Build your own 'spyder' demo model

[Richard Moody]

Its getting late and a little cold.  We might have our first frost tonight.  So
rather than trudge out to the heap and get some sound board material, I  C clamped a
piece of a yardstick, probably sugar pine, to the edge of a table. I spring clamped
an aluminum fork, (Scisoco) to the middle on top,  struck it listened, bent the wood
and listened.   It got louder as the wood bent. 
	But now for the interesting part.  Attach a C clamp to other end of the wood.  It
bobbles up and down like a spring board. If the fork is sounding while the board is
springing  its volume does a vibrato at the rate of of bobbling. This is most
dramatic with the fork near the middle of the stick. Another interesting effect is
when you lift up on the C clamp on the free end.  The sound disapears, but returns
when you let it down.  When you move the fork towards the free end, you must lift up
on the clamp a little to get an increase, but lift up too much and the sound rapidly
diminishes. 
	Now for the weird part.  Clamp the fork to the underside of the stick.  There is
little sound no matter which way the wood is bent. I suppose one could conclude the
"enhancement" is better from the top side of the bent wood. Where the fibers are
under tension.   ---ric

   



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> From: harvey <harvey@greenwood.net>
> To: pianotech@ptg.org
> Subject: Build your own 'spyder' demo model
> Date: Monday, September 27, 1999 2:43 PM
> 
> Ric wanted one of the variable crown models for experiments.
> 
> The original fork on a board demo was to illustrate the effect of the
> "spyder" (tension resonator) on Mason & Hamlin's. Yes, it was point-of-sale
> gadget, a simple bit often effective one. In case anyone has never seen one
> of these models, after the following setup remarks is the idea in words...
> Overall dimensions: 5-5/8"W x 12-3/8"L x 3-3/8"H (minus tuning fork)
> Panel (soundboard) thickness: .165" (supporting rationale below)
> [Thanks to Bob Mair for confirming these dimensions]
>