Renault e.dams appears to be utilising a manual selector to change between gears in its two-speed Formula E powertrain. Scarbs explains how it works.
As the second season of the FIA’s Formula E series gathers momentum, it is clear that the increased technical freedom has generated some fascinating powertrain solutions.
Renault’s entry seems to be particularly high-tech and particularly secretive. The French team’s two-speed powertrain has been designed by Renault Sport and appears to make extensive use of carbon fibre to make the car as light as possible.
Yet, we’ve discovered that despite all of the advanced technology of the Renault e.dams car, an age old idea has returned to the electric racing car’s cockpit: the gear lever!
The first generation Formula E racing cars featured five-speed Hewland gearboxes, with pneumatic shifting mechanisms powered by an on-board pump and controlled by the driver via paddles on the steering wheel. Elsewhere in the paddock, teams using revised Hewland gearboxes with multiple gears in season two have swapped on-board pumps with air tanks, in a bid to reduce weight and complexity.
In the second generation Renault, instead of steering wheel paddles, a manual gear lever is situated on the inside of the cockpit, on the right-hand side. It is a short metal lever with a black, round knob and is connected via control rods and cables to the carbon fibre gear casing at the back of the car.
At the gearbox end, the control cable is clearly visible when the rear fairing is removed. The cable pulls on a rocker set-up, which then pulls a rod emerging from the gear casing. This casing houses the two gears, which sit between the transversely mounted motor and the oversized differential ring gear.
The gear system has been devised in conjunction with French racecar gearbox manufacturer Sadev. It’s likely that the gears are the dog ring type typically found in racing cars, although the unique application in the Renault Formula E car could also use something more innovative.
The drivers use first gear to get off the line at the beginning of the race and then simply pull the lever to engage second gear. The powerful electric motor has enough torque that the drivers won’t need to shift back into first for the rest of the race (with the possible exception of at very tight hairpins, such as in Malaysia).
While the manual gear selector seems to be overly simple and fairly old-fashioned for such a technologically advanced powertrain, it does offer Renault several advantages: a fast start as well as effectively gear shift-less racing, combining the best of geared and direct drive systems; reduced weight; and a simpler, cheaper assembly that is less likely to go wrong.
The results thus far this season, with two wins from three races, support Renault’s decision to mix the old and the new.