Q + A with Roger Stone, Torotrak’s engineering director

Q. What is Torotrak’s IVT technology all about?

A. At the heart of our system is a full-toroidal traction drive, called a variator, that transmits torque using a specially developed traction fluid between loaded rollers and discs, giving a simple and robust Continuously Variable Transmission (CVT). When configured with an epicyclic gear train, we convert this into an IVT or Infinitely Variable Transmission providing a smooth, seamless spread of ratio from forward to reverse, including the fascinating geared neutral condition – where we can provide output torque at zero speed.

Q. How does it work and what industries can it benefit?

A. A pair of parallel discs, one connected to the input, the other to the output, create a cavity shaped like a ring doughnut (a toroid) which houses a group of rollers (two or three per cavity) which are carried on their own axles. The discs are pushed towards each other, contacting the rollers, and the ratio is changed by tilting the rollers.

Torotrak’s technology is highly scaleable and can be used in a broad range of applications. Benefits vary by application. The potential benefits as a main drive transmission, for example, are improved overall powertrain efficiency (due firstly to the possibility of running the engine at close to optimal conditions regardless of road speed and secondly to the high efficiency of shunted IVTs) and also increased functionality, when compared to conventional automatic transmissions. In agricultural applications, our technology provides similar functionality to the most sophisticated hydrostatic drives but at much reduced cost; for truck and bus applications we provide similar functionality to automatic transmissions but at efficiency levels more usual in manual transmissions. In industrial vehicle applications such as forklift trucks, we provide incomparable shuttling capability with significant fuel consumption improvements. The KERS flywheel hybrid concept, developed for F1 racing, has the potential to provide road vehicles large and small with fuel consumption benefits similar to battery electric hybrids for a fraction of their cost and weight. Furthermore, this technology transfers to trams, railways, off-highway equipment and, as a load levelling device, all sorts of industrial machinery. Other industries, such as marine, alternative energy, mining and others can benefit from our technology because it decouples the input speed from the output speed while transmitting the required torque; for example, this means boats can maintain the optimum prop speed while the engine runs close to its best lexapro online, efficiency or wind turbines can maintain the required generator speed over a range of wind speeds.

Q. At what stage are you with IVT, in terms of development and production?

A. IVT is on sale now, in a ride-on mower application, where it provides functionality equal to hydrostatic transmissions with superior performance and economy at a much lower cost. We are also working closely with our customers to develop our technology for commercial vehicle and agricultural applications. It’s a well proven technology and the development emphasis currently is to optimise individual applications. For the ride-on mower we had to develop a very cost effective solution with a small package size; for other applications the priority is CO2 emissions reduction or greater functionality. The availability of torque control as opposed to ratio control is a difficult concept but it unlocks amazing potential – marine winches, for example, could be arranged to maintain constant line tension regardless of relative movement between the cable ends.

Q. Can IVT be applied to hybrid electric vehicles and what are the advantages of doing this?

A. It is perfectly possible to integrate Torotrak’s technology into today’s hybrids and produce improved fuel economy and better CO2 emissions by so doing. However, far more cost effective results can be obtained by using the KERS technology I mentioned earlier in an entirely mechanical hybrid using a flywheel as the energy storage device. This will produce a much “greener” all round product because the fuel consumption advantage in an urban driving cycle will be at least as good as battery-electric, vehicles while under motorway cruise conditions we avoid the CO2 penalty incurred by power split battery-electric systems. Efficiency levels of up to double those of an electrical approach can be achieved; furthermore, the environmental load relating to the manufacture and end of life disposal of a mechanical hybrid system is dramatically less than that of the conventional hybrid route. In our recent SAE paper we outlined fuel savings of approximately 33 percent over the London bus test cycle, using energy recovery from a mechanical flywheel, coupled to the powertrain through one of our IVTs. Even as a “bolt on extra”, we expect savings of 20 percent.

Q. Torotrak also offer the market TCVT – what is this and what benefits does it hold for the various market sectors?

A. Toroidal CVT is the simplest embodiment of the toroidal variator principle. It requires a clutch for starting from rest but offers the market a low cost option, ideal for emerging market automotive applications where the combination of automatic transmission functionality and manual transmission levels of efficiency offers a solution to the problems of variable standards of driver skill and high fuel prices in relation to income. These benefits apply particularly to sectors such as light cars and two- or three-wheeled vehicles. Market sectors such as forklift trucks, dump trucks and city buses can derive CO2 and fuel savings from a TCVT-driven flywheel to recover braking energy during the stop-start duty cycles typical of their operation, as I mentioned a moment ago.

Q. What is the greatest challenge facing automotive transmission suppliers and developers?

A. Increasing pressure on vehicle manufacturers to reduce CO2 emissions, while preserving the attributes that appeal to purchasers, is placing demands on transmission engineers to play their part in achieving vehicle targets. Torotrak’s full-toroidal variator technology can help in numerous ways, apart from main drive applications. There is the potential for use on auxiliary drives; reducing the parasitic losses incurred in driving the alternator, power steering, aircon and other auxiliaries can certainly provide worthwhile savings in fuel consumption and we are very actively working on these opportunities now. The range of applications becomes even wider if we consider supercharger drives and the potential that these might present for engine downsizing, leading to very significant fuel consumption savings. A more heavy duty opportunity is turbocompounding; this technology is currently of limited application in the truck world but a toroidal CVT could transform it into a CO2 reduction tool of much wider benefit.

Q. Looking into the future, where would you like Torotrak to be in ten years time?

In ten years time, I hope that Torotrak’s extensive development work will have paid off, and that Torotrak’s technology has reached the stage of mass commercialisation and is being used extensively not only in our current target markets (commercial vehicles, off-highway, outdoor power equipment and automotive), but also in the new markets we want to address – marine, industrial, mining etc .

I would also like Torotrak to be a recognised supplier of leading edge, ”green” technology especially in the form of mechanical hybrids – with Torotrak’s KERS-CVT playing a key role in the system being adopted as a viable alternative alongside electric hybrids.

Q What career did you want when you were growing up and what was your first job?

 I wanted to design motor bike engines but by the time I was old enough the British motor cycle industry had committed Hara Kiri!

 My first job was with Ricardo Consulting Engineers in Shoreham where I became a Design Analyst and worked a tremendous range of engines – all the way from motor bikes to 20 litre/cyl marine diesels.

Q. What are the best and worst elements of your job?

Best: so much to do; so little time!

Worst: so much to do; so little time!

Q. What OEMs do you have particular respect for?

 Ah! Now that is a question that invites indiscretion and comparisons can be odious. I think that, especially in these days, the automotive industry is incredibly tough and I respect any company that can survive the challenges that we all face.

 Q. What personal career goals do you have for the future?

 To see Torotrak technology adopted across a wide variety of applications in a similarly wide variety of industries – automotive obviously, agricultural, marine, industrial, process, oil & gas – the list goes on and on. The technology has such a wide range of potential applications which I am keen to see exploited now that we have broadened our ambitions from “merely” automotive main drive transmission applications.

 About Torotrak

Torotrak is the world’s foremost developer of full-toroidal traction drive technology. The company designs and develops Continuously Variable (CVT) and Infinitely Variable (IVT) transmissions which deliver outstanding levels of performance, functionality and refinement along with improved fuel economy and reduced emissions. Torotrak develops main drive transmissions as well as variable ratio transmissions for application in flywheel-based mechanical hybrid systems and for use as auxiliary drives.

Torotrak operates in the automotive, truck, bus, off-highway and agricultural markets, in motor sport and in outdoor power equipment.  Its customers are widely spread across Europe, North America, India and Japan, and include major vehicle makers and tier one transmission manufacturers.

 Torotrak plc is fully listed on the London Stock Exchange.


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