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MMD > Archives > September 2012 > 2012.09.21 > 07Prev  Next

Odd Behaviour of Duo-Art Striker Pneumatic
By John Phillips

Hello MMD.  I have removed the upper player action from my Steck
Half Duo-Art, for the umpteenth time.  This time it was to enable me
to remove the piano action, in order to replace the buckskin on all the
hammer butts.  That operation seems to have gone successfully, but it
necessitated me adjusting the heights of all the pneumatic push-rod
fingers, dowels, pitmen, or what have you.  After all this, it seemed
to make sense to check that all the valves and pneumatics were working
properly, before returning the player action to the piano.

Well, they are indeed all working, but pneumatic no. 70 behaves
differently from all the others.  When no vacuum is applied to the
valve chest, it is possible to place a finger under any of the
pneumatics and push upwards to close it, without significant effort.
Any pneumatic except no. 70, that is.  When I try to push it shut, it
resists, and closes quite slowly.  However, if I apply vacuum, and open
and close the tracker bar port, it seems to behave exactly as its

My recollection (and I haven't dug out my notes) is that I set all the
valves to have a travel of 0.038".  If I peer through the tracker bar
tubes I can just see the tops of the valve stems, and no. 70's stem
seems to move up and down the same as do its neighbours, when I blow
into the appropriate tracker bar port.  When I try to shut pneumatic
no. 70 with my finger, the valve stem doesn't move.

Does anyone have any idea why the air in pneumatic no. 70 can't get
away quickly?  When I apply vacuum to the valve chest, and pull a test
roll over the tracker bar note by note, no. 70 seems to behave just
like all the others.

John Phillips in Hobart, Tasmania

(Message sent Fri 21 Sep 2012, 12:51:55 GMT, from time zone GMT+1000.)

Key Words in Subject:  Behaviour, Duo-Art, Odd, Pneumatic, Striker

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