Are single-regime CVTs the way forward?

Step-less automatic transmissions continue to fascinate the automotive industry.

Only recently a patent was published for a Ford design of 11-speed transmission, surely a further step along the road towards a step-less transmission (or continuously variable transmission – CVT), the holy grail of all vehicle transmission.

News of the 11-speed transmission should not be that surprising. It is only one ratio short of the 10-speed automatic that will be made available for the 2017 F-150 Raptor. The 10-speed transmission could then trickle down through the remainder of the F-150 model lineup and maybe beyond. (NOTE: the Fiat 500X has a nine-speed gearbox and 100bhp/litre gasoline engine.)

But could there be automatic transmissions with higher ratios than 11- and 12- speed gearboxes? Or will the CVT make a comeback? Ford has dabbled in CVTs before and eventually opted out. It even dabbled with UK innovator, Torotrak. But is Ford still interested? In Germany, both Bosch and Getrag have taken out patents for CVTs - the notion of taking out patents appeals to many researchers in transmission businesses.

And what about off-highway uses for CVTs? JCB, for example, has Fastrac models with 24 ratios.

A recent spike of interest in the last few days regarding an item published here in January 2014 suggests the interest in CVTs is far from waning.  An item in Auto industry Newsletter – the obituary to Forbes Perry in January 2014 – has attracted attention and suggests that someone, somewhere has more than a passing interest in toroidal continuously variable transmissions.

It is known that before his death late in 2013, Forbes Perry – the inventor of the Perbury transmission, which formed the initial basis of Torotrak's foray into CVTs (and before that the British Technology Group (BTG) and before that the National Research Development Corporation (NRDC)) – was working on single-regime toroidal CVTs. Up to the time of his death, Perry probably knew more about toroidal CVTs than any living person. He certainly had been associated with them far longer than anyone.

Ever secretive when journalists were present, but nevertheless extremely clever and with contacts the world over, Perry produced a multiplicity of designs for single-regime (and other) CVTs which could have paved the way to a low-cost transmission.

This type of CVT can have either a roller epicyclic (like a variator but with a fixed ratio) which returns the direction of rotation to input as well as balancing the end load, or it can take the form of a conventional (even shorter) epicyclic which deals with the direction. However, this design requires a thrust bearing for the end load with the result that the design is not very efficient.

Single-regime CVTs are slightly less efficient, however the fact they are compact makes them ideal for small, low-powered units – such as lawn mowers, quad bikes and small city cars. The offset to their lower efficiency arrives in the form of small size, low weight and lower cost. However, efficiency becomes increasingly important as the torque numbers go up. It is this that rules them out for higher powered vehicles.

Nevertheless single-regime CVTs, with a single rotor, do offer advantages for vehicles in certain applications where fuel economy might not be so critical. For example, transmission efficiency alone may not be a deciding factor compared to being able to run a diesel engine close to its optimum during much more of the operating cycle.

This may be one reason why specialist equipment makers, such as JCB, have shown more than a passing interest in CVTs. Single-regime CVTs might offer certain advantages as a replacement for a hydrostatic transmission.

JCB discloses little about its work in the area of CVT, just as years ago it denied all rumours that it was planning to make its own range of diesel engines, when in fact the company’s founder was working on the concept and today JCB makes its own diesel engines.

Nevertheless, in the clandestine world of CVT technology it is known that JCB is knowledgeable in the area of toroidal film drive transmissions. There is just the possibility that this type of transmission could cover all or part of JCB’s vehicle range allowing its engineers to be rid of hydrostatics. And these transmissions could be made in-house.

In November last year (coincidently just short of one year following the death of Forbes Perry) we reported that Jeremy Deering was stepping down as chief executive officer of Torotrak plc and Steve Hughes, formerly engineering director at JCB Transmissions, would be joining the group as chief operating officer.

                                           Share price chatter

At the time, we said “It will be interesting to see if the arrival of Hughes increases the group’s momentum and propels it in the direction of developing Torotrak’s technologies for off-highway applications. JCB has a huge range of equipment (it also makes its own engines and transmissions) that could benefit from the fuel saving technologies Torotrak has developed. This could pave the way for business with other OEMs.”

Since then Adam Robson has joined Torotrak as chief executive and, almost immediately following his arrival, made a £13.8 million cash call to fund Torotrak’s various transmission developments, including CVTs. This cash call only served to depress private shareholders further; they question if Torotrak will ever deliver.

Torotrak share price chatter is depressing to read. Such chatter questions whether Torotrak can rise from the ashes? This is just one of the big questions asked of this small, innovative automotive group by private investors who appear to remain gloomy.

The following quote is typical of some of the share chatter regarding Torotrak Group which could head off in the direction of Flybrid’s KERS instead of CVTs, or even clutched flywheel transmissions (CFTs).

"Oh dear... what a dog of a share...This share really is doomed....One big science experiment with nothing of any value created that can be sold...Such a disappointment... To invest in the new share issue you'd have to be a blithering idiot!"

Torotrak has experienced numerous chief executives over the years; each has wrestled with bringing new technology to market. The entire business model could be at fault. Even so, for its sake, and to prove that it can generate shareholder satisfaction with the date of 22 July fast looming, the new team at the head of Torotrak has to show it can succeed where others before have failed in this one regard. Could JCB be one area that proves profitable for Torotrak? Or have transmission engineers so perfected double-clutch technology and hyper-multi-ratio gearboxes to such a level of refinement that CVTs are obsolete even before they have taken a significant hold of the market?