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General Motors "Powerama" 1955 Chicago automobile Motorama show

Sunmobile was a model of a solar-powered automobile.[1][2][3][4] William G. Cobb of the General Motors Corporation built and demonstrated his 15-inch long model at the 1955 General Motors car show in Chicago on August 31, 1955.[1][2][3][4][5] The automobile was a futuristic miniature representation to show the possibilities of solar energy. Since it was a miniature model, it could not be driven by a person.[2][4][6]


The name of the 1955 General Motors Motorama car show where Cobb's model car was shown was General Motors Powerama.[1] General Motors at the time said the car that showed futuristic capabilities was not practical because even if the solar cells ran at 100% efficiency they would only produce 12 horse-power, not enough to propel an average automobile of the time.[7]

Cobb showed and introduced the field of photovoltaics to a car show that had over 2,000,000 visitors. At the time all automobiles were run by gasoline engines. Cobb's Sunmobile model had 12 selenium photoelectric cells on top of a balsa wood body. These solar cells were connected in series-parallel and converted the sun light directly into electricity, which in turn ran a small low-inertia electric motor. The motor rotated at 2000 r.p.m. and ran on 1.5 volts. The motor's energy in turn was transferred to the model car's drive shaft, which then in turn transferred the energy through its rear axle by a pulley to the car's wheels which moved the car forward.[8]

The model car balsa wood body was in five sections. It had two center sections that were hollowed out to receive a pine chassis, the electric motor, and the drive mechanism. There were precision gears from the electric motor to the wheels. They had a 3 to 1 ratio, with the smallest gear on the motor and the larger gear on the drive mechanism that propelled the rear wheels. These gears were connected with a ladder-type chain connected to their sprockets. The rubber tires, obtained at a hobby shop, were one and a half inches in diameter. The rear axle was one-eighth inch in diameter. The wiring for the solar cells to the electric motor was by standard No. 20 insulated stranded copper wire.[8]

See also[edit]


  1. ^ a b c William Cobb demonstrates first solar-powered car
  2. ^ a b c August 31, 1955 : William Cobb Demonstrates Solar-Powered Car Archived July 24, 2011, at the Wayback Machine
  3. ^ a b Solar Energy, the best solution
  4. ^ a b c First Solar Car Archived 2012-04-14 at the Wayback Machine
  5. ^ Future Solar Cars Archived 2011-01-28 at the Wayback Machine
  6. ^ Popular Mechanics, September 1955, Vol. 104, No. 3, ISSN 0032-4558, Published by Hearst Magazines
  7. ^ Popular Science, October 1955, Vol. 167, No. 4, ISSN 0161-7370, Published by Bonnier Corporation
  8. ^ a b Popular Mechanics, Feb 1957, Vol. 107, No. 2, p. 233, Published by Hearst Magazines, ISSN 0032-4558

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