hammer acceleration

[jolly roger]

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Hi David,
              The Abel shanks are lighter than the Renner, this can add to you
observations.  Also no graphite depending on the humidity in your area, this
can be a significant difference re friction.  These are the two reasons I
prefer the Abel shanks.
It's been a while since I used Renner shanks, so things may have changed.
  I have not noticed any thing amiss with any of Wally's knuckles with regards
to friction, and I know he is very vigilant with regards to dimensions, 
alignment and friction.  He gets a lot of feed back, so talk to him, he may
have some extra ideas.
Is this a Steinway?  If so the capstan and heel geometry is critical.  1mm
change can mean a whole lot, so check carefully.
Just some random thoughts.
Roger


At 11:48 AM 8/24/01 -0700, you wrote: 
>
> Roger/Newton:
>  
> In this case it is new parts.  Renner wippens, Abel shanks.  Center pins are
> fine everything is lubricated properly and adequately.  I am aware of the
> static friction element but it seems more than that.   I do notice that the
> leather on the Abel shanks is much different than the leather on Renner
> shanks, which I have generally used in the past.  The Abel knuckles seem not
> as smooth and soft as Renner's.  Any comments on that?  
>  
> David Love
>>
>> ----- Original Message -----  
>> From: <mailto:baldyam@sk.sympatico.ca>jolly roger  
>> To: <mailto:pianotech@ptg.org>pianotech@ptg.org  
>> Sent: August 24, 2001 10:13 AM 
>> Subject: Re: hammer acceleration
>>
>> Hi David, 
>>                 Are you noticing this on new parts?  Once static
friction is
>> broken, I have noted that this happens more frequently with worn or loose
>> keybushings. e.g.  Changing a prehung set of Yamaha shanks, with out
>> rebushing keys. At one time I used to change just the hammer sets at the
>> University.  Now I insist on rebushing keys along with hammer replacement. 
>> It makes a big difference. 
>> If the friction is high on the knuckle and centre pinning friction is very
>> low it can give similar results. To trouble shoot.  Remove a hammer and
>> wippen assembly,  and measure the friction of the flange C/P's, Holding the
>> flange horizontal, if it drops under it's own weight, will give you a quick
>> check, but start measuring and repinning if there seems to be problems.
This
>> eliminates these as the cause. Next examine the capstan, and wippen cloth, 
>> polish the capstan, and if it's old capstans steam out the cup, dry iron
>> smooth, and burnish in some teflon powder. 
>> FWIW. I have repinned more than one set of flanges on new parts.  
>> With friction happening with the right amounts in the right places, the key
>> should go down nice and and steady. Many new Korean pianos have way too
much
>> friction on the knuckles, shrinking the C/P bushings has been a common
>> practice to over come friction.  It will mask the problem,  and give
>> acceptable DW readings. Change the knuckles, and WOW, watch the the
friction
>> figures change. 
>> To to look at geometry issues you have to start with the magic line, key
>> ratio, etc. 
>> The old adage, "divide and conquer", applies here.  Just eliminate one
thing
>> at a time. 
>> Regards Roger
>>
>>
>>
>>
>>
>>
>>
>> At 09:00 AM 8/24/01 -0700, you wrote: 
>>>
>>> I notice, when I am doing a weigh-off on a key board, that on some actions
>>> as the hammer rises the acceleration is relatively slow and steady.  Other
>>> times, once the hammer starts to rise, the acceleration is quite rapid.  
>>> What is responsible for that difference?  Friction would seem to be the
>>> logical answer, but friction where?  I heavily lubricate actions before I
>>> do a weigh-off.  There seems to be something else at work in the
>>> geometry/leverage.  Among other things, with the rapidly accelerating
>>> hammer, it is more difficult to determine the measured downweight.  I
there
>>> any way around that problem?  
>>>
>>> David Love
>>
>
>
>
>

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