Upright loss of repetition

[John Formsma]

On 10/27/07, William R. Monroe <pianotech at a440piano.net> wrote:

> Nope, adjusting blow distance is SOP for me on this job, along with lost
> motion.  I've wondered though, about this change.  Unless you are filing
> hammers past the grooves, the blow distance hasn't really changed pre-filing
> to post-filing.  It seems that it has changed gradually over the years, and
> only those little fingers of useless felt either side of the grooves are
> still at proper (original) blow distance, right?

With the above description, yes, blow distance would be essentially
the same.  I file hammers just past the grooves so there will be new
felt.

> Also, I'm unclear how filing away felt from the strike point affects the
> jack to butt clearance.

Because the hammer has a longer distance to travel.  The jack is still
pushing on the butt when it normally would be beginning to trip out.
That equals less clearance at the end of the keystroke.  Bill
Spurlock's Vertical Regulation booklet has a good illustration of
this.

> I would think it would be let-off that is now a problem
> (too great) and probably checking, and................

Probably not...IF it wasn't a problem before, and IF you didn't change
the blow distance all that much.

One thing you might check is the lost motion, since you adjusted that.
 It might be set too close, which definitely causes poor repetition.
The correct check for proper lost motion is when the jack returns
under the butt when the key is released very slowly.  If the butt
leather is worn, you might have to allow greater lost motion.

-- 
JF

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