Blog 8- G10

 Blog 8

    For the period between March 23rd and April 13th the team has moved on to the final portion of the project, testing the prototype. The team has completed the validation tests for dimensionality, cooling, and initial waterproofing.

    For the dimensionality test, the dimensions were measured using rulers and calipers and compared to the maximum allowed dimensions. Table 1, shown below, shows the dimensions measured. Additionally, a bounding box, depicted in Figure 1, was constructed to visually illustrate the maximum allowable dimensions on the wheelchair, providing a clear visual representation of the boundaries and the prototype is well within the bounds

Dimension	Distance (in)	Distance (mm)	Real Distance (mm)
OD of Motor	3.875	98.4	N/A
Length of Motor	7.875	200.0	N/A
Flange Height (Square)	3.6875	93.7	N/A
Flange Thickness	0.5	12.7	N/A
DTI Back of Motor	0.5	12.7	5
DTI Right Side (Left Motor)	6	152.4	70
DTI Left Side (Left Motor)	1.5	38.1	10
DTI Bottom of Motor	6	152.4	70
DTI Top of Motor	0.375	9.5	8
Ground to Bottom of Seat	18.5	469.9	N/A

Table 1. Table of dimensions of the prototype

                                               Figure 1. Bounding box around the prototype.

    Figure 2 illustrates the setup utilized for conducting the cooling validation test. Inside the casing, a heater was positioned to mimic the heat generated by the motor. There were three thermistors used, one was situated inside the casing while the other two were placed externally—one near the base of the fins and the other on the fin tip. The thermistors were calibrated by being hooked to a multimeter as a constant temperature and the other side was heated water which was allowed to cool. There were 18 data points taken and they have been used to construct the graph shown in Figure 3.

    To prevent heat leakage from where the motor would connect to the rest of the wheelchair, clay served as an insulating barrier. The test took 1.5 hours and throughout the duration of the test, the temperature difference between the internal and ambient environments was below 20 degrees Celsius. This outcome confirms the device's efficacy in dissipating heat to maintain the motor's temperature within a safe range. Notably, a theta value of around 70 or higher would have been necessary for the motor to risk overheating. Furthermore, the test affirmed our assumption regarding the similarity between internal and external casing temperatures, as evidenced by the minimal disparity between the two recorded temperatures.

                                                Figure 2. Setup for cooling test

                                                       Figure 3: Thermistor Calibration Data

                            Figure 4. Difference between outside surface and inside surface over time.

    For the waterproofness validation testing there are two tests. The initial proof of concept waterproofing test has been conducted and was successful. The purpose of this test was to see if the device was waterproofed in any capacity before moving to the full IPX7 test which involves submerging the prototype in 1 m of water for 30 minutes. The casing was sealed with a mock motor and water leak strips inside and submerged underwater in a kitchen sink for 5 minutes. After opening the casing, the water strips did not change color showing there was no water leaked into the casing.

    These validation test results give the team confidence in the prototype’s success. Only two more validation tests are remaining. The first is a deeper water IPX7 test where the casing will be submerged in 1m of water in a trash can for 30 minutes. The second is the torque test where the motor is hooked up to a generator to see if the torque output was affected with the casing on. At this point of the project, the prototype will most likely not be changed as there is not enough time to improve upon the prototype. The only part of the prototype that can be modified is the silicone seal as that can be taken off and reapplied in the event of a leak.