Technology for the poor

This website is a great example of what I am trying to Illustrate in this thesis.
http://technologyforthepoor.com/

STANDARD BICYCLE WITH PEDAL POWER ATTACHMENT

(DUAL-PURPOSE BICYCLE)

Job S. Ebenezer, Ph.D.
President, Technology for the Poor,
877 PELHAM COURT, WESTERVILLE, OHIO - 43081
technologyforthepoor@yahoo.com

INTRODUCTION

This manual describes the design and construction of a device which, when attached to a standard bicycle, will permit it to be used as a pedal‑power machine. The resulting machine, known as a dual-purpose bicycle, can be used to power numerous small‑scale mechanical devices such as grain threshers, grinders, water pumps, electrical generators, and a variety of small machine tools. When desired, the dual-purpose bicycle can be converted from its transportation mode to its pedal‑power mode, or vice versa within a matter of minutes.

It should be noted that the design criteria, materials used, and the procedures adopted in construction may be modified to suit local situations. It is suggested that low-cost and readily available materials and standard bicycle parts be substituted whenever possible. Changes in construction method and in dimensions should be made according to the availability of materials and manufacturing capability.

I. DESIGN CONSIDERATIONS

When designing our attachment, the following considerations were taken into account:

1. The device should be suitable for local manufacturing capabilities.

2. The attachment should employ low-cost materials and manufacturing methods.

3. It should be accessible and affordable by low-income groups, and should fulfill their basic need for mechanical power

4. It should be simple to manufacture, operate, maintain and repair.

5. It should be as multi‑purpose as possible, providing power for various agricultural implements and for small machines used in rural industry.

6. It should employ locally available materials and skills. Standard steel pieces such as steel plates, iron rods, angle iron, and flat stock that are locally available should be used. Standard tools used in machine shop such as hack saw, files, punches, taps & dies; medium duty welder; drill press; small lathe and milling machine should be adequate to fabricate the parts needed for the dual-purpose bicycle.

7. It should make use of standard bicycle parts wherever possible.

8. The device should adapt easily to as many different bicycles as possible. No permanent structural modification should be made to the bicycle.

9. Though the device should be easy to take off the bicycle, it is assumed that it would usually remain attached to facilitate readiness and ease of transport from site to site. The device, therefore, should not interfere with the bicycle's transportation mode.

10. The broad stand, which provides stability during power production mode, can be flipped upward during the transport mode. This stand/carrier would be a permanent fixture of the dual-purpose bicycle.

11. The power take‑off mechanism should be as efficient as possible, and should develop relatively high r.p.m. (close to 200) for versatility of application. We had seen designs for devices that take power from the rear tire by means of a friction roller pressed against it, but we had doubts about the efficiency of this arrangement. In order to improve efficiency we used hard bearing surfaces such as roller chains, sprockets and ball bearings. We decided that the most appropriate location for this power take-off mechanism would be at the front of the bike near the fork tube (see photographs).

12. Care must be exercised to insure that the power take-off assembly is far enough forward so as not to interfere with pedaling. Most standard adult bicycle frames have plenty of room for the power take-off mechanism and pulley. Power is supplied to the shaft by means of a chain from the bike's chainwheel (crank) to a ratcheted sprocket on the shaft. During the prime-mover mode, the bike's regular chain is slipped off of the chain-wheel, and the specially sized chain to the power take-off mechanism is slipped on.

13. The device should be able to transmit power to a variety of machines, and changing drive ratios should be as simple as possible. We decided that a V-belt and pulley arrangement would be most appropriate for this. Belts do not require the precise alignment that chains do. Belts can even accommodate pulleys that are slightly skewed with respect to each other. Changing drive ratios is as easy as changing pulleys. Also, belts are reasonably efficient.

14. The device should contain a ratcheting mechanism that would let the operator "coast " periodically to rest and conserve energy. A free wheel from any bicycle can be easily adapted for this purpose.

15. Excessive weight should be avoided, as durability is a prime consideration.

DUAL-PURPOSE BICYCLE

Figure 1 Transportation Mode

Figure 2 Power Production Model

There is a lot more information on the site, what I find to be so interesting about this is that details very simply a solution to the problem, its not overly designed to the point that it would cost a great deal to create and for the people of this developing nation to create and use.