Larudee's mystery - Was: Ditch the bushings

Overs Pianos sec@overspianos.com.au
Thu, 17 May 2001 19:06:43 +1000


Paul and other commentators,

>Wouldn't torque from string tension be strictly a matter of the 
>distance of the
>string from the axis of the pin (radius) and the amount of tension? 
>It's basically
>the same thing as torque from a tuning wrench (sic!) on a smaller 
>scale.  The same
>force results in more torque when applied to a wrench with a longer 
>handle than
>with a shorter one.

Absolutely, but the friction surface is larger also with the larger 
pin, which makes it therefore just as capable of withstand the higher 
resultant torque loading.

>Similarly, the string doesn't have as much leverage on a
>smaller pin

Do you mean here that it cannot generate the same torque forces due 
to the smaller leverage radius?

>The part that counts is the radius at the point of string contact.

Sure, but its the relative holding power of the friction between the 
pin and the block, and its torque resistance as compared to the 
actual torque developed by the string tension with a given size pin, 
which will determine the pin holding ability.

As Ron N wrote:

>  . . . With the moment arm of the string torque being the radius of 
>pin diameter

(plus the radius of the core wire)

>and the block contact surface area varying with the circumference 
>(pi*D), doesn't this
>  proportion scale?

Sure does!

>Remember that I'm missing the standard math receptors in my
>  alleged brain, and am prone to orders of magnitude estimation errors in these
>  things.

Your disclaimer is not accepted Mr Nossaman.

Ron O
-- 
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