Belleville Washer Flight Test #2

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These two pictures show the configuration I used for my second round of flights with belleville washer 6-stacks under four of the six propeller bolts.

Oblique view of Belleville Washer Stacks

Rear View of Hertzler Prop with two standard bolts and four Belleville Washer Stacks

After 2.8 hours of flight with the previous configuration, I added two more belleville washer bolts. I flew four flights with this setup, for a total of 3.5 hours of flight time.

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. Heat transfer through the extension and measurement inaccuracy could easily be the source of the difference. Once again, there was no overall drift of the hub thickness.

Again, so far, so good - I'm pleased. The next step is to put in the last two belleville washer bolts.

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Copyright 2007, All Rights Reserved, Marc J. Zeitlin

Last updated: April 15, 2007