Build your own windmill

A simple windmill that works like a hammer drill and for which the material for the head, wheel and tail cost less than K4 500 (R6 000/US$450) is a cheap and reliable solution to supplying water to livestock watering points.

The first windmill Casper van Tonder built and erected is still working after 45 years – with its original bearings and cylinders. Casper has had a passion for working with metal for many years and boasts several designs and patents to his name.

He and his wife, Corrie, live with their son Jacobus and his wife Tanya on the farm Ruigtevlei, near Reddersburg in South Africa. The farm was originally purchased by his grandfather, also Casper, and has been owned by the Van Tonder family since 1928.

The first windmill, which Casper built in 1970 and which has been operating since then without any major problems, is serviced annually.


The wheel of the windmill is attached to a 40 mm crankshaft with three bearing assemblies. Two of them are used to attach the wheel shaft to a rectangular base frame made of 50 mm x 6 mm angle iron, with the third bearing connecting the crankshaft to a frame hinge.

A sketch of Casper’s homemade windmill. It’s cheap and works perfectly.

PHOTO 1 shows the angle iron base and where the wheel shaft is attached on the right-hand side to the two base angle irons.


PHOTO 2 shows the attachment of the bearing assembly to the crankshaft, as well as its connection to the upper frame hinge. The picture also shows the other moving parts: the two axles with lubricating nipples for the connecting rod and the rear frame hinge.


When the wheel of the windmill turns, the crankshaft lifts the third bearing and thus the frame hinge, which lifts the pump-rod up about 4 cm to 6 cm (PHOTO 3). Casper says the relatively short stroke length of about 50 mm does not hinder the operation of the windmill and there is not much more wear and tear than with a longer stroke length.



The maintenance of his windmill is minimal. Grease should preferably be applied every 6 months. If the 3 bearings need to be replaced, they cost less than K80 each. So far this has not been needed with his existing windmill.

If the bearings need to be replaced, he just loosens the 6 bolts of the bearing assemblies and lowers the windmill wheel with its shaft to the ground. After the bearings have been replaced, the wheel can be hoisted back up and bolted together.

Casper makes windmill wheels of 2.74 m (9 ft) and 3.048 m (10 ft) in diameter. The frame structure of the wheel and the tail are sturdier than the windmills available on the market, but the vanes, on the other hand, are made of thinner material. If one of the vanes or tails need to be replaced, it can simply be cut from a 0.8 mm metal sheet.


One of Casper’s other famous patents is the crossbow he used when he won the South African Championship in 1991 at the age of 43. He patented the bow, but it was not economical. He recalls how the participants at the event in 1991 were impressed with the performance and accuracy, but said the appearance was disappointing “because it didn’t look like Rambo’s bow”.

The bow worked on the principle of a rigid steel bow with a string, strung between elastic material on the sides. Casper has also built a pipe-car for a neighbour to drive in his lands. And then there’s a small garden tractor that he built for doing the occasional small task on the farm.

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