Saturday 15 February 2014

Dana set to commercialise truck CVTs

Industry insiders are awaiting the next stage in the development of the NuVinci continuously variable planetary (CVP) transmission developed by Fallbrook Technologies Inc. of Cedar Park, Texas.

Developed originally for cycles, the company claims the transmission has applications in passenger cars, light commercial vehicles and certain off-highway duties.

Fallbrook Technologies Inc. last month created new management positions in Europe in a bid to expand its level of interest still further beyond cycles into other areas of application.

In December last, Dana Holding Corporation based in Maumee, Ohio, announced plans to open its sixteenth global technology centre in Cedar Park, adjacent to Fallbrook Technologies Inc. with which it has a licence agreement.

According to Dana, established 110 years ago, the company was formed ”with a game changing innovation that helped to commercialize motorised transportation and our new technology centre in Cedar Park will propel the development of the next generation of fuel-efficient  transmission technology.”

Dana notes that in September 2012 it secured an “exclusive licence from Fallbrook Technologies Inc. to engineer and produce continuously variable planetary (CVP) technology for use in light-vehicle and certain off-highway transmissions in the end markets that Dana serves.”

Dana plans to market the technology under the VariGlide brand name.

Significantly, also that same month, Fallbrook Technologies Inc. announced that Allison Transmission Holdings Inc. and Dana Holding Corporation had formed a strategic alliance with Fallbrook Technologies Inc. to “develop, manufacture and commercialize high-efficiency transmissions for passenger vehicles, commercial vehicles, and off-highway equipment.”

That alliance is interesting as Allison Transmission also has an exclusive licence agreement with Torotrak plc in the UK, again for infinitely variable transmissions (IVTs).

Presumably the three companies are not embarking on conflicting vehicle products and markets.

The two transmissions have common elements. Both rely on friction to transmit torque using rolling elements and elastohydrodynamic traction fluids of the type manufactured by Shell. Shell and Torotrak have worked closely for many years in the development of such fluids for traction drive continuously variable transmissions (CVTs).

According to Lawrence E. Dewey, chairman, president and chief executive officer of Allison Transmissions: “Ours is an ideal collaboration for developing new technology optimized for the next-generation of commercial-duty vehicles.”

Fallbrook Technologies Inc. claims the story of the CVT can be traced to 1490 when Leonardo da Vinci developed a drawing describing what many believe represents how a CVT would work.

In reality, the practical development work lies much closer in time and is associated with the Hayes transmission developed pre-World War 2 for passenger cars. Frank Anderson Hayes of Middleton, Monmouth, New Jersey developed a method of transmitting power at a variable speed but at maximum torque.

Hayes took out various patents in the US and the UK in the late 1920s and early 1930s. During his travels to the UK, Hayes met Herbert Austin through J. L. Cloudsley who had an engineering company in the form of Cloudsley Engineering Ltd. Herbert Austin’s company manufactured Austin cars.

This collaboration led to F.A. Hayes and Cloudsley Engineering Co. Ltd. signing an agreement to supply continuously variable transmissions (CVTs) to the Austin Motor Company for installation in its Westminster and York models. This took place in the 1930s.

After World War 2, the outcome of this development led in the 1950s and 1960s to the creation by Forbes Perry of the Perbury transmission. Most, if not all, the patents for the Perbury transmission were acquired by a UK Government body, the National Research Development Corporation (now British Technology Group – BTG).

The present Torotrak plc was spun out BTG and is based in Leyland, Lancashire where the company is undertaking development work on IVTs with Allison Transmission, among others.

Leyland Vehicles, formerly based in Leyland, Lancashire, embarked on development of the Perbury transmission for buses and explains the reason why Torotrak is based at the same location.

Torotrak expects to make a major announcement this year regarding its association with Allison Transmission.
                                     Gears into spheres

Fallbrook Technologies Inc. describes its system as “transforming gears into spheres”. And it is here the system differs from the Perbury arrangement, although the concept is similar.

The Fallbrook CVT is based on a set of rotating, tilting balls arranged between two rings. In the case of the Torotrak system, variable ratio is achieved by means of rollers running in conjunction with a toroid.

Fallbrook notes that “torque from an engine is transferred through the input disc to the balls using a thin layer of traction fluid. The torque is then transmitted through the balls to the output disc through another layer of traction fluid.”

“The input disc and output disc are “clamped” onto the balls tightly so that the requisite amount of clamping force is provided for the amount of torque being transmitted,” claims Fallbrook.

“The speed of the output disc compared to the speed of the input disc, or speed ratio, is controlled by the angle of the ball axes relative to the axis of the transmission,” the company adds.

Both overdrive and underdrive are possible with the arrangement; as with the Torotrak system.

Significantly, Fallbrook claims its system is scalable across various applications, though most of the applications thus far are with bicycles.  The Torotrak system is also a scalable technology that has been applied to grass-cutting machines, passenger cars and heavy commercial trucks and buses.

More significantly, perhaps, the US company claims the NuVinci arrangement can be “manufactured at low cost globally with standard industrial materials and processes, and has been commercialised.”

It will be interesting to see how this development matures; and if the claims can be achieved.

As far back as 1981, Peter Stubbs of BL Technology Ltd, part of British Leyland in the UK and based at Gaydon, produced a technical paper for the American Society of Mechanical Engineers (ASME) on the development of the Perbury traction transmission for cars.

Even at that point, work had been under way for over a decade in developing the Perbury transmission. One system was installed in a Hillman Minx passenger car. So, a great deal of development work has been acquired by various sources, most notably Torotrak plc. It is understood that even now, development of the Perbury system is by no means dead.

If there is one thing that can be said about CVTs and IVTs, both technologies have found many large companies wanting in their attempts to ‘crack’ the problems, including Ford Motor Company and General Motors.

The link between Fallbrook Technologies Inc. and Allison Transmissions and the more mature link between Torotrak plc and Allison Transmissions implies there could be a transfer of highly complex technical information from one source to another.

Among the areas of technology most likely to be affected by such information flow are: traction fluid dynamics, traction fluid composition, surface friction characteristics, internal system forces, computerised transmission control, the effect of computer control on transmission instability, materials selection for balls and rings, and the required level of machining tolerances required to achieve the extended levels of durability demanded by modern vehicle use.

Fallbrook Technologies Inc. claims that “various problems, such as cost, scalability, efficiency and weight have kept CVTs from widespread adoption and limited their practical applications.”

This statement might be seen by some to imply that Fallbrook Technologies Inc. of Cedar Park, Texas, has solved all these relevant ‘problem’ areas and produced the ideal solution for a wide range of applications.

No doubt the introduction of the new Dana Technology Centre will go some way in helping to further develop and iron out any faults the NuVinci traction drive transmission might have.

Fallbrook Technologies Inc. had not replied to our request for further information at the time of publication.

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