E-Mobility Engineering 016 l Aurora Powertrains eSled dossier l In Conversation: Thomas de Lange l Automated manufacturing focus l Torque sensing insight l Battery Show Europe 2022 report l Sodium batteries insight l User interfaces focus

on these sections), the front half is very different from the traditional layout. “Normal snowmobiles integrate a continuously variable transmission, air intakes, exhaust mufflers and other components that take up a huge amount of space and strongly define the outer frontal shape of the vehicles,” Haavikko explains. “Remove those and you gain major opportunities to improve your design. For instance, we’ve done the front suspension in an entirely new way that allows motorcycle-style intuitive banking during turns, and we’ve kept to a rather minimalistic design without any unnecessary outer parts, such as fairings or covers, that don’t really add to safety or aerodynamics.’ The suspension system is a dirtbike- inspired solution, absorbing shocks towards the rider and the centre of mass. Redesigned spindle and A-arm geometries, together with a stiff frame design, allow a major improvement in impact strength over the old kit, and mitigates any damage from users tipping the eSled over. “Overall, this enables a far more comfortable riding experience than on regular snowmobiles,” Haavikko says. “What we’ve made is a rising- rate suspension, which was practically impossible to achieve on conventional systems because of the number of subframes you’d need to somehow fit around the IC engine; there’s generally just never enough space. “Our shock absorbers are supported all the way to the top of a pyramid- type structure, which is a further refined design based on Bombardier Recreational Products’ (BRP) snowmobile model from 2002. That included the pyramidal frame structure with very high torsional stiffness and strength-to-weight ratio. “It was a huge leap forward in snowmobile design conventions, and I like to think that the simple but very robust front suspension we’ve invented is a leap of comparable scale. As well as improving rider comfort, it pushes the maximum range figure up quite a bit, because the ski pressure adjusts well regardless of trail conditions, and there’s good balance between the front and rear ends. That reduces the burden on the powertrain and really gets you more mileage for your energy capacity.” The chassis, including the multi- functional composite structure, forms a key part of this innovation. By replacing the multi-part A-frame of the BRP pyramidal structure with the redesigned spindles and A-arm geometries, this single-piece structure supports the vehicle frame (which handles the mechanical loads) as well as the battery modules, and the weight of the driver and the seat. The company estimates that several tens of kilos were saved by developing this kind of structure. A brief note on suspension terminology: Aurora cautions that the A-arms of the front suspension must not be confused with the A-frames of BRP’s pyramidal frame structure. Bombardier’s classic frame structure included front, middle and rear A-frames, which create a virtually pyramidal shape when assembled. Aurora Powertrains has combined the middle and rear A-frames into one composite structure, which enable it to support the battery and the driver. The front A-frame by contrast has been eliminated, as the shock absorbers now mount directly to the top of the pyramid. “The chassis is effectively an exoskeleton, made partly from Dossier | Aurora Powertrains eSled The new eSled, pictured here in Aurora’s workshop, has been designed in-house from a blank sheet for far superior range Iattery capacity comfort and Oandling tOan tOe first model 22 Winter 2022 | E-Mobility Engineering