Heritage of a very different past flows through every inch of Lordstown Motors’ (LM’s) Ohio plant. The Fanuc welding robots ready to assemble electric pickups have spark scars from the Chevy Cruze models assembled there less than two years ago. Signs in the parking lot point to special spaces reserved for electric vehicles (EVs) – Chevy Volt EVs, that is. Employees’ shirts may sport Lordstown’s lightning bolt logo, but signs at the work stations have GM and Chevrolet logos.
Yet the 54-year-old auto plant that GM sold to LM last year also promises to push EVs in a new direction that could radically change the cost and complexity of vehicles in the future.
“There’s a simplicity to this vehicle that we don’t think anyone’s going to be able to match,” LM CEO Steve Burns says. “Four moving parts in the drivetrain, the four wheels. That’s it. There’s not a gear on this vehicle; there’s not a U-joint; there’s not a differential; there’s not a driveshaft or a drive axle.”
When it launches next year, Lordstown’s Endurance EV pickup will use electric hub motors in each wheel instead of following the traditional EV layout of a large electric motor with a transmission that sends power to the wheels.
It’s an idea that’s been around for decades, and Burns says the technology is finally ready.
As Burns notes, the appeal of hub motors lies in what they shed – most notably the entire power transmission system. The four independent motors only need to connect to the rest of the vehicle through electrical and data lines. Rotating drive shafts, often exposed to elements, aren’t needed, lowering vehicle weight and parts costs. The underside of the vehicle – absent shafts, tailpipes, axles, and a differential – becomes a nearly flat plane, giving designers more ground clearance and freedom to design enclosures for battery packs.
Lordstown is targeting the commercial pickup fleet market – vehicles used by utility companies for service calls, or by plumbers, electricians, or landscaping companies. Burns says those companies can benefit from EVs because electricity is generally a cheaper way to power vehicles than gasoline or diesel, adding that the hub motors will make his truck uniquely well suited to fleet users.
With no engine up front and no transmission sending power down the middle of the pickup to the rear wheels, the Endurance gains dozens of cubic feet of space for batteries, storage, and safety crumple zones to absorb crash energy in an accident.
“We’re going to try to utilize all that space,” Burns says. “We can offer extra storage space, better seating arrangements. We’ll have room for bigger batteries, not just for vehicle range but as a power take-off for people’s tools. You won’t need a Honda generator in the back of the truck.”
The promise of eliminating dozens of heavy, expensive parts and gaining more space has attracted automakers for more than a century. In 1900, Ferdinand Porsche showed off the Lohner-Porsche Electromobile in Paris, a hub-motor-powered EV reaching up to 23mph. Throughout the past decade, most automakers have shown concept cars powered by hub motors or have discussed using in-wheel power to add all-wheel drive to front-wheel drive or rear-wheel drive vehicles.
Challenges to adoption
Yet, despite enthusiasm and more than a century of research, hub motors have never made it into production cars and trucks. Some wheelchairs use such motors, as do electric bicycles and a handful of golf carts.
Three electric motors experts, when asked about the challenges of hub motors, all listed the same concern first – unsprung mass. Each Endurance hub motor weights about 88 lb, and that mass rests below the vehicle’s springs. So-called unsprung mass is harder to isolate from the rest of the vehicle, making it harder to mitigate noise, harshness, and vibration (NVH). Put simply, adding several hundreds of pounds of weight to the vehicles could make the trucks really bumpy.
James Kirtley, an electrical engineering and computer science professor at the Massachusetts Institute of Technology’s (MIT’s) Research Laboratory of Electronics says other big challenges include:
Exposure – In traditional cars and most EVs, designers isolate the engine or motor from the abuse of the outside world, keeping water and dirt away and lowering vibration with shock-absorbing engine mounts. Hub motors will experience every pothole and puddle, and the only thing protecting them will be the air in the tires.
Systems integration – Hub-motor-powered EVs will still need traditional friction brakes, and coordinating those with regenerative braking systems in the hub motors will be difficult, especially given the limited real estate inside the wheel.
Ian Brown, an electrical engineering professor at Illinois Tech in Chicago who also listed unsprung mass as his top concern, adds that many high-powered electric motors now use liquid cooling systems, so hub motors will still need fluid lines and pumps.
“Hub motors, though, do give some potential advantages in terms of torque and torque vectoring control,” Brown says (more on that later).
And all of the experts mentioned costs – four smaller motors cost more than one big one. However, they all agreed that eliminating dozens of other components and systems will likely lower vehicle costs in other ways.
Burns says his engineers have spent a lot of time on handling, and prototype Endurance models have performed well on test tracks. One advantage that commercial pickups have is easy competition. Traditional commercial trucks already ride pretty rough, especially when empty. Without cargo weight to balance the engine’s weight with the rear wheels, pickups can bounce around quite a bit. With EVs, the massive battery pack balances weight better, and Burns adds that the heavy wheels further improve weight distribution.
As to durability, Burns acknowledges that moving propulsion outside of the protected engine compartment is risky, but LM addresses that with tough safety cages around the wheel hubs and has tested those extensively.
“You’ve got to make the physical motor tough enough, and that we’ve proven out on the road and in the lab,” Burns says. He adds that LM also needed to keep the vehicle as light as possible because weight kills range in EVs, so protecting the motors requires expensive, lightweight materials.
The launch version of the Endurance is keeping things fairly simple, Burns says. The advantages the truck will bring to market are cost (the Endurance will cost about the same as a Ford F-150 but will have lower operating costs because volts are cheaper than gas) and storage capabilities.
Longer term, however, using four independent motors could open some fascinating abilities in steering and control, the most promising being the torque vectoring idea that Brown mentioned earlier.
Vehicle wheels need to spin at opposite speeds in everyday driving. When you take a left turn, the wheels on the right side of the car travel further than the ones on the left. If the wheels spin at the same speed, the outside wheels will get pulled along the arc, skipping and jumping like a shopping cart or wagon. Traditional cars handle this with a differential, a mechanical system that effectively spins the outside wheels faster than the inside ones. Hub motors would allow far more sophisticated ways for managing spin, making it possible to take corners faster with more confidence.
Theoretically, a hub-motor-powered car could ditch the steering system entirely, handling direction changes entirely with wheel speeds. Imagine vehicles such as tanks and skid-steers that can spin in place by turning the left track in the opposite direction of the right one.
Burns says such ideas will have to wait until second- or third-generation versions of hub-motor-powered EVs. For now, the focus is getting the first model on the road. LM already has pre-orders for a year’s worth of production at the Ohio plant from fleet customers. The biggest short-term challenge is staffing the plant and getting equipment in place during the pandemic.
“We’re convinced that the time is right for these. The idea’s been around a long time, but the technology is ready. The engineering man-hours in the last hundred years that have gone into trucks, it’s got to be the most engineered things humans have ever made,” Burns concludes. “When I say our version 1.0 vehicle is going to be better in some respects, I don’t say that lightly.”