When asked by thenational.ae if he preferred to drive his McLaren F1 or Mclaren-Mercedes SLR to work everyday, the man who designed both legendary hypercars, Gordon Murray demurs:
I wouldn’t say the SLR is quite an everyday car but I certainly like to drive it to work. But for me, despite all those cars and my single-seater Rocket [a car he privately designed], it’s the [eight year-old Smart Roadster] I’m most taken with. For one, it’s a great-looking car. It has a power roof, heated seats and air con, and it all weighs just 830kg. In fact, it’s got all you’d want from a car. It nips around corners and it’s fun to drive.
So, other than proving that Murray has exquisite taste (I’d kill you all for a Brabus Smart Roadster Coupe), what’s the point? That, having been there and done that in the world of high performance, Murray’s taking on a less obviously sexy but ultimately significant project that first occurred to him in a traffic jam back in 1993: the T.25 and T.27 city cars. We’ve written about Murray’s T.25 before, but the real news today is the release of specs for the T.27, an all-electric version of the tiny three-seater. And yes, it weighs 1,500 lbs on the nose (including batteries), and ekes 100 miles of range out of just 12 kWh. That beats the efficiency of competitors like the Smart EV (by 29%), the Mitsubishi iMiEV (by 36%) and MINI E (by 86%). So, how does it do it?
The lightweight body is just one part of the equation, allowing not only high efficiency, but also a radically low-energy, low-capital assembly technique called iStream, which does away with the steel stamping-based manufacturing process that has dominated automaking since Henry Ford. Murray explains the process in the video above, clarifying that his firm is not interested in actually manufacturing these vehicles, but that they are talking to other firms who might be interested in licensing the iStream process and building the T.25 and T.27.
But one of the most fascinating developments that keeps the T.27 so light and efficient is its drivetrain, which was developed by a British firm called Zytek. GreenCarCongress explains some of the most salient features:
Minimizing the torque requirement of the motor (to allow it to be smaller, lighter and more efficient) while maintaining vehicle performance, requires a high motor speed. Zytek analyzed a wide variety of motor topologies and designs using 2D and 3D simulation tools, leading to a reliable maximum motor speed of 14,500 rpm. This high operating speed allowed motor torque to be reduced to 64 N·m (47 lb-ft) while maintaining vehicle based performance targets.
The peak motor power of 25 kW (available for 30 seconds) means vehicle performance is maintained in all expected usage conditions.
The second major powertrain component is the three-phase inverter. Zytek concluded that the inverter should also combine battery charging and high-voltage switching capabilities. This has the added benefit of reducing the weight of high-current copper cable and also avoiding any reliability issues associated with use of high voltage connectors.
The total weight of the motor, inverter and gearbox is less than 50 kg (110 lbs), approximately 45% of that of a comparative, current production, water-cooled drivetrain with its associated radiator, cooling fluid, pumps etc. This light weight contributes to the low overall vehicle weight while the highly compact size means that luggage space can be increased compared to the regular internal combustion engined vehicle.
Gordon Murray has long compared his T.25 project with his other great accomplishment, the McLaren F1, arguing that building this kind of tiny, efficient and affordable (estimated cost: $9k for the gas-powered T.25 and about double that for the electric T.27) car requires the same kind of innovative thinking, only the task is made even more challenging by the absence of unlimited budgets and the need for creature comfort. With the T.27’s tiny powerplant, it’s radical front-hinging door, unique manufacturing process (said to require 10% of the startup capital of a typical auto plant), and all-round funky uniqueness, the Murray City Car is proof that the coolest cars need not be limited to the insanely wealthy. An argument, in fact, that the Smart Roadster once made in a slightly less convincing manner. Now the question seems to be: who’s going to build this thing?