Summary:
All of Spring quarter for the 2023-2024 School year has been devoted to testing of the RC Baja. The goal of the testing that is done is to see if the car meets all of the listed requirements that can be found in section 1d of the engineering report. If the design that was chosen by the engineer is the best design than all requirements should be met or exceeded. Testing will consist in controlled and uncontrolled settings to see how the car reacts to normal and extended use. Some tests for example are drop tests, steering/slalom testing, jump testing, and in more controlled environments, deflection on certain individual components on the Instron machine. All requirements are tested in some way shape or form. A detailed schedule of said tests can be found in Appendix E. If the result of a test is failure or the car does not meet the requirement, changes are made to make sure the car meets the requirement. Once all of the testing is done and confirmed adequate, the car will then be ready for the ASME RC Baja competition.
Up until week 4-5, the Instron machine had been the primary source of testing for the RC Baja steering and suspension. This is so that the engineer can conduct compressive and tensile testing on individual components of the steering and suspension system. The RC Baja competition (Drag race, Slalom, Baja) is scheduled to take place at the end of week 4 of Spring quarter. Because of this, all non destructive testing is done prior to the competition so no component failures and or missing components can cause the team to not compete at the competition. It was initially planned at the beginning of the quarter for all testing to be done before the competition was to happen, but there had been changes to the schedule. However, because of the testing of the components that have been tested up until week 4, the engineer has complete confidence in the suspension and steering components working as intended after most of the components had been tested on the Instron machine. Post competition more testing that has to do with the overall function of the suspension and steering system will be done.
Weeks 5-6 consisted of the RC Baja steering angle and radius test. A problem that the engineer encountered was that the steering was not working the way that it was intended to. The tie rods continued to bind while the car turned left to right which resulted in the car not being able to turn as far and as efficient as it was designed to be. This was easily fixed by re-configuring the tie rod connection points and getting the ride height of the car lower so that the tie rods were not operating with such a sharp angle. This sharp angle was contributing to the binding issues the engineer was encountering during the testing primarily. Once this was resolved the overall car maneuverability was extremely better, and the car was able to turn the way it was intended to. However, the car was still able to turn further to the right than it was to the left. This has since been corrected by changing the start and end points of the servo so that the car is capped at how far it is able to turn to the left and to the right so that it is the same to either direction.
The methods used for the steering angle and radius test was to test the turning angle and if the turning angle was successfully met then in theory the turning radius test should also be a success. However, this is not always the case in real world scenarios. This was the method that the engineer brought to this test and the engineer was correct to assume this. The car met the turning angle requirements, and it did not fully meet the turning radius requirements with the achieved angle even though in theory it should have been able to. The reason for it not passing the test with success has been highlighted previously in this section.
Tests:
Figure 17: Rear trailing arm deflection test on Instron.
The very first test that was conducted was a deflection test of the rear trailing arm. The rear trailing arm is a vital moving/active component that allows for the rear suspension of the RC car to function. This rear trailing arm suits as a mounting location for the lower shock end as well. And at this location approximately at the center of the trailing arm the shock is mounted and because of this a force is introduced to the rear trailing arm that could cause deflection. The listed requirement for this scenario is that the rear trailing arm must deflect less than 1/16" to be suitable for extended use and cycles. In analysis #1 in the analysis section of the website an analysis was done to calculate deflection under a 5 lb load. A 5 lb load is troublesome to acquire accurate data from on the Instron, so a higher 20lb force was introduced. The total amount of deflection was 0.008" under a 20 lb load. The rear trailing arm was also put under a 400 lb load and it deflected 0.04". At a 20lb load, and a 400 lb load the rear railing arm is still well under the 1/16" deflection requirement and it successful in this test. The rear trailing arm design is deemed suitable for use in this application.
Figure 18: Turning Radius Test (3.5' Radius, 7' Diameter)
In figure 18, the turning radius is tested of the RC car turning to the left and turning to the right. The reason for doing this test was because there was a requirement set that it had to make a 180-degree turn in less than a 3.5' radius (7' diameter) circle. And for this to happen there was a green sheet done that stated the car needed a 25 degree turning angle to successfully complete the turn, even though the car may have had the required turning angle, the turning radius still had to be tested to ensure it can still utilize the turning angle that it has. The car turned sharper to the right than it did to the left. Turning to the left failed, and turning to the right was a success.
Figure 19: Turning Radius Video
Here is a video showing how the turning radius test was done roughly. Except for the actual turning radius test the car would make 1 full 180-degree turn then stop when it completed the turn and the test administrations would then measure from the blue tape to the outside portion of the wheel to see how far over or shorter the car was able to make the turn. And in this video it can be seen that the car does not fully meet the turning radius test/requirement of a 180-degree turn in less than 3.5' radius or a 7' diameter while turning to the left. Doing the same test the car does make the 180-degree turn turning to the right successfully within 5'- 6' turning diameter or 2.5'- 3' radius.
Figure 20: Turning Angle Test
In figure 19, an image of how the turning angle was measured/tested is shown. The test is simply done by taking an engineering formated green sheet and drawing a straight line with a straight edge down onto the paper. And from this the cars front wheels are turned to the left and turned to the right to measure the angle that the wheels were able to turn. And this was done using a protractor to measure the angle. The angle was greater than 25 degrees so it meets the requirement for the turning angle turning both left to right with both wheels.
Figure 21: Turning Angle Test
Figure 20 represents the line that is drawn parallel to the wheel/tire to represent the turning angle that the car is able to achieve. As long as this line was parallel with the wheel/tire the angle at which it can turn will be accurate when measuring the angle between the original vertical line drawn on the paper, and the line with an angle. This was done with both the left and right wheels turning left to right. In both cases the car turned further to the right than it did to the left. And this aligns with what the turning radius results showed the engineer.
Figure 22: Suspension Articulation Test
The final test that was done was an articulation test of the overall suspension system. The car was required to be able to articulate 1" without any of the wheels coming off of the ground. 1", 2", and 3" tall 3D printed blocks were created for the vehicle to sit on. If a wheel was able to lift off the ground the test was a failure. But in this case in figure 21, the tallest block created (3") was used to show the suspension articulation and the vehicle articulated with ease without any of the wheels being lifted off of the ground. If a wheel is ever lifted off of the ground the test is a fail because the vehicle essentially loses power to that wheel, and overall control.
Figure 23: Articulation Test Demo
Requirement #7 on the analysis page of this website states that the rear axle must be able to articulate 2". In figure 23, a test is demonstrated showing that the rear axle is able to articulate using a 1" block placed under the front left tire, and the rear right tire to measure the amount of articulation the car can withstand without any of the tires coming off of the ground. In the test demonstration the 1" 3D printed block is shown first, and then a 3" tall block is shown next. The RC car can articulate 2" easily as well as 3". In fact, it takes 5 total inches of articulation for any of the wheels/tires to lift off of the ground. The front and rear suspension system meets requirement #7 with ease.