keybed spring

[David Ilvedson]

When the keyframe is out of the action cavity...can you still see the keybed move up and down?   Can you actually measure it moving up with your finger pressure?   Not good...just make sure it not something to do with bedding the keyframe...

David Ilvedson, RPT
Pacifica, California



----- Original message ----------------------------------------
From: "David Renaud" <drjazzca@yahoo.ca>
To: pianotech@ptg.org
Received: 2/24/2006 9:42:25 AM
Subject: keybed spring  


>  Korlore & Campbell, for a music school, one year
>old, tuned twice so far.

>   Call for sticky key. 

>   Key is rubbing on the key slip. 

>   Upon removal of the keyslip, I notice how tight the
>key slip screws are, and all the powder sawdust coming
>out with the screw. 

>   Upon inspection the key slip appears straight.

>   Placing the keyslip back, it touches the keybed
>at the ends, but there is a bow towards the middle
>with over a 1/16 inch gap at center. I push upward
>on the bottom of the keybed with my thumb only and
>watch while the keybed wood itself flexes up and down
>in the center and also observe the keys rising and
>falling. The keybed is a spring

>   I notice that with the key slip removed the entire
>middle of the piano has severly bubbling hammers.
>Putting the keyslip back stops the bubbling, but 
>the keyslip rubs the front of the keys. 

>  I determine that the keybed is warping. The downward
>pressure is forces the keyslip to torque
>towards the keys. Tight key slip screws were due to 
>torque of bending the keybed upwards. The dust
>coming out with the screws was the light material 
>developing stripped screw holes under the torque. 

>  Being a squeezed emergency appointment for a  sticky
>key , I comprimise by leaving one screw out so as not
>to torque the keyslip and keybed together so much,
>adjusted extra let off to eliminate bobbling hammers,
>and said I would e-mail a report.

>  I can not see a solution to this other then perhaps
>putting a strip of plate steel under the keybed to
>freeze it straight. With nothing but dust to screw it
>into, bolts through would be required. 
> 
>  I can bend the keybed about with my thumb alone. 
>How can one be expected to regulate that, the keybed
>itself is a mushy energy absorbtion spring. 

>  The first time I tuned this piano I was impressed to
>find a clean sounding chinese piano that was tunable.
>I am not so pleased afterall. This is bad for
>business, it smells of mechnical instability,
>callbacks, and unresolvable issues. I piano I actually
>can not work on mechanically  

>1) Steel plate?? thoughts.......
>2) How many have seen this.....other solutions

>  I will try to fix anything, but this looks like 
>soft, spongy warping material that can not be worked
>with. I feel it is a total waste of time to regulate
>it, come spring everything will have changed
>dramaticly. grrrrr

>   Somebody is going to think up a fancy technical 
>name.....accelerated keybed spring action.....and
>someone else is going to think it is a good idea and
>patent it.......sorry.....
> 
>                       Feeling dramatic
>                       Dave Renaud  






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