Session: 13. Bellows and forge design
Total Time: 50 minutes
* To list and describe design criteria for a forge and bellows
* Attachment 13-A, "The Japanese Style Box Blower"
Materials: Newsprint and felt-tip pens
This traditional blower has been used in China and Japan for hundreds of years. It may be constructed in varying sizes. It is used in large lever-powered applications for foundries. Medium sizes (12"x18"x30") are used for forges and small versions are used for home cooking fire blowers.
Blowers may be made from almost any kind of scrap planks, if well-sealed around seams and cracks.
The inner slide chamber should be smooth and preferably waxed or varnished.
The two air inlet valves should be made of fairly heavy leather, and the hinge for the air exit flapper valve should be centered carefully. The bevel-cut on the side should align for a good seal.
It is a good idea to leave the top accessible by not sealing it with glue.
HOW TO BUILD A BLACKSMITH'S BELLOWS
Allen R. Inversin, Appropriate Tech. Development Unit, Lae, Papua New Guinea
The idea for this bellows came from the time-tested, valved, teardrop shaped design which has been in use since about the fourth century. However, as leather is not readily available in Papua New Guinea, a slightly modified version was designed using the inner tube of car tires which can be obtained anywhere in the country. The bellows cost very little to build and require no special skills for construction. It provides a continuous blast of air to the forge, which is more than sufficient to fabricate machetes, chisels, chains, hinges, spikes, etc.
- Two normal-size car tire inner tubes in good condition and one tube to cut up,
USE OF THE BELLOWS
Although they are easy to use, the bellows should be stroked in a particular way to prevent the user from becoming unduly tired. Two points should be kept in mind:
- Rather than making quick, short strokes, make smooth, full ones starting with the lower board all the way down, and stroke to compress the lower inner tube almost completely.
- The air reservoir (upper tube) should never be fully extended. If a greater air flow is needed to increase the fire temperature, place weights (pieces of iron, stones, etc.) on the upper board to obtain desired heat. Only stroke fast enough to keep the upper tube partially full at all times. A full stroke every 5-10 seconds should be sufficient; stroking any faster produces more sweat than heat.
LORENA STOVE DESIGN
Lorena is a rammed-earth technique that uses a moist combination of screened sand and clay. The sand/ clay mixture is applied in layers and pounded and compacted into molds. The primary advantages of Lorena mix include its low cost, general availability, and good heat-holding capacity. For a complete explanation of the techniques involved in working with Lorena mix, send for a copy of Lorena Stoves, by Ianto Evans and Michael Boutette, from Volunteers in Asia Press, Box 4543, Stanford, California 94305 USA.
FORGE PUMP DESIGNS
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