Aptera says they’ll be delivering their new electric car this year. I assume that the single rear wheel is to save weight, and eliminate any need for a differential (though that’s not really a problem with an electric, if it has separate motors on each wheel). Of course, it’s not like they’re the first to think of it.
15 thoughts on “A Three Wheeler”
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Of course, it’s not like they’re the first to think of it.
The Granville Brothers, who built the Gee Bee racing planes, designed a three-wheel car to compete in the Indianapolis 500. Their design was quite innovative in many ways and was the first race car to incorporate crash protection features decades before they became standard. The design was never built, however, because they overlooked one obvious problem. According to race promoters, a three-wheel vehicle was by definition a motorcycle, not an automobile.
In many states, a three-wheeled vehicle is licensed as a motorcycle rather than a car, which reduces the safety and other regulations the manufacturer has to meet, saving a bunch of money when you’re trying to create a new car company.
The major reason to start with 3 wheels is to license as a motorcyle. This eliminates the requirements for air bags, shatterproof glass, and other items that add to cost, weight, and schedule. The rear wheel drive is impractical in the snow, but having front wheel drive with anti-lock would work. I’ve included the most complete 3 wheel website in the link above.
no, not the first:
Messerschmitt_KR175
The original Aptera design had a belt-driven rear wheel, but they switched to a front-wheel drive layout last year. The three-wheel choice is partly for efficiency reasons (at least that’s what Aptera will tell you), but also because as other commenters have noted, that allows the car to be registered as a motorcycle, presumably eliminating a lot of red tape. The vehicle will however include airbags and I seem to recall Aptera claiming it will pass automotive crash tests.
I imagine air resistance can be lowered quite a lot that way as well as the rear body can be very narrow.
The two in front, one in back configuration offers more steering stability too than the traditional trike configuration. I’ve played around with the idea of building one using the back half of a Burgman as it has a CVT transmission and I wouldn’t have to find workarounds for clutch and shift levers. The problem for me has always been where I could scavenge a front end steering system without doing a lot of major redesign.
Its being a three-wheeler certainly adds to the futuristic look, too. And it’s been observed in the past that among hybrid cars, the ones that look unusual sell best.
Sales of a three-wheeled electric car that looks like a grounded James Bond mini-jet will undoubtedly be better than sales of a three-wheeled electric car that look like a Ford Focus with a birth defect.
Is there a difference in road traction between the three- and four-wheeled cars? Do three-wheelers make sharp turns as safely as four-wheelers?
mz, you’re thinking of low Reynolds number aerodynamics, I think — and one would hope they’re enough folks here that know more about aero to correct me if I’m wrong. I think at the high R number characteristic of cars zipping through air, you want a sharp, squared-off backside so that the turbulent vortices break off as fast as possible.
Carl,
Cars are relatively low Re (roughly 2-6 million), which is still fast enough for the boundary layer to transition to turbulent. However, most cars (not trucks) are reasonably streamlined, and base drag is a major component of their overall drag, so keeping the flow attached at the backside is important – squared-off, bluff backends are bad because they promote a large region of separated flow, which means bad base drag. The other consideration is to try to taper from the roofline to the end of the car as slowly as possible to reduce the tendency of the flow to separate. This is where spoilers can help – they can keep the flow from separating before it goes over the back of the vehicle.
The Aptera wins in one other way – skin friction drag. As you might expect, skin friction drag is proportional to surface area (called “wetted area” in the trade because it’s defined as the surface that would get wet if you submerged the vehicle in water), and the Aptera certainly has less wetted area than a typical car.
I might also mention that I’ve seen the Aptera prototype on the road a few times, and it looks a bit larger and spiffier than it does in the photos – if the engineering and reliability hold up, they may have a winner.
rolling resistance– less wheels less resistance. Some tires reduce resistance so much that they yield 1-2 mpg more over competitors. Eliminate a wheel and you gain a advantage.
Is there a difference in road traction between the three- and four-wheeled cars? Do three-wheelers make sharp turns as safely as four-wheelers?
From what little I’ve read and with absolutely no personal experience, I understand that a 3 wheeled vehicle with two wheels in the back isn’t very stable in a sharp turn unless the body leans into the turn (as the “Lean Machine” prototype did). The Aptera has two wheels in the front and a single wheel in the back. From what I’ve read, that’s a stable configuration.
As for traction, the Aptera is now front wheel drive. An earlier prototype was rear wheel drive but they’ve changed the design. The vehicle’s traction will depend on a lot of factors such as the type of tires used and the weight on each tire. From my Colorado perspective, it doesn’t look like it would do all that well in snow because of low ground clearance and light weight. That would make it a “sunshine car” in my vernacular (good for sunny places like California but not so good for places where it snows) but I may be wrong. It’s an aggressively cool design and I hope to learn a lot more about it.
Two in front is definitely more stable, though I do like the way the “Lean Machine” leans into turns like a motorcycle. Check out Bombardier’s CanAm Spyder. It’s a slick 3 wheel sport trike that has two in front.