Hero's Windmill

[Marcus Minucius Audens]

The machine in the sketch is obviously a toy, however, what is unusual, is the fact that this machine was not expanded into a larger usage which could do the work of many men. Perhaps the answer lies in the slave economy of the Roman Republic and Empire. The machine, as shown, has several items which could have been very useful, but these were not utilized for the benefit of all citizens. There is no assurance that this machine was ever constructed and used for the purpose that it was designed, It is the only mention of any attempt to use wind power and it is found only in Hero’s Pneumatica (I, 43) in Alexandria.

The windmill structure was placed on a second separate stand, probably in order to move as the wind source shifted about. The radial rocker arm was operated by two radial rods (shown on the drawing) which in turn operated a piston. The word translated as ‘vanes’ is (platai) is used elsewhere to name oar-blades. This association would indicate that the meaning also indicated that the fan ‘vanes ‘ were both wooden and as stiff as oar blades. The name labeling the whole fan assembly is (anemouria). Now this word appears nowhere else except as a proper name for a promontory in Asia Minor. This would indicate a meaning related to “wind-fan," or something similar.

Apparently only two radial rods were used, which would allow the weighted piston time to drop, and force the air into the air reservoir. Considering this time cycle, it is also apparent that the fan was designed to turn slowly with only a pitch of 5% to 10% on the blades. This period of “longish intervals” (ek dialeimmatos) between the rods striking the rocker-arm, fits with the time it takes for the piston to operate.

Clearly, from its size, and from the power that it could develop, this machine was merely a model of something perhaps larger. However, should it have been expanded in size into replacing the efforts of single man or a small animal — something which could develop at least 1/4 horsepower, it would have been very useful. Considering the efforts of the Greeks, and Romans, in other areas of power usage, the situation, from what is currently known, is very puzzling!

Respectfully;
Marcus Audens