Image description: This photograph, taken by Lt. deBerri of the Signal Corps on May 1, 1918, shows a broken blade from a slate regulating air fan. The fan, of type Model "R," had undergone a centrifugal test and reached a speed of 6,500 revolutions per minute. The photo was taken at the Bureau of Standards in Washington, and was not intended for publication.

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Size: 9183px × 6305px
Photo credit: © piemags/NSC / Alamy / Afripics
License: Licensed
Model Released: No

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