THE FLYWHEEL BUS

About 25/Mo of the energy consumption in this country goes for transportation, and most of that is accomplished by internal combustion engines with woefully low efficiencies (about 20to). With presently used fuels, they pollute; and they are noisy to boot.

One of the obvious solutions is to power transportation by electricity. This just about doubles the overall conversion efficiency, drastically reduces the noise, and lets pollution be controlled centrally.

Battery storage is still waiting for a major breakthrough, but there are now two other methods of electrical transportation on the horizon: One is magnetic levitation for fast, long distance mass transportation, to which we will return in a future issue.

The other is an idea which is brilliant in its simplicity: flywheel storage, basically the same idea as used in children's toys (a flywheel inside a mouse or car is rewed up and the toy then runs over the floor until the inertia of the flywheel is spent). This idea is now being used for urban buses, but it holds far greater possibilities for the future.

An electric trolley bus is better than a gasoline powered bus where efficiency, noise and pollution are concerned, but it has other disadvantages: It is tied to a fixed route of overhead wires, and electric buses cannot overtake each other, much less leave the wiring for a detour.

In the early fifties, the Swiss company Oerlikon introduced a bus that did not have these disadvantages of inflexibility. The Oerlikon "electrogyrobus" had a flywheel which was rewed up by an electric motor on its axis. The power supply came from overhead points at the bus stops, where the bus would contact them. But between stops, the motor was used as a generator, driven by the spinning flywheel, to run a second electric motor which drove the bus. The bus was thus electric and free to go where it pleased, provided it returned to one of the recuperation points before the flywheel ran down. Conversion of kinetic to electric energy has an unusually high efficiency (up to 98%), which makes the system highly economical.

Now Lockheed has used the same principle in a perfected version for a bus to be produced for the San Francisco Municipal Railway, which needs to make its buses more flexible. The main improvement is the 3.5 fit diameter, 600 lb flywheel, which spins at no less than 18,000 rpm in a reinforced vacuum canister to generate 200 kW (275 HP). Called "KEW" (for kinetic energy wheel), the bus will be able to travel for 6 miles before it has to tap a recuperation point (600 V DC) to rev up the flywheel again. The recuperation lasts 2 minutes. only a little longer than would be needed for liquid refueling.

Safety considerations have led to a design that operates the wheel at only 40/Mo of its capacity, and the flywhecls are rneticulo usly tested by X rays and other means for perfect symmetry.

The first two KEW buses are expected to be ready for field tests in the streets of San Francisco some time in 1975. That will also be the time for an experimental flywheel train to go on the DoT's test track near Pueblo, Colo. This train is now being developed under a $18 million federal grant by Garret AiResearch, Los Angeles.