Machines: Saw, Trap, Hoist, and Automata
Bib. Nat. ms. fr. 19093, fol. 44
This image is perhaps the most dear to historians of technology. This collection of machines, including an automatic sawmill, automaton, and what has been claimed as one of the earliest illustrations of a mechanical clock escapement, have generated much interest, many pages, and at least one video (a computer rendition of the sawmill in action). The images on the page are:
Top
Sawmill: "How to make a saw operate itself."
Crossbow trap: "How to make a crossbow that never misses."
Middle
Escapement(?): "How to make an angel keep pointing his finger toward the sun."
Hoist: "How to make the most powerful engine for lifting weights."
Bottom
Automaton: "How to make the eagle face the Deacon while the Gospel is being read."
All the images are less than crystal clear, and are the sorts of technical sketches that make perfect sense to someone who is familiar with the item being drawn, but to the uninitiated may not make much sense at all. The sawmill is a good case in point. It is drawn in absolutely flat perpspective, so one gets both a side and top view simultaneously. In the upper left corner the faint wavy lines indicate a stream which turns the top (spoked) waterwheel, despite the crudely-drawn talon-like paddle blades. This axle then turns the center, smaller wheel with the six spikes on its rim which is the automatic feed mechanism for the log, shown resting in four pairs of guide posts. The waterwheel's axle also turns the spokes at the bottom which engage on the triangular frame at the bottom left of the illustration. As the axle turns, each spoke in turn comes down on the right leg of the frame, pushing it (and the saw blade with it) down, cutting the wood. The saw is then lifted by the sapling pole (indicated by branch stumps along its length) back up to ready it for the next powerstroke. In order to make this saw work, one would have to gear the feeding mechanism to feed it a bit slower than is shown here, but its principles are sound.
The crossbow trap is fairly straight forward, although the purpose of the funnel-like piece just below the stock is not clear. It may perhaps be a "tiller" of sorts, allowing the crossbow to pivot towards whatever crosses the taut line below. The hoist, too, is fairly clear, although Villard's ability to draw a helical screw leaves a lot to be desired. The eagle automata agains shows his superior ability to draw animals (at least compared to his ability to draw machines), and the mechanism follows from late Hellenistic automata construction manuals such as Heron's. The escapement has presented some problems, not only for its completely misunderstood perspective, but also for its operation. It could be a simple method for a vertical wheel to turn a vertical shaft remotely with a rope (the less interesting option), or it could be a primitive verge and foliot (the more interesting, but less likely, option). All that can be said for sure is that it was designed to make one revolution per day, since the angel (presumably attached to the vertical pole pointing up towards the saw) would need to track the sun with its finger. The regulation method and the drive mechanism are left unspecified, unless the weights are the motive force, in which case the mechanism makes even less sense. Villard obviously saw something interesting, but unfortunately, his mechanical drawing ability left it shrouded in mystery.
On the saw in particular, see Jean-Pierre and Varène Adam, "La Scie Hydraulique de Villard de Honnecourt et sa Place dans l'Histoire des Techniques," Bulletin Monumental, 143.4 (1985): 317-32.
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