Restoration of a Duo-Art Expression system for Skyp Harmon
91) 
92) 
93) 
91) The three pneumatics have been recovered. The
hinge portions are sealed by gluing pouch leather over the gaps. It is very
important to get the pouch leather sealed well against the edges of the hinges. That
is why I made the hinges too long when I installed them. When I trimmed the hinges
down flush, it left them with a good, square edge to receive the pouch leather. I've
also lapped the valve mating surfaces, taped them off and then lacquered the wood around
them. You can see the pouch leather reinforcing has been placed on the corners as
well.
92) Here you see the crank shaft and slide valves blown apart and ready for new
materials.
93) All new bushings throughout as well as some wood repairs and new pneumatic cloth
has this ready to put back together. The slide valves have been lapped on glass and
are ready to be lubed with dry graphite.
94) 
95) 
96) 
94) Here, the motor is being run at high speed for a while
to break it in and reveal any flaws in the restoration. This also gets the bushings
broken in.
95) The "almost" finished wind motor. These motors have a bad habit
of being hard to get to seal really well around their hinges. The pouch leather dots
are very delicate little items to try to block all the air in these very powerful motors.
I have actually run a supply of Dow 111 down into the motor and am letting it soak
into the hinge and pouch leather from the inside. The motor is pretty tight but I
want it tighter so I'll keep working it until I'm happy. This design of wind motor
is very powerful. However, there are two weaknesses to this style. One, they
can be less quiet running than other types and, two, they don't seal up as tightly with
the same ease as other designs.
96) The spool box before work began. Most of the box is functional rather than
needing rebuilt. However, cosmetically it's awful. Getting them new looking again is
the really big job when it comes to these spool boxes. They are complex items with
lots of parts and they have to be totally blown apart in order to polish and repaint
everything.
97) 
98) 
99) 
97) The box has been largely blown apart. Here, the
one side that holds the selector switches is ready to be taken apart.
98) The finished selector switch side. The valves have been lapped and cleaned
and polished, and the wood repainted. I have a photo of the other side as well but
it came out fuzzy so I'll take a new one tomorrow.
99) This shows many of the parts of the spool box laid out on a table. I have
repainted, polished and otherwise restored each component as I removed it.
100) 
101) 
102) 
100) The other side of the left portion of the spool box. This is the part you
see normally during use. It is now finished and a picture I feel comfortable posting
has finally been taken.
101) This is the other side of the spool box where the transmission lives.
This photo is of the transmission after it had been totally blown apart, cleaned and
polished. The leather nuts and felt that operate the spool brakes have also been
replaced. These are very tiny leather nuts hidden deep inside the transmission.
Most amateur rebuilders would not realize they were even there and would doubtless
fail to recognize how important they are. The originals were so rotten that they
disintegrated when I tried to spin them off. The new nuts will leave the system
working perfectly. Because every component has been polished to a high gloss, it is
not necessary to glob the transmission with all sorts of oils to make it run smoothly.
I coat the metal with a light high tech lubricant which doesn't draw dust and
doesn't get gooey and sticky over time. This is all the lubrication this
transmission should ever need. I apologize for the fuzzy nature of this and some of
the other photos taken today. I was not feeling well today (probably shouldn't have
come to work at all) and I didn't always hold the camera steady enough. My camera
requires a very steady hand to get clear photos...
102) The finished transmission after it had been reinstalled. You will see on
the other side of this piece that the tracker mechanisms that follow the paper roll and
keep it centered have been thoroughly cleaned and releathered. The first one I did
went uneventfully. However, the spring on the right side was broken and had to be
reworked to get it functioning again. I think I got it so it won't be a further
problem. These arms move very little distance and the springs need not be very
strong. I might still have gotten the repaired spring a bit different in tension
from the spring on the other side. It should work, OK but it took an hour of working
under a bright light to squint at the very tiny hidden spring inside this device to rework
it and get it functioning again. It's very delicacy makes it prone to breaking and
it did break twice while I tried repairing it. Since nothing else could be done but
to repair the spring which was there, I spent the time to get it so I felt it would be
reliable again. Needless to say, the process left me with a headache once I had it
right...
103) 
104) 
105) 
103) The finished spool box ready for reassembly. The only thing I won't put
back in are some very tiny machine screws with copper washers. I have restored them
and will attach them to the box. However, they are very difficult to install and
will have to come right back out again later when the owner tubes it up himself so I left
them out to make both our lives simpler.
104) The finished spool box.
105) The expression regulator before work began. I have already taken the time
to examine and sort out the accordion pneumatics and get all the individual boards back
into their correct orientation. It takes a practiced eye and a lot of experience
with these accordions to be able to get these boards back in their original order when the
leather has been let go to the point of disintegration. However, even if one can't
figure out what the order is supposed to be, they are close enough to each other that you
can mix them up without much additional work. It just takes a little longer to
regulate them later so long as you don't mix the theme and accordion sides. That
mistake can't be made!
106) 
107) 
108) 
106) The expression regulator has been totally blown apart
and the first job of getting the expression box itself restored has begun. My first
task is always to add additional screws in strategic places to line up with the inner air
channel dividers. I will not be gluing the expression box back together. The
old and new screws together will do all the work of holding the box together. A
quality gasket will see to it that no air leaks and future restoration will not require
splitting the box apart like I just had to do.
107) A photo of the blown apart expression. Even now, all the parts are not
disassembled. There are still lots of sub-assemblies which need to be dismantled.
108) I like to have the new gasket showing clearly on the edge of the expression.
So I take this time to repaint the box. The sides had to be sanded clean to
find the spot needed to split the box apart. This splitting process is probably the
most dangerous and delicate operation in all player piano rebuilding. I've done it
enough times by now that I actually accomplished it quite successfully while talking on a
phone I had crooked on my shoulder. I wouldn't recommend such a cavalier approach
for most... This sealing up and repainting is done now so I can let everything set
up over night before I proceed to the next operations. Actually, the outside will
probably get a light sanding, a heavy scrub with a tack rag and one more coat before I
move on with it. I have also resealed all air channels inside the box. When
the box is done tomorrow, there will be a nice clean gasket line to demonstrate that this
has been professionally restored and that it will be an easy rebuild the next time it
becomes necessary.
109) 
110) 
111) 
109) The expression box has been gasketed with packing
leather. The new theme valves and crash valves are in place. The original felt
and fiber that give these valves there thickness is usually kept. In addition, a
layer of rubber cloth backs up the leather to keep the hide glue from soaking into the
felt and keeping the leather from sticking well. This layer of rubber cloth is often
reusable. In the case of these valves, the fiber disc on one was not reusable and
one of the valve's rubber cloth backer could not be used. Otherwise, I reused the
usual components while replacing the leather facings and pouches along with replacing the
fiber backer disc which could not be reused. I used chrome tanned leather in this
unit. Normally, I only use the brown colored leather which is tanned in such a way
as to make it more flexible. However, the size of these pouches makes this less
important since the leather has room to move. Second, I recently acquired a dozen
skins of chrome tanned pouch leather that is thinner than anything I've ever seen before.
It is very flexible. Finally, chrome tanned leather seals better and more
completely than the other variety. With these valves, a tight seal in the leather
and air channels between the pouches and the valves that signal them in the action cavity
is more important than all other considerations.
110) These are flap valves which the accompaniment air pressure runs through.
When theme suction is sent to one side or the other, these flap valves prevent the high
theme suction from leaking into the accompaniment area. The original leather was
good but these are easy to make and there is no good reason not to just replace them.
While I used the original felt discs, I replaced the paper separator and leather.
You can see the original flaps with their paper discs still in place in the photo.
111) Gluing the recently recovered regulator pneumatics onto the theme box.
These are gasketed with leather and glued into place. While there are three screws
that reinforce this joint, they are not enough to close the joint so that an air tight
seal is accomplished. This means that they must be glued down and clamps must be
employed to tighten the joint until the glue sets thoroughly. This is one of the
trickiest operations in the restoration of these expressions. The glue must be
applied, the screws tightened (because of how they are accessed through a number of holes
in the pneumatic, they are hard to reach and harder to tighten so you must move quickly)
and the clamps put into place and tightened before the glue can gel. Needless to
say, I don't answer telephones while doing this!
112) 
113) 
114) 
112) These arms actuate the spill valve inside the
expression box. While the system is running at low suction supplied to the stack, an
avenue for spill must be supplied to the pump to prevent it from bogging down. As
more pressure is sent to the stack, the spill is not needed and so the spill valve closes
and stops the leak. These arms follow the expression arms and open and close the
spill to the pump as needed. The original leather which is glued and riveted to
these arms is rotten. It must be replaced. This means tearing off the rotten
leather to gain better access to the rivet. Then a bastard file is used to file away
the mashed side of the rivet until it can be extracted from the arm. Then new
leather is cut, packed with dry graphite on its outer surface and holes punched to line up
with the rivet hole. Then the leather is glued to the arm (I like to use PVC-E glue)
and the rivet reinserted. Then the rivet is pounded again against a steel backer to
spread it again and lock the leather in place. In this photo, the left unit is not
restored yet but the right one has been done.
113) The restored knife valves and all the connecting arms have been reinstalled.
I rebushed the felt bushing that the control arms pass through with leather.
I'm a real big one for getting tight seals. The felt bushings did not stop air from
leaking into the system. The felt simply kept the leak from making any noise while
holding the arm securely. I usually rebush these types of points with leather.
You will see later, that I goofed and got the tension inside the joint too tight.
The finished unit proved this to me when the return springs weren't strong enough to pull
the arms back into their rest positions. Because of this, I will be tearing part of
the expression apart again later in order to correct the tension in the bushing. I
will keep the leather but readjust things to get a free motion that doesn't leak either.
114) The top of the expression box, showing the accompaniment flap valves
reinstalled and the spill valve located in the upper right of the photo. I've
already rebuilt the crash valve's primary but didn't show it in photos. It got new
leather pouch and new seal cloth which was of a heavier weight than was used originally.
All the metal was polished and the nipples sealed with burnt shellac. It has
been reinstalled onto the box along with the supply nipples that run into the box and out
to the stack. These have also been releathered and polished along with their screws.
This part of the box is ready to have seal cloth glued over it. I will place
the felt backer and the hard board over the cloth after gluing it down. Screwing the
board and felt over this helps to press the seal cloth hard onto the dividers and get
everything sealing well. The technique for gluing on the seal cloth safely requires
letting the glue gel first. I flood as much glue onto the wood as it can take
without dripping and let the glue gel. Then, I place the cloth over the glue and
press it onto the still slightly sticky glue. It usually holds itself there
temporarily with just that. Then, the box is turned over and the cloth heated with
an iron. This loosens the glue and forms the bond. Any glue that squeezes out
at this point, simply squeezes onto the cloth rather than running down into the box and
onto important items like the flap valves or spill valve.
115) 
116) 
117) 
115) The finished expression box. All the hardware has
been polished and reinstalled. I will print new labels for the "Theme" and
"Accompaniment" tags that go on the pneumatics later.
116) Now it is time to restore the accordion assembly. I do the easy part
first; recovering the accordion pneumatics. For a beginner, this is one of the
hardest recover projects of any pneumatic every built. However, once you've done a
few and got a system going, they aren't hard at all. The first job was to figure out
which order the boards went in since they had been mixed up long ago. Happily, they
were still all present. Often times, some or all of these are missing entirely.
When covered in pneumatic cloth instead of pouch leather, this is much less likely
to happen. In the future, these accordions should be much safer from being lost than
they were originally.
117) The accordions after being blown apart.
118) 
119) 
120) 
118) Each accordion is set up in order, lined up and clamped
tight. Care is taken to get every board perfectly in line and square and the entire
assembly square before the sanding begins. Then I can put them onto the big belt
sander and get a perfectly square and clean result.
119) Now my spacer blocks have been placed between the boards and the assembly
clamped up again. Much care is taken to get the boards all lined up perfectly and
then the first three sides glued up. After the glue sets enough to make it safe to
put a little stress onto it, the clamp is removed, the spacers pulled out and the final
side glued down. The overlapping side is always done on the edge which contains no
regulator blocks or nipples. Some rebuilders I have followed up on, put this overlap
in odd and unpredictable places, proving they don't understand the principles under which
this unit functions...
120) The restored accordions, ready to be reassembled with their regulator blocks
and nipples.
© Copyright 2010 {David Rodgers' Piano Rebuilding}. All Rights Reserved.