VITA - Volunteers in Technical Assistance

Hydraulic Ram - 01/01/1987

A hydraulic ram is a pump that uses the power of falling water to force a small portion of the water to a height greater than the source. Water can be forced about as far horizontally as desired, but greater distances require larger pipe, due to friction. No external power is necessary.

With only two working parts, little maintenance is needed. Leaves and trash must be cleaned away from the strainer on the intake and the clack (automatic valve) and nonreturn or delivery valve rubbers must be replaced if they get worn. The original cost is almost the only cost.

Two things are needed to make the ram work: (1) enough water to run the ram, and (2) enough height for water to fall through the drive pipe to work the ram. A small amount of water with plenty of fall will pump as much as a greater amount of water with only a little fall. The greater the height to which the water must be raised, the less water will be pumped.

Overshot Waterwheel A Design And Construction Manual - 01/01/1980

Improved use of water as a power source has potential for much of the developing world. There are few places where water is not available in quantities sufficient for power generation. Almost any flowing water--river, brook, or outlet of a lake or pona--can be put to work and will provide a steady source of energy. Fluctuations in the rate of flow usually are not too large and are spread out over time; water flow is far less subject to quick changes in energy potential and is available 24 hours a day.

The uses of energy from water are about the same as those for energy from the wind--electrical generation and mechanical power. Water-powered turbines attached to generators are used to generate electricity; waterwheels are generally used to power mechanical devices such as saws and machines for grinding grain.

Development of water power can be advantageous in communities where the cost of fossil fuels is high and access to electric transmission lines is limited.

A Design Manual for Water Wheels With Details for Applications to Pumping Water for Village Use and Driving Small Machinery - 01/01/1989

Supplying power to many remote locations in the world from central generators using customary distribution methods is either economically unfeasible or will be many years in coming. Power, where desirable, will therefore need to be generated locally. Various commercial machinery is marketed, but the required capital expenditure or maintenance/running cost is beyond the capability of many potential users. Some effort has been expended at the Papua New Guinea University of Technology to devise low cost means of generating modest amounts of power in remote locations. This paper reports on one such project involving the development of low cost machinery to provide mechanical power. Regardless of the final use to which the power is put the natural sources of energy which can be utilized are fairly readily categorized. Among them:

1. Falling water
2. Animals
3. Sun
4. Wind
5. Fossil fuels
6. Nuclear fuels
7. Organic waste

Low Cost Development Of Water Power Sites - 01/01/1987

Flowing water tends to generate automatically a picture of "free" power in the eyes of the observer. But there is always a cost to producing power from water sources. The cost of developing low-output water power sites should be checked against available alternatives, such as:

1. Electric Utility - wherever transmission lines can furnish unlimited amounts of reasonably priced electric current, it is usually uneconomical to develop small and medium-sized sites.
2. Generators - diesel engines and internal-combusion engines may use a variety of fuels, for example, oil, gasoline, or wood. In general, the capital expenditure for this type of power plant is low compared to a hydro-electric plant. Operating costs, on the other hand, are very low for hydro-electricity and high for generated power.
3. Solar Heat - extensive experimental work has been done on the utilization of solar heat. Equipment now available may be less costly than water power development in regions with long hours of intense sunshine.

Men's Work Shirts - 01/01/1987

This Industry Profile is one of a series briefly describing small or medium-sized industries. The Profiles provide basic information for starting manufacturing plants in developing nations. Specifically, they provide general plant descriptions, financial, and technical factors for their operation, and sources of information and expertise. The series is intended to be useful in determining whether the industries described warrant further inquiry either to rule out or to decide upon investment. The underlying assumption of these Profiles is that the individual making use of them already has some knowledge and experience in industrial development.

Savonius Rotor Construction - 01/01/1977

The text on the following pages provides data compiled by various investigators on the amount of energy available from S-rotors at various wind speeds. The author feels the potential rotor builder should use these data carefully to see if an S-rotor can meet his needs--before he begins the construction process.

Simple Washing Machines - 01/01/1988

This easily-operated washing machine can be built by a good carpenter from materials easily found in most countries. It is easy on clothes, effective, and sanitary. The machine, which can take 3-kilogram (6-pound) load of clothes, can be shared by several families.

Clothes will last much longer if they are washed in this washing machine rather than beaten or scrubbed on rocks. Washing with the machine is also much less work. Under test conditions, a comparison with standard electric commercial washers was very favorable. If the cost of the machine is too much for one family, it can be used by several. However, if there are too many users, competition for times of use will become keen and the machine will wear faster.

The machine reverses the principle used in the usual commercial washer, in which the clothes are swished through the water for various degrees of a circle until the water is moving, and then reversed. In this machine, the clothes stay more or less stationary while water is forced back and forth through the clothes by the piston action of the plungers. One plunger creates suction as it rises and the other plunger creates pressure as it moves downward. The slopes at the ends of the tub bottom help the churning action of the water caused by the plungers.

Village Technology Handbook - 01/01/1988

The Village Technology Handbook has been an important tool for development workers and do-it-yourselfers for 25 years. First published in 1963 under the auspices of the U.S. Agency for International Development, the Handbook has gone through eight major printings. Versions in French and Spanish, as well as English, are on shelves in bookstores, on desks in government offices and local organizations, in school libraries and technical centers, and in the field kits of village workers around the world. The technologies it contains, like the chain and washer pump, the evaporative food cooler, and the hay box cooker, have been built for technology fairs and demonstration centers throughout the developing world-and more importantly, have been adopted and adapted by people everywhere.

Understanding Stirling Engines - 01/01/1984

Stirling engines are external combustion engines that use air or other gases as working fluid. They can burn any solid or liquid fuel as their heat source. This makes them very attractive, particularly in situations where conventional fuels are expensive and hard to obtain. Because some types of Stirling engine are so simple to make and yet so effective, they are excellent choices for power generation in developing countries.

This paper describes the basic Stirling engine, as well as some of the most promising modern varieties. The intent here is to familiarize people in developing countries with the engine's operation and range of applications.

Silk Screen Printing - 01/01/1987

Silk screen printing is a simple, inexpensive method of producing multiple copies of attractive visual aids, posters, and other materials, including typewritten pages. A squeegee forces very thick paint through those parts of the silk screen that are exposed by the stencil onto paper placed underneath the screen. The silk-screen process presented here is used for educators and trainers who must prepare their own training materials. It would require considerable upgrading of equipment and materials to be appropriate for commercial painting operations.