New Car Can Lean Into Curves, Literally 243
cartechboy (2660665) writes "You know how motorcycle riders lean into the corners, sometimes even touching their knee to the ground? Mercedes-Benz has developed new technology that replicates that sensation by leaning the car into bends. It's called Dynamic Curve and it's part of the Active Body control suspension system on the new 2015 Mercedes-Benz S-Class Coupe. In turns, special plunger cylinders raise the suspension struts and lower the opposite side, depending on the direction of the bend. This has the result of tilting the car body slightly towards the inside of the corner, countering centrifugal cornering forces. Mercedes says it's not design for increasing cornering speeds, but increasing pleasure for the driver and passengers."
Re:Gimmick (Score:4, Informative)
Except the current suspension compresses on the outside of the curve. This system sounds like it compresses on the inside of the curve, redirecting the g-forces into the occupants' buttocks and not the sides.
Re:Gimmick (Score:2, Informative)
Except sway bars counter that effect by lifting the inside wheel. Stiffer/bigger sway bar, you can get it to do what mercedes is doing with a lot more work. Lets not even get into torsion bar systems.
Re:Poorly Designed Roadways Addressed By This (Score:5, Informative)
But note that the suspension makes the occupants more comfortable but does nothing for stability, so the mis-designed roads are still dangerous.
Re:Gimmick (Score:2, Informative)
A sway bar, no matter how stiff, can only reduce roll, not counteract it completely. What Mercedes is doing goes much further than that: it actually makes the car lean inward, resulting in a more comfortable ride.
Re:Gimmick (Score:5, Informative)
There is no such thing as centrifugal force... when you talk like that you basically show why dumbasses shouldn't be involved in car design.
Stock XKCD counterpoint: Centrifugal Force [xkcd.com]
Re:Gimmick (Score:3, Informative)
Sway bars have downsides. This system shouldn't have those.
Sway bars are cheap and the bushings are the only thing that can wear out. This system probably isn't cheap and will cost a hell of a lot more than bushings do to fix it.
Fictitious forces are still very real (Score:5, Informative)
Actually, the force that is pushing you against the seat is centripetal force, not centrifugal force.
Depends on your reference frame [wikipedia.org].
The only real force is the angular one
Centrifugal force is quite real. So is the Coriolis force and the Euler force . All three occur when the reference frame used to describe the force accelerates relative to another reference frame and in fact you cannot accurately solve many classical mechanics problems without them. For example the surface of the Earth is a rotating reference frame. Don't confuse the meaning of the term "fictitious force" to mean that it doesn't exist. A fictitious force is one that simple doesn't exist in an inertial reference frame. There still are non-inertial reference frames.
Re: Poorly Designed Roadways Addressed By This (Score:5, Informative)
Re:Gimmick (Score:5, Informative)
Think. Cars naturally lean THE WRONG WAY on curves. They tilt over toward the outside.
There's no "right way" or "wrong way" for a car to lean on a level surface with all four wheels on the ground. The motorcycle metaphor doesn't work well here because part of turning a two-wheeler involves moving the center of mass off the centerline and letting gravity pull you through the turn. To paraphrase Douglas Adams, turning a two-wheeler involves throwing yourself at the ground and missing.
This magnifies the centrifugal force you feel by adding a gravity component to it.
On the contrary: being thrown towards the outside of the turn means the turn radius increases, which results in a decrease in centrifugal force.
They tilt toward the inside, like a banking airplane.
Another poor comparison. Airplanes roll while turning because their wings are their largest working surface areas and need to be tilted off of horizontal to get the lift vector pointing "that way." The comparison here would be in banking the road surface itself (the working surface for a ground vehicle) rather than any shifting done by the suspension on a level road surface.
Vectors 101 (Score:4, Informative)
Force requires energy and the only energy being put into the system is rotational, and everything else that appears to be a force is simply some aspect of momentum
Congratulations, you just described movement in a non-inertial reference frame but you flunk vectors 101. Force requires mass and acceleration and nothing else - energy is merely a derived result in this case. The acceleration can be straight line or rotational. Acceleration occurs any time you have a change in velocity which is a vector. Change the magnitude (speed) or the direction (heading) and you have accelerated. So-called "fictitious forces" occur in the later case due to Newton's second law. The effects are real - they are only fictitious in the same sense that imaginary numbers [wikipedia.org] are different from "real" numbers. You need both "real" and "fictitious" forces to accurately describe certain phenomena and the force (or force-like depending on reference frame) effects are demonstrably very real. In curved spacetime, ALL reference frames are non-inertial and in the real world spacetime is curved as far as we can tell. So saying "fictitious forces don't exist" is equivalent to saying we live in flat spacetime. This does not match our observations.