[CAUT] Jack speed, (was Tight balancier

Fred Sturm fssturm at unm.edu
Tue Nov 14 08:06:02 MST 2006


> Fred,
> You mention reaming to get down to 4-6 gm.  Reaming introduces  
> heat, which, I would think, would swell the felt.  As the felt  
> cools, it would seem there would be a tendency towards lower friction.
>
> Just a theory,
> Jeff

Hi Jeff,
	What was really puzzling me was that merely removing and replacing  
pins raised the friction from 1-2 to 3-5 gms. Nothing beyond removing  
and replacing. But then they went back to 1-2 in not very long,  
without being played. I expect the teflon impregnated felt expanded  
in the absence of the pin. Then, with the pin back in, it "conformed"  
to the pin. But the real issue here is whether or not one can trust  
what one is doing and measuring with this material - or, at any rate,  
to what extent one can predict what will occur in the future. If I  
pin standard felt centers at 6 gms, I can feel fairly certain that  
they will stay as high as 4 gm for a good while. They will certainly  
still be at 6 gm when I finish pinning all the flanges, and before  
the piano gets played a lot. With Teflon impregnated, I'm not so  
sure. Over the years, I'll get enough experience to come to more of a  
conclusion, but I was hoping that others who had done more pinning on  
this material might share their experiences.
Regards,
Fred Sturm
University of New Mexico
fssturm at unm.edu
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