[CAUT] Teflon and felt bushings

[Fred Sturm]

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On Nov 14, 2005, at 11:25 AM, Barbara Richmond wrote:

> Fred,
>
> Ah.  When I started at IWU, I followed a technician who was hard of  
> hearing--so he couldn't hear the Teflon clicking the faculty  
> complained of.  His solution was to pin everything fairly tight.   
> <wince>   Anyway, I repinned the worst of them, but they were still  
> on the heavy side.  There was no rebuilding budget at the time (and  
> David Stanwood was just coming out with his touchweight stuff when  
> I moved away).  I simply said that I had done what I could until  
> the action could be replaced.
>
> So, if there isn't a touchweight issue with a Teflon repetition and  
> a felt hammer flange, the bulk of the problem must be in the hammer  
> shank/flange.  Did the knuckle mounting distance change from Teflon  
> to felt or was it just the nature of the Teflon?  Or, did the  
> knuckle size change (or whatever)?
>
> Barbara Richmond

     I'm not up on the exact history, but the geometry change  
(knuckle placement for the most part, but other changes as well)  
occurred during the early 80's, around the same time as the switch  
from teflon II to impregnated felt. There was probably a period of  
transition when it would be anyone's guess what combination you might  
find. With the hybrids, you would expect less effect on touchweight  
from centerpin friction of wipps than from hammershanks. Tight  
repetition centers are rarely a problem, usually a virtue.
     For the old teflons, it's hard to figure out just what is the  
issue. In my teflon B's from the mid 60's, I also have residual  
graphite grease on the knuckles. There are just too many factors, and  
it isn't worth the trouble (to me) to sift through them.
     The clicks in my B's are from those original teflon inserts -  
the small smooth ones without the ribs - clicking against the wood of  
the shank, for the most part. Replace insert, ream, install pin,  
check friction, swear, un-pin, re-ream, re-install pin, check again,  
cuss at Steinway for providing reamers that aren't the right size.  
It's a vicious cycle. I've tried the intermediate reamers (.0005  
increments) from Pianotek, and they make it too loose.
     Bottom line: since I can' t get that friction within parameters,  
and since the knuckle/rep top is problematic, and wipp cushions are  
worn, yadda, yadda, I just call it good enough and look forward to  
the year I get around to replacing parts.

Regards,
Fred Sturm
University of New Mexico
fssturm@unm.edu
  "Art is not a mirror held up to reality, but a hammer with which to  
shape it."
Bertold Brecht



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