The Midgley Optical Indicator:
A Relic of Automotive and Aviation History is Rediscovered.
 New Information!  Revised 3/9/00
The year was 1916; the place was that hotbed of invention and innovation, Dayton, Ohio.  Charles F. Kettering assigned Thomas Midgley, Jr. to the job of finding the cause of engine knock, or "pinging". They first used a Dobbie-McInnes manograph to show that the knock was not the result of pre-ignition, which was a popular hypothesis of the time; but that it was actually the result of a violent pressure rise FOLLOWING ignition. The Dobbie-McInnes apparatus was deemed unsuitable for further detailed research, so Midgley and his assistant T.A. Boyd developed a high speed camera to record what was happening. They also developed a "bouncing pin" indicator that measured the amount of knock.  After years of trial-and-error testing of various additives with this device, in 1921 tetraethyl lead was discovered to have the optimum properties and "Ethyl" gasoline was born.  Leaded gasoline was first sold in 1923.
The device pictured below is believed to be Midgley's first apparatus which did not make use of the Dobbie-McInnes pressure indicator.  It was recently "rediscovered" via the internet and purchased by Ohio native Mark R. Everhart, now a resident of Boise, ID.  It is currently on loan to Carillon Historical Park in Dayton, Ohio, where it will reside with other artifacts of GM's Dayton Research Labs, such as the first automobile self-starter.
Any information on the history and operation of this device would be greatly appreciated.  Send E-mail to Mark Everhart:
Latest Development 3/8/2000:
The Second-generation Indicator head has been acquired by Mark Everhart.  Pictures of the new acquisition are directly below.  This component more closely resembles the device depicted in the Patent Drawing (shown further below).
It is planned for this piece to be put on exhibit later in the year at the Carillon Historical Park with its predecessor.

Below is a copy of the Official Gazette of the U.S. Patent Office
for April 15, 1924 announcing the granting of
Patent Number 1,490,223 for the Midgley Indicator
Below is an illustration (based on the photograph at top) from the circa 1950s book "Short Stories of Science and Invention" by C.F. Kettering, published by the G.M. Information Rack Service.
More Links!
Charles F. Kettering, enshrined in the National Aviation Hall of Fame
A more personal view of Thomas Midgley, Jr.
Quotations of Charles F. Kettering
Updated 3/9/2000
Copyright 2000 by Mark R. Everhart, all rights reserved.

Michael "Miserable Failure" Moore