Cardboard, Gears, Pulleys and Rubber Bands
By Richard Williams 7/31/09
Hi teachers, are you enjoying the summer? Maybe some of you are now looking for ideas for the coming year. Here is an idea for you to consider for a class project. This first screen shot down below here was really meant for the younger grades, but it could easily be expanded to do reduction gear trains, ratios, etc… for the higher grades. I used cardboard, small nails and rubber bands as my materials. Straightened paper clips could also be used and left bent over in the backside and front so they do not pull out so easily.
The rubber bands were placed on the outside circumferences of the cardboard cut outs in order to increase the friction between gears. The decorations I put on the gears were used to make it easier for the younger children to see what relations areoccurring between the cardboard gears and they are fun to turn by hand. Anything here would work okay like colored pencils or crayons. You could also usestick on ornaments. Yes, even straight lines with arrow marks could be used for starting alignments used to obtain data on the turning ratios. If similar vertical and horizontal lines are also drawn on the backboard you can line up the ones you drew on the cardboard gears for starting positions. I was able to easily animate them within the SolidWorks program. Just use your own imagination like the reduction gear train and other configurations I did down below here for an example for you. Hope you can get some mileage out of this idea. Office Depot and similar stores have good selections of rubber bands, in some assorted sizes and bags. String could also be used but I didn’t try that. There is one word of caution to be used here. Use the minimum amount of rubber band or string pressure between gears or pulleys. You do not want the elastic rubber bands shooting pins, paper clips or nails around the classroom. A little experimentation here will show you the optimum distances between them to accomplish the turning relationships. A more stable setup would be to make the backboard out of a more substantial material like wood and drill holes to mount bolts washers and nuts for the pivot separation points. I can see lots of equations down below here for advanced or high school classes. Bye.