• Aug 19, 2011
UK transmission engineering and control specialist Vocis will show off its electric vehicle-specific, two-speed transmission during the Low Carbon Vehicle Event 2011 at Rockingham Motor Speedway over in the UK.
This will be the first public demonstration of the Vocis two-speed trans, which will be fitted to a prototype electric minibus developed in conjunction with powertrain supplier Zytek.

Vocis transmission guru Andy Turner explains, in simple terms, why two-speeds supposedly beat one:
Electric motors have a very wide operating range, but that doesn't mean that they are equally efficient at every speed. The torque curve of a typical traction motor is well suited to vehicle propulsion, having maximum torque from zero speed and a wide constant power region. However, there is a sweet spot, typically at medium speed and medium to high loads, where the delivery of power is most efficient. A choice of gear ratios allows the motor to be kept in this operating region during more of the drive cycle.
Simulations have shown that Vocis' two-speed unit could reduce energy consumption by up to 10 percent, compared to a single-speed trans. Furthermore, Vocis says that its twin-speed setup doesn't cost much more than a one-speed unit and could even extend battery life. What's interesting is that Tesla learned the exact opposite lesson back in 2008.


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