Tuesday, October 06, 2009

Piston Bellows (1)

The next step in the ongoing series towards a replica of the Vinland iron smelting furnace is encorporating bellows delivered air. The illustration below is my working drawing, and is pretty sketchy.
The core of the system is a small bicycle rear frame, cut down to retain the 6 speed gear set, rear forks holding a 20 inch rim, and the peddle crank set. I am mounting this so that a 1/4 HP electric motor (scrounged at the dump) will drive the system, via a pulley onto the wheel. In turn the gears / chain / crank converts the rotation into straight line thrust. Using a pivoted push bar, the mechanicals will operate a modified box bellows.

By calculating the chamber size against throw distance (in this case 12 inches / 30 cm) I can match the theoretical delivery volume against possible air requirements for our standard small furnaces. Stokes per minute will be the adjustment. This can be changed by two methods, first gears on the 6 speed derailer, second by placing a light dimmer switch on the incoming electric power to the motor.

The point of all this is to give us experience with the type of air delivery created by a double chamber bellows compared to that from the electric blower system we normally work with. A blower produces a constant air blast, while the bellows 'pulses' its air. The use of a mechanical system avoids the major problem with a human powered bellows - the huge labour requirement. The norse double bag bellows will require roughly one stroke every 1 - 5 seconds (depending on size and volume required) over the entire 4 - 6 hour firing of the smelter.
The primary experience point that I want to introduce to the team is the different sounds created using this pulsing air delivery.

(Expect some working photos upcoming of the construction and unit in operation)

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February 15 - May 15, 2012 : Supported by a Crafts Projects - Creation and Development Grant

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