Testing
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Testing will be done in the Spring quarter. The testing will consist of two major tests, a drop test and a turning test.
The drop test will drop the vehicle repeatedly from increasing heights, up to the maximum of 1' to meet one of the requirements for the vehicle. This will be done in intervals of 0.25' with a final trial at 1' for a total of 4 trials. The shock absorbers will be monitored for each of the drops using slow motion capture.
The deflection test will be used to measure the deflection of the upper control arm under two different loads, 25lb+ and 50lb+ and its requirement is that it does not deflect more than 0.1".
The turning test will be measured with guide lines placed slightly larger than the vehicles overall width and over a 180° arc with the inner radius being the required turn radius of 3.5'.
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The drop test needed to be reworked because the vehicle was failing the drop test much earlier than previously predicted and desired. The drop test started to fail at all heights beyond 1' with the vehicle bottoming out. This issue was corrected by making the highest height for the drop being 1' and have smaller drop increments to gather more data points.
Drop Test
The drop test is performed to test the spring constant for the shock absorbers used on the vehicle. This test was performed with 4 trials at heights of 3", 6", 9", and 1'. The displacement is then measured and used to calculate the spring constant by the conservation of energy formula. From this test, the average spring constant was determined to be 44.7 lbf/in. A portion of the experiment is shown in this video followed by screenshots of the drops.
Video 1. RC Drop Test
Fig 1. 3" drop
Fig 2. 6" drop
Fig 3. 9" drop
Deflection Test
The deflection test is used to determine the strength of the weakest component, the upper control arm. This component has broken on two different occasions, so it was important to test its strength after its second revision. This test is performed using an instrom machine to apply a force onto the component at the center where it is subject to the most amount of force. From this test, the component had a small deflection of less than 0.5" under the force of 50lb+. The setup of the test is shown to the left and the results of the two trials are shown by the graphs below.
Fig 4. Deflection test setup
Fig 5. Deflection Test trial 1
Fig 6. Deflection test trial 2
Turning Test
The turning test is used to determine the minimum turning angle of the front tires due to the steering system. This test is based off of the requirement of making a 180° turn in a radius of 3.5'. To meet this requirement, the turning angle was required to be 19° for the tires. However, after testing, the minimum turn angle was only 4°, substantially lower than the required 19°. This requires a new steering system to be designed and installed in order to meet the requirement. This problem most likely comes from the use of 3D printed parts with lose dimensions in order for them to rotate, rather than the use of bearings and tighter fitting parts. On the right is a demonstration image of how the test is conducted using a protractor and turning the tires to the their maximum potential turn angle.
Fig 7. Turning Test - right tire right turn
Table 1. Turning Test results
