From: tjgerman@53iss6.Waterloo.NCR.COM (Trevor German)
Newsgroups: sci.electronics
Subject: FLYWHEELS
Date: 17 Dec 92 20:15:10 GMT
Organization: Imaging Systems Division, NCR Corp, Waterloo, Ont., CANADA


	I have been following the thread about exploding flywheels and 
	would like to make the following contributions.

	1. Yes, when a fly wheel lets go or is suddenly stopped for some
	   reason, a hell of a lot of energy is available in a very short
           period of time. Unimpeded, these flywheel bits can do a lot
	   of harm. Testiment to that is a machine shop in the steel works
	   in Hamilton Ontario where a grinding disk exploded killing one
	   guy and leaving a neet line of holes in the walls and roof.

	2. Gas tanks do not explode unless there is air in them, and even
	   then only the fuel air mixture will explode, not the liquid part.
	   Holywood must take the blame for this myth. They fill the car with
	   a type of Napther (I think) and explode that in the movies, actual
	   gas tank explosions are so undramatic. (Mind you I would not
	   want to be sitting over one when it burst)

	3. Containment vessels. It has been stated that the energy still has
	   to be absorbed in a short period of time which will melt any
	   flywheel containment vessel. Wrong. The trick is not to stop the
	   ballistic parts but to deflect them within the vessel such that
	   they rattle around inside the vessel gradually releasing their
	   energy. Granted the inside of the vessel will wear during this
           process and will heat, but such vessels are practical. However,
	   the weight penalty associated with such a vessel would probably
	   be impractical for a personal vehicle.

	4. break-away. Significant effort must be applied to ensure that a
	   partial fracture of the flywheel results in its complete 
	   destruction. Imbalance caused by loosing part of one side
	   can cause more damage that a complete failure if not properly
	   handled.
	
	5. Gyroscopic effects. Particular care must be applied to ensure
	   that the flywheel is mounted in such a way that its gyroscopic
	   effect does not disturb the handling of the vehicle. The flywheel
	   must be mounted with a verticle axis and gimbled slightly to allow
	   the vehicle to tilt either fore-aft or sideways. Horizontal
	   axis flywheels would make cornering intresting.

	6. All of the above requires significant engineering and expensive
	   hardware that is way out of the price range of domestic transports.
	
	7. Losses. For long duration energy storage, use of magnetic bearings
	   or somesuch and containment in a vacuum would be required to 
	   prevent significant power loss, esp in town. MORE EXPENSE
	
	I sound as if I'm mostly knocking here, in fact, I'm not really. This
	technique has been used, in Holand I think, where they built an
	experimental bus that had electric drive with regenerative braking
	that used the flywheel as a load for the braking-generators. The
	energy was extracted from the flywheel during acceleration. 
	Apparently is was succesful but canned due to cost.

	Interestingly, using super-conducting coils for energy storage can
	be though of as a kind of electron flywheel and has much more
	promise due to simpler mechanics. Carrying around all that liquid
	gas is a bit of a problem though.

	That brings up another point though. Why can't compressed air be
	used directly to drive a vehicle. I guess it's a quantity thing,
	but I can visualize a compressed air turbine being used as a power
	plant. A large chunk of industry uses the stuff for a power source
	after all.

	It is intresting, however, when talking efficiency, that people
	ignore big chunks of the equation. Electic cars are always touted
	as being highly efficient, however, no-one ever talks about the
	efficiency of how the electricity was made and transmited in the
	first place. This is bad enough when discussing Hydro but when its
	coal or oil fired the efficiency of the whole equation is not that
	great. Like whats the point making the cars electric if it just puts 
	more smoke up the electric companies chimney. Concentrates the problem
	of pollution also.

	Enough Already

 
--
       >|  "Only average people            | Trevor J German BSc    |<
       >|        never make mistakes."     | NCR, Waterloo, Ontario |<
       >| tjgerman@53iss6.Waterloo.NCR.COM | Canada.                |< 
Xref: sparky sci.electronics:21099 sci.energy:6245 rec.autos.tech:16876