h a l f b a k e r yViva los semi-panaderos!
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rear steer
front wheels steer but rear wheels just get draggged | |
If you have shunted into a tight parking space, back and forth, why not move the rear of the car by steering those wheels also. Dumpers, combine harvesters and fork lift trucks all have rear wheel steer. A number of specialist vehicles have all four wheels steer in both crab and combined arrangement.
Let's have it on our cars, Eh?
c r.mellersh 22/03/01
Buckminster Fuller's Dymaxion Car
http://www.pbs.org/wnet/bucky/car.html
The ultimate in rear-wheel steering, it could turn within its own length. [egnor, Mar 22 2001]
[link]
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Yep, 100% baked. Also, see link. |
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At the Twine Day parade near St. Cloud, Minnesota, a few years back, I saw a two-headed car. Each half of the car had seats facing outward, and a steering wheel, although I think only one half had an engine. By co-operating, the drivers could do four-wheeled steering. They could also lurch sideways at really alarming speeds. |
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What I would give for a car that could move sideways. No more parallel parking hassles. |
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Ah, the classic HalfBakery role-allocation (or roll-allocation - ha ha). PeterSealy says 'Baked' and egnor provides the link.
Don't very long fire engines (the kind used in the US to carry big ladders) have someone sitting on the bck whose job it is to steer the rear wheels? Or am I imagining this as a result of being exposed to too much Richard Scarry as a child? |
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PS - I think you are mistaken (gasps from the audience), certainly in the case of production cars - as opposed to whacky experimental jobs. The rear wheels pointed towards the same direction (I won't say parallel because the movement of the rear wheels was much smaller than that of the front) at high speeds and in opposite directions at low speeds. Always having the wheels move in opposite directions produces alarming handling characteristics at speed (something to do with slip angles I believe). But moving them in the same direction improves stability on high speed corners and changing lanes. At low speed, manoueverability is improved by the wheels pointing in different directions. |
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The Honda mentioned by UnaBubba used electronics to gauge the speed to decide which way to turn the rear wheels, but another Japanese manufacturer (maybe Mazda) used mechanical linkage: a small turn of the steering wheel (typically done at high speed) would cause the rears to turn in the same direction. A larger steering wheel movement would cause a crank in the steering linkage to go "over centre" and the rear wheels would come back and point in the opposite direction. |
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UnaBubba is right that the complexity of these systems meant they weren't really worth the extra cost and maintenance especially as rear suspension design has now improved so much. Modern rear suspension layouts nowadays "steer" passively to improve stability. |
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Rear wheel steering on its own poses too many problems at high speed (although Thrust 2 the land speed record holder used such a system but didn't have to go around any corners) |
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As any commercial vehicle driver will tell you, if you want to get into a tight spot, reverse in. |
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