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This year, we would be remiss, if we did not acknowledge a very special centenarian. 2015 marks the 100th anniversary of the Self-Oiling Aermotor windmill. It wasn’t the first self-oiling windmill to enter the market: that was the “Wonder model A” in 1912. However, by the late 1930s, Aermotor Windmill Company of Chicago had put most other companies out of business, because of their efficient, high-quality manufacturing techniques, and their ruthlessly aggressive marketing strategies. Consequently, when we spot a windmill in the field these days, chances are, it’s an Aermotor Self-Oiling model.

Before self-oiling windmills came onto the market, farmers and ranchers – or their children – had to crawl up the shaking towers once a week to apply grease and oil to the gears and moving parts that whirled and meshed 30 to 80 feet above the ground. This task was universally loathed and feared. It seems bizarre, then, that it took almost 75 years for the first successful self-oiling windmill to enter the market. Self-oiling windmills reduced the frequency of trips up the windmill tower from weekly to annually. Instead of the gears meshing out in the open, vulnerable to rain, ice, dust and sand, all the moving parts ran in a year’s supply of sealed-in oil.

Aermotor’s Self-Oiling windmill entered the market in 1915, and was an instant success. So excellent was the design that it is still made in present day factories, largely unaltered. However, there were a few design elements of the 1915 windmill, known as the “Aermotor 502,” that were peculiar only to that model. The most obvious is the sheet metal tail, which was stamped, corrugated steel. This was a brief departure from the distinctive Aermotor vane, with its wishbone-shaped brace on the front, used from 1888-1914, and from 1916 until the present day. For reasons known only to the designers (and they’re all dead), this corrugated vane was used only one year, and then replaced with the earlier design.

Another feature peculiar to the 502 are the buffers. On the back of the gearbox sprouted two “buffer springs,” like small horns on a bucket calf. These were designed to absorb the shock of the tail, as it directed the wheel into the wind. A steel member shaped like a number “7” was bolted to the top of the “tailbone”, and this is what bumped up against the springs. This worked fine in light winds, but in storms, strong winds banged the tailbone against the buffers with enough force to break them completely off the back of the gearbox. In 1916, a heavy, two-piece cast iron buffer replaced these small springs, and this resolved the problem.

The oiling system on the 502, and later models, is nothing short of brilliant. A year’s supply of lightweight, straight-grade oil (10 weight or lighter) bathes all the moving parts. A sheet metal helmet keeps dirt and moisture from getting in. The hub that carries the wheel is hollow, and, as the wheel turns, a thin stream of oil gradually works its way down the main shaft and fills the cavity of the hub. An “oil collector” scrapes the oil off the inside of the hub and sends it into a special groove in the main casting, which dumps back into the gearbox, to be recycled ad infinitum. Thus the main shaft, along with all other moving parts, is constantly bathed in oil.

One problem with the 1915 design (which was corrected by 1919) was a springy wire oil flipper, which took oil from the large gears and flung it onto the upper mechanism that controlled the pumping motion of the windmill. When the windmill ran backwards in changing or light winds, the springy wires got tangled up in the gear teeth, and bent. Consequently, they no longer flipped oil upwards, and the upper mechanism would wear out. In 1920, the flipper was replaced with an oiling ring, which rolled on top of the gear, carrying oil to the upper mechanism. This corrected the lubrication problems found in the 1915 model.

100 years after its introduction to the buying market, the Self-Oiling Aermotor is still manufactured in San Angelo, Texas, with “clone” Aermotor-type windmills being made in various places around the world. Their strength, efficiency and high quality have made them an enduring and vital part of rural life, and the most frequently spotted windmill by observers. They stand as testimonies to American ingenuity.

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