Bloomery: Double Action Box Bellows

Double Action Box Bellows

I built this box bellows for my bloomeries in 2011. This type of bellows is known from ancient asia only as far as I know, but I wanted to try them for my "roman" style furnances. The reason for that was, that I found it very inconvenient to handle the bellows and charging the furnace simultaneous. So I made a compromise, engaged some mechanics and constructed this ancient air blower, driven by an electric motor instead of the commonly employeed vaccum cleaner motors for this purpose.

The bellows is basically a modified -commercial available- wooden box with a wooden piston inside. On one side of the box I attached an air tunnel, receiving the compressed air of the bellows by two valves, which are on each end of the box. The air tunnel is enclosed at each end by wooden caps. In the middle of the tunnel I drilled the air outlet, as you can see on the photos. The piston is moved like an inversed steam engine, and the motor shaft is powered by a 350 W three-phase asynchronous motor (modified for two phase current by a capacitor)

The box bellows was made from a modified wooden box

The piston of the box bellows. A lining of coney fur was used as gasket

The air tunnel enclosed with a wooden cap

The final stage of the box bellows

The first runnings were performed by a belt driven worm gear

The box bellows with an adjustable friction gear in action

Detail of the motor unit

In the final stage the fixed driving speed of the bellows was stepless adjustable by a friction gear. With that modification the assessable air outlet was somewhat between 500 to 1000 L/min