Mr. Haselby's Site: Mr. Haselby: PLTW GTT Summer Training Day 3: Measurement, Skimmers, Design Process, and Autodesk Inventor

Blog entry by Mr. Haselby

4B inveestigates density and buoyancy
by Mr. Haselby - Tuesday, 21 June 2011, 07:50 PM
Anyone in the world

We started off today's training by discussing topics in the measurement section of the curriculum. One notable thing we were shown was this ruler game. I think it is a simple and elegant way of honing skills with the English system. I know for a fact that the students could really benefit from using it and I suspect they'll enjoy it besides. I wonder what the highest score ever has been?

Next we worked on doing precise measurements with dial calipers. This tool lets you accurately measure up to a thousandth of an inch or so. I was introduced to tons of different ways to use the calipers that I hadn't figured out just from my little experience with them. I think using the calipers will be a great way to hit some measurement GLEs as well as writing numerals and words that communicate values out to the thousandths place.

A nice heavy duty dial caliper I used in training today

This is the dial caliper I used. You read the ones and the tenths place on the blade and the hundredths and thousandths place can be read off of the dial. There are no fewer than four ways to use it as well.

After putting up our calipers we began working on the project associated with the measurement section. In this project students have to produce a hovercraft like vehicle starting from some orthographic projects.The science at work in this project is the Venturi effect, which is just an application of Bernoulli's principle. Stripped down to the barest bones, it states that when a fluid flows faster, it has a lower pressure and that when it flows slower it has higher pressure. This venturi meter might give you a hint on what I mean:

Venturi meter

The project was really fun, and it had all sorts of great ties to the measurement principles. However the procedure included in the curriculum resources left a lot to be desired, plus the master teacher at the session had some really good tips and hints that I wanted to record, so I put together these steps and snapped some photos to go along so that we could all remember them. Here's what I put together.

1.    Neatly and accurately use the plan sheet and measuring tool to draw your skimmer main body, air scoop, and two (2) fins onto the material that you will use to make your skimmer. You should lay out your different parts on the paper to use as many pre-cut straight edges as possible.

This shows how you lay out the different parts

2.    Carefully cut out your skimmer parts. Cut only on the solid lines. The dotted lines are where you will score and fold. Make sure to cut 3 in slits along the dotted lines in the back of the main body panel. These slits will be used to mount your fins to the main body panel.

3.    Use your ruler to draw the dotted lines on your cardboard air scoop and main body, and then fold on these lines to create a 90° angle. You should use the ruler or an edge of a table as a guide for folding. Use one clean crease along your fold lines, do not pinch or fold it multiple times; this will cause your paper to loose rigidity.It is important to get really clean and crip creases

4.    Use a bead of glue to fix the back part of the main body at an angle as shown in the orthographic drawing. The very back edge should be flush with the folded down edges. Be careful not to get glue on any edges that contact the floor. Glue on the running edges will snag and create lots of friction, resulting in shorter skimming distances.

Here is how you glue the back part of the skimmer

5.    Next, glue the fins to the outside of the half inch tabs along the sides of the main body panel. You should put glue on the fins and then carefully press the fins to the taps at an angle so that glue is squeeze upwards, thus avoiding glue oozing out on the running edge of the skimmer. Note that the back end is angled down, and this is where the fins are mounted.

This shows how to glue on the fins so that you don't get glue on the running edge

6.    Glue the flaps of the air scoop to the inside edges of the main body with the narrow end flush with the front of the main body as shown in the orthographic drawing.

Attaching the air scoop

7.    You may want to put a paper fastener behind the air scoop and use a rubber band to propel your skimmer across the floor.

8.    Innovation is an important part of the design process! Check out these modifications. Can you explain why these modifications were made?

Modifications - hot rodding the skimmer

After launching our skimmers down the hall (mine was only average) we moved on to discuss the design loop - which is the cyclical process that engineers and designers go through to move from problem to product. One of the better illustrations for this was the PBS series "Design Squad." I watched two episodes between breaks and once I got back to the dorm rooms we're staying in. The series does an excellent job with explanations as well as showing great team work.

We finished off the day with some work time on building exemplar projects for designing furniture and also honing our Autodesk Inventor skills. Here is part of the homework for tomorrow.

A monkey bar part for a playground

I want to end by talking a bit about the furniture project, because it involves some mathematical reasoning. So we were given the assignment of designing either a table or chair. Instantly I thought of my classroom, since I know that there are going to be much larger class sizes for this up and coming year and the tables I have now won't sit everyone properly. I remembered that my classroom is 7 m wide and 9 m long. I knew that I had to plan for about 28 students, and that experience has taught me that students work best when they are sitting two to a table. That means I needed 14 tables. However 14 is only factorable by 2 and 7, so there is no real plausible way to lay out 14 tables in even rows and columns, so I reasoned that I should have five rows, and three columns of tables with the last row containing only two tables. I know that I need 0.75 m wide aisles between the columns of tables and students need at least 0.5 m of seating space behind their table rows. Lastly, I need1.5 m of space between the board in the front of the room and the first row of tables.

This can be summed up in the following graphic. Note that the aisles are green, the seating areas are yellow, and the board and front room area is blue.

Graphic showing the table top layout problem


The $20 question is this: What is the width and length of a single table top, assuming all the tables are the same?

[ Modified: Tuesday, 21 June 2011, 09:47 PM ]

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