Rear Wheel Steering

[ross]

I haven't seen this subject broached anywhere on this site (I searched) and if it has, Gooyone will move it for me. Thank God for Goofyone and Zelio without which this site would not be nearly as much as much fun. Anyway, I've seen talk about handling drive through lanes and avoiding potholes, and as a Journeyman Ironworker who 'flags' cranes for a living I know from experience how easy it is to put a large crane into a small space if you can steer both front and rear axles. Any of you rock crawlers know the same thing, for those who don't, a You Tube search of 'Rock Crawlers' will show you.
Anyway, you enter the drive through lane at the bank, as you pull up to the vacuum tube port, you hit a toggle switch on the dash that engages a servo motor that steers the rear tire to the left which causes the Elio to go right, you turn the steering wheel left to correct and pull up within arms reach of the vacuum port or ATM, complete your business, toggle switch the rear wheel back to neutral and motor on.
I wouldn't want to engage this at highway speeds, but I haven't really noticed many potholes in the center of the road on the highway where no tires run, but around town, under 35 or 40 MPH, you see a pothole coming up, slow down, miss it with the left front tire and toggle the rear tire into the same track.
Should make a very fun vehicle even more fun

 

[OctoberGlory]

This is for folks who always seem to be running in circles..

 

[karl]

And complex and expensive...I don't see the bang for the buck here.

 

[Mike W]

It's one of those technologies that definitely has it's place but I think it will probably only be modded in later by the rare, few owners. With my luck, I would be scooting down the freeway, bump the switch and then get to see what kind of driver I really am/get to see what the Elio is made of (maybe figuratively, maybe literally).

 

[Rickb]

The Totota i-Road Concept rear wheel steers. I wonder how that would relate to the Elio's handling?

 

[BillJ]

The Totota i-Road Concept rear wheel steers. I wonder how that would relate to the Elio's handling?
View attachment 3576

More importantly, how would it relate to the cost of the car ? ? ? ? Not cheap I would imagine.

 

[BilgeRat]

Interesting concept; I like the idea.

 

[Lil4X]

Honda and other Japanese manufacturers have offered rear-wheel steering combined with front-wheel steering in a few limited editions. But RWS has a couple of built-in problems. At speed, you'd want the rear wheels to steer in the same direction as the fronts, producing a slight "crabbing" vector that would allow you to change lanes quickly without much disturbance to the stability of the car. At low speeds, you might want to have the rears counter-steer, to cut the turning radius and make the vehicle handle more nimbly in parking lots and drive-up windows. The problem appears when trying to switch between those two modes - intuition goes out the window.

With counter-steering rear wheels, it's easier to flip the vehicle at speed, when the rear wheels increase the effective steering angle and you wind up attempting to violate that second part of Newton's First Law:
"An object in motion continues in motion with the same speed and in the same direction unless acted upon by an unbalanced force" . . . Think of it as mechanically-assisted oversteer.

There just doesn't seem to be a way to transition between the two steering modes, "crab" and counter-steer, without at some point getting dangerous. A few manufacturers have addressed this problem by making the rears steer only tiny fraction of what most of us think would be effective. My limiting the steering angle to only a degree or two, you get some benefit, but can't get in so deep as to become a threat to your own safety. Like many other automotive innovations, the legal risks probably exceed the actual customer benefit - so don't look for this to be in production soon.

 

[Mike W]

Honda and other Japanese manufacturers have offered rear-wheel steering combined with front-wheel steering in a few limited editions. But RWS has a couple of built-in problems. At speed, you'd want the rear wheels to steer in the same direction as the fronts, producing a slight "crabbing" vector that would allow you to change lanes quickly without much disturbance to the stability of the car. At low speeds, you might want to have the rears counter-steer, to cut the turning radius and make the vehicle handle more nimbly in parking lots and drive-up windows. The problem appears when trying to switch between those two modes - intuition goes out the window.

With counter-steering rear wheels, it's easier to flip the vehicle at speed, when the rear wheels increase the effective steering angle and you wind up attempting to violate that second part of Newton's First Law:
"An object in motion continues in motion with the same speed and in the same direction unless acted upon by an unbalanced force" . . . Think of it as mechanically-assisted oversteer.

There just doesn't seem to be a way to transition between the two steering modes, "crab" and counter-steer, without at some point getting dangerous. A few manufacturers have addressed this problem by making the rears steer only tiny fraction of what most of us think would be effective. My limiting the steering angle to only a degree or two, you get some benefit, but can't get in so deep as to become a threat to your own safety. Like many other automotive innovations, the legal risks probably exceed the actual customer benefit - so don't look for this to be in production soon.

I have a feeling all the problems you discussed may eventually be worked out but there's just something about a complex solution that makes me uncomfortable. Like the Korean jet that crashed in San Francisco, they had come to be so reliant on the technology that they simply didn't know how to fly the doggone thing. Technology is a wonderful thing, I wouldn't want to trade any of my tech away, but on the other hand, what happens if something cuts out? Can we handle the result, like in the above mentioned vehicle. Simpler, as much as possible, is better and possibly more elegant.

 

[karl]

http://www.popularmechanics.com/cars/news/auto-blog/the-return-of-four-wheel-steering-16311550