Kawai let-off (poor jack design?)

[Ron Overs]

Hi list,

Frank Cahill wrote
 I tuned a kawai KG-1 today. It's a gray market piano...two pedals. 
There was very little let-off and in some cases, no let-off.

Frank,

this symptom is not unusual for a Kawai KG action.
The geometry (ie. built in friction) of the KG jack at the let-off button 
is one of the best examples of poor action design in the business.

Try mounting a wippen on the workshop bench (hold it horizontally by 
clamping the wippen flange onto a support block), substituting the 
let-off button with a plain wooden dowel (also held horizontally).
Examine the relative motion between the jack tender and the let-off 
button during escapement.

And how does the KG let-off button cloth survive under real life service? 
It doesn't! As the jack tender gouges a groove in the felt  the let-off 
setting moves toward the string.

Ron E. Overs
Sydney, Australia


Email: ron@overspianos.com.au
Website: www.overspianos.com.au