THE FLYWHEEL ADVANCES

So what's new in flywheels?

For one thing, they are moving from the drawing boards to the test tracks, and from the test tracks into experimental operation. Garrett Corporation's vehicle, which we reported on the Colorado test track in Jan. 74, is now running in two experimental versions in New York City's subway. Each car is fitted with two flywheel units spinning at up to 15,000 rpm, and saves from 25% to 40% of the formerly consumed energy per car. The city's subway fleet has 6,700 cars, and if the cars were massproduced, they would cost about $100,000 each (not counting the $1.4 million the Urban Mass Transp. Admin. paid for the development by Garrett). But it's a start.

On the other hand, the two San Francisco trolleybuses that were to have been fitted with flywheels by Lockheed under a $900,000 UMTA contract (AtE Jan 74) were abandoned UMTA decided that the materials for the flywheels were not yet adequate.

That is a problem a small California company, US Flywheels Inc., is working on. Using Du Pont's Kevlar, a material with a higher strength-to-weight ratio than steel, and a $200,000 UMTA-grant, the company hopes to develop a prototype of a commuter automobile running at 60 mph for 50 miles at a cost of 1 cent/mile from a single overnight charge drawn from a 220 V household outlet to have the flywheel spinning in the morning. US Flywheels will work on the car with Lear Motors Co., hoping that the latter will do better than they did with their steamturbine bus.

From any point of view, flywheel storage is still embryonic, but an important event took place last month - the publication of the Proceedings of the 1975 Flywheel Technology Symposium held last November in Berkeley, Calif., sponsored by ERDA, with the hard work done by the Lawrence Livermore Laboratory. Its 39 papers, though most are theoretical, represent an excellent (and also the only) comprehensive report on present flywheel technology and its applications. ($3.85 from the Government Printing Office, Washington, DC 20402 allow 4 weeks for delivery even if they get it right the first time.)

There are new bearings, materials, compositions, shapes, configurations, and applications; and there are new records in speed, reliability, energy density and other parameters (unfortunately not attained simultaneously).

Much of the research is devoted to the magnetic (contactless) bearing that lets the flywheel float in space (it is ready for small flywheels of a few inches in diameter, but not yet for the big stuff, where hermetic vacuum seals are not readily available, either); and much of the research is devoted to materials and configurations evidently the future belongs to composite flywheels with non-metallic materials arranged in rings of different widths and varying thickness. As so often in engineering, the materials themselves are a crucial problem for development.

Quite obviously we cannot summarize several hundred man-years of research in a few short paragraphs, but here are summaries of two of the many impressive papers that caught our eye: