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MMD > Archives > September 2000 > 2000.09.17 > 02Prev  Next

Welte T-100 Test Roll With Graduated Holes
By Pete Knobloch

Mike Kitner from MMD 00.09.07 reported - Since Red Welte-Mignons that I
have seen have adjustable bleeds I have always assumed that these are
"Go-No Go" bleed adjustment tests.  You would adjust the bleed so the
valve would respond to the larger hole but ignore the smaller one.

In thinking more about the use of the progressively smaller holes used
on some of the Welte T-100 test roll, I believe that Mike is right.
The graduated holes are intended for adjusting the variable bleeds
only.  What is interesting is that this test roll provides a means to
adjust the variable bleeds to each valve and key pneumatic.  If a wood
channel had a slight air leak or one pouch leaks more than another, the
variable bleed screw can be tweaked to compensate for the problem.

John McClelland from MMD 00.09.03 reported - The smaller test holes can
also be used to set the smoothness of each note, at low vacuum levels.
Therefore, if all notes sound the same amount (a subjective judgement
at best), then the first set of small holes could be used to insure that
the minimum intensity level (if you will) is correct for each note.

I don't know if this type of test should be used just for adjusting the
stack and action for playing softly as stated by John.  I am sure John
would have had the piano action working perfectly before attempting any
player adjustments, which is absolutely necessary.  He didn't talk about
this in his notes.  With the action working smoothly from note to note,
then the adjustable bleeds can be adjusted to play smoothly from note
to note just as he stated.

What is most important is consistency from note to note through out the
entire player piano system.  Whether this is in the regulation of the
action, keyboard touch weight, or the player valves, bleeds and
stiffness of the hinges in the key pneumatics, each system must be as
consistent as possible in its operation from key to key.

I believe there are problems in using the smaller test holes on the
T-100 test roll to set the minimum playing level at low vacuum levels.
The valve pouch is probably only operating at less than 1/2 of its
capability when the smaller graduated test holes are used to operate
each note without striking the key. The top valve seal may or may not
be sealing properly when the valve is turned on.  This may cause a
lower vacuum level to reach the key pneumatic because of the top valve
leaking to the atmosphere.  You want the valve to operate in a hard ON
and hard OFF state if at all possible when playing at the low vacuum
levels for playing softly.  You don't want to use the smaller test
holes on the T-100 test roll for final low level vacuum adjustments for
quiet mezzo-piano playing.

Pete Knobloch (Tempe AZ)

(Message sent Mon 18 Sep 2000, 04:28:27 GMT, from time zone GMT-0700.)

Key Words in Subject:  Graduated, Holes, Roll, T-100, Test, Welte

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