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Exploration

Now that you've finished the build, test what it does. Explore your build and then answer this question in your engineering notebook.

How would the speed of the arm change if the High Strength 84 Tooth Gear in the build's Step 33 was changed to a smaller diameter High Strength 60 Tooth Gear?

A set of VEX Robotics gears and hardware, including large and small red plastic gears, hexagonal drive shafts, and other mechanical components.

For help with this question, compare the rotational speed (RPM) of the High Strength 12 Tooth Pinion (from Step 36 of the build) to the rotational speed of the 84 Tooth Gear on the robot by gently moving the arm up and down. Be sure to justify your answer with your observation.

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Answers should indicate there would be a speed change for the arm. These could include observations that the pinion with fewer teeth and a smaller diameter rotates faster than the larger diameter gear with more teeth. A correct conclusion is that the arm will rotate faster.
If the student uses the term gear ratios, be sure it is used correctly. Gear ratio = Number of driven teeth/Number driving teeth or 7:1 gear ratio with the 84 & 12 Tooth Gears and 5:1 gear ratio with 60 & 12 Tooth Gears.

The following is an example of gear ratios.

Gear Ratio Table. The first row reads 1st Gear Ratio = # of driven gear teeth (36) over # of Driving gear teeth (12) which reduces to 3 over 1 or a 3 to 1 ratio. The second row reads 2nd gear ratio = # of driven gear teeth (60) over # of Driving gear teeth (36) which reduces to 5 over 3 or a 5 to 3 ratio. The third row reads Resulting Ration = 3 over 1 times 5 over 3 = 5 over 1 or a 5 to 1 ratio.

For more information on gear ratios, view the following article, "How to use Simple Gear Ratios."

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