Hybrid Powertrain Inspired by Lego

The Renault E-Tech powertrain arose from experiments with building blocks

When Renault launched its first electric vehicle in 2010, it also set about gaining experience with electrified powertrains to develop hybrid technology that would provide customers with a smooth transition towards going all-electric. To do this, the engineers needed to demonstrate that they had the ideal way of meeting a particular set of specifications.

According to Nicolas Fremau, Renault’s Hybrid Architecture Expert, it presented a significant challenge because the design team needed to keep things simple, compact and light using a clutchless transmission with gearbox synchronisers, utilising dog clutch technology normally found in motorsport.

“When I saw my son playing with LEGO Technic sprockets at home, I said to myself ‘well, it’s not so far from what I’d like to do’. So, I bought what I needed piece by piece to have all the assembly elements”, says Fremau.

He used the Christmas holidays to make a model of the innovative transmission out of LEGO that he’d first imagined on paper. “I had the idea of doing this first to help me understand what to do. After about twenty hours of ‘work’ under the slightly surprised eye of my son, the model was born,” he explains.

This wasn’t a case of just fitting bricks together. Fremau had to assemble the different axes and transmission rings, glue them and drill them to fit into a cradle, as well as motorise the whole system. It was a piece of engineering that allowed him to live-test the different modes of operation between the engines.

The process of trialing the possible modes of operation also allowed Fremau to discover new ones that he hadn’t previously thought of in theoretical analysis. This strengthened his conviction that he was on the right track with this prototype.

Presenting the model to project manager Gérard Detourbet and Director of Research Rémi Bastien was a tense moment for Fremau. Despite Renault being a very open company when it comes to research, Fremau was doubtful about how the management team would react.

“They walked around the model, they touched it and they felt that we had a real object. And I will always remember Gérard Detourbet’s remark: ‘If we can make it in LEGO, it will work!’”, recalls Fremau.

Work began on creating a full prototype and the result was the E-TECH powertrain used in the current range of hybrid models from Renault.