Testing and Failure

Tests:
1) Rpm test (using stroboscope)
2) Pressure test (using pressure gauge)
3) Volumetric flow test
4) Air-tightness test (using soapy water)

1) We used a stroboscope to test for the rpm of the impact driver in 2nd gear.
     The stroboscope read 1640 rpm for the drill, this will be the same for all of our testing.

2) We used a pressure gauge that we purchased to determine the pressure created by the air compressor under normal testing conditions (~1600 rpm).
     The pressure gauge consistently read 9-10 psi for the time the compressor was run at maximum speed.

3) We completed a volumetric flow test to determine the compression rate of the compressor by timing the inflation of a balloon.
     The balloon was filled in 17 seconds to a circumference of 24". Using (4/3)*pi*(24/(2*pi))^3 the volume was calculated to be 233.4 in^3, or .1351 ft^3. Knowing that flow rate is Volume / time we calculated the flow rate to be .477 cfm (cubic feet per minute).

4) We conducted an air-tightness test using soapy water while running the compressor. If any air leaked out, the soap would cause bubbles to form allowing us to identify areas of leakage.
     We had predicted certain areas would potentially have leakage being the crankshaft hole, the perimeter of the rubber gasket, the screw holes, and the hose connection. The test identified that only the hose connection had leakage which we already had plans in place to fix. For the final design delivered the hose will be secured into the main housing using epoxy which will completely seal the connection from leakage.

Failure:
     During the soapy water test, we ran the compressor in reverse and the compressor failed. David thinks that the failure was likely from accidentally tilting the drill, causing the eccentric hub to break through the wall of the weakened wall of the rotor. After dissembling the compressor the group realized that the failure was more widespread, with the eccentric hub, rotor, and main housing's stationary gear all deforming due to the high temperatures created from the friction between the gear teeth.