keybed spring

[Joe And Penny Goss]

1/2" angle iron 4' long
Joe Goss RPT
Mother Goose Tools
imatunr@srvinet.com
www.mothergoosetools.com
----- Original Message ----- 
From: "David Renaud" <drjazzca@yahoo.ca>
To: <pianotech@ptg.org>
Sent: Friday, February 24, 2006 3:42 PM
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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