[CAUT] Worn whippen cushions / VS Profelt

[Fred Sturm]

On Mar 15, 2009, at 10:25 AM, Ron Nossaman wrote:

> For what is costs in time and materials to replace them, I don't see  
> much justification for trying to save worn letoff punchings. The  
> aggravation factor alone in trying to regulate anything less than  
> uniform thickness is worth replacement. For me, at least.
> Ron N

For me, it's a judgment call. Replacing the punchings doesn't take  
that long, maybe 20 minutes by the time you have saturated them to  
loosen the glue, taken them off, fired up the glue pot, and put on the  
new. OTOH, it takes me about 5 minutes to run a sand paddle over a  
set, blow off the fibers, brush on a bit of water, follow with a  
clothes iron, and lay on some teflon (using a pipecleaner, laying it  
along a bunch and rolling to transfer the material).
	I start by assessing a sample. I might just iron one and see if it  
goes flat. If there is enough dimple, I'll add some water to the  
picture (apply with a brush, then apply the iron to make steam). If  
the dimple is still there, I figure I'll sand enough to take the rest  
of the punching down to that level, so I work accordingly, and as  
described above.
	If the dimples are quite deep, I replace. This is typically when I  
replace other parts. But if I am in a hurry and cutting corners, I  
might just do the sanding routine. When it's routine, on-going re- 
conditioning, I'll typically do the sanding thing (or just steam and  
iron, if sanding isn't needed).
	In any case, I keep harping on this because of the regulation hassle  
if they aren't level. I have the impression that a lot of people don't  
pay attention to this, based on the number of stories of how the  
regulation changes supposedly because of humidity change or whatever.  
I'm not saying humidity doesn't affect regulation, but when you have  
an article in the Journal (a couple years back) saying you need letoff  
on a concert grand to be 1/8" for a safety factor, somebody is doing  
something wrong, IMO. My guess is the big missing/ignored factor is  
those dimpled regulation punchings.
Regards,
Fred Sturm
University of New Mexico
fssturm at unm.edu