h a l f b a k e r yThere goes my teleportation concept.
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Normally when an aircraft is descending with its wheels down, they do not rotate until they SCREECH up to speed (0-200+kph in 1 second) upon impact with the ground. There's quite a bit of smoke and burned rubber involved in that.
I've read about how some aircraft might be equipped with electric motors
to pre-spin the wheels, so that they don't screech, and thus the tires don't get so much wear and tear. But motors are weighty, so most planes don't have this feature.
However, there is an alternative. Let's start with a gadget known as a "Pelton Wheel" (see link). Let's imagine cutting it in half so we have two disks instead of one. Now let's make it out of rubber, and attach the halves to the side-walls of an aircraft tire (actually the tires should be constructed this way). The part of the wheel that contacts the ground is not changed in any way. Only a small amount of weight is added!
It's important to mount the tire so that at the ground, the concavities of the rubber cups are facing forward, and the convexities of the cups are facing rearward. Now consider a decending plane that is lowering its wheels: It is moving through the air at 200+kph, and those cups on the sidewalls are going to catch some of the air passing by. The wheel will therefore start to spin.
Some experimentation may be needed to figure out big the rubber cups really need to be, so that the wheel spins up to just the right speed as the plane lands on the ground.
Pelton Wheel
http://en.wikipedia...g/wiki/Pelton_wheel
As mentioned in the main text [Vernon, Sep 12 2008]
June 16 2008 tire blow out
http://abcnews.go.c...ireStory?id=5180508
Airliner's Tires Blow out Upon Landing in Phoenix [piwoslaw, Sep 12 2008]
Preserving Aircraft Tires
http://mb-soft.com/public/planetir.html
Numbers... [piwoslaw, Sep 12 2008]
Patent already filed
http://www.med.miam...dspace/UM06-23.html
The only difference I see is rubber "impellers" vs. rubber "cups". [scad mientist, Sep 12 2008]
Literature on the subject
http://yarchive.net...tire_prespin.html#2
Published landing gear design book addresses this and says that research shows this is not cost effective. [scad mientist, Sep 12 2008]
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I think this will not only save the ground crew some work and the airline some money, but will increase the safety of landings. Tire blow-outs are a nuicence at least, and a real safety hazard sometimes. For example on June 18 2008 a Southwest Airlines jet's tires caught fire [see link] (this was from an overheated brake, but the forces acting on a tire at landing can also cause high temperatures). Even if a tire blows and noone gets hurt, then the runway is closed for some time, causing delays... |
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[Vernon] You're not the only one who good got this good idea. See link for some calculations. |
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Tires are designed to take those loads. |
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If you are going to add material to the wheel, you might as well put it in the treads, where it is most needed. |
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I just started wondering: What does the airflow look like under a landing airplane? Might there be some turbulence etc. that would somehow interact with the wheels, messing up the direction and/or speed of their spin? This is probably a dumb question. Sorry. |
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// put it in the treads, where it is most needed. // |
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Well, why not indeed? Make the tread thicker, and appropriately cup shaped. |
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There's actually an advantage to the sudden drag induced when the tyres contact the runway. |
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In the final stage of landing, called the flare, the aircraft is in the ground-effect region and actually experiencing increasing lift as it descends, even though it is shedding forward momentum. As the tyres contact, the plane brakes, the airspeed drops, and the lift is reduced, thus reducing the chances of rebounding into the air ...... |
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There's no way induced drag from LG tyres does anything to a 747. |
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A Savonius turbine, as you seem to be describing, will never reach wind speed, as it relies on drag i.e. turning slower than the wind to operate. So delete the last paragraph in the idea body and I'll be happy. |
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//I've read about how some aircraft might be equipped with electric motors to pre-spin the wheels, ... ...But motors are weighty, so most planes don't have this feature.//
Well, just consider hydraulic motors instead. I believe they are just a fraction of the weight of your proposed "pelton-wheel" tire construction. |
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a small gas turbine to spin up the wheels using pneumatics would be sooo simple, small compact light, soo easy, how can you resist it? The simplicity, the robustness the flaky crust. Edit the idea, you know you want to, it'll be so great! Please? Everyone is doing it! |
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