A regular reader took this picture...
...of an impressive piece of antique finger-grabbing agricultural equipment, and suggested it as another illustration for the "pulley paradox". Again, if you don't know about crowned pulleys, contraptions like this look offensively impossible.
As a weekend project, I suggest commenters point to the most belt-and-pulley-infested machinery they can find on the Web.
I am also pleased to note that unless the corporate copyright enthusiasts manage to extend terms yet again, the works of W. Heath Robinson should pass into the public domain at the end of 2014.
(A few works illustrated by Robinson are already in the public domain, but I don't think any of the stuff for which he's most famous is, yet.)
27 July 2012 at 6:08 pm
whats with the crossed pulley on the top? was that put on incorrectly or is there some advantage in doing that?
27 July 2012 at 7:53 pm
Hi westmn,
It allows one pulley to rotate clockwise and the other counter-clockwise. A simple belt forces both pulleys to rotate in the same direction.
27 July 2012 at 8:01 pm
ah, seems obvious now. neato.
28 July 2012 at 10:47 am
Yeah, this is the standard way to reverse the drive of a belt. The edges hardly even abrade each other if you set it up right, and there's close to zero efficiency loss; a much better solution than throwing in a reverser gear.
At this point, you may be wondering if people used Möbius-strip belts to get even wear on both "sides":
Yes, they did! Quite frequently!
28 July 2012 at 10:05 pm
Far out.