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Avery 25-50


There is a 1920s vintage Avery 25-50 Model in the Museum collection. It has a four-cylinder horizontally opposed engine with a 6½ x 7 inch bore and stroke. This type of engine was popular with various manufacturers from 1912 to the mid 1920s. This configuration of engine is only currently used in a few small modern engines and not with today’s industrial agricultural engines.

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Two 12-25 hp engines were put side by side with each other on a platform to create the 25-50 sliding engine used in this tractor. A sliding engine consists of the engine mounted on a frame that slides back and forth on the main tractor frame. The whole engine is mounted on a plank that when slid back, causes the tractor to go forward. And when the whole engine is moved forward it causes the tractor to move backwards. There are two gears on this tractor. The first is a crankshaft, or pinion, gear. The second is the intermediate/reduction gear. This gear meshes with the forward or reverse driving gear.

This tractor runs on kerosene, with an engine speed of 700 rpm at full throttle. It has two forward speeds and one reverse gear.

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