Purpose: Engineering an Idea

The purpose of this lab is to explore the question of how to implement an idea for a technology device. In this case we will explore how to construct a simple wind turbine called a pinwheel. Reproducibility of the process and model driven improvements to that process will also be explored.After developing this lab I found this Scientific American activity which is quite similar.

Equipment:

To complete this lab independently you need a number of sheets of heavy paper (more like card stock or paper plates -- not the burly ones, just the regular ones), scissors, a reasonably straight wooden stick or dowel, and some heavy pushpins or finishing nails. Regular printer paper is too floppy to make pinswheels out of but if you had some manila folders that is about the right stiffness. The paper that is used for notebook dividers might also be about right. The stick can be round or square as long as it's straight to the pinwheel can spin without hitting it. You may be able to use a pencil for this and stick the pin into the eraser. The pin or the finish nail is used to provide an axle for the pinwheel to spin around. I am relying oh you to be able to safely cut and poke holes in the paper without cutting or poking holes in you! You will also need access to a fan or a hair dryer (on cool!) to test your pinwheel in a controlled way.

Procedure:

The process of having an idea, building a prototype, testing the prototype, learning from those tests what might be changed, and then developing the idea is central to all technological developments. I am hoping that you will focus on the exploration of how your pinwheel works and what might be changed. The following are the steps we will take:

I) Build a pinwheel: The starting point for this lab is to build a pinwheel. There appear to be hundreds of videos on the web each just a little different. This one is pretty good. Various cutting supplies will be provided as well as a means to get a “wind” blowing in the lab (besides your instructor’s hot air). There are many small considerations that might make your pinwheel sticky or unwilling to spin. Remember that it is spining on the axle provided by the pin. If you push the pin too tight the friction will stop the spinning. If your paper is too floppy or you cut too far into the center the paper will bend and hit the support stick. Some builders cut flat disks of paper to form washers on either side of the pinwheel. If you have long pins you can put a bead in between the pinwheel and the stick to help it turn more smoothly. I do not normally use glue to hold the tips together and instead just rely on the pin to hold things in place. Be sure the pinwheel spins pretty freely before starting any testing. Do not be frustrated if you have to try this a couple of times to get a pinwheel that spins well.

II) Initial Explanation: Once you get a pinwheel constructed and tested to see how it performs I want you to describe, in a paragraph or two, how you think it works. How does the “wind” make it turn and what aspects of the design slow it down? The point is to get you to think about what you believe about how it works so you can imagine how to make it perform differently.

III) Initial Testing: Take your pinwheel and hold it in front of a fan. Turn it in different directions. Observe whether it spins the same way around the axle when it faces the face or is faced 'away' from the fan. What does it do when it's 'sideways' to the fan? What about when only part of the pinwheel is in the air stream (if you are using a hair dryer this may be the only option for you) Any surprises that you notice? How far from the fan can you go and still have it start turning? Is that distance the same forwards and reversed? Describe what you observe about the performance of your pinwheel in one or two paragraphs. Be sure to discuss whether your observations are consistent with your initial explanation. Pay particular attention to the fact that nearly everybody's pinwheel works 'backwards' which is not consistent with many common explanations.

IV) Process Consistency: (Skip if you are doing the lab independently) If you are doing this in a f2f lab there will be other students testing their pinwheels. Do they spin differently than yours? Talk to someone who has one that is faster or slower than yours. Speculate, in a paragraph, why theirs performs differently based on your ideas from II) and what you observe about their implementation.

V) Model Driven Changes: At this point you’ve built couple of pinwheels and done some very rough testing. You have been forced to describe how you think such a pinwheel works. Now the question is “How can I make it work better within the limitations of this problem?”. I want you to describe a change to your pinwheel design that you think will improve its performance. What specifically will you do with the materials available to you? I also need you to describe why you think this might make the pinwheel perform better. This description must connect with your statements in part II) where you described how you think a pinwheel works. You may build your “improved” pinwheel design only after you have convinced your instructor of the brilliance of your reasoning.

VI) Development Testing: When you have completed your new and improved (or less successful) pinwheel give it a rough test. Describe clearly how the new pinwheel behaves. Does it spin more easily or faster? Are there problems you didn’t anticipate? Do your test results suggest that your understanding of how a pinwheel works is incomplete or consistent so far? Be sure to test your 'improved' pinwheel is all orientations relative to the fan. There are a lot of different reasons for the behavior of your pinwheel to change?

VII) Self Reflection: Consider how successful you were at affecting the performance of your pinwheel. Did the modification(s) you made have the results you expected? Are there other possible reasons for the change in performance (or lack of it)? Do these results suggest changes to your understanding of how a pinwheel works? Does this process feel like an effective way to improve the design of a 'machine'?

LAB DELIVERABLES (turn in):

I) Include an image of the pinwheel you constructed along with the usual header information for your lab report.

II) Initial Explanation: In a paragraph or two explain how you believe the moving air makes the pinwheel turn. This is often challenging because it would be much easier to point at an actual pinwheel at the same time. Annotating your pinwheel image could be a successful strategy.

III) Initial Testing: In a paragraph or two describe the results of your initial testing as discussed above.

IV) Model Driven Changes: Describe the change you made to the design of the pinwheel. Explain why you expected this change to improve or reduce the performance of pinwheel

V) Development Testing: What do you observe about the performance of your pinwheel after your modifications. Explore all of the same tests you did initially to get a complete picture of the changes.

VI) Self Reflection: Respond to the prompts about this process and it's potential value.