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The automatic tripods of Hephaestus
They were programmed auto-mobile tripods which, according to Homer, were built by Hephaestus ''with golden wheels that could automatically enter the assembly of the gods and again return to their residence''.
The development and application of the relative technology, by the Alexandrian engineers (Philon, Heron) to corresponding auto-mobile vehicles, allows us its hypothetical re-establishment.
The motion producing mechanism of the tripod consisted of a) a cylindrical clepsydra filled with millet, b) a lead weight placed inside the clepsydra, c) two ropes which connected the weight and the axles of the two rear wheels with the help of loops and transversal pins and d) a sliding operation switch.
The motion programming mechanism consisted of three types of rope circumvolution on the two independent driving axles of the wheels. The right circumvolution ensured the right turning of the wheels and therefore the forward course of the automatic tripod. The left circumvolution ensured the left turning of the wheels and therefore the reverse course of the automatic tripod. The free circumvolution ensured the immobility of the wheels and therefore the stillness of the automatic tripod for ''the serving of the gods''. The right circumvolution on the right wheel and simultaneously the free circumvolution on the left wheel ensured the turn of the automatic tripod towards the left while the free circumvolution on the right wheel and simultaneously the right circumvolution on the left wheel ensured its turn towards the right.
With the pulling of the slide, the clepsydra began to empty at a steady pace and the lead weight fell at the same speed pulling the ropes of the drive wheels.
The combination of circumvolution on each driving axle ensured whichever desired automatic course of the tripod in its space, its required stops and finally the return to its starting position.
SOURCES: ''Heron of Alexandria, Automatopoetike'', ''Homer, Iliad''