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<P>Gray- </P>
<P>Excellent as always - and as always I'm confused at a MUCH higher level now! Maybe You can explain it better in Muncie - I'll buy the first round... </P>
<P>Interesting that the pushrod failure that nearly killed my plane on its 4th flight occurred at the beginning of the threads on the servo-end 2-56 metal rod... </P>
<P>besides, during the repair effort I wasn't energetic enought to put my foam damper in the center anyway... there was a former a couple of inches behind pushrod center that seemed PERFECT for my little balsa / foam damper. </P>
<P>That and a 4-40 threaded rod ... and a 3/8" dia carbon tube pushrod... have resulted in a solid elev control the last 400 or so flights. </P>
<P>Rick </P>
<DIV class=RTE>>"Agree w/ John about using foam as a vibration damper. Also, someone much </DIV>
<DIV></DIV>>wiser than me pointed out that whatever is installed should NOT be
<DIV></DIV>>halfway, 1/4 way, or any reasonable fraction of the pushrod length because
<DIV></DIV>>these may end up as stationary nodes in the vibrating rod, and end up
<DIV></DIV>>doing no good.
<DIV></DIV>>Rick"
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<DIV></DIV>>Rick
<DIV></DIV>>Could happen but consider this.....The resonance or flutter results from a
<DIV></DIV>>combination of factors. One is the modulus of the item and one is the
<DIV></DIV>>mass. In the case of our push rod scenario, the cf rod has a consistent
<DIV></DIV>>stiffness the length of the rod, so that is constant, but the longer the
<DIV></DIV>>rod the easier it is to buckle. A full length rod has a certain mass and a
<DIV></DIV>>half length rod (foam in the middle) has half that mass. The apparent
<DIV></DIV>>stiffness of the half rod is greater and the mass is less therefore what
<DIV></DIV>>make a full length rod resonate most likely will not make the half rod do
<DIV></DIV>>the same. In addition, having the rod in contact with the foam dampens the
<DIV></DIV>>resonance, as opposed to a situation where the rod is hard fastened, and
<DIV></DIV>>therfore sets up a new set of resonance factor based on the mass and
<DIV></DIV>>modulus again.
<DIV></DIV>>Hopefully this makes sense...I absorbed this primitive knowledge hanging
<DIV></DIV>>around true stress weenies...
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<DIV></DIV>>
<DIV></DIV>>
<DIV></DIV>>Gray Fowler
<DIV></DIV>>Principal Chemical Engineer
<DIV></DIV>>Composites Engineering
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