Testing
Upon completing the chassis and drivetrain prototypes, the group members needed to evaluate the design against a multitude of success criteria and design requirements. The following offers a rundown of the testing phase and the design's overall success.
At the beginning of this project, the group members created a list of design requirements for the drivetrain and chassis prototypes. To evaluate the project’s success, the engineers needed to determine if the final prototype met the design requirements and success criteria. Although it would have been ideal to have tested each design requirement, available time in the Spring quarter limited the testing phase to only three major tests. The results of these tests can be seen below. ​
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While the chassis deflection testing went rather smoothly, there were issues related to top speed and acceleration test setups. The original setup for these tests featured an iPhone with a GPS speedometer app being zip-tied to the top of the roll cage to measure the speed. Although the vehicle was able to reach 18 MPH with the initial setup, the car was basically uncontrollable at high speeds due to the higher center of gravity than normal and soft tire inserts. To fix this issue, the team purchased a radar gun to eliminate the phone attachment altogether, lowered the car by adjusting the shocks, and purchased stronger silicon tire inserts. These modifications lowered the center of gravity and in turn, increased the vehicle's stability at high speeds making the top speed and acceleration requirements achievable.
Table 2 - RC Baja Results
Chassis Deflection Test
Figure 29
The graphics above show the setup and completion of the chassis deflection testing. This test was conducted using an Instron 34sc-1. The Instron machine pushed downward slowly onto the center of the chassis until the required force was met. With a deflection of 0.028 inches under a 25-pound load, the chassis deflection test was considered an absolute success. The chassis was more than 7x more rigid than the design requirement while still remaining relatively lightweight. Given the extreme strength of the chassis, the team had decided there was ample room for weight shaving. Additional updates will be added if the team decides to go through with the modifications.
Figure 30
Chassis Deflection Graph
Top Speed and Acceleration Test
Figure 31
The velocity of the car was measured using a Bushnell Speed Radar Gun. It has an accuracy of +/- one MPH and is a highly rated brand meaning the measured results were as precise and accurate as possible.
To the left is a video of the setup for the top-speed and acceleration tests. The tests were conducted in the Nicholson Pavillion parking lot at CWU. The car's velocity was measured using a Bushnell Speedster II radar gun. Both tests were performed on the same dry, non-windy day in May. The second half of the video shows the results of extensive high-speed testing. After running the first acceleration test trial and slamming the brakes, the set screw running through the right wheel hub and axle sheared completely off meaning only one trial could be conducted. This set screw lasted the entirety of the end-of-year competition, many top-speed trials, and a great deal of rollovers meaning it took a beating throughout its lifetime.
Figure 32
Shown above is the bumper deformation due to an accidental dead-on impact with a curb at 18 MPH. The bumper deformed a large amount but it did its job well and the vehicle remained operational after the crash. The diagonal reinforcing bars were an excellent addition to the design. The team was very happy with how the chassis and roll cage handled the impact.
End-of-Year Competition Results
In addition to this, the most important test of them all was conducted at the end of the year: competition day! During this test, the vehicle competed against multiple other student-designed vehicles in a drag race event, slalom event, and Baja event. During the drag race event, the vehicles competed one at a time in a straight line on top of a concrete surface, racing the finish line as fast as they could. During the slalom event, the vehicles competed on the same concrete surface as the drag race event and slalomed around cones as fast as they could, competing one at a time. The Baja event was a rough multi-terrain race with an emphasis on completing the course as fast as possible. This event will undoubtedly put the most stress on the drivetrain and chassis components and test the vehicle in the most effective way: a fast-paced bash through a rough-terrain course.
Figure 33
The photo shown is the results of the end-of-year competition. The team got fourth in the drag race, second in the slalom event, and first in the Baja (Rally) event. With all of these points added together, the team was awarded first place overall! Also, while the team technically got fourth in the drag race, the team had the second fastest car competing that day and got fourth due to the point system being used based on hitting jumps and beating the other person competing at the same time.
Figure 34
During the competition, the beadlock tires kept debeading due to the large amounts of torque. The picture shown is team member Chayce Williams inserting the rubber back into the wheel before tightening the bolts. This issue was later fixed for the top speed testing when the team purchased thicker silicon tire inserts that performed more alike life-size offroad tires.