Restoration of a Duo-Art Expression system for Skyp Harmon
61) 
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61) The new hinges are in place. I put inside and
outside hinges on these. Originally, they only had an inside hinge but these
pneumatics are under considerable stress during operation so I like to make them tougher
than they were originally built. So long as the flexibility isn't compromised, this
is the better way to go.
62) This photo is included because I like to keep truth in advertising. The
pneumatic is totally recovered but I tried using a double lap hinge technique in closing
the cloth over the hinge end. I just couldn't get this as air tight as I wanted it.
I ended up pulling this cloth off and recovering this pneumatic again. The
next time, I used a different method where only a narrow strip of cloth folds over the
hinge end. Then a single layer of pneumatic cloth is placed over the hinge end to
bind it off.
63) The finished pneumatic is being tested to see that it's air tight. The
nipples are being blocked and the photo shows that the pneumatic is not opening.
This means there are no leaks.
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65) 
66) 
64) The finished pneumatic which is the best angle to reveal
why I like to call this device the "lobster."
65) This is the damper pedal pneumatic. This is one of the best designed
damper pedal pneumatics made by any company. They operate at lightning speeds and
are very air tight. Provided they're rebuilt right...
66) This photo shows the damper pedal pneumatic blown apart. It's amazing how
many parts these things have. The inner air channels are all getting sealed even if
they weren't sealed by the factory. Anything that might have developed seepage over
the years gets a seal job just for safety. The original double cross valves will all
get replaced with new round valve seats.
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68) 
69) 
67) The valve box is totally rebuilt, the pneumatic tests
air tight and the leather gaskets, pouches and valve facings are all new. The felt
muffler cover got pranged pretty badly getting it off so I'm making a new one here.
68) I forgot to photograph the finished pneumatic so I put this photo here
temporarily to remind myself to take a picture of the finished pneumatic. The final
product was very air tight and operated lightning fast just as I expected.
69) This is the wind motor governor. This is a rather complex item to rebuild.
This and the modulator are very similar and both take an entire day to rebuild.
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70) Another photo taken from the other side.
71) The inside that shows the tempo plate and its slide valve along with the tempo
plate bypass that speeds the motor up during rewind. The springs that hold the slide
valves in place are made of copper and always are covered in corrosion. I will
polish these springs to a super high gloss and then coat them with Dow 111 Silicone Grease
to ensure that no dust can stick to them and that they will not corrode in the future.
72) The valve chamber after everything has been removed. The felt bushings
that the tempo and bypass control arms pass through get replaced as well. I'm in
favor of replacing these felt bushings with leather ones. The felt bushings are
quiet in operation but they do not stop all the air. In other words, they leak.
The leather will not leak. However, it will be slightly stiffer in its
operation for a while until it gets broken in some. You can see that the tempo plate
has been removed so it can be polished and lubricated as well. The surface that the
bypass rides on is flat wood that is graphited. That surface looks good so I will
give it more dry graphite and it should be good to go. Of course, the valves that
ride on both of these openings will get new chrome tanned pouch leather covers. The
chrome tanned leather is more durable than the traditional stuff. I will also seal
the new leather with Dow 111 and burnish it with graphite. Finally, the connecting
arms will be highly polished and lubed as well.
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73) This is the pallet valve which governs the air passing
through this device. As the system's suction levels vary, this valve will keep the
wind motor running at the same speed all the time. The trick to making sure that
this device works perfectly is to get the pallet valve really air tight. The gasket
must be perfect and the mating surfaces must be perfect. Although this valve is
never really asked to close completely (blocking off all air) if it isn't able to do so,
it won't work right.
74) The wind motor governor all blown apart.
75) The slide valves have been restored and this section reassembled.
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78) 
76) Getting ready to recover the movable board of the
governor. The poplar box has been taped off and painted in those areas where
pneumatic cloth won't be covering it. These poplar boxes are famous for stripped
screws so I will be spending quite a bit of time repairing stripped screw threads as well.
77) The slide valve after it was removed. From its black color, it's hard to
even tell that the spring is made of copper.
78) Each aspect of the valve has been restored and new felt and leather cut.
The inside felt was dirty and had glue soaked in areas that didn't belong, so it all got
replaced. It took several attempts at lapping the valve before it was perfectly air
tight.
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81) 
79) The finished pallet valve.
80) The finished motor governor.
81) This is the modulator. It's function is to either allow the air to pass
from the pump into the expression system unobstructed, reroute the wind through the spring
loaded pallet valve in order to quiet the music without eliminating the expression or to
stop the air completely so the system won't play during rewind.
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82) The modulate after it was blown apart.
83) This photo shows how the poplar box of the modulator has cracked. These
cracks will let air seep but they aren't structural at this point. I will make sure
anything that could possibly form a leak some day will be covered in pneumatic cloth.
84) The various components of the modulator have been restored. All metal has
been polished to a high gloss, all leather has been replaced and so forth. Since the
control valves don't have to operate with lightning speeds on the modulator, I use the
tougher chrome tanned pouch leather for those. They are pictured at the bottom right
corner of the photo. This leather takes a better seal and resists rot a bit better
than the brown style.
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85) The finished modulator.
86) Another angle.
87) The wind motor before restoration began.
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88) The motor has been blown apart in this photo.
89) Here, the pneumatics have been cleaned up and the old leather hinges have been
removed. When sawing out the old hinge on one of the boards, I got too deep and
spoiled the moveable board. Rather than try to repair the weakened board, I made a
new one and threw the original out. The new leather hinges have been glued into
their slots and clamps used to squeeze them in snuggly until the glue can gel a bit.
After the glue gels, the clamps come off and I seal the wood with fresh lacquer.
When the lacquer is dry, I make sure the leather is well sealed as well and then
clean the wood one more time to make sure that no drips of lacquer will spoil my glue
joints when I glue on the pneumatic cloth.
90) The cloth is glued onto these pneumatics one side at a time. Here, one
side has been done. Many rebuilders make the mistake of using too thick a cloth for
this job. This leaves these pneumatics weak and stiff. The original cloth was
quite thin and should be replaced with material of the same thickness. I do add a
punching of pouch leather to the corners to ensure a long lasting result because the cloth
is so thin. Aeolian didn't always do that but I always do.