As an 18-month, GB£9 million development project part-funded by the UK’s Technology Strategy Board draws to a close, Gordon Murray Design (GMD) has unveiled the prototype T.27 lightweight electric car.
In fact, five prototypes have been built. An early T.27 muletto for powertrain testing was running as early as June 2010. Two cars are being crash tested; another is for chassis durability work; and finally there is the fully finished blue car pictured here.
The ultra-compact T.27 is said to be the world’s most efficient electric car, and follows hot on the heels of another efficiency champion, the petrol-powered T.25. The innovation-packed three-seater is powered by a 12kWh Li-Ion battery driving a rear-mounted 25kW electric motor. Zytek was responsible for the design and manufacture of the complete drive system, working with the gearbox supplier Vocis. The result is a machine that uses 29% less energy per kilometer than a Smart EV.
It’s also aiming to set new standards in small-car dynamics. Suspension is via MacPherson struts at the front and GMD’s own, iLink independent setup at the rear. The latter is the company’s answer to the long-standing problem of making independent rear suspension cost-effective on a small car. It has also been adopted for some of the cars GMD is working on for other manufacturers.
“The dynamics work so far has been a mix of simulation and physical testing,” Professor Gordon Murray, CEO of Gordon Murray Design, tells VDI. “We’ve learned a lot from T.25, which has been running for a year – knowledge that we’ve been able to pass on to the T.27. T.27 is 100kg heavier than T.25, but has similar characteristics. T.27 is also closer to a front [-biased] weight distribution than a rear [-biased] weight distribution, and it has a lower center of gravity. But apart from that the architecture is the same.
“T.27 is a much easier proposition from a stability point of view because of the lower center of gravity. We’ve done things like due diligence on windshear testing – motorway testing at full size – because that’s a big issue with small, flat-sided cars. It went very well. We’ve also managed to reduce the Cd from the petrol to the electric one by three points, so now we can go back to the petrol one and apply that there, too.”
Murray adds that the flexibility offered by the monocoque construction and iStream manufacturing process means that petrol, electric and range-extender versions of the car could all be built in the same factory. Powertrain aside, there would be about 98% commonality between them.
With just 33 staff on its books, GMD needs to work closely with third parties for testing work. Michelin, one of GMD’s technical partners, has played an important role in the T.27’s dynamic development so far. GMD has used the rigs, test tracks and test engineers at Clermont-Ferrand in France, while Michelin has used T.25 and T.27 to help develop a new family of tires for lightweight cars.
“Most tire companies’ current low-energy technology only goes down to about 1,000kg,” Murray explains. “All the cars we’re doing for customers are below that. Even the four-door hatchback only came out at 750kg with iStream. So they need to downscale the low-energy tire technology.”
GMD currently has projects with seven OEMs and seven other customers.
“Some people we’re already building prototypes for. For others we’re doing what we call a Phase 1 study, to see if it’s worth going forward with iStream. And we’re talking to three potential manufacturers for T.25 & T.27.”
The car is not yet ready for production. Another two years’ of development – coincidentally the minimum amount of time it would take to build and ready an iStream factory for production – would be required, including items such as ABS/ESC application. This particular system is currently packaged but not operational.
Yet the T.27 is clearly much more than a running show car. Most of the difficult thinking around how to put it economically into production, and even preliminary crash testing to prove the structural integrity of an iStream manufactured chassis, is done. Let’s hope somebody signs a production licence soon, so that the project can reach its logical conclusion.
Tech spec – Gordon Murray Design T.27
Dimensions: 2.50m (L) x 1.30m (W) x 1.60m (H)
Turning Circle: 6.0m
Weight: 680kg (incl. battery)
Electric motor: Zytek 25kW
Battery: Zytek Li-Ion, 12kWh
Tires (on XP1EV prototype): Michelin Energy 155/70 R13
Top speed: 105km/h
Acceleration 0-100km/h: < 15 seconds
Range: 100 miles NEDC, 130 miles ECE15