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MMD > Archives > October 2014 > 2014.10.10 > 07Prev  Next

Standard Pneumatic Double Valve System
By S. Lee Walker

I just read in the latest MMDigest that the force-fit collars are
available.  On the valve system that I rebuilt, the original collars
were .200" O.D., .044" thickness.  There was no accurate way to
measure the I.D.  The valve stem shaft is .092" O.D. so the I.D.
will be smaller.  The replacements from Steaves's Piano Services were
.213" O.D, .048" thick, not plated.  However, the replacements were

There is a way to make a temperately fix until the proper part are
available.  I have used solder to coat the collars.  I mounted a
soldering iron in a vice.  You need a solder tip which is machined
to a point so the I.D.  of the collard will fit over the pointed end.
I used a paste flux and solder for electrical wires.  Use an awl 1/8"
diameter to smooth the entrance.  One way to salvage old parts.  They
were very tight on the stem.

You know the repair manuals tell you to adjust the wooden buttons by
using a long nose pliers tight on the stem to make the adjustment for
clearance to the pouches.  Many of the wood buttons were too tight to
turn.  The result was bent valve stems and burring the area where the
felt busing rides, causing a tearing action of the felt.

There was no way that I could find to replace the felt bushings tight
enough to support the valve shaft.  Too much movement caused SS washers
to ride on the brass seat.

Another quick fix.  Use a Hobart 770514 3/32" copper coated steel rod,
cut to same length as the brass valve stems.  You need a #4-40 thread
chaser or die and thread the end same as the original.  Installed the
collars and valves but the original collars are tight on this
replacement stem.  The problem: the button may be too loose so, you
have to either make a new button or glue a dowel rod in the existing
hole and tap a new thread.

I have a wood lathe and can make a replacement button.  Quick fix for
valve guides the fiber valve guides are just about had it!  So, I used
the heavy pump bellows cloth and glue a small piece over the hole and
then punched a hole the same size as the stem.  This material is rubber
and rubber will cause friction so I coated it with silicon Lube.

The leather valves were purchased from Columbia Organ Co.  They were
just a little stiff and not as flexible as the originals.  The valve
stem has a thread on one end which has been installed by process called
thread rolling.  No metal is removed; it is just displaced, which
increases the diameter.  There is no way to install the fiber valve
guide over this larger diameter.

I was a layout designer in jet engines manufacturing.  Part of my work
was to stack parts together for the high tolerances as well as the low.
Also to see if any interferences exist.

I believe that Simplex designed this valve system to be assembled and
no adjustments were necessary.  So, you start at the opposite end of
the thread, slip on the fiber bushing support, brass valve seat, and
force-collar seals valve spacers and force collar.  Put into a drill
chuck on lathe and screw on the wood button until it bottoms on the

When you look at the design of the wooden buttons, some are spherical
others are flat.  The flat button will contact the outer circumference
of the pouch whereas the spherical contacts the middle.  With regard
to the flat face, it would take longer for the pouch to move the valve.

I have an AutoCAD to scale drawing of the secondary valve system which
shows how all the parts fit together.  To get a copy I will send you
an e-mail with and the drawing as an attachment.

Let's grind or seat the leather to the brass seat.  Go to the lathe,
put the valve assembly in a drill chuck with the brass seat loose.
Spray some silicone on the brass seat, turn on the lathe and very
gently hold the brass seat up, next to the leather.  You see a polished
portion on the brass seat where the leather is rubbing also, the high
spots on the leather will now be flat.  The same technique is used on
auto engines valves.

I have a test fixture to test the tightness of the valves in the valve
chest.  I subtitled or replaced the pouch board with a flexible glass
cover which is vacuum tight.  I now can apply the vacuum and use a
manometer on the opposite end to view the vacuum level.  The vacuum is
in the high 'teens.  I can see the valves and the pneumatic are all
open.  I can push open and close the vales to see if they maintain
their seal.

S. Lee Walker

(Message sent Sat 11 Oct 2014, 02:57:36 GMT, from time zone GMT-0700.)

Key Words in Subject:  Double, Pneumatic, Standard, System, Valve

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