I was looking at a picture the other day that most readers are undoubtedly familiar with - Pieter Breugel's The Tower of Babel:
Click on it to enlarge if you like. In the foreground there are some figures - apparently the Kingly figure with a few serfs bowed down in front is Nimrod. You know, I am certainly no bible scholar, but I managed to make it to my mid-forties without knowing that 'nimrod', a term of insult not uncommonly shouted out in my primary school days, actually referred to a historical person. Anyway, the oil painting by Breugel is quite stunning I think, especially since it involves construction of a tower! Looking more closely at it I noticed the timber framed devices and structures of various sorts, and a few different sorts of cranes - by far the most intriguing is this one:
Again, click to enlarge. What a funky looking thing! See the two men walking in one of the wheels? I did some digging and researching, and it turns out that is a type of crane called a treadwheel crane. Like a wheel for mice to run in, these cranes operated on the basis of having several people walk in the wheels. The crane pictured in the painting is quite accurately done - here a 1886 photograph of a treadwheel crane from Brugge, Belgium, attributed to Roger Kokken:
Wikipedia has a write up on these cranes of course. I also found a great site with an excellent article on the history of human-powered cranes: Low Tech Magazine. Worth a bookmark - also most definitely worth a read is the article on Chinese wheelbarrows on that site.
What appeals to me about them is their quirky shape and their fairly complex woodwork - here's another example from Brugge - a modern reconstruction:
These cranes with their boarded up covering were quite durable - several of the one's I've come across in my reading seem to have lasted 300~400 years, and such cranes were in use until the latter part of the 1800s when steel cranes began to supplant them.
I wonder what sort of emergency braking mechanisms these cranes had, if any? I mean, you can imagine the consequences with some huge stone lifted high up and then one of the walkers trips...
I've come across many references to cranes and their construction in old French Carpentry texts - Mazerolle, for example, shows a couple of small carpenter's hoisting cranes - chèvre - in the first part of the book, along with other carpentry tools of the day (mid 1800's):
A similar crane, and all it's parts, is shown in the J. Krafft book Traité Sur l'art de la Charpente Théorique et Pratique at the library of Congress in D.C. . Also in that text is shown a larger version for lifting stones:
While this looks at first glance like a treadwheel crane, the front elevation view shows that such is not the case.
It's a great pleasure, if not a voyage of discovery, to look through old carpentry texts to see the sorts of work once considered part of the trade - cranes, timber centering for bridges arches and tunnels, wall reinforcement, performing arts stages with moving floors, etc. The replacements for wood in all these fields is invariably metal, which, while it serves it's purpose admirably, is a product of comparatively high technology, high embedded energy, and industrial organization.
I suspect such a system as we have is but one of the many unsustainable bubbles piggybacked upon cheap, abundant sources of concentrated energy (timber then coal, and finally petroleum). It would not be far-fetched to think, given the opposing directions in which the supply and demand curves for energy are heading, that some of these old-fashioned devices made of timber, and the techniques for constructing them may one day have use again. In a funny way, I hope so. I'd rather make a traditional Chinese wooden wheelbarrow than buy a metal Chinese-made piece of junk from a box store. Wooden trestles, wooden cranes - bring 'em on!