kubota G5200 new in 1982, and I have since inherited it and 3000+ hours later this machine has had no hydro problems whatsoever, and it has been beat to death its entire life and been used for things the manafacturer could not imagine. The only thing that has been replaced drivetrain wise is the driveshaft that couples the engine to the trans 3 times in 24 years when I or my grandfather tried to do something way to stupid with the little kubota. Now let me say that I am not bashing gear tractors either, I own a farmtrac 270 and it is a gear tractor. When I am doing loader work, I wish it was a hydro, when I am york raking and brushhogging, I am glad I have a gear tractor. Personaly, I feel that it depends on how you use your tractor the majority of the time, your personal preferences and what your budget will allow. A gear guy may get on my old G5200 and think its a pos., and a hydro guy may get on my farmtrac and call it a pos. but in the end, all that realy matters is what you think of your tractor, so what will it be, a blonde or brunette. I will say, being a government highway department fleet technichian, I have changed more clutches than I care to remember, been inside many tractor diffs and changed a couple hydraulic drives in excavators, dozers and most recently a case 85xt skidsteer, [ we do not have any hydro tractors] most failures in both gear models and hydro units could be traced back to misuse and operator error, not all, but most.

 

[jinman]

A Hydrostatic Transmission is not an "Automatic" tranny. It is entirely diffirent in it operation compared to an automatic trans.

Hydrostatic transmissions transmit all power with hydraulics; there is no solid coupling of the input and output. One half of the tranny is a variable displacement pump and the other half is a hydraulic motor. A movable swah plate controls the piston stroke to change the displacement.

An automatic trans basically uses hyd pressures to select the appropriate gear ratio without operator intervention and use a torque converter between the engine and transmission rather than a clutch.

Absolutely correct! A hydrostatic transmission is more like a FEL or the 3PH than it is like an automatic transmission. Actually it's like a FEL that goes in circles and has multiple hydraulic cylinders, each providing power for only a segment of the circle.

Now, let me quit before I take this analogy any farther.

 

[Doc_Bob]

I've never had even the slightest desire to own a Montana tractor, so I cannot comment on their hydro transmissions since I've never even sat on a Montana tractor.

I had the chance to use Onsight's Montana and wow! Great machine, great hydro. I have also used Kubota and NH. Love them all. The Montana was very nicely built and worked like a dream. I would buy a Montana in a second.
Bob

 

[Dargo]

I would buy a Montana in a second.
Bob

Cool! I heard that Mitsubishi builds their engines? In my business, Mitsubishi engines and transmissions are considered several steps below Yugo. Although this is the auto and fork lift areas, Mitusubishi most certainly does not have a good reputation at all. Maybe I'm wrong and MrBitchi does not make Montana?

 

[gemini5362]

Anyone that wants to correct me please feel free to do so. I am basing this post on knowledge I was given in an hydraulic class from a manufacturures rep. According to what the rep was telling us that on the really big earthmoving machines they actually have big hydraulic pumps that power hydraulic motors at each wheel. these are controlled by flow valves and do not have a transmission per se. If this is incorrect I would love to have the correct knowledge. I do know that we bought some of these units for the steel mill I was working in and it would take a very very dull saw blade and cut through an solid 8 inch steel bar in a matter of seconds.

I do not know about mitsubishi in fork lifts etc. But I am of the opinion that they have been making diesel engines for the marine industry since the 1940's at least

 

[NewToy]

Anyone that wants to correct me please feel free to do so. I am basing this post on knowledge I was given in an hydraulic class from a manufacturures rep. According to what the rep was telling us that on the really big earthmoving machines they actually have big hydraulic pumps that power hydraulic motors at each wheel. these are controlled by flow valves and do not have a transmission per se. If this is incorrect I would love to have the correct knowledge. I do know that we bought some of these units for the steel mill I was working in and it would take a very very dull saw blade and cut through an solid 8 inch steel bar in a matter of seconds.

I do not know about mitsubishi in fork lifts etc. But I am of the opinion that they have been making diesel engines for the marine industry since the 1940's at least

What did you put the saw blade on? I missed the point here, you put the saw blade on the earth moving machine?
John

 

[Egon]

diesel engines for the marine industry since the 1940's at least

Diesels have been on the water since their orign.

 

[jinman]

What did you put the saw blade on? I missed the point here, you put the saw blade on the earth moving machine?
John

John, I think he was just saying that they used large hydraulic pumps driving motors attached to saws, and that they had lots of power. At least that's the way I read it.

 

[indianaEPH]

Since these transmissions have gained popularity, why haven't they been developed for eighteen wheelers ("Big Rigs")? Since most big cities freeways turn into "70 MPH parking lots" during rush hours, a drivers clutch foot might geat very painful!! Am I missing something here, as these drivers inch their way along these cities, constantly starting and stopping? Several years ago on this site, a gentleman from Canada had a fleet of Kubota tractors towing trailers along side highways for clean up maintenance purposes. He traded them because of high fluid temps in the hydro, poor performance, and high fuel consumption. I see Kubota has auxillary coolers for some of their hydros now?

Reponding to the original question, you could put a hydrostatic transmission on a big rig but it would not be a very good machine. Hydros are well suited for applications that are not fuel econmy sensitive. They are just not an efficient transimission of power. Class 8 trucks are VERY fuel economy sensitive. 1/10 of % fuel economy is a big deal. A hydro trans would reduce fuel econopmy by a huge amount (10 - 20 % ?? ). Then you would have to add additional coolers to get rid of the heat. A bad deal all around.

There are many trucks running with Allison automatic transmission with a hydraulic torque converter. This is not the same as a hydrostatic transmission. The Allisons have 6 to 8 gear ratios in a planitary gear arrangement. They are very good transmissions. The big drawback for these transmissions is fuel economy. They are 5 - 7 % less efficent then a manual.