Water Pumping
How much more power do you think that you can generate with your legs than your arms? First, estimate the answer.
Then, look up the answer in David Gordon Wilson’s paper “Understanding Pedal Power” (PDF) (Courtesy of David Gordon Wilson. Used with permission.)
Record both.
In the lab, how much power were you able to generate using your arms? How much power were you able to generate using your legs? How do these values compare to each other, to your estimate of the power difference, and to the actual difference? If the result of the lab showed that the difference between your arms and legs did not match the common, documented difference, hypothesize the reasons for the discrepancy.
If we were able to harness the power that you generated and use it to power LEDs, how many of the LEDs that we provided to you would you be able to power using your arms? What about your legs?
As a class that focuses on design as well as energy, it is important for you to start thinking about where the technologies that you will be exposed to in this class can be applied. In order to start you on this path, review instructions for each pump:
- “Building an EMAS Pump” by Paul Cloesen (DOC)
- The Full Belly Project Rocker Pump
For each pump:
- Discuss five things you particularly liked about the design.
- Discuss five things you could improve about the design.
- In one or two paragraphs, describe a scenario in which this pump could be used to benefit people in developing regions.
Another commonly used pump in the developing world is the IDE India Treadle Pump. Read this treadle pump case study:
- Ashden Awards. “Case Study Summary: International Development Enterprises India (IDEI).” May 2009.
- and this page in Appropredia: Treadle Pumps
How does this treadle pump compare to the cement pump?
Shop Introduction
In the shop introduction, you were exposed to and trained on a variety of tools, some of which may have been new to you. However, as part of the design process, it is important to consider which tools and techniques our target communities will likely have access to. It would not, for example, be appropriate to have a critical component in your design be something that needs to be waterjet cut (though an experienced metalworker may be able to cut a similar component using a chisel). For both the cutting and drilling parts of the shop intro, discuss the different techniques you were exposed to paying particular attention to:
- The relative difficulty of the process
- The speed of the tool
- The likely availability in the developing world
Water Carrying
First, write down your impressions of each method of carrying water. Rank the methods from easiest to hardest for you. What are the pros and cons of each method?
If you had to carry 5 gallons of water a mile every day, and a q-drum was not available, which method would you use?
Now, read the following abstracts
- Maloiy, G. M., N. C. Heglund, L. M. Prager, G. A. Cavagna, and C. R. Taylor. “Energetic Cost of Carrying Loads: Have African Women Discovered an Economic Way?” Nature 319, no. 6055 (1986): 668-9.
- Bastien, G. J., B. Schepens, P. A. Willems, and N. C. Heglund. “Energetics of Load Carrying in Nepalese Porters.” Science 308, no. 5729 (2005): 1755.
If you find them intriguing, it’s easy to get the entire paper online through the libraries; many of the citations are also interesting.
Did the findings from these papers in terms of the efficiency of the methods described surprise you or match your experience? Why?
Propose some reasons – from a physics standpoint – why the efficiencies of the methods described might be so superior.
