Torotrak’s full-toroidal traction drive is the vital link between the flywheel energy store and the base powertrain

Drive specialist Torotrak will be presenting a mechanical hybrid assist system at the SAE Commercial Vehicle Engineering Congress sometime this week. Torotrak says a mechanical system similiar to some F1 KERS implementations is a fundamentally more efficient approach as energy remains in the mechanical state.

When it comes to electric motor assist systems that are used in all mild hybrid systems now, mechanical energy harvested from brake energy regeneration has to be converted into electricity, then converted into chemical energy in the battery, and then later converted back into electricity and into mechanical energy again when it is used. At each conversion stage, there is an efficiency loss.

The basic architecture of the mechanical hybrid is a lightweight high speed flywheel connected with a CVT to the engine. Torotrak’s paper will highlight past successes with flywheel hybrid bus applications and F1 systems.