Since March 23, the construction of the validation aircraft and assembly of its electronic components has been completed. Additionally, all the machined parts for the hangers have been returned from the university machinist and have been assembled and attached to the aircraft as well. The internal assembly of the hanger mounts and frame within the wing are shown in Figure 1, and the assembled aircraft is shown in Figure 2.
Figure 3 shows the aircraft on the completed zipline structure. Additionally, a few pre-validation tests have been run to determine the success of the planned validation. The zipline feature for the aircraft was set up and tested, and the speed threshold of 25 mph was found to be achievable for a short period. Figure 4 provides the speed vs time graph of one of the test runs.
The RC motor has proved that it can exceed this threshold, but the goal of 35 mph has been set on hold due to the aircraft’s structural integrity and onboard weight of validation equipment. Three test runs with the original hangers have been run using a temporarily provided 100lbf load cell with the resolution of 0.05lbf. The expected values are very small and under the 0.05lbf resolution, requiring much more sensitive equipment. However, load cells can be damaged if overloaded past their rating, so these pre-tests with the low-resolution load cell was to verify that the actual drag force values would be within range of those projected last semester and prevent damaging other equipment. These three runs yielded peak drag values within the range of 0.05lbf and 0.1lbf, indicating that the actual drag force is within the same scale of values as the expected results, but to verify the difference in drag between the original and designed hangers, retests will need to be completed with the requested load cell.
For now, the 1:10 scale has provided satisfactory results which fall within the expected range of last semester’s calculations. Remaining validation experiments will include original hangers empty, the original hangers with the spray boom, the designed hangers empty raised, and the designed hangers empty lowered. Originally, the plan was to collect drag force vs time and speed vs time to plot drag over velocity for the drag coefficient, however the force indicator does not collect force over time unless connected to a laptop, which is not possible when the aircraft is flying. For now, the peak force readings stored on the indicator will be used until an alternative method is determined.
On the 1:3 scale, the team managed to get the whole system working and the issue of the hangers not being able to return to their starting position was fixed. Also, the first couple runs of motion validation were conducted, and the angle of rotation for the arm (21 degrees) was verified utilizing a digital angle gauge.
Figure 5 shows the results obtained from the motion validation during the week of Project Demo. These results were taken from hanger # 3(Right Hanger). As shown by the figure, we were still off the target parameters by (~½" Vertically, and ~¾" Horizontally). One of the factors affecting these results was the fact that one of the hangers was broken causing the pipe to sink on one side, leading to inaccurate measurement results for the whole system. However, to fully determine if only the structural integrity of 3D printed parts was playing a part in the inaccuracies. We opted to isolate the system and only measure displacements on the middle hanger (#2) without the pipe.
Figure 6 shows the results for the middle hanger. As shown by the graph we were only off the target parameters by ~1/10” Vertically and ~¼" Horizontally. The middle hanger results give us high confidence that utilizing machined parts will enhance the system’s stability and ensure attainment of the target point. With the time remaining, for the 1: 3 Scale we are planning on replacing all the 3D Printed Components with machined aluminum parts. However, as of 04/12/2024 we are still on hold to get these parts. The machinist informed us that he had major delays in the machine shop and would resume the machining process early next week. The remaining validation experiments will consist of the motion test to verify that the hangers attain the target point, and the drag test on the whole system.
Comentários