Motor and Gearboxes lab - When Coef1 friction 1 we tested...

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Figure 1 Table 1 Friction Loss Coef of friction test 1. When we tested the motor by itself, we found it had an average speed of 16544 rpm, and used a current of 0.254 A. Then we applied a force to the motor and the speed decreased whereas the current consumption increased. Under stall condition the current consumption was 3.75 A. Next, we added the gearbox (101:1) and hex shaft (Figure 1). The speed of the hex shaft at this point was 145 rpm with a current of 0.41 A. Next, we added the flexible tube and Aluminum shaft to attach a load. We measured the speed/current with no load, with scissors (1.75 oz), and with a wrench (3.625 oz). Then we changed the gearbox ratio from 101:1 to 269:1 and repeated. Our values are recorded in Table 1. We calculated the torque by using the equation torque = force * radius. Both trials lifted the same force so the torque was the same; however, the speed and current were considerably lower in the 269:1 gearbox. 101 to 1 F (oz) R (in) T (in oz) speed (rpm) current (A) 1.75 0.125 0.21875 96.17 1.265 3.625 0.125 0.453125 77.2 1.84 0 0.125 0 109 0.955 269 to 1 1.75 0.125 0.21875 50.15 0.45 3.625 0.125 0.453125 46.67 0.567 0 0.125 0 58.6 0.38
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Above, we plotted speed (rpm) vs torque for the two different gearbox ratios. Based on our data, it is evident that the lower gearbox ratio has a much steeper slope that the higher gearbox ratio. With the lower gearbox ratio the speed was 96.17 rpm and the amperage was 1.265. The higher gearbox, on the other hand, was way down at 50.15 rpm and 0.45 amps with the same torque and voltage. It seems that as the gear ratio is increased, the speed decreases and the amps used decreases.
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