The skateboard chassis just might be the most important piece of automotive hardware created this century. Not only is it key to making EVs viable, but it has helped kick open the door to dozens of new automakers.
The way Chris Borroni-Bird sees it, the skateboard chassis — the architecture that underpins most of today's battery-electric vehicles — would have been invented by someone else if General Motors hadn't done it first two decades ago.
"When you think about a ground-up design for an electric vehicle, the skateboard is the obvious choice, the obvious solution," Borroni-Bird, GM's former director of advanced technology vehicle concepts, told Automotive News. "You lower the center of gravity, improve road-holding, have more freedom in design, you get better crash protection for the front of the vehicle, and there's more storage, so it creates a lot of benefits."
The skateboard chassis just might be the most important piece of automotive hardware created this century. Not only has it been key to making EVs viable, it has also opened a door for dozens of startups looking to seize the opportunity.
"There's no doubt the move to electrification has taken massive barriers to entry out of the automotive business," said Greg Fraker, president of engineering services at Detroit's Roush Industries, one of the auto industry's largest engineering and product development firms. "The business of fossil fuels, internal combustion engines, managing the emissions and certifications — those are very mature industries that require massive investments. Electrification and the skateboard are the great equalizers. They allow a lot of startups a better cost advantage to get involved."
Borroni-Bird: “The skateboard is the obvious choice.”
It was Borroni-Bird's team, empowered by former GM R&D chief Larry Burns, that created the AUTOnomy skateboard concept, which debuted at the 2002 North American International Auto Show in Detroit.
That first skateboard was not designed for BEVs, however. GM's vision for the first application was for a hydrogen fuel cell and drive-by-wire technology, all of which was packaged in the 6-inch-thick skateboard chassis. Later, a skateboard would underpin GM's fully driveable Hy-Wire hydrogen concept car.
Designed for energy efficiency
Changes to automobile chassis are extremely rare. For at least the last six decades, many of us have driven every day in a vehicle built one of two ways: with the body mounted on a separate frame — usually made of steel — or with the body and frame integrated as one, commonly known as unibody.
Body-on-frame and unibody architectures were designed to package transmissions, radiators, exhaust systems, fuel tanks and other components not used in EVs. Early EVs converted from internal combustion engine vehicles had traditional body-on-frame or unibody chassis, such as the now-discontinued Toyota RAV4 EV, Chevrolet S-10 Electric and Ford Focus Electric. They performed reasonably well but had short driving ranges in part because the batteries were stuffed wherever there was space.
Even GM's EV1, which was designed from the ground up as an electric vehicle, placed the batteries in a T-shaped structure that ran down the center of the car and struggled to get more than 100 miles between charges. Those same cars would have longer driving ranges with today's better batteries.
With a skateboard chassis, the battery pack is wide and long and placed below the floor. It usually runs from under the forward dash to the aft edge of the rear seat/trunk area and is a structural part of the vehicle.
"Once you decide you are going to make battery-electric vehicles at scale, the arguments in favor of a ground-up vehicle design are compelling. You get much better performance and better range, and it is far more likely to sell than a compromised vehicle based on last century's vehicle architectures," said Borroni-Bird.
Taking shape
Other automakers made car bodies with integrated floors before GM. The classic Volkswagen Beetle, for instance, had the car's stamped floorpans welded into the frame in a layout VW called "body on pan." In the 1990s, Mercedes-Benz's A-Class subcompact had a flat floor. But neither car housed any of the vehicle's powertrain components or electronics in the floor.
The genesis of the skateboard chassis, Borroni-Bird says, is rooted in a blending of the A-Class and the Opel Filo concept car shown at the 2001 Geneva auto show. The Filo, created by Italian design house Bertone and Swedish bearings supplier SKF, featured drive-by-wire technology and had a flat floor. The steering wheel could slide across the width of the dash so the driver could sit anywhere in the front.
The Opel Filo concept, shown in 2001 in Geneva, featured drive-by-wire technology and a flat floor.
At the turn of the century, GM was investing billions of dollars in developing hydrogen fuel cells, a technology — still under development at the automaker today — that could solve two problems: driving range and emissions.
Borroni-Bird says GM's original skateboard was envisioned to accommodate not only the fuel cell and drive-by-wire technology the company was developing, but an electric motor at each wheel. Though GM invented the skateboard, other automakers put it into mass production first. GM's EV plans were derailed by financial issues and other problems. Nissan, with the 2010 Leaf, and Tesla, with the 2012 Model S, beat GM to market with their own skateboard EVs.
Borroni-Bird said he was not surprised when Tesla showed the Model S concept in 2009 with the skateboard chassis. "I knew that the economics of the [electric] powertrain were such that if you could up production, the best solution at scale was the skateboard. Once the battery costs came down — and obviously Tesla was first to do that — then other automakers jumped on board," he said.
Newfound freedom
It's no exaggeration to say designers love the skateboard chassis as much as engineers. It has given them unprecedented freedom to focus on getting the proportions of a car just right and to maximize interior room.
Simcoe: No interference with vehicle’s top hat
"The architecture doesn't interfere with the top hat of the vehicle," said Mike Simcoe, global vice president of design at GM. "Structurally, the skateboard effectively stops at the floorpan. And so everything above that is free. In a traditional build, things like the cowl and dash panel and the front hinge pillars are controlled by things coming out of the chassis, such as engines, fuel tanks, etc. But in a skateboard, it's all down low, and you've got more freedom.
"You ... express it by proportion. You can do a long dash-to-axle, you can do a tall vehicle. It's all governed by the H-point," he said, referring to the theoretical pivoting point of a passenger's hip, which influences everything from roof height to interior space to ease of entry and exit.
Some of the latest EVs, such as the Lucid Air, Rivian R1T and upcoming Cadillac Celestiq, demonstrate the advantage of the skateboard chassis. These vehicles have generous interior space relative to their body sizes, and in the case of the Rivian's pickup, ample storage areas not available in body-on-frame trucks.
Because electric motors are smaller than gasoline engines and require fewer umbilicals, such as cooling and exhaust hookups, engineers can put drive motors in the front axle, in the rear axle, or both in the case of all-wheel-drive vehicles. If the Lordstown Endurance pickup launches, it will be the first modern regular production vehicle to have the motors in the wheel hubs. The Endurance has its battery pack mounted between the frame rails, though it still uses a fairly traditional rugged steel truck frame.
Roush's Fraker believes one of the skateboard's limitations is that it isn't suited to replace the frames used on hardworking vehicles, such as heavy- duty trucks that haul huge loads.
"I think it will be quite a few years before we see significant trucks that handle large loads go to the skateboard," he said. Those frame rails give us excellent strength, and I think they will persevere in the commercial market. But everything in the lighter classes, you will see more integration of the battery and the vehicle."
Lindsay Brooke, editor of SAE International, the magazine of the organization formerly known as the Society of Automotive Engineers, says designers can create longer vehicles on the skateboard chassis, and engineers can easily accommodate those changes without disrupting the assembly lines. But the width of a skateboard vehicle is not as flexible.
Cadillac Celestiq: Generous interior space, thanks to the skateboard
"There are some restrictions. A vehicle can only be so wide to be able to sit on the production line," Brooke said. He also noted that the skateboard design might not be the best option for sports cars because of the weight of the battery pack and the limited driving range. So where does the skateboard go from here? As batteries become smaller and more powerful — requiring less room — the body of a skateboard chassis might start to handle more of the structural load of a vehicle, Fraker believes.
Borroni-Bird sees plenty of room for the skateboard chassis to be improved. He believes that as engineers solve the wheel hub motor's technical issues — protecting it from the elements, reducing weight and improving cooling — it will be the next evolution of the skateboard.
"When you talk about Uber-type vehicles that have well-understood driving patterns and range needs on a daily basis, and if you think about all the effects of fleet vehicles in city centers, those vehicles, in my mind, are ideal for wheel motors and the skateboard. Because wheel motors would solve several problems. They would allow the vehicle to be smaller and shorter but have the same storage space, and the vehicle could be more maneuverable. It could turn on its own axis."(Source:Automotive News)