Catching, Restoring and Releasing Old Windmills

Old windmills make for a surprisingly exciting hobby.


| April 2003



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The Aermotor Model 502 windmill

Restoring old windmills is sometimes more exciting and adventurous than it sounds. One day a while back, a neighbor bought an old Aermotor Model 502 windmill at auction. The only hitch was that it was still standing on the same farm where it was erected in the 1930s, and it was up to us to catch it, restore it and then release the windmill back into the wilds of South Dakota.

Actually, I didn't know it was an Aermotor windmill until I climbed up 45 feet past the bees and grapevines to its perch high above the old farm site. My helper stood on the ground, frantically waving a board at a swarm of mosquitoes. Above the tree line, a stiff breeze took away the insects, and the last 30 feet was easier to climb. I instantly realized that the windmill's tail was different when I got a better look at the top, because corrugated steel was installed to stiffen the design. When I finally turned the mill's motor around, I discovered it was a rare Model 502.

Before work on the windmill could start, we cleared a path through the grove of trees to make room for the long trailer and crane we needed to move the windmill. We attached a bridle high enough so the mill sat upright after we torched off the legs. As the crane lifted the mill, it overbalanced and the tail just barely missed the crane's boom. Mike, the crane's driver, lowered the unit, and we carefully removed the tail. Next, we laid the tower on the trailer, wired the tail to the top and collected all the fan sections and brace rods that had been piled by one of the towers. It was amazing to imagine that those parts had sat undisturbed beside the mill since the 1930s when electricity arrived at the farm and the windmill was decommissioned.

The man who'd bought all the iron on site for $25 offered to sell us another open-geared Aermotor head, fan and tail he discovered on the property for $50. It was difficult to pass up, because that mill originally sat on the tower we'd just moved. As luck would have it, the farm was owned by the same family for more than 100 years, and all that remained were the windmills in the grove. Sometimes, dumb luck plays a big part in collecting.

The 502 was the first attempt at a self-oiler made by Aermotor. The model is fragile and tends to bend. Worse yet, the mechanism didn't oil the guide roller and upper yoke, which caused premature failure. Aermotor only built the 502 in 1915, followed by the better-manufactured 602 for 16 years. The Model 702 is still in production, while the 802 is a recent addition to the line. Several shops around the United States build and rebuild mills; we get our work done at Dakota Windmill and Supply, in Hurley, S.D.

Very early mills used a direct stroke for each revolution of the fan, with an up-and-down stroke in the pump rod. The design worked well in a good breeze, although the rods could get a bit jerky as the mechanism aged from wear. All early mills had open-faced gears. Ideally, the gears were greased weekly, but that didn't usually happen until the mill stopped spinning. Later, open back-geared mills came out, which featured smaller gears on the fan shaft and a larger set of gears on the pumping shaft, generally in a three-to-one ratio. This design enabled the mills to pump water with lighter breezes and smoother operation.