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Here’s a quick hands on project you can use in the classroom to teach students a variety of math and engineering concepts.
It involves using a laser cutter to cut out a ruler and two different size gears as well as a 3D printer to print sliders that allow students to attach the gears to the ruler. If you’re starting from scratch, you’ll also need design software. Otherwise you can download my design files (found at the end of this blog post).
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You can use any design software, laser cutter or 3D printer for this project. I used SolidWorks Education Edition to design each component. The ruler and the gears were cut on a Universal Laser Systems VLS 3.50. The sliders on the ruler were printed using a MakerBot 5th Generation 3D Printer (with a Smart Extruder+).
Here are a few examples of learning concepts you can teach with this project.
Gear Ratios
There are a number of different ways to calculate a gear ratio. One way is to count the teeth on each gear. Let’s assume Gear 1 has 24 teeth and Gear 2 has 12 teeth. For every one turn of the 24-tooth gear, you can expect two turns of the 12-tooth gear. For every one turn of the 12-tooth gear, you can expect a half turn of the 24-tooth gear.
How to Set the Correct Center Distance Between Two Gears
The objective of this learning concept is to teach students the distance gears need to be from one another in order to properly mesh. If the gears are too close together, they will jam. If the gears are too far apart, there will be backlash.
If you know the pitch diameter of each gear, how far apart do they need to be in order to mesh properly? The answer is found with this equation:
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(Pitch Diameter of Gear 1 + Pitch Diameter of Gear 2) / 2 = Center Distance
After students uncover the Center Distance using this equation, they will be able to set Gear 1 and Gear 2 a certain distance apart and check their work visually, which really shows the value of hands-on learning in this lesson.
I have also included an excel file with the pitch diameter listed as a decimal and fraction for each gear size.
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Converting Decimals to Fractions and Vice Versa
Here’s another fun idea that involves math. If you laser cut a 16th-inch fractional ruler, student will need to know how to convert between decimals and fractions to determine where to place the gears on the ruler.
For example, if you determine the gears need to be 3.2 inches apart in order to properly mesh, have your students examine the ruler and figure out exactly how to place Gear 1 and Gear 1 exactly 3.2 inches apart (hint: it won’t be 2 notches past the 3” mark on the 16th-inch fractional ruler!)
If you’d like to avoid the fractions learning concept in the project, simply design a tenth-inch decimal ruler to use instead.
The great thing about this project is that it’s fairly quick to design and produce. You can cut several of the rulers and gears on a laser cutter in a single run, and the 3D printed smarts are small and can be produced quickly on a printer like a MakerBot.
Feel free to download the below design files (SolidWorks, STL, DXL files) and let your students get to work!
http://amtekcompany.com/files/solidworks/Gear%20Project.zip
