hammer acceleration

[jolly roger]

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Hi David,
              A quick and easy check of where the friction may be coming
from. 
Measure the strike wt. of a few hammers. Find one or two old hammers with
similar strike wts. Install them, then remeasure the friction.  This will give
you an indication of the knuckle friction, old vs new.   PS Make sure the CP
friction is similar.
These type of comparative measurements can be illuminating.
A habit I have started, that I have found helpful, Is to rebush/resize and
fully rebuild the keybed before starting touch weight analysis.  This I
feel is
a fixed component with regards to friction. If the BR pin hole is correct, and
there is .002" clearance at the BR bushing, and .005" at the FR bushing.  Then
I have removed one more variable from the before and after evaluation.
I then do a few samples, wippens only, and compare,  then finally hammers and
shanks.  For the samples I just use all the C's.
Your friction seems a little high for me.  10-12gm range is where I like to
see
it.  But this is only one of the components.
Taking a lot of little steps, like this, just helps to stop me from getting
lost.  <G>

Roger


At 10:37 AM 8/26/01 -0700, you wrote: 
>
> Friction was pretty uniform ranging from 15-12 g from bottom to top. 
> slightly high due to heavy Steinway hammers probably.  I do check the
knuckle
> heights since you mentioned that on a post some time ago.  They were very
> consistent on this set.  The acceleration characteristic was there after I
> re-weighed the piano for uniform balance weight.
>  
> David Love
>>
>> ----- Original Message -----  
>> From: <mailto:jon.page@verizon.net>Jon Page  
>> To: <mailto:pianotech@ptg.org>pianotech@ptg.org  
>> Sent: August 26, 2001 5:00 AM 
>> Subject: Re: hammer acceleration
>>
>> At 06:04 PM 08/25/2001 -0700, you wrote:
>>>
>>> Roger: 
>>>   
>>> The action is workable.  The key ratio is .53 for naturals and .55 for
>>> sharps.  The knuckles are 17mm and the dip is not excessive.  The caps are
>>> centered under the heels.  It's not grossly out, don't misunderstand me. 
>>> The action feels nice.  I just noticed that the acceleration rate was
>>> different and have noticed this variation periodically.  In this case once
>>> the static friction is broken the hammer begins to accelerate more quickly
>>> than many I have weighed off.  Anyway, on to the next one.  I'm tempted to
>>> try S&S parts on the next one I do, I'm glad to hear you were happy with
>>> the quality control. 
>>>   
>>> David Love
>>
>> Could it be that the ones which accelerate faster also have a lower
friction
>> or Balance Weight? 
>> Check knuckle height, there may be a noticeable difference from note to
>> note; 
>> another process prior to shank installation is measuring knuckle height
and 
>> grouping similar ones together.
>>
>> Regards, 
>> Jon Page,   piano technician 
>> Harwich Port, Cape Cod, Mass. 
>> mailto:jon.page@verizon.net 
>> http://www.stanwoodpiano.com 
>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 
>
>
>
>

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