These are rare photos of the Chalk Bicycle Wheel wind turbine from the 1970s that are in the collection of Vaughn Nelson. The source of the photos and their location are lost to the fog of time. Nelson, one of wind energy’s pioneers at West Texas State University thinks some of the photos are from Chalk himself. One is of the Rocky Flats test center.

Here’s some specs that Nelson found in his files. The turbine was developed by Thomas O. Chalk, a Florida airplane mechanic. He’s mentioned in Volta Torrey’s Wind-Catchers on page 161. The turbine was marketed by American Wind Turbine Company.

Outside diameter    15ft.3in

Inside diameter      5ft.3in

Length of blades    5 ft

Number of blades  48

Chord of blades

Blade pitch         9° outside,  18° inside rim

Blade twist    9°

Support wires           0.062 in diameter

Number of wires      not covered by blades = 96

Length of hub in axial direction     2 ft

Airfoil Clark Y