Gear system is radical but workable

New gear technology is being developed that, if commercialised, will offer benefits to gearbox and power transmission-related industries. Dean Palmer reports During a recent meeting with Leptech in Hull, this magazine had no less than three separate ‘Eureka moments’ during the presentation of what can only be described as a radically new concept in gear transmission technology. Unfortunately, at this present moment, Eureka can only reveal a fraction of what it saw of the technology, but keep an eye on future issues, because as the technology becomes recognised and (hopefully) funded for further development, Eureka will reveal much more of the technical aspects behind this ground-breaking concept. Industry is continuously being bombarded with ever more stringent regulatory, customer and social demands regarding fuel efficiency, disposal and recycling, comfort and safety. To help manufacturers address these requirements, Leptech’s managing director, Ian Leppert, a systems engineering consultant with more than 20 years’ experience in the aerospace and avionics industry, told Eureka that the company “went back to basics” and looked at the fundamentals of gear technology. Object-oriented Leptech technology is based on an object-oriented perspective of transmission systems and addresses the fundamental attributes of and relationships between components, such as geometry, position, mating and coupling, selection, actuation and control. Rather than considering coupling techniques and addressing shift quality directly, Leppert said he first wanted to address more fundamental issues such as manufacturing costs, raw material requirements, size and weight, and so on. “Coupling technologies only provide a benefit during a ratio change,” he explained. “While offering benefits in shift technology, they seldom result in addressing more fundamental issues such as ratio count, weight and size. Typically, gearboxes spend only a small proportion of their working life performing ratio changes.” The technology provides increased discrete/fixed ratio (DR) selections while reducing the transmission footprint. Numerous configurations were shown to Eureka that enable integration with current (and future) coupling technologies, including dog tooth, synchromesh dual clutch and other ‘seamless’ techniques. But the technology goes even further and incorporates a continuously variable ratio (CVR rather than CVT) mode in addition to the standard DR mode. This allows the transmission to continuously vary the ratio about any selected discrete ratio. The control function can also extend the ratio transfer beyond the selected ratio range, or reverse the drive direction. Leptech believes that adoption of one or more of its technologies can help manufacturers reduce the gearbox size by 25%-80%, depending on the number of ratios required and the type of selector assembly and coupling technology employed. As well as reducing gearbox size and weight, the ability to offer an increased number of selectable ratios, allows a reduction in the forces involved in changing between sequential ratios. This helps improve shift quality and enables the engine to remain at its ‘sweet spot’ for longer periods. Multitude of uses As for potential applications, Leptech said that automotive is the obvious one. Cars, trucks, agricultural vehicles and motorcycles are all clear beneficiaries if the technology becomes available. However, the technology is equally applicable to any system that requires a variable transmission and is particularly suited to the transfer of power from any combination of singular or multiple input shafts, to any combination of singular or multiple output shafts. Leppert cited an example: “A typical application would be in a production plant, driving multiple outputs at different speed ratios with single or multiple [load sharing or redundancy] power sources. “A major advantage of our technology is that it overcomes the disadvantages suffered by mechanisms that can only select one of two associated gears. Also, the assembly can select any combination of associated components at once. This allows multiple output or input shafts to be connected or disengaged individually from one selector assembly. It therefore provides benefits for vehicles that require power take off capabilities. “We believe our technology is unique. DR+CVR mode can be used to allow the transmission to ‘skip’ discrete ratios to reach the optimum discrete ratio faster. Selecting the optimum discrete ratio available for the driving conditions and then applying CVR capabilities around this ratio, greatly reduces the CVR power and torque requirements,” he added. As a final, major benefit, Leptech showed how its technology can be used to acheive perfect seamless shifting, without any power or torque losses and without the need for dynamic friction control or engine speed/torque modification. Leptech believes this provides manufacturers with a single, production gearbox that can be dynamically configured by the driver [control system] for DR mode, CVR mode or combined DR+CVR mode. The core technology is patented and covers a number of unique inventions, each of which may be adopted independently. As part of the development strategy, Leptech is seeking discussions with companies that may have an interest in the new technology.