Re. Bobbling hammers on Yamaha upright

[Isaac OLEG]

Hello,
It is not buckskin but ecsaine on Yamahas a kind of micro fiber
product. I doubt it may react to water like leather.

That said I also wish to be sure that the hump noticed is not due to
some play or bad position of the jack dat the beginning of the stroke.
If the cushion compress too much, the there is very high friction
occurring between the jack top and the "buckskin" , can this friction
push the buckskin or rob the tension from it, causing that deformation
?

Good lubrification with Teflon powder should certainly help, but not
very easy to attain there.

Possibly there are more side effect to leave with too much play some
actions than we believe.

But also, taking back the play with the key capstan, while half the
cause is lowered balance point induce a bad geometry also, this can be
causing premature wear as well I'd say.

So shimming under the balance is done , even with thin paper , before
going farther in regulation - at the same time the dip can be
corrected fast /rough shimming under the front rail.

Checking the jack's alignment at rest may not be easy, but if we know
what we are after it is certainly possible.

I don't have a such large amount of vertical Yamaha under heavy use to
treat so I only can hope for you that these are not hidden problems to
come. I'll ask my friends of the conservatory about it.

Best regards.

Isaac OLEG



-----Message d'origine-----
De : caut-bounces@ptg.org [mailto:caut-bounces@ptg.org]De la part de
Jim
Busby
Envoye : lundi 19 avril 2004 22:41
A : College and University Technicians
Objet : RE: Re. Bobbling hammers on Yamaha upright


So Jim, others,

What's the real fix? File the buckskin, iron it, reglue it, water
shink
it (with distilled water)? I've had that "hump" and never found a
quick
way other than what Vinny said, or by tweaking the regulation. If only
a
few are bad ones, were they defective from the beginning, or did too
much lost motion cause the jack to pound the hump there?

With 337 uprights (203 of them Yamahas) you can see how this might
interest me. Thanks.

Jim Busby BYU

-----Original Message-----
From: caut-bounces@ptg.org [mailto:caut-bounces@ptg.org] On Behalf Of
James Ellis
Sent: Monday, April 19, 2004 1:53 PM
To: caut@ptg.org
Subject: Re. Bobbling hammers on Yamaha upright

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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