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Element F: Application of STEM principles and practices through analyses (M5)
In element F I will showcase the preliminary detailed analysis performed on possible designs, utilizing STEM principles.
Preliminary analysis: Pin release
The main issue that I foresee with this concept is the relatively high force that will be needed to dislodge the pin from the coupling, which the PLA arm will have a hard time doing given its light weight. For this reason, I will analyze the force needed to dislodge the pin, and identify if the arm can move it.
The pin starts at equilibrium, being acted upon by gravity and friction. The friction comes from tension from a rope. Tension force is F=m * a, which is Ft = 0.454 kg * 9.81 = 4.45 N. Because the system is in equilibrium, the F normal will also be 4.45 N. This means that the friction force will be 4.45 * (Coefficient of friction). Given that these will be steel pins and couplings, that coefficient will be 0.8 according to a table that I found on an engineering website. Therefore the Force friction will be 3.56 N. This is problematic for the arm, so I will either need to lubricate the steel pin/ couplings, or change the material used for them to lower friction.
Preliminary analysis: Torque
Given the circumstances, my motor will heavily prioritize torque over rotational speed for its application. The ball will weigh 2.5 ounces, or 0.07 kg, and needs to be raised 1 meter. Torque is calculated using T = Power / Angular velocity, so in order to increase the torque I can always lower angular velocity of the motor. This means that I may need gears in order to do this if an economical motor cannot be procured, and my power source will need to be able to power it long enough to raise the ball. Motors are available for as cheap as ten dollars which meet my specs, and batteries which meet my needs can be procured for as little as $20.
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