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Ball shape tire in a magnetic socket. Direction and movement achieved by magnetic energy on the tire inner metallic structure threads.
More directional possibilities, less friction, less spare parts, easy change by desactivation of magnetic field..
Orb-it
http://www.halfbakery.com/idea/Orb-it
prior art by [FarmerJohn] [krelnik, Oct 06 2004]
Etek
http://www.robotmar...rketplace_etek.html
8 "poles", big power--see also the PMG 132 on the same site, which I think also has 8 poles and is even more powerful [5th Earth, Jan 18 2006]
Audi RSQ
http://www.seriousw...udi-RSQ-Concept.htm
From "i,ROBOT". [BJS, Jan 19 2006, last modified Dec 06 2007]
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Replacing a tire with a sphere, touching the ground at one tiny point only, would surely reduce friction to the point of zero control...? |
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A rubber sphere would touch the ground at a tiny point? Sit on a basketball and take a look.
Miasere, the amount of power needed is minimal as magnetic power can be stored using the right material. You simply recharge the poles electrically when flat. Read the first description for movement control and you will understand..maybe.. |
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Would this mean that when you steered your ball tired car at a corner, she'd go round it but you'd stay facing the same direction? |
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Holonomic wheels are baked. The magnetic force you propose, for driving these wheels, is prohibitively inefficient when compared to almost any direct drive system. |
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Actually, contact area is fairly crucial in car tires because traction changes as the tire rolls along. The maximum coefficient of friction can occur anywhere in the contact area, so that the greater the area, the greater the likelihood of maximum traction. Thus, under identical load and on the same surface, the wider tire has a greater contact area and develops higher traction, resulting in greater stopping ability. |
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Sit on your basketball and roll down a slippery hill to learn more. |
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I think an improvement on this idea would be to reduce the size of each ballwheel and increase the number greatly. They should be made of clear plexiglass and rather than magnets, be powered by a hamster. The direction of the vehicle would be determined by the vector sum of all wheels. |
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By the way, [Belgarath], welcome to the HB. Any idea with an educational discussion like this is a good idea, bones or no bones. Keep them coming! |
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I believe that, the Audi RSQ from the movie "i,Robot" has four spherical shaped wheels, and a magnetic propulsion system, very similar to the "tire" you described... |
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Belgarath, is your system of a ball shaped wheel intended to levitate the vehicle, so there is a gap of air between the body and the wheel? or will they be in contact with each other in some way? |
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[BJS] beat me to the I, Robot comment, but since it wasn't a widely advertised point in the movie, and you make no mention of it, I'll ignore the potential WTCTTISIAMWIBNIIWR. |
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[Miasere], actually electric motors are very effecient compared to internal combustion engines--otherwise the recent crop of hybrid cars would be pointless. Speaking from experience, electric vehicles have the problems they do because of limited battery technology, not motor technology. I think you're also greatly underestimating the power of modern rare-earth magnet technology--a magnet the size of a basketball lifting a car is very easy to believe. Ferrous "Fridge" magnets are to rare-earth magnets what butane is to nitroglycerine. |
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Finally, there is no reason for the motor to be bi-polar. It is perfectly common for electric motors to feature 4,6, or 8 poles, and on a structure as large as a tire more poles are probably easily implemented. I rather doubt the tire would be monopolar though, without some serious breakthroughs in technology and physics. |
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[DrJake], do your car tires contact the ground along a line only? There's a reason tires are squishy. Anyway, you're right that contact area affects traction, but for the wrong reasons. You're ignoring adhesion and tire deformation (macro and micro-scale), which are much more significant in tire physics than basic friction. |
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[5th Earth] is there any way you could post a link on multi-polarity? A quick search turned up pages & pages of nueroscience. |
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This has been baked on a small scale (by a university, I beleive) with a small plastic ball imbedded with perminant magnets and a hemisphere with electromagnets arrainged on the inside. |
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I don't know how well you could hold up a car by repelling magnets, and the inertia of these ball-wheels would cause problems. I think it would be better to support the ball-wheel on ball bearings so that there is a small gap between it and the hemisphere. |
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[Zimmy], now that I think about it I was rather unclear/inaccurate. When I say "poles" for a permanent magnet motor, what I should have said is locations where magnets are. Most PMMs have two "poles"--two magnets, placed opposite each other in the motor. Some motors have 4 magnets, arranged as points on a square, or more magnets, AFAIK always in pairs. Having more "poles" (wrong term really, I should be saying magnets) means you can get more torque out of a motor of a given size with only a moderate increase in weight (ref. the Briggs & Stratton Etek motor I've linked--has 8 "poles" and a rather frightening power-to-weight ratio). |
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When [miasere] suggested a mono-polar wheel, he was using pole in the classic sense of the word, as meaning one end of a magnet. Magnetic monopoles have never been seen and are theoretically assumed not to exist--magnetic fields always have two poles, North and South, and you never see one pole by itself. In the case of an electric motor, however, it can be semi-meaningful to think of the magnets as being single poles, because only one end of each magnet actually does anything. |
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If the tire, as suggested above, is bipolar, can't we treat that with medication? |
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he he he = HU HU HU HAHAHAHHA, AHem i mean Holy Moly whata GREAT idea... SHould be a movie! A+ |
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5th earth, take a look at the original date of the idea, and compare it to the release date of "I, Robot". For this reason, I don't think this quite qualifies as WTCTTISIAMWIBNIIWR. |
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Magnets are not monopolar. They just can't be. Therefore, stationary rare earth (or any other permanent) magnets can not be used to provide the constant field to support these wheels. |
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Rubber is non-magnetic. Magnetic force decreases as the cube of the distance between magnet and affected object. You'll need large, dynamic, high bandwidth magnets to track whatever pattern of magnets is used on each wheel, and respond appropriately with the correct force at any instant. |
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Could it be done? I don't see any solid reason why not. Could it be done efficiently? I seriously doubt it. |
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But...since this is the halfbakery, I'll forget any requirements for practicality or efficiency. [+] |
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I dispute the statement that stationary magnets could not be used as the constant support field (not the control field, just the field to hold the wheel in place). Arrange thin magnets radially, such that each one has the same poles facing inward and outward. The wheel will present a semi-uniform field of a single polarity to any outside magnets (the opposite field will be drected into the center of the wheel--perhaps the repulsive forces could be used to supplement air as a means of keeping the wheel spherical but deformable). |
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Yeah [21], but the book never mentioned the spherical wheels that were in the movie. |
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Also, [belgareth], how would shocks work with your wheels? |
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My mouse balls gets a lot of grit, hair, and other frictive (my word) particles lodged up inside them. How would you keeps your balls clean? |
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