Cars
Published on December 23rd, 2020 |
by Jennifer Sensiba
December 23rd, 2020 by Jennifer Sensiba
One of the big departures Aptera is making from today’s automotive world is the use of in-wheel hub motors. This leaves potential buyers and reservation holders (get $30 off your reservation here) with a lot of questions. Here’s what we’ve figured out so far:
Durability & Water
One of the most important questions is how durable they’ll be hanging out there in the elements instead of protected inside the car’s body. Elaphe, the supplier of Aptera’s hub motors, has a couple of great videos showing just how much of a beating they can take.
Apparently they can handle some pretty bad conditions. While not the exact model Aptera will be using, the motors are built the same way and will be just as capable of taking on whatever we can throw at it.
The first part of the video shows them trying to bend the wheel out of shape with the loads a car would throw at it doing turns, hitting bumps, etc. This would put a lot of loads on only part of the bearings and try to warp other parts out of shape, but the motor does just fine.
Next, they try to break the motor doing a shock test. Driving a vehicle, you’re going to hit bumps, bump into curbs on occasion, and otherwise give a hub motor a sudden shock. The motor won’t be protected by the vehicle’s suspension, either. Off-road users would have it even harder. Elaphe’s motors do fine with shocks. They also do fine with vibration, which you’re also going to get a lot of.
Another problem you’ll get more out at the wheels is water. Sprays, immersion, and other tests didn’t hurt it. Other forms of water, like mud, ice, and salted mist like you’d get on a road in winter also failed to screw up the hub motors. They also tried salt water (both sprays and immersion), which would cause serious issues if it got inside. It took that, too.
Laboratories are one thing, but the real world is another. Elaphe tried that, too. Hitting bumps, driving on slippery spraying ice, potholes, rocks, and other things couldn’t hurt the hubs. Even going fast over a bunch of speed bumps didn’t hurt them.
They even did what my cats would do: they pushed a running motor off the table and onto a hard floor. Turns out the motors are cat-resistant, too.
Keep in mind that they conducted these tests not just once or twice. They put the hub motors to the test for hundreds or thousands of hours, and then looked to see how they did. If they were going to get worn out too quickly from the things we will throw at them, Elaphe would know by now.
Aptera isn’t the only new EV company going with Elaphe’s hub motors. Lordstown Motors, a truck maker, wanted to show us all how tough they were. Doing all the stuff most truck owners never do (driving in mud, going over big bumps, and otherwise getting dirty) doesn’t hurt them, even when carrying around a battery pack big enough to power a truck.
Apparently even the off-road package Aptera isn’t going to eat hub motors.
What About Unsprung Weight?
Myself and many others asked Aptera what kind of effect we can expect from the in-wheel hub motor’s unsprung weight. This is what Aptera has to say:
“It is accounted for and largely offset by using other lightweight materials in those areas. But we haven’t had enough testing compare against our previous driveshaft driven version. Our intial impressions; having the motor weight out on the wheels makes this very light vehicle “feel” more grounded than the previous versions. But we will have more info on this as our testing continues.”
We will definitely let readers know as soon as we get more information about this.
Where are the Brakes?
While the hub motors look like drum brakes, they do have disc brakes inside. Part of this is probably because they need to put the electric components out toward the wheel for more leverage, and that leaves a lot of room inside for the brakes. Also, given that regenerative braking will take a lot of the load, having the little-used brakes put away out of the elements might help.
It’s going to look a little strange to people used to seeing big disc brakes behind a wheel’s spokes, but with the Aptera the whole wheel is going to be covered up.
Having brakes inside the hub motor does raise other questions, like how much work will be involved if you need to change brake pads, where the brake dust will go, and how you’ll inspect brakes periodically. We are checking with Aptera and Elaphe about all of that, and will let readers know when we have more information.
Why Haven’t Automakers Used Hub Motors Before?
Hub motors aren’t actually new to cars. Early electric cars from over a century ago often had hub motors, and did quite well with them.
With gasoline engines, hub motors aren’t impossible, but it’s much simpler to mount the motor in the car for several reasons. Electric hub motors aren’t new at all to cars, but when gasoline engines took the industry over around a century ago, they fell out of style like any other type of electric motor.
Most current EVs follow the gas approach, keeping the motor in the car. Concerns over unsprung weight have been part of the question, but it’s also due to cars just being made a certain way for so long. It has been a lot easier to keep doing what automakers have been doing.
I know we didn’t cover every possible question readers might have about hub motors, but it’s good to know that they can take a beating and work in lousy conditions. It’s also good to know that other concerns are being considered by automakers using them in the future.
If you’re going to preorder an Aptera, and you feel like we’ve given you good information about Aptera, feel free to use our referral link to make your preorder. You’ll save $30, and we will get an Aptera of our own for detailed testing.
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About the Author
Jennifer Sensiba Jennifer Sensiba is a long time efficient vehicle enthusiast, writer, and photographer. She grew up around a transmission shop, and has been experimenting with vehicle efficiency since she was 16 and drove a Pontiac Fiero. She likes to explore the Southwest US with her partner, kids, and animals.
Follow her on Twitter for her latest articles and other random things: https://twitter.com/JenniferSensiba
Do you think I’ve been helpful in your understanding of Tesla, clean energy, etc? Feel free to use my Tesla referral code to get yourself (and me) some small perks and discounts on their cars and solar products. https://www.tesla.com/referral/jennifer90562