In the November 1989 issue of Gas Engine Magazine was a history of the Aermotor Windmill Corporation. It is a good history of the Aermotor windmill business, but it does not mention that they also built gas engines. Their small pumping engine must have been made in considerable numbers, as examples are frequently seen in shows. Collectors call it the ‘eight cycle’ engine as it fires once in four revolutions. This alleviated any need for a cooling fan. Figures A and B show design details of the engine. Note the very small fuel tank. The owner put in just enough fuel to pump the amount of water needed.
The picture of the power engine with fluted hopper shows the Aermotor general purpose engine which was built in 2 and 4 HP models. Convection air flow over the fluted cooler would carry away some heat and reduce water consumption.
Aermotor also built heavy back geared pumping engines. These seem to be the same basic engines as those with the fluted cooler, except that the engines are cooled with well water. The pump was in a pit under the engine. The pumps were built with 3,5, or 7 inch cylinders.
The figures are from the May 1, 1922 parts list for Aermotor gasoline engines. The company was then Aermotor Co., 2500 Roosevelt Rd., Chicago. All the engines were make and break, battery powered. A magneto was an option for the small pumping engine, but I have never seen one.