|Basic techniques of blacksmithing: A Manual for Trainers |
source ref: t0021e.htm
Total Time: 50 minutes
* To list and describe design criteria for a forge and bellows
* To evaluate forge and bellows designs
* To discuss the feasibility of introducing new forge and bellows designs to local blacksmiths
* Attachment 13-A, "The Japanese Style Box Blower"
* Attachment 13-B, "How to Build a Blacksmith's Blower"
* Attachment 13-C, "Lorena Forge Design"
* Attachment 13-D, "Forge Pump Designs"
Materials: Newsprint and felt-tip pens
Explain the session objectives and briefly outline the procedures. -
Explain that the design and construction of a bellows and forge will be only briefly discussed during this training since the design of this equipment is extremely relative to and dependent upon the needs, desires and resources of local blacksmiths.
Have the participants list and describe the design criteria for a bellows and forge.
* Write their responses on posted newsprint according to the example below:
ease of pumping
control of air blast
evenness of heat
heat holding capacity
* Assist participants in developing the lists by providing a few examples and asking the following questions:
- Do the forges and bellows used here at the training meet the criteria? If so, how?
- Do the forges and bellows used by local blacksmiths meet these criteria?
- If not, how might they be improved?
Distribute Attachment 13-A, "The Japanese Style Box Blower,'' Attachment 13-D, "How to Build a
Blacksmith's Blower," Attachment 13-C, "Lorena Forge Design," Attachment 13-D, "Forgo Pump Designs," and ask participants to review them.
Have participants discuss the feasibility of introducing new forge or bellows designs to local blacksmiths.
Some questions for discussion include:
- Do the designs outlined in the Attachments offer any advantages over traditional types of forges and bellows? How?
- Do the new designs meet the criteria developed earlier in the session?
- What difficulties might you encounter in attempting to construct one of the new designs at a local blacksmith shop?
Conclude the session by asking one of the participants to briefly summarize the major factors which should be considered in designing a forge and bellows.
Caution participants against making recommendations regarding forge or bellows innovations without taking time to thoroughly consider the needs, desires and resources of local blacksmiths.
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,
- Four 1-2 cm. boards, each about ½ m. square, of plywood or narrow boards laminated together.
- Wooden strips around 2x5 cm., totalling about 6 m. in length.
- Used steel pipe, 2-3 cm. in diameter, length 6 m. or more.
- Sheet metal or used steel banding straps.
- Four metal rods about 5 mm. in diameter and 10 cm. long.
- Nails, about 2 and 4 cm. long.
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