My L3 Project...A 7.5" LOC Goblin...AMA

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rharshberger

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I worked with Barry (former owner) on modifying a Bruiser EXL which I originally purchased from Ken Herrick at Al's Hobby Shop in Elmhurst, IL. Barry cut new fins based on my Rocksim modifications.
Looks like the lower fins are slightly smaller than the upper set, would you mind sharing the Rocksim file, I might want to build a smaller scale version as its a nice looking rocket.
 

Speaknoevil

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JLebow

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Rolling shutter doesn't change the motion - it just doesn't capture all motion at the same time.

The excursions you see are very real.
The excursions in the image are "real", and a good portion of the displacement is likely the fins. From the amplitude of the waves in the previously straight road, a significant portion of the excursion in the image is also bending and deflections in the camera mount. The frequency of the fin flutter, the camera structure, and "sampling rate" of the rolling shutter all superimpose in the image you see. You have quite a puzzle to try and back out which structure is shaking and in what amplitude. If the resonant frequency of any of the fluttering parts is more than 15 Hz (half the frame rate of the camera, which I assume to be 30 Hz), then there will also be alias artifacts that can give some pretty interesting mode shapes in the image. This can include what I observed, that a few frames, between very wavy frames, show the fins to be straight, when they might not be static - just captured at the same phase of periodic motion, each time the next scanned line in the frame captures part of the image.

I don't know that any of this changes the conclusion that the fins shook until they failed.

DAllen, good luck with the rebuild. Thanks for posting what happened, even though it sucked.
 
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