Īfter describing the device's construction (see above) he concludes: He describes them as:īrazen æolipylæ, which clearly shew that an attentive examination of human inventions often leads to a knowledge of the general laws of nature. Vitruvius, on the other hand, mentions use of the aeolipile for demonstrating the physical properties of the weather. Hero's drawing shows a standalone device, and was presumably intended as a "temple wonder", like many of the other devices described in Pneumatica. A source described it as a mere curiosity for the ancient Greeks, or a "party trick". It is not known whether the aeolipile was put to any practical use in ancient times, and if it was seen as a pragmatic device, a whimsical novelty, an object of reverence, or some other thing. As the cauldron gets hot it will be found that the steam, entering the ball through E F G, passes out through the bent tubes towards the lid, and causes the ball to revolve, as in the case of the dancing figures. Opposite to the extremity G place a pivot, L M, resting on the lid C D and let the ball contain two bent pipes, communicating with it at the opposite extremities of a diameter, and bent in opposite directions, the bends being at right angles and across the lines F G, L M. 50), containing water, and covered at the mouth by the lid C D with this the bent tube E F G communicates, the extremity of the tube being fitted into a hollow ball, H K. A fire is ignited under a cauldron, A B, (fig. PLACE a cauldron over a fire: a ball shall revolve on a pivot.
#ANCIENT CITIES STEAM HOW TO#
10–70 CE) takes a more practical approach, in that he gives instructions how to make one: As soon, however, as the water begins to boil, a violent wind issues forth. Prior to the water being heated over the fire, but little wind is emitted. 15 CE) mentions aeolipiles by name:Īeolipilae are hollow brazen vessels, which have an opening or mouth of small size, by means of which they can be filled with water. He wrote the first treatises on the science of compressed air and its uses in pumps. This can be seen in the illustration of a classroom model shown here.īoth Hero and Vitruvius draw on the much earlier work by Ctesibius (285–222 BCE), also known as Ktēsíbios or Tesibius, who was an inventor and mathematician in Alexandria, Ptolemaic Egypt. Alternatively the rotating chamber may itself serve as the boiler, and this arrangement greatly simplifies the pivot/bearing arrangements, as they then do not need to pass steam. Where this is the case, the boiler is connected to the rotating chamber by a pair of pipes that also serve as the pivots for the chamber.
Typically, and as Hero described the device, the water is heated in a simple boiler which forms part of a stand for the rotating vessel. Aerodynamic drag and frictional forces in the bearings build up quickly with increasing rotational speed ( rpm) and consume the accelerating torque, eventually cancelling it and achieving a steady state speed. When the nozzles, pointing in different directions, produce forces along different lines of action perpendicular to the axis of the bearings, the thrusts combine to result in a rotational moment (mechanical couple), or torque, causing the vessel to spin about its axis. When the vessel is pressurised with steam, the gas is expelled out of the nozzles, which generates thrust due to the rocket principle as a consequence of the 2nd and 3rd of Newton's laws of motion. The aeolipile usually consists of a spherical or cylindrical vessel with oppositely bent or curved nozzles projecting outwards.
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