bobbling hammers, again

[Overs Pianos]

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>Several months I asked about bobbling hammers in a grand. I 
>discovered that the shank lenght was too long.
>
>I now have a similar problem with a D. But this time, I've rebuilt 
>the action with new Steinway parts, (new h,s,f and wipps). There are 
>three notes that are driving me nuts. Unless I really smack the 
>note, the hammer doesn't want to check. They boble so bad that they 
>hit the string on the rebound.
>
>The regulation is just like the other notes, (dip, l.o.,drop, etc.). 
>Not only is key dip just like its neighbors, but when I increased 
>key dip, it didn't solve the problem. There is enough damper lever 
>clearance. I've adjusted the back checks to where the hammer checks 
>almost back down on the cushion. When I try to make it check 
>earlier, it catches. I've bent the checks so that the rake is enough 
>to clear the hammer on the way up, but still catches it on the way 
>down. I've reduced spring tension to the point of almost no rise, 
>and I've sanded the backs of the tails. I even changed wippens on 
>one key, but the problem is still there.
>
>What are some other things I should look at?
>
>Wim

Check that the capstan line is straight. An out-of-line capstan can 
cause the hammer/key ratio to be too low if the capstan is positioned 
towards the key balance pin. This could result in insufficient 
clearance between the roller and jack when in the check position, 
which can cause unreliable checking. Similarly, an out-of-line roller 
(if it is positioned further out towards the hammer head) will affect 
the ratio also. The jack should ideally just clear the roller when 
the action is in check. If it clears by too much it will have a 
deleterious effect on repetition speed. If it is contacting the 
roller it may cause the checking to be unreliable.

Another outside possibility is an out of position balance pin hole, 
which may similarly effect the leverage ratio. I've seen some pretty 
ordinary balance pin hole alignment, even in Kluge keyboards in 
recent years, so this problem can occur even with some of the most 
reputable keyboard makers.

Ron O.
-- 
OVERS PIANOS - SYDNEY
    Grand Piano Manufacturers
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Web http://overspianos.com.au
mailto:info@overspianos.com.au
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