E-Mobility Engineering 015 l EMotive Scarab off-road truck dossier l In Conversation: Giulio Ornella l Hall effect and magnetic sensors focus l Challenge of batteries for heavy-duty EVs l Alpha Motor Corporation digest l Automated charging insight l HVAC systems focus

from profile folded steel sections. They are connected by welded steel plates to form a ladder frame. Underslung from these rails are the bolt-in axle assemblies, which consist of a central steel truss on which fabricated steel upper and lower wishbones are carried on bushed pivots. Each axle bears weight on a pair of air springs, one either side, the upper mounts for which are welded to the chassis rails, with each spring controlled by two Koni telescopic dampers. “That gives us a large suspension travel,” Williams notes. “Ride comfort, stability, traction control and so on will all benefit from that.” The air springs themselves are commercial truck units, which are well- proven, robust and even somewhat overspecified for the vehicle’s weight to provide a margin for running on more demanding surfaces. “They will do the hard work of supporting the payload and withstanding the extreme impacts of shocks and bumps over harsher terrain,” Williams says. “The air springs will take out all of that, and the twin Koni dampers will take out the high frequencies.” Each axle assembly forms a module, and with the disconnection of the air springs and a few electrical and fluid connections, the entire drive system can be unbolted and dropped out. “That’s good for maintenance, and also means it can be built on the production line as a sub-assembly and bolted in.” At the moment, the Scarab prototype has front-wheel steering only, but the team is preparing to add a powered rack to the rear axle. “With modularity there’s nothing stopping us from having the same axle sets in all three stations,” Williams notes. “You could have six-wheel steering for example, as in some applications it might be useful to crab the vehicle. The whole mindset is modularity and adaptability to perform many roles for many users. “Air springs allow us to carry a large payload,” he adds. “One target was to keep kerb weight as low as reasonably possible. “In doing so, we are keeping all the components low in the chassis, which then means we can carry a larger payload higher up and still keep the centre of gravity reasonable. We are targeting a kerb weight of between 4.5 and 5.5 t, depending on the type of range extender and fuel tank installed, allowing up to 5.5 t of payload.” That adds up to 11 t, although the allowable maximum gross weight is 12 t, plus some margin for future- proofing. “As the platform is scalable, we can design components such as axles and wishbones that allow us to go up a little more again without starting from scratch.” Together, the chassis and suspension provide strong support for the driveline. Williams explains that the team is in the process of working out how much power they can extract from the Dossier | EMotive Scarab off-road truck When the Scarab gets its production-standard motors and reduction hubs it will be able to generate up to 6000 Nm of torque and 150 kW per wheel (Author’s photo) 22 Autumn 2022 | E-Mobility Engineering