Keyframe Bedding

[erwinspiano at aol.com]

  Hi David
  good post.
   Now let's exercise a little techno prudence with this idea before some one raises the balance rail higher than a car changing a flat.
   I have safely raised key heights 20 to 30 thou without negative affect. For me that's the limit. Ok? Enough to effect a slight but significant change in key level ,dip & aftertouch when needed. This maneuver may not always be appropriate & the real fix is to start over as described below.
   As far as pre mature wear due to increased stress I think more of that would come more  by all the leads found in the keys of many famous pianos. Stwy,M&H, Baldwin etc.
   I like to set the keybed/keyframe contact with keys off & action screwed to frame (as per Yamaha) so I can really understand the unloaded strength of the keyframe I am working with.  This is a good starting place.  It is also to experiment with turning bolts up & down to judge the effect of the back rail ie.  is it lifting tapping etc. All is  visually accessabile
  Well I do not know what the deficiencies of Setting the glide bolts on Steinway pianos are but I have not found one case on a new Steinway where the glide bolts were any where's near the keybed. I can't explain it. It must be the dealers responsibility..sic...GRRR...Loudly
  Dale



Requesting a little perspective:
What are the deficiencies of the Steinway method of setting glide bolts? 

Establishing the practical parameters of frame bedding, once I've established defined contact to effectively preclude any knocking, how much additional stress could I introduce into the system before beginning to observe negative effects?  :
        - increased resistance of una corda shift
        - premature squeaking at glide contact
        - increase in friction and wear of keyblock plates and frame guide pins
        - change in keydip, aftertouch, 
        - create knocking at front rail or back rail
        
Regarding dags:
        - are dags essential to proper function of the action? i.e.: would back rail [necessarily] slap in their absence?
        - how much force (at glide bolt) would be required to compromise otherwise firm contact of back rail, to the point where        firm capture by dag is required? 
        - if the dags are used to compensate for insufficient care in back rail bedding, then wear and seasonal variation could         allow for the slap of Jude's observation.  (another cause could be flat, un-arched front to back profile).

I'm not sure that Andre's tuning fork analogy is operational here.  I would need to hear a more thorough explanation.

I do love finding new uses for my caliper.  Especially fond of them in key leveling.

David Skolnik
Hastings on Hudson, NY


At 10:29 PM 7/7/2008, you wrote:

I've experienced the tonal improvement but I've also noticed an occasional increase in the volume of keyslap on the backrails and sometimes extra knocking in the treble hammers. To my knowledge, the backrail was well secured by the dags and it's definitely not keyframe knocking. 
 
Jude Reveley, RPT
Absolute Piano Restoration, LLC
Lowell, Massachusetts
(978) 323-4545
 
 
----- Original Message ----- 
From: "andre oorebeek" <oorebeek at planet.nl>
To: "Pianotech List" <pianotech at ptg.org>
Sent: Monday, July 07, 2008 5:41 PM
Subject: Re: Keyframe Bedding

> And, turning the bolts tighter also increases the tension in the tone.
> The bolts are in a way like tuning forks.
> If you press down a tuning fork hard on a wooden surface, the tone it  
> generates will intensify.
> That way it is possible to 'voice' by adjusting the bolts.
> 
> friendly greetings
> from
> André Oorebeek
> 
>> 
>> -----Original Message-----
>> From: erwinspiano at aol.com
>> To: ilvey at sbcglobal.net
>> Sent: Mon, 7 Jul 2008 2:33 pm
>> Subject: Re: Keyframe Bedding
>>
>> The key frames in modern grands all have a somewhat arched/pinched  
>> key frame arrangement  front to back & end to end. Adjusting the  
>> bedding bolts to a neutral position to start with & then turning the  
>> bolts tighter against the key bed is where the stressing comes  
>> from.  You can measure the subsequent rise at the front of the keys  
>> as the bolts are being turned as  per Jon Pages suggestion.  The  
>> back of the frame is held down by the dags & the ends by the key  
>> blocks
>>   Actually this is also a bit of a buffer or safety factor for  
>> climate changes. This way the bolts will hopefully stay in contact  
>> with the bed in each season & not be so prone to change with  
>> humidity & temp.
>>   Dale
>>


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