"Behold the upright shaft!"
An upright shaft like this one is at the heart of every mill. Without the vertical, rotating main gear shaft, you wouldn’t be able to mill the grain. Up in the cap, the upright shaft is connected via the wind shaft to the sweep, and it transfers the wind energy to the millstones that grind the grain. If you stand by the banister and look up, you’ll see the various gears that drive the upright shaft.
The upright shaft does wear a crown of sorts: a large gear wheel called the great spur gear. Its cogs are evenly spaced around the entire circumference. The upright shaft stands on what’s known as the footstep bearing, which allows it to rotate. When the shaft rotates, the cogs of the great spur gear mesh with those of the smaller stone nut. That drives the stone shaft, or stone spindle, which in turn sets the upper millstone, or runner, in motion. We’ll be telling you more about the milling process at the tun – that’s the wooden case that encloses the millstones.
The upright shaft has to be regularly maintained so it runs smoothly. The footstep bearing is oiled once a month; the cogs are rubbed with beeswax once or twice a year to keep abrasion to a minimum. To ensure minimal wear, they’re made of different kinds of wood, including beech and oak. The oak beam that serves as the upright shaft is about 500 years old, and will hopefully do its job for many more years to come.
Photos: © Dagmar Trüpschuch und Förderkreis Alte Mühle Donsbrüggen