Adjusting Hammer Drop & Up Stop Screw

[David ilvedson]

> To:            pianotech@ptg.org
> Subject:       Adjusting Hammer Drop & Up Stop Screw
> From:          pianobiz@juno.com (Dave Sanderson)
> Date:          Tue, 24 Jun 1997 07:27:21 EDT
> Reply-to:      pianotech@ptg.org

How about the drop/stop screw...stop/drop screw...

> Del
> Thanks for taking the time to analyze the "drop" screw function 
> for me and for others.  I really appreciate the dialog. Your 
> suggestion that 1.5 mm hammer drop in the treble and 2 mm 
> hammer drop in the bass are desirable target amounts on a 
> properly adjusted action gives me the proper result to shoot for 
> beyond just the concept of "simultaneous contact".
>   
> Does your post then confirm the legitimacy of inspecting the jack 
> in the window relationship as a secondary marker based on the 
> primary result of 1.5 to 2 mm of hammer drop as a test?  (Thinking 
> of it as a similar marker, like the setting of the back checks on an 
> upright, how we get the end ones to adjusted properly and then bring 
> the others into like spec using a straight edge.)  
> Once this marker is properly ascertained, i.e. the proper location in 
> the upward and forward movement of the jack for rep lever up stop 
> to occur, I'm proposing that it is a very good, quick and accurate 
> indicator of where the other up stop screws should be adjusted.
> 
> Based upon this look at the adjuster and what its function is, perhaps
> we should begin calling it the up stop screw?   (or  "the screw formerly 
> know as drop?")
>   
> David Sanderson
> Littleton, MA
> Pianobiz@juno,com
> On Sun, 22 Jun 1997 12:45:34 -0700 Delwin D Fandrich
> <pianobuilders@olynet.com> writes:
> >Dave:
> >
> >Hi
> >
> >I came in on the middle of the exchange about the proper method of
> >adjusting the hammer drop screw. If this duplicates anything that went
> >on before, please accept my apology.
> >
> >Perhaps it might be helpful consider the function of the drop screw. 
> >
> >First of all, it is misnamed. The only time it has anything to do with
> >hammer drop¶ is while the action is being regulated. The rest of the
> >time its function is to stop the motion of the repetition lever as the
> >wippen reaches the end of its cycle. Generally, this should happen at,
> >or just before jack let-off. If the repetition lever were not held 
> >down
> >slightly after jack let-off it would continue to press against the
> >hammershank knuckle and would subsequently hold the hammer against the
> >vibrating string causing all manner of possibly interestingbut
> >uncontrolled and generally undesirablepercussive noises to come from
> >the piano. A better name for this screw might be the repetition lever
> >stop screw.¶
> >
> >During the old fashioned regulating process it was (usually) adjusted 
> >by
> >slowly pressing down on the key until the action cycle went through 
> >jack
> >let-off. The drop screw was then adjusted so that the hammer dropped 
> >by
> >an amount roughly equal to the let-off distance. In numbers this meant
> >that, if the jack let-off occurred at 1.5 mm then the hammer would 
> >drop
> >an additional 1.5 mm for a total of 3.0 mm. As the key aftertouch
> >distance was taken up the hammer would rise some amount known only to
> >the gods.
> >
> >There were some problems with this method. Specifically, it did not 
> >take
> >into consideration the varying geometry of the different types of 
> >action
> >designs. If the action required a longer than normal amount of key 
> >dip,
> >say 10.5 to 11.0 mm to function reliably the hammer could end up
> >dangerously close to the string, especially in the bass section. 
> >
> >Whatever procedure you choose to actually adjust the screw you should
> >end up with a setting that will insure that the hammer does not 
> >contact
> >the string with the key fully (and firmly) depressed. You should find
> >that, with the action correctly adjusted (including precise key height
> >and dipaftertouchsettings) and with the keys fully depressed using
> >uniform pressure on each to hold them down, the hammers will end up
> >level and about 1.5 mm from the strings through the tenor and treble
> >sections. I generally like to see them end up about 2.0 mm from the
> >strings in the bass section for obvious reasons.
> >
> >As to having the repetition lever contact the drop screw at the same
> >instant the heel of the jack contacts the jack let-off button; Im not
> >convinced it matters all that much. Ive run several tests using both
> >piano technicians and concert¶ pianists and unable to compile any
> >statistically valid evidence that, during normal playing conditions,
> >either group could tell the difference between an action adjusted that
> >way and one adjusted so that the repetition lever contacted the drop
> >screw slightly early. The only way the technicians could tell the
> >difference was to cycle the action through let-off so slowly that the
> >hammer did not actually strike the string hard enough to produce any
> >sound.
> >
> >I hope this helps.
> >
> >ddf
> >
> >
> 
> 
ilvey
Pacifica, CA
ilvey@a.crl.com