The guy behind Primitive Technology (aka my favorite YouTube channel) is back with a video on how to build a forge blower, a device for fanning a fire to make it hotter.
This device produces a blast of air with each stroke of the bow regardless of whether it is pushed or pulled. The bow makes it possible to operate the blower without using a complicated belt and wheel assembly used in traditional forge blowers. There is a brief pause at the end of each stroke where the fan stops to rotate in the other direction, but this is effectively no different to the intermittent blast of a double acting bellows of Europe or box bellows of Asia. The materials used (wood, bark, bark fibre and clay) are readily available on most continents. No leather, valves or precisely fitted piston gaskets are required as with other types of bellows.
The way he shoots & edits these videos is so good…packing, what, dozens or even hundreds of years of technological evolution into a minute or two of wordless video.