air-motor

"Exactly, and the air-motor turns over the dynamo which starts generating electricity right away."

The Boy Inventors' Radio Telephone Richard Bonner

Just then, however, she came across a paragraph in a German newspaper in Munich which said that a great scientific man in Berlin had completed an air-motor at last, after years of study, and that it worked tolerably, enough to demonstrate the principle, but could never be of any practical use because the chemical product on which it ultimately depended was so enormously expensive.

The Little City of Hope A Christmas Story 1881