I "reverse engineered" a commercial leakdown tester and built a unit for my
own use. The particular one that I copied was set up for a 60 psi input
pressure. I did "A-B testing" in order to determine the flow rate of the
orifice since I didn't want to take the high-priced unit apart for
measurement. I found the units flowed the same when I used a orifice of
.043". Your experience will likely vary.
The test gauge was calibrated:
60 psi = 0% leakdown
30 psi = 50% leakdown
0 psi= 100% leakdown
and all the intermediate calibrations . .
I believe that the pressures and calibrations are arbitrary and not to be
viewed as absolute true data but the tool is a great diagnostic aid and
basis for comparison.
I found "Aircraft Spruce" sells a neat tester for "cheap" after I built
mine.
Use a restraint to keep the motor from unexpectedly revolving with the air
pressure.
Tony Clark
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