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Emergency descending elevator (EDE) that requires no electrical power. By Kwei K. Chang, 9/12/2011

When an emergency occurs in a very tall building (such as 911 Twin Towers), escalating all people is very difficult if not impossible. One of the main reasons is the power breakage. When power is unavailable. elevators become useless. In fact people are always advised to use stairs. Standby backup battery may be relatively safe, but complicated cable systems can fail. Even if everything is OK, the descent speed might be too slow for quick escalation. Mountain climbing mechanism is for skilled people and not for mass escaping at all. What we need is an emergency descending elevator (EDE) that does not need power supply and does not involve complicated mechanical suspending system, and that can descent people with high descending speed and slow down to safe speed upon landing. One might think, this kind of design, even exists; will be very complicated to make. On the contrary, sometimes things are not as complicated as they appear.

Lenz’s law According to fundamental physics, whenever a magnet moves through conducting coils, electrical current will be generated in the coils. The direction of the current is to try to oppose the motion, In other words, if a moving magnet is inserted into a conducting coil, the magnet will slow down by the motion resisting force. In vertical direction, the resistant force can balance the weight of the magnet, causing the magnet to fall with constant speed instead of free falling by g force （an object thrown out from a window of the twin towers， for instance， can reach a speed of 200 miles per hour when lands on the street）. For EDE， the landing speed can be controlled to any comfortable speed like a regular elevator does. Not only no power is needed for this to happen, electricity is actually generated in the coils. In fact this is exactly how falling water from a dam generates electricity, a principle that has been long used. The falling water turns a turbine, the turbine converts the kinetic energy into electrical energy. A good turbine is the one that has almost zero exit water speed. The EDE mentioned above applies exactly the same principle. Here we have people standing on top of a magnet surrounded by coils. When the system falls, electricity is generated and the end speed of the magnet plus passengers can be made very slow. For EDE, coils can be replaced by a metal pipe (copper, aluminum etc) with the inner diameter slightly larger than that of the cylindrical magnet. For a pipe, the current generated is eddy currents and will eventually become useless heat， thus，energy is conserved. Of course, here, our EDE is not interested in power generation at all.

As to the descending speed， one may insert plastic pipes in between metal pipe. By doing this the EDE will free fall in the plastic section and accelerates to desired high speed （because insulator is not subjected to magnetic effects）， followed by slowing down in the metal sections.

Another good thing about this is that if one put a piece of metal on the outside surface of the pipe opposite to the magnet, the metal acts as a brake or speed reducer, with no need of electricity control To deal with descending speed, portion of the pipe may use non-metal (such as plastic). The EDE will free fall in the non metal section gaining speed, and then slows down when reaches the metal section. The metal brake can aid to the control of the speed.

Since the EDE practically floats in the air （with the help of the metal brake）， complicated cable system is not needed. There is no need to worry about the possibility of mechanical failures.

Everybody can test and observe the EDE effect by purchasing a strong cylindrical shaped magnet, plus a copper or aluminum pipe slightly larger in diameter.

The following need to be considered. 1.	fire resistant material for pipe protection 2.	Ventilation 3.	The access to the braking element by the passengers can be a task since the brake is on the other side of the pipe surface 4.	The magnetic shielding, one must deal with the fact magnetic field has very low impedance and can easily penetrate metal. So the passengers need to be isolated from the strong magnetic field comes from under. 5.	The EDE is used for coming down; many EDE may be needed unless the EDE can be sent up for reuse. 6.	Possible use of magnetic powder to save storage space

These (together with mass, thickness etc) are a matter of detail engineering and are not the subject of this writing

One may wonder, if EDE applies basic physics principle, how come people never mentioned it before. The fact is, many physicists are only interested in nature phenomena and are not application oriented. A typical example is television screens. In the old time television were very blurring under sun light. The reason is that screen reflects ambient light which competes with the pictures we want to view. The solution is to make the screen totally black (plus other design consideration of cause). This is a very fundamental physics principle, yet, surprising enough, nice daytime viewable TVs have not appeared in markets until lately.

EDE was originally patent pending. The author now decides to publish the content， so that people are encouraged to contribute to the design improvement. The schematics below （to be added） are for illustration only.