Belleville Washer Flight Test #3

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These three pictures show the configuration I used for the flights with belleville washer 6-stacks under all of the six propeller bolts.

Oblique View of Belleville Washer Stacks

Close Up View of Belleville Washer Stacks

Rear View of Belleville Washer Stacks

After 3.5 hours of flight with the previous configuration, I added two more belleville washer bolts for a total of six. I have now (as of 4/15/2007) flown 7 flights with this setup, for a total of 4.2 hours of flight time.

Again, prior to each flight I measured the large area washer spacing on each bolt, and then after each flight examined the prop/bolts again. In each case, there was no movement of anything. While there was a small difference (a few thousandths of an inch in a few cases) between flights or between takeoff and landing, that could easily be measurement inaccuracy. There was no OVERALL drift of the measurements.

I also measured the thickness of the prop hub, and it was always within a couple of thousanths of an inch of the previous measurement. Once again, there was no overall drift of the hub thickness.

I'm still very pleased with this experiment. Other than a few extra pounds of metal at the back end, there seems to be no downside to this installation. Obviously, I do NOT have very much time on the system yet - fatigue, corrosion, or other time-dependent issues may yet crop up, so I won't make any conclusions until I have at least 25 - 50 hours on the system.

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Copyright 2007, All Rights Reserved, Marc J. Zeitlin

Last updated: April 15, 2007