Xtrac's latest P1166 addition to its family of Integrated Lightweight Electric Vehicle (ILEV) transmission systems is being incorporated by Williams Advanced Engineering into its innovative modular lightweight electric car platform. The high-performance chassis concept known as FW-EVX unveiled at the UK's premier low carbon vehicle event at Millbrook this week.
Xtrac has considerable experience of designing transmissions for high performance hybrid and electric road vehicles, and has been involved since the inception of low carbon vehicle technologies, having presented its technology to policy makers with a special display at the House of Lords as long ago as 2008 in response to the growing interest in EVS. Since then the company has produced hundreds of innovative high-performance transmissions for technology evaluation in all manner of innovative low carbon powertrain configurations and for low volume production.
There have been numerous milestones, including the REEVolution project, a collaborative research and development programme funded by the Technology Strategy Board (now Innovate UK) in 2011; designed to create new high-performance range extended electric vehicles (REEVs) and plug-in hybrid electric vehicles (PHEVs). Jaguar Land Rover led this consortium, which included vehicle manufacturers Lotus and, through its Infiniti brand, Nissan, with Xtrac supplying its P1092 torque vectoring transmission.
Xtrac said the continual development of its driveline systems for a rapidly expanding market of supercars and hypercars, will provide additional valuable insights into how highly efficient transmissions can be designed for mass market road-going EVs.
"Important lessons can be learnt when designing, testing and validating technology for extreme applications," says James Setter, head of the most rapidly growing part of Xtrac – its Automotive and Engineering business unit, whose focus on road vehicles complements the company's world-beating motorsport activities.
"There is significant intellectual property to be gleaned from these advanced automotive technology development programmes; not least being the pursuit of silent drivetrains, where we're focusing significant effort. When you remove the internal combustion engine it reveals the slightest transmission noise, vibration and harshness. Road vehicles demand a high level of NVH refinement that is simply not required in motorsport, so we tailor the design of our high-end transmissions for these vehicles accordingly."
The P1166 transmission, fully integrated with YASA P400 motor-generator, meets the tight packaging and lightweight requirements for the front axle of Williams' innovative modular lightweight electric car chassis. It's complemented at the rear by Xtrac's P1227 transmission with torque vectoring capability, which made its debut in 2016, and which has already been selected by customers for high performance EV applications.
The mass of 17-20kg (P1166) and 28-45kg (P1227) respectively for each transmission, dependent on configuration, reflects the high-power density achieved. Despite their tight packaging, each transmission is rated for a maximum speed of over 10,000rpm and peak torque of 1,000Nm (740lbf ft). In combination with three YASA P400 series motors, the overall rating of the William's powertrain is 480kW (640bhp).
"The design philosophy for our EV transmission family is directed towards meeting the silent running, innovative packaging, power density and efficiency demanded by the high performance EV sector of the market," said managing director Adrian Moore, who was previously technical director and represents Xtrac and the motorsport industry on the Automotive Council Technology Group.
"By developing a whole family of EV transmissions for two-wheel drive and four-wheel drive applications, we can provide solutions for numerous possibilities," said Setter. "Either transmission can fit a front or rear axle. It's all about flexibility in the package to meet customer requirements."
Whereas the P1166 features a bevel gear set and differential, the P1227 features a transverse motor installation with helical gears that can accommodate single or dual motor inputs and be configured as a differential or with torque vectoring capability. Both transmissions are optimised for road-going refinement and durability.
Typical of the motorsport industry, Xtrac's ability to innovate quickly, and transfer its technology to the mainstream, is reflected in the rapid development timescale of its ILEV transmission programme, which from conceptual design, through rig testing to customer handover for prototype vehicle evaluation is only a few months for each new transmission design.
With its manufacturing capacity, not only able to support the short timescale requirements of motorsport, but also able to meet the demands of the high performance hypercar and EV market segments, Xtrac can supply over a thousand units per annum of ILEV products.