Re. Bobbling hammers on Yamaha upright

Richard Brekne Richard.Brekne@grieg.uib.no
Mon, 19 Apr 2004 22:09:33 +0200


Jim... I'd bet ten to one if you lessened the jack return spring 
strength, and made sure the jack centers were as friction free as you 
could get them, your problem bobblers would go away.  I know you are 
going to make sure theres a good regulation on the thing, and if it 
doesnt happen to more then just some few... then the likelyhood of the 
damper system being involved is very small.  So I'd bet that if the 
jacks let themselves more easily get pushed out of the way... your 
problem would dissapear.  I routinely find return springs way stronger 
then they really need to be.

Cheers
RicB

James Ellis wrote:

>Yes Vince, changing to a thicker butt felt, and then re-regulating, might
>stop the bobbling, but it's not the fix I would like to see.  That would
>also change the leverage ratio a little bit.  The ratio is just fine the
>way it is.  The problem is too much of a hump at the very front of the butt
>leather, making the jack have to move too far out before it will clear.
>
>This is the only Yamaha upright that I tune regularly that does this.  It's
>about two years old, in a church chapel, and does not get used a lot, so
>it's not a matter of wear.  As I said, the funny thing is, a few hammers do
>it badly unless I pound hard and really knock the jacks way back at
>let-off.  The others don't, no matter how I play.  Everything is lined up
>right on the money.  At full key-stroke and let-off, neighboring jacks line
>up perfectly - same distance out.  One bumps the butt leather, but the
>other does not.
>
>The other funny thing is, no one has complained about it.  I don't think
>they even notice it.  Next time I tune it, I expect to find a few more
>bobbling, at which time I will fix it.
>
>I'm glad I read all your various posts on the subject before it came time
>to tune this piano again.  This is the first time it has started doing
>this.  Having read your posts, I looked closely to see what was going on,
>and that's what I found.
>
>Thanks, Guys,
>
>Jim Ellis
>
>
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