VOGEL, S. : Muscle as Engine: A Biomechanical Look at Some Ancient Tasks

Using muscle to power large-scale tasks presents specific difficulties. For instance, the relatively uniform size of people and draft animals imposes problems of scaling, and muscle’s inability to produce rotary motion means that non-functional mass must be accelerated and decelerated. Thus (1) the blocks used for the Egyptian pyramids may have deliberately been made large in order to minimize the surface area that had to be cut and dressed�perhaps we should focus less on how they were moved than on how the quarries could produce a well-cut stone every two minutes. The blocks were certainly dwarfed by stones moved long distances by less socially-elaborate cultures. (2) Oars and paddles do well for small boats, but if oar power is to scale with anything close to hull area, multiple manning of each is necessary. As a result, the masses of the oars of the great triremes and galleys, often over 100 kg each, imposed excessive inertial loads. A good alternative, treadmill-powered paddle-wheels, saw little use outside China. (3) Ballistae, using stretched tendon as energy store, minimized non-functional moving mass but were limited in both force and power to what one or two artillerymen could generate. By contrast, medieval trebuchets, using gravitational storage, could employ large numbers of operators, but their massive arms imposed low inertial efficiencies.