A Science Project for Today’s Classrooms
By Corporal Willy, August 18, 2009
There is no way anyone should ever confuse me with those that are engineers or teachers. I’m simply not either one of them. But I have been teaching for years to youngsters mostly and have also been dabbing into the world of engineering with different projects. I do these things today to encourage young adults and even younger students to think about becoming an engineer or some other technically trained worker for all those jobs that American industries cannot find enough trained people for.
Part of my job today is to help awaken the interest of young students to the world around them. I’ll have to use my own bag of tricks learned over many years to spark their interest in my “Hands On Engineering” course ideas. One of my first lesson plans for teachers to use in class, is to construct a Block and Fall that can be tested against other designs to see how much weight it can pick up. This is another way to challenge the young student minds, that love those Bridge Building Classes. In those classes they build bridges out of sticks and then perform destructive testing on them to see how much they can hold up in mid-span. It teaches them about the strength of materials and the basics of good solid designs. Down below here are a couple of screen shots of what I am talking about. There are four sheaves (pulleys) in each section. Eight total for both the Block and the Fall sections. The fall reference is to the part that the load is hooked up to that goes up and down and hopefully not both parts. I have no ropes shown here.
These could be made in the classes by the students. No wood. No metal. It will be made from foam core boards that I picked up in the Michael’s Craft Store by me. Pretty cheap stuff and I got four 30 x 20 inch sheets of it for a little over 5 dollars. I tried cardboard but there are too many inconsistencies and irregularities with that material for this project. But I will use it for other projects I dream up.
Now let me show you the real prototype using the foam board materials. Keep in mind that even the axle is made up of tightly rolled standard printer paper. It took two sheets of paper to make a half inch axle and it is pretty darn strong too with a snug fit and I didn’t use any glue, just tape. I taped the overlapping seams down the full length of the seam or overlap. I did a few things over because I never saw the problems in my MCAD program until I actually built it.
Taking shape now.
I was completely convinced that I would not use anything else but this foam board and paper for this school science project. I could not make a rope or cord so I decided to buy that. The side view down below here will show you my paper axle. The kids in my school district are not allowed to use certain types of tools that I used to build this assembly and I guess that is pretty universal. It is forbidden to let them use things like box cutters in school so I will do the cutting out. That will be my home work as part of the project. But they will draw all the part shapes out onto the pieces that I will pre-cut for them. Rules are rules. I think teams of three or four will work out well in building this project. When they are all done then we will test them to see who has the strongest model that can pick up the most weight. That is what they do in those Bridge Building classes that are so popular today in many schools around the world.
Here is a screen shot of the shape and dimensions needed for the bottom Block section of the project. There are many more dimensions shown here in the sketch then are really needed to layout these parts but my class will be young kids and I will work on things like that as time goes by. Two of these sketched parts down below will be needed for the bottom section or Block Fall. The Imperial System of measurements is being used here but for those metric orientated schools they can be converted easily.
Twelve of these side axle support pieces (sketch down below here) will be needed for the complete project. Eight are needed for the top Block section and four will be needed for the bottom Fall section for a total of 12 of these parts.
Here is a screen shot of the dimensions for the upper Block yolk part. Four of these will be needed
Down below here is a place where I thought it would need to be reinforced more because it is only foam board. I decided that in this particular area there was going to be a lot of stress on the frame, especially on that hole area so I would glue pieces in there on both sides and then of course make the hole through all the pieces. “A picture is worth a thousand words.” You can trim it out to match the top portion with the angles if you wish. One note here is that the pieces that you will glue inside of this area should extend down long enough to be about a 1/8 of an inch, above the pulley wheels. That keeps the rope from jumping off of the pulleys once you “rope them up.” Even closer if you have done a great job on cutting out the diameters. Glue these reinforcement pieces on the face and two sides where they will be placed inside of these areas. Do both sides of it so the upper Block yolk should be pretty strongly reinforced. At least as far as the materials that are used will be. Make sure you cut to size and try it before gluing. Measure twice and cut once is also a great tip.
I used two sizes of metal hole saws that we electricians use to cut round holes through metal cabinets to install raceways like pipes. There are a number of ways to cut these out. I was looking for a fast way to do it. These come in all different standard sizes up to 4 inch. I did use a small drill press to help me with the drilling and it is much easier to control the foam being cut through. If you are no good with power tools please use a scissor or even a razor blade knife.
A great sanding job is required all around the outer edges to remove fibers and other pieces after cutting them out. You want them as smooth and round as possible. Sanding can be a little messy but I found out that by doing it over a small garbage can it worked very well. Paper bags could be used also in classrooms. This material cuts easily so even a scissor could be used after making a template to trace around or by using a compass. Here are the diameters of my pulleys but you could make them almost any size you want, but you will of course have to adjust the frame accordingly. They are 2¼” for the smaller ones inside or between the two outside big ones and 2¾” for the big ones. There are eight needed for each of the two blocks upper and lower assemblies. There are four needed for the smaller ones in each block.
The inside pulley disks must be lined up carefully so the holes are concentric or lined up with each other when you are joining them together. I used a ¼ inch drill bit to line them all up as I glued them together because when they were drilled out it had a ¼ inch center drill in the hole saw. After drying, I them enlarged the holes to the ½ inch size needed for the axles. Glue the side of a smaller disk and place it on top of the bigger one. Then glue the other side of the smaller disk and carefully place another bigger one on top keeping the holes lined up as perfectly as possible. Do four like that and let the glue dry well. The axles are made up of two tightly wound sheets of standard printer paper. Go Green and use wasted sheets. Cut to size with a hacksaw blade or maybe a paper cutter but I didn’t try that.
You will need ten small spacer shims to separate the pulleys from rubbing on each other. You can use very thin sheets of plastic or a manila file folders for this. Cut up ten pieces into small squares about 1 ½ inches. Then make a hole slightly larger than the axle itself in the center of the squares. I used a dime to trace out what was needed to be cut out of the center of these little squares. When you have ten of these done you are ready to assemble the pulleys and axle. Push the axle through the side of one of the support frames. Place two spacer shims on the inside axle and then push one pulley on top of the spacer shims. Two more shims and another pulley etc… When the last pulley is on the axle then carefully slide two more shims in between the support frame and the outer surface of the last pulley. I used a pencil point tip to help me guide them over the axle. Then of course you push the axle through the other side of the support frame. Make sure the axle protrudes a good distance beyond the support frame. You can roll up a piece of sand paper to open up the holes a little more if needed in both the pulleys and the support frame. However you want them to fit tightly and not too loose. I used a rat tail file or round file to get a better fit for the axles. I had to be careful not to take too much out of the center hole and to also keep the hole in the middle of the parts. It is important to remember here that you do not have to make this absolutely like the one I did. With a little planning ahead of time, you can create your own pulley system, with your own sizes and frames to do the same thing or even better. It is good to at least know beforehand that this Foam Board stuff works as a cheaper school building material and also that the concept behind this particular project works. It should be at least as much fun as the Bridges are.
Now comes the “roping up” of the pulleys. This is pretty hard to explain so I am going to do most of it with pictures. You have to start somewhere with a weight to stretch out the ropes so experience told me to go get my old small paint bucket out and load it up with what else?; nuts and bolts. This can weighed in at 5.4 lbs for the load that I am going to put on this Block & Fall mechanism. I did not increase the weight until something broke. I have to use this for demonstration purposes in school, so I have to hold onto it for now, but I might allow the kids to perform that test. Remember this is foam board and glue and not wood or metal.
There it is hanging from my garage ceiling with no obvious signs of stress or distortion anywhere with a weight of 5.4 lbs.
Here is a little different view. I was a little disappointed in the pulleys. They did not turn as easily as I thought they might have. However, with a little weight on it like in the pictures here that seemed to go away. The chord is pretty stiff, because it was made from plastics and it does not bend as nice as a clothes line cord would have. Build and learn, right?
Down below here is another view from the other side.
Here is a real act of faith. Looking straight UP at the bottom of the can. This could be classified as stupid but I believe in what I built. But it is also a different view as well.
Nothing broke and after this testing was done it showed no signs of breakage or stress cracks, distortion, etc… anywhere. Since it did not even seem to strain during this test, I’m really wondering where the point of failure might be. What would you think it could lift? This would be a good test for the kids in school to do as scientifically as possible. Maybe even get the Guinness Book of World Records people out there to judge it at the schools. So far I have set the unofficial record at 5.4lbs and that can easily be beaten I am sure.
So eight pulleys are working to pick up the can and as we all know the first pulley only changes the direction of the pull and adds a little more resistance to the load. I don’t have enough testing equipment to measure that but I can tell you this. With a five pound load and using foam board pulleys it was easy to lift. You should have a mechanical advantage here of seven.
Now here is a thought. Remember those donuts that we all love to eat; well what do you suppose happened to all those "thingys" cut out of the middle? Someone made a lot of money by reusing them and frying them up. Tasty little things aren’t they. Well I hope to have the very same fame and fortune if I can figure out what to do with these things after cutting out my pulley sides.
Some very important principals of mechanical engineering and physics are expressed here and I would like the young engineers of the future to have some fun learning about them. It can also be suplimented with math, destructive testing like those bridge making classes and things you might can come up with. Enjoy the rest of our summer or winter depending upon where you are going to read this from in the world. Bye for now.
Here is that silly test that I like to give to young people to impress upon them the importance of listening and following directions. No grade is given and you can adapt this to the age and abilities of your students. Only one young lady ever passed it and she was off to college in the fall to study to be a lawyer. Figures right? Tell your students that they must work very fast and to read everything first. Enjoy.
Name: Date .
Instructor: Your score .
Timed Test = Three minutes total
Instructions for test: This is a three minute timed test so you must work very fast. Read everything before doing anything.. Remember that your first answer is usually the right one. Don’t go back and waste time on an answer. It’s more important to finish the test and if you have more time left then go back to those that gave you problems.
Questions 1-20
1. Count up how many young ladies there are in this class and place that number down on this blank line.________
2. Do the same thing for all the young men in class on this line. ________
3. Stand up by your desk and count how many Fluorescent light bulbs there are in just one row above and nearest to you and put that number on this blank line. _________
4. What color paint was used on the walls in this classroom? _________
5. Why did you want to take this class? Ten words or less down below on the line.
__________________________________________________________
6. Can you follow directions well as a student and young adult? Yes or No circle your answer up above.
7. Stomp your feet where you are sitting three times so I can hear it.
8. Count how many floor tiles there are on the floor from the front of the classroom to the back wall of the classroom. You may get up to count them. Hurry.
______
9. How many are going across the classroom from one side to another. Hurry now.
______
10. What time do you think it is right now. Guess if you do not have a watch and place your answer here. Don’t ask anyone. _______
11. How many brothers or sisters do you have? If you have none then how many pets do you have? Answer here. _______
12. How old are you right now in years only. _______
13. Write the name of your school here. ______________________________
14. Were you born in Nevada? If not where were you born? Include other States or Countries. ___________________________________
15. Do you know the name of the President of the United States at this time? Write his name here. _______________________
16. What do you hope to be when you finish school? If you have any idea then write it on the line here. ______________________________________
17. What is your favorite kind of car? _________________________________
18. What is your favorite color right now? ______________________________
19. What did you expect to learn from this class? In ten words or less. ______________________________________________________________________________________________________________________________________
20. If you have read and followed all the directions for this test as you were supposed to, do not answer any of the 20 questions. Just sign your name at the top and put in the date and sit very quietly. Do not talk to any others that are still taking the test.