If Mr. Houser's instrument is a Simplex with a transposing tracker bar,
there is no special sliding seal mechanism behind the tracker bar.
Rather, the lead tubing goes from the stack only to the back edge of
the 'shelf' in the spool box.  Short lengths of rubber tubing go from
the ends of the long lead tubes, to the nipples on the tracker bar.
This provides the flexibility to enable the tracker bar to be shifted
laterally.

In order to do this, Simplex used an unusual size of lead tubing.
Normally, the extruded lead tubing in most players has an inside
diameter of 5/32", so it fits snugly over a standard brass nipple, and
is easily sealed with shellac.  The smaller Simplex lead tubing has an
outside diameter of about 5/32", so the short rubber tubes (nominally
9/64" ID) will stretch tightly over the ends of the lead pieces at the
back of the spoolbox.

Lead tubing in a player often has to be replaced because of corrosion
or failure of poisoned alloy'.  Some of the ends of the old lead tubing
where the rubber piece is slipped over, are liable to be cracked or
broken off, and it would be hard to get the rest of the rubber tubes
off without further damage.  Since lead tubing in this odd size is hard
to get, most people replace the whole length with rubber tubing, all
the way to the stack.

Player Piano Company sells the standard 5/32" ID lead tubing, but one
would have to add nipples or elbows to make the transition between lead
and rubber at the rear of the Simplex spoolbox.

Count me in with the purist camp when it comes to materials and
techniques; and lead tubing is fun to work with once you get the hang
of it.  On the other hand, many players used rubber tubing for the
entire circuit, so it can be considered an historically acceptable
material for an ethical rebuild.  What do others in MMD think of the
idea of using rubber in place of lead tubing?

Richard Vance