Lego Prototype Inspires Renault's New Transmission

lego prototype leads to new transmission
Lego Prototype Leads to New TransmissionCourtesy of Renault Group

From the May/June issue of Car and Driver.

In 2010, to the dismay of his family, Renault hybrid expert Nicolas Fremau spent his holiday break assembling a small-scale transmission out of Lego Technic parts. Fremau didn't know it at the time, but the prototype he pieced together in his living room would kick-start the development of Renault's E-Tech hybrid system. The integral piece in Renault's hybrid powertrain is the transmission Fremau invented and christened the LocoDisco Box. It's a name as colorful as the blue fasteners, yellow crossbraces, and red, gray, and black cogs in the plastic plaything Fremau built to test his loco concept, which ditches the typical friction clutches of a traditional automatic transmission for very efficient dog clutches. The canine name is derived from how opposing teeth of the clutch interlock like a dog's jaw. This type of coupling is also very fast to engage and disengage, and it allows the E-Tech transmission to quickly select from one of 15 operating combinations, including four gears for the engine and two gears for the drive motor. Most important, it isn't another CVT.

lego prototype leads to new transmission
Courtesy of Renault Group

Even in this nascent stage, the Lego LocoDisco Box showed promise as a tool for efficiency, courtesy of its quick cog swaps and reduction in friction. And just 18 months after Fremau finished his Lego concept, Renault started testing the first functioning full-size LocoDiscoBox prototype. The setup eventually debuted in the hybrid Clio E-Tech, revealed at the 2019 Geneva auto show. Since then, Renault has fit its E-Tech powertrain into a number of models, bringing Fremau's Lego concept to market and changing what it means to own a car with a "bricked" gearbox.

Along with a working gearset, Renault engineer Nicolas Fremau's plastic plaything includes a small electric motor and drive belts, allowing him to demonstrate his concept in action.

Driving Is Believing

To experience how Fremau's transmission feels in practice, we got behind the wheel of Renault's Austral E-Tech. Though a gas engine is onboard, the E-Tech powertrain pushes the Austral off the line on electric motor power alone. With a 1.7-kWh battery pack feeding the SUV's 67-hp drive motor, the hybrid Austral requires a light right foot to keep it from seeking the assistance of its miserly 129-hp inline-three.

lego prototype leads to new transmission
Courtesy of Renault Group

What the 1.2-liter engine offers in efficiency, it lacks in refinement. The switchover between power sources, how ever, happens seamlessly, and the 15 gear combinations offer plenty of options for varying situations. The modes range from full electric (good up to a claimed 81 mph) to full power (196 horses).


The approximately $44,000 Austral E-Tech is not particularly quick or exciting to drive. But it's an impressive package, thanks to its smooth operation, competitive pricing (around $6000 less than the Honda ZR-V hybrid it competes against in Europe), and fuel economy (better than the Honda's). Not bad for a utility vehicle with a powertrain birthed from bricks.

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