Tractor News Need New Tech Forum Subject: Better than HST, Great Transmission Design

[mike69440]

I suggest a new Forum heading to discuss new technologies.

Take a look at these three Videos about an infinitely variable transmission.

Efficiency, ease of use, productivity and range of ratios beat anything I know of.

I think MF will be offering this transmission also
Torotrak's full-toroidal variator
Torotrak | Torotrak's full-toroidal variator

The Torotrak full-toroidal variator configured as a continuously variable transmission
Torotrak | The Torotrak full-toroidal variator

Carraro VaryT video incorporating Torotrak's full-toroidal traction drive technology
Torotrak | Carraro VaryT video

HST's are about 70- 75% eff, this is about 85% A great fuel saver. A 50 HP tractor would put 43 HP to the ground instead of 36. Looks the balls for loader work.

 

[tsteahr]

Very nice, very interesting. Thanks for the links. Seems like a much better concept then the belt driven cvt.

 

[oldmech]

Hi! Thank you ! Very interesting. This system as the CVT could replace HST on small tractors. For me the reliability is a big ? With time may be Can have a lot of slipping on the inside steel wheels. On big tractors as big trucks For fuel economy Nothing can beat Gears. On Highways near all trucks van use gears for fuel economy. Good Luck ! Oldmech

 

[mike69440]

Hi! Thank you ! Very interesting. This system as the CVT could replace HST on small tractors. For me the reliability is a big ? With time may be Can have a lot of slipping on the inside steel wheels. On big tractors as big trucks For fuel economy Nothing can beat Gears. On Highways near all trucks van use gears for fuel economy. Good Luck ! Oldmech

Slippage is controlled by the disks always being hydraulically preloaded at one end, therefore the load stays constant with wear.

These designs can transmit 500 HP. They use a friction fluid for cooling lubrication and traction with unique properties.

The fact that this has been adopted by Carraro says a lot as they certainly have a reputation as a high end tractor to uphold.

A simple gear train will transmit power more efficiently than anything; well designed belts are a close second. However when you have clusters of epicyclical sun gears in a modern transmission train, depending on which gear your in has a lot to do with the efficiency of the transmission. In some cases you loose 20% or more.

 

[MessickFarmEqu]

HST's are about 70- 75% eff, this is about 85% .

Thats not totally true. There are 85% HST's out there.

 

[farmall40]

Very nice, very interesting. Thanks for the links. Seems like a much better concept then the belt driven cvt.

The CVT in my Case is chain driven by the hydo pump.

 

[slowzuki]

I owned a CVT car about 20 years ago, it worked ok but wore the sheaves where it spend all the time at highway speed. It was not the same as HST though, you couldn't "variate" to infinitely small speed. I don't think most CVT/IVT's can go to zero either can they?

Other than that I hear they are a nice rig to operate. The JD's have a drop out unit so when it burns up from slip or whatever you can just change out that section. Lots of them in the field in europe.

 

[mike69440]

I owned a CVT car about 20 years ago, it worked ok but wore the sheaves where it spend all the time at highway speed. It was not the same as HST though, you couldn't "variate" to infinitely small speed. I don't think most CVT/IVT's can go to zero either can they?

Other than that I hear they are a nice rig to operate. The JD's have a drop out unit so when it burns up from slip or whatever you can just change out that section. Lots of them in the field in europe.

I wish I could give some more information on long term wear.

Regaging the mechanical netural, this can be computer controled to give a true mechanical neutral.

If I were the control engineer, I'd tie the transmision to the mechanical load of the engine, giveing plenty of adjustment to the operator to suite his task at hand and preferences.

I'd also have a defiite detenent in the transmision selector for nuetral and have a minimum creep forward / reverse speed of about 0.1 MPH so the machime could not be inched at 0.01MPH accidently.

 

[mike69440]

Thats not totally true. There are 85% HST's out there.

I believe they are 85% eff. HST's, but is that overall effieciency or operating at its best efficiency ratio point and input power?


A little more investigation and I found a tech paper indicating that a 45 KW unit (60 HP) efficiency is between 86.4% and 89.2%.
For a 60kW (80 HP) unit the module efficiency is between 88.0% and 89.5%, depending on ratio.
That is combined efficiency with an attached reduction gear. The variator itself can approach 92%, which is getting close to a manual box.

Ratio spread goes from 0.4 overdrive to a 2.2 reduction or a 5.5 ratio spread.

For comparison, the new automotive transmissions have a 6 to 7 ratio spread, and the Metal belt CVT's range from 5 to 7.3 (Nissian) Not sure of their efficiency.

In a tractor there are additional losses in the spur or sun gears at each drive wheel, differentials etc.