RCJoh-@attglobal.net

Ah, you're all wrong.  The proper approach is to make it out of carbon

fiber (low mass / high rigidity) and charge 10X what it's really worth

because anything that looks that cool has to be good.

Then go home laughing.



Rick



Joel Morrissette wrote:

<blockquote cite="mid1790415409-1463-@boing.topica.com"

type="cite">

<blockquote class="gmail_quote"

style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">stiffness..

(natural freq = square root of stiffness over mass, so to

get higher frequency either decrease mass or increase stiffness or do

    

both)





Actually, you needn't increase the mass along the entire fender, just

farthest from the attachment point.  I'd have to find my mechanics

text, but you basically want to increase its moment of inertia about

the attachment point (the pivot).  One way to do this is stiffen it,

another to increase mass.  Another is to move the CG as far from the

pivot as you can.  Putting a large mass at the end increases its moment

of inertia and therefore lowers the frequency.  Think of the difference

between, say, the antenna on your car with and without one of those

antenna toppers.  Pluck it without one, and it will resonate at a

higher frequency than with.  Move the mass down the antenna, and the

natural frequency should increase.





So the short answer might be to zip-tie a couple cut washers to the end

of the fender, thereby increasing its moment of intertia about the

attach point.



I think that's right...I've been doing o-chem homework for 4 hours, so

this is a MAJOR context switch.





-Joel