A maximum traction double truck. This type of truck has four wheels, two large and two small. The larger wheels make up seventy percent of the weight of the truck. The motor is hung and geared to the larger wheels. Enough pressure is applied to the large wheels that the smaller wheels are able to stay on the track while going around curves.
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International Correspondence Schools A Textbook on Electric Lighting and Railways (Scranton, PA: International Textbook Company, 1901)