Analysis
​The purpose of the analyses in this project is to fulfill the requirements outlined in the project proposal. Engineering analyses are valuable as they offer precise solutions to problems, eliminating the need for guesswork. These analyses will draw upon the knowledge acquired in prior CWU classes, including mechanics of materials, dynamics, basic electricity, and physics, to address various aspects.
Requirements
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The RC car will have a top speed of at least 25 mph.
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The RC car will reach top speeds in 10 seconds.
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The RC car will have a length of 14” long.
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The RC car will have a width of 16” wide.
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Max deflection of the chassis does not exceed .30”
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Max deflection of the gear shaft does not exceed .25”
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The RC Car will have max weight of 8 lbs.
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Rear Axle max deflection of .25”
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Use common bolts such as ¼ -20
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Max force to break bolts will not exceed 750lb
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The chassis must withstand internal and external loads of 15lbs without failing.
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The car will be operated by a radio-controlled remote with a minimum range of 16 meters.
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The max heat transfer of the bearing does not exceed 1°C
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Max frictional torque must not exceed 1 Nm
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The chassis will not break at a 2ft drop with a load of 80lbs
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The RC car will be able to sustain a speed of 25 mph for a duration of no less than 2 minutes.
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The RC car will have a battery that will last for a minimum of 25 minutes at full power.
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All components of the RC car will not exceed the cost of $800.
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Gear ratio of the wheels will be less than 10:1
20. The actual Power from the motor will be less than the max power of 150W.
The primary aim of Analysis one was to establish the precise power output of the motor, which was accomplished through fundamental electrical principles. The determined actual power output of the motor was 138.38 watts. Given that this calculated value falls slightly below the motor's specified power rating of 150 watts, the team is satisfied with the results.
Figure 1 Actual Power Motor Provides
Analysis two aimed to find the top speed of the car with a gear ratio of 7:1. Using all given information the student was able to conclude that the vehicle can reach speeds of around 25 mph.
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Figure 2 Top Speed of the vehicle
Figure 3 Diameter of Gear (Drive) shaft
Analysis 3 was conducted to establish the smallest required diameter for the drive shaft, drawing from the principles of mechanics of materials. Upon completing the calculations, the minimum diameter was determined to be 0.0583 inches. The team ultimately opted for a larger drive shaft diameter of 0.25 inches, surpassing the minimum requirement to ensure structural integrity.
Analysis 4 assesses if the chassis can endure an 80lb load without deflecting more than .30 inches, given its desired thickness of 3/16 inches. Results indicate that under an 80lb load, the chassis deflects by .27 inches. However, due to variations in chassis width, the student subsequently computed the stress on the smaller part at the top of the chassis to ascertain if it would fail before the entire chassis. The assessment, illustrated in the accompanying image on the right, indicates that this smaller section can indeed withstand the load, as its deflection value is significantly lower.
Figure 4 Chassis Deflection
Analysis 13 as shown on the left, shows the calculation done to determine the acceleration of the RC vehicle before testing. The analysis shows that with a top speed of 25 mph in 10 seconds, the RC vehicle should have a minimum acceleration of 3.667 ft/s^2.
Figure 5 Chassis Deflection
Analysis 9 checked if the chassis could withstand a 2ft drop with an 80 lbs load, meeting specified criteria. The student calculated the maximum stress and ultimate shear, confirming the chassis's resilience. Results showed the maximum stress as 3,658.03 psi, below the safe limit of 40,030 psi for Aluminum 6061-T6. The ultimate shear was 365.42 psi, under the safe threshold of 30,022 psi. The chassis passed the drop test.
Figure 6 Maximum Bending Stress at 2ft Drop