let's talk about hydrostatic

[k0ua]

I keep meaning to ask what is the large difference from kubotas hst to its hst plus?

Here is a youtube video that might answer some questions about HST+

https://www.youtube.com/watch?v=hzO_-LCd838

 

[diesel lover]

Here is a youtube video that might answer some questions about HST+

https://www.youtube.com/watch?v=hzO_-LCd838

I remember now that the 50 horse power tractor I spent time operating had hst plus, auto throttle advance and all the features shown in this video. This is what got me sold onto hydrostatic tractors after operating this moving fallen trees, pulling them with a chain, etc the power out of this Kubota hst was very satisfactory. There was lots and lots of pulling torque. I know he had pulled some trucks, dead cars etc with this tractor and it really was a miniature backhoe!! This was an L series or grand L series tractor that was turbocharged.

So far I am sold on a 40 horse power hst plus Kubota. This way if my 25 horse tractor is unusable or I need to work in slightly smaller spaces this will be possible while having power to push snow, tow larger items etc

 

[DennisFolsom]

Both the newer Kubota and John Deere tractors, with the electronic control systems on their hydrostatic transmissions, have features which "muddy the waters" with respect to the traditional explanation of how a hydrostatic drive works. In addition to multiple "ranges" built into the hydro system, they sense torque and mix throttle control with the transmission control on the foot pedal. I have used a Kubota L39 with this kind of setup and it works very well. There are options in the controls to make the system behave in different ways, depending on user needs and preferences. Depending on the settings, you can use the foot pedal more like a "gas pedal" and the response is likely more like some of the heavy equipment.

Even though these new systems are great (when everything is working), I am glad that my John Deere 4600 has the older, simpler hydrosatic technology. There is less to go wrong. I have adjusted my techniques to the capabilities of the machine, and I don't expect the machine to adjust to me! I know that a lighter press on the pedal gives me a "lower gear." I can work with that, just fine.

 

[Arc weld]

There are many different hydrostatic configurations. TLB's and large loaders don't use hydrostatic transmissions. They use torque converters. There are a few smaller loaders and/or TLB's that are hydrostatic though. If a tractor is used for constant pullling under load like plowing, a gear transmission is much better. Getting back to hydrostatics there is constant torque, constant H.P., constant torque/constant H.P., variable torque, variable H.P., load sensing, pressure compensating and a host of other features. Modern track excavators are basically hydrostatic with cylinders instead of motors. Hydrostats are best run at full throttle.

 

[Redneck in training]

Automotive automatic transmission uses hydrodynamic torque converter while HST stands for hydrostatic transmission. The hydrodynamic torque converter has three parts: pump, guide vanes, turbine. The turbine and the pump are identical in design. The torques in hydrodynamic system is controlled by guide vanes between the pump and the turbine. The turbine might function as the pump and the pump becomes the turbine in example when going downhill and using engine as a brake. The pump and the turbine are very close together in the converter assembly.

In HST the pump and the hydraulic motor can be in single assembly (like in HST tractors) but often are distance away connected by piping (in example in combines)

The main difference between those two systems is that hydrodynamic torque converter uses dynamic pump and turbine while HST used positive displacement pump and motor.
Another difference is in power loading. HST has power loading limits around 50HP while hydrodynamic converters can be designed up to many thousand HP.
Hydrodynamic converter can be locked to prevent slippage and power loss. Then the trany works like pure mechanical transmission.

 

[oldnslo]

In HST the pump and the hydraulic motor can be in single assembly (like in HST tractors) but often are distance away connected by piping (in example in combines)

The main difference between those two systems is that hydrodynamic torque converter uses dynamic pump and turbine while HST used positive displacement pump and motor.
Another difference is in power loading. HST has power loading limits around 50HP while hydrodynamic converters can be designed up to many thousand HP.

All true except for the HST power limitations. Sauer Danfoss, Kawasaki, Bosch Rexroth, and probably others all make HST pumps that will stall 500 HP engines. Granted you won't see one of these on your 50 HP tractor but they are out there since the pump alone weighs over 300 lbs.

 

[CJONE]

All true except for the HST power limitations. Sauer Danfoss, Kawasaki, Bosch Rexroth, and probably others all make HST pumps that will stall 500 HP engines. Granted you won't see one of these on your 50 HP tractor but they are out there since the pump alone weighs over 300 lbs.

The HP limit like oldnslo said is wrong. I have personally built a unit that requires 400HP and it runs 24 hours a day, 7 days a week. I have plans for a unit that requires 975HP and the limiting factor is the hydraulic hoses will "only" handle 6000PSI. The 27 series Sauer Sundstrand pumps [I know "old school"] are capable of almost 7000PSI. So all this info on HP limits is wrong. A lot of new dozers at 150-200+ HP are hydrostats and they are a pleasure to run. CJ

 

[diesel lover]

Automotive automatic transmission uses hydrodynamic torque converter while HST stands for hydrostatic transmission. The hydrodynamic torque converter has three parts: pump, guide vanes, turbine. The turbine and the pump are identical in design. The torques in hydrodynamic system is controlled by guide vanes between the pump and the turbine. The turbine might function as the pump and the pump becomes the turbine in example when going downhill and using engine as a brake. The pump and the turbine are very close together in the converter assembly.

In HST the pump and the hydraulic motor can be in single assembly (like in HST tractors) but often are distance away connected by piping (in example in combines)

The main difference between those two systems is that hydrodynamic torque converter uses dynamic pump and turbine while HST used positive displacement pump and motor.
Another difference is in power loading. HST has power loading limits around 50HP while hydrodynamic converters can be designed up to many thousand HP.
Hydrodynamic converter can be locked to prevent slippage and power loss. Then the trany works like pure mechanical transmission.

Thank you for straightening that out! Good knew ledge to know off hand. The way the two drive lines connect from a stand still are different but when operated correctly I am 100% positive both can produce a lot of useable pushing and pulling power/ torque straight to the wheels

 

[Redneck in training]

While HST units can handle 1000 HP, hydrodynamic units can handle upto 200000 HP.