During the testing of the R/C Baja Car drivetrain and steering, the max velocity, acceleration, and steering angle will be found. The requirements for this project are as followed:

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Requirements:

• The R/C Baja Car must meet/exceed a final velocity of 20 mph.

• The R/C Baja Car must accelerate to max speed at a rate of 17.2 ft/s^2.

• The R/C Baja Car must have a steering angle of at least 60 degrees.

 

In the analysis process, the final drive speed was found without the factor of friction due to the type of surface the car will be performing on, this could deviate the results found. The deviation allowed will be plus/minus 5 mph of the final drive speed and 5 ft/s2 of acceleration. If the results do not obtain the correct speed, redesign work will be done to increase the performance of the vehicle.

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Predicted Performance:

The predicted performance of the final velocity of the vehicle is 54 mph. this value was found at 100% efficiency in the system, neglecting the weight of the vehicle, subsequent power loss, or any friction between the tires and ground. More calculations were made, and another predicted value was found, this value was 40 mph in consideration of having a 75% efficient system.

The predicted performance of the vehicle’s acceleration was based off the 40-mph predicted velocity; the predicted acceleration was calculated to be 67 ft/s^2.

The predicted performance of the steering angle was 60 degrees.

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Data Acquisition:

Data during this test will be collected by using a tape measure and stopwatch, to have a known distance and time of the R/C Baja Car to pass through said distance. This data collecting method will be used for both velocity and acceleration. Data for the steering angle test will use a protractor and metal rod in which will record the degree of turn per movement of the remote control.

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Resources:

During the testing process some resources were needed to complete the test. Each test had a requirement for a team of two people. One person was required to operate the R/C car, while another was required for taking time measurements or angle measurements and recording the data on the tables. All other resources were used from acquired equipment that was common in the household such as measuring equipment and timing equipment (iPhone).

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Data capture/doc/processing:

Data capture was done by human. The data capture only required the start and stop of a time watch and by eye measurements of turning angle. The data was then recorded on the printed-out Excel sheets to later store on the actual Excel program.

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Test procedure overview:

The report consist of three different tests, final velocity, acceleration, and turning angle. Final velocity test is done by timing the vehicle at a constant speed for a set distance. The acceleration test is done by timing the amount of time it took for the R/C car to reach its final velocity. Both tests are done on two different surfaces to compare the effect of the terrain on the results. The steering angle test consist of taking measurement of wheel angle at different increments of turning the remote control. This test is done for both left- and right-hand turns.

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Operational limitations:

Limitations in the testing come from the ability to accurately measure the time and angle of the wheel. More precise equipment would be recommended to get a more accurate result of data. There are no limitations to the device itself, other than needing two people to operate and record data.

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Precision and accuracy discussion:

During the testing, the precision and accuracy of timing the R/C car can vary. To narrow down the possibility of error, a test was done to see how fast a human thumb can start/stop the stopwatch on an iPhone. This resulted in a precision of around +/- 0.1 seconds. The precision of the steering angle measurements remained around +/- 2.0 degrees of deviation per measurement.

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Data storage, analysis, and presentation:

Data was stored into an Excel sheet in different tables per test once the test were completed. The data was then used to find the final calculation for each trial. These calculations were then used to find the average final giving the result of the test. The results of the test will be presented as tables and graphs. These will be used to compare the results of different terrains and the comparison of passenger side wheel and driver side wheel in steering angle.

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Issues during Testing:

            Some design issues were found prior to getting to do any test runs. The first test to be done on the R/C Baja Car was the velocity test. The issues that occurred were in the drive gear system. The first gear used was a 26 T drive gear that was made of casted steel. However, the amount of torque that is applied from the motor, shredded off the gear teeth of the drive gear. After figuring out the material issue, the old drive gear was replaced with a machined steel gear of the same tooth count. The machined gear is stronger and held up to the torque applied in the drive gear system.

            After the drive gear was replaced, a test run was done to make sure there was proper gear alignment in the system. The gears did not skip or chatter, resulting in the only issue being the material the gear was made from. During this test run, the Main Gear Locker (Appendix B.10) sheared. This was another result of the piece being too weak for the torque from the drive gear system. The piece was also 3-D printed hollow and not solid, causing a weakness in the part. The Main Gear Locker, was then redesigned with a greater collar thickness, adding 2 mm, and reprinted solid to prevent the issue happening again.