I am trying to restore an 1890 John Malcolm roll player organ and
I am a bit baffled about the roll playing mechanism.

Starting from the wooden tracker bar of 61 holes, after a right angle
turn the air passes through very small holes (31 one side and 30 the
other) and continues down about 8 inches into the air chest.  On the
way it passes through 61 very lightly sprung flap valves the complete
width of the air chest.

There appears that there is a vacuum on both sides of these valves so
only part of the vacuum air actually is sucked through the tracker bar.
Having passed through into the chest, I understand that a suction will
activate another leather diaphragm that in turn opens up a valve to
sound the reed.

I find it very hard to explain, but I am sure there is someone out
there who can explain why all the notes play with all holes uncovered
on the tracker bar and the valve that allows air to escape.  Close
off all tracker bar holes except the ones you want to play and there
is no sound.  The valve that allows air to escape is closed in reroll
mode so of course no sound.

The name John Malcolm is on the left and on the right is a gauge that
I presume registers the speed of the bellows motor.  You can email me
direct if you wish.  I will look forward to your replies.

John Vallings
New Zealand
john@bbp.co.nz.geentroep [delete ".geentroep" to reply]