Anatomy of a WurliTzer Theatre Pipe Organ
The rebuild process was done starting with the pneumatics done one half chest at a time.
This was a convenient size of parts to work on at a time and allowed each set to be kept
seperated. While it is true that all valves are the same and interchangeable, as are the
primary pneumatics, keeping them in sets seemed like a way to easily keep track of them.
The secondary pneumatics and pallets do come in various sizes so keeping them in sets
makes it easier to ensure they all go back with the right sizes in the right place. The
pallet arms are also bent to various shapes to align the pneumatic stikers with the pallets.
In theory they should all be straight but they are not so putting them back in the same
place will reduce the amount of adjusting at re-assembly time. The secondary pneumatics and their
striker blocks also have variation as far as angles, screw and pin positions so the
pneumatic tops and strikers also need to be kept together.
To make this easier each pneumatic top and striker had a number stamped into it before they
were seperated. Each pallet was numbered before it was removed from the top board.
Seperating the stikers from the secondary pneumatics seems to be a vary variable process.
They were attached with burnt shellac which is not water soluable. Some fell off as soon
as the screw was removed, some came away with a gentle tap and others were much more stuborn.
The stuborn ones I found were more likely to come apart if they were left in place until
the leather had been soaked off the pneumatic and the timber fully dried. Sometimes a
strong tap would work, sometimes a chisel tapped under the back of the striker would
do it but a few resisted so much that some wood did split, usually off the pneumatic side.
When they were reassembled they had a little fish glue to hold them securely but it should
be more easily seperated if that is ever neccessary again.
As each bottom board was removed it was striped of its valves and the primary pneumatics.
The secondary pneumatics were removed and all the leather cleaned from all the pneumatics
and the strikers removed from the secondaries and their felt blocks removed.
Each piece of wood was then polished and prepared for releathering. When ready the secondaries
were rehinged and then releathered along with the primaries. I found that cutting the
leather for the secondaries first generally left enough "scraps" which were enough to cut
the primaries from. Cutting the primaries first would leave no use for the "scraps" when the
secondaries were cut.
The secondaries then had the strikers reunited and refelted. Gaskets were cut ready for the
secondaries and in the spare moments during this process the valves were stripped and rebuilt
with the valve disks which had been prepared earlier and all the related screws had their heads
sanded and painted. The gaskets were not cut for the primaries as these can be cut from the
punchings created when the gaskets are cut for the bottom boards.
Each set of primary and secondary pneumatics, secondary gaskets and screws fits
conveniently into a plastic 4 litre icecream container for storage until they are
needed at reassembly time. All the valves were bagged in their sets and stored in
With all the pneumatics and valves completed and stored safely away it was time to to the
top boards. These are one piece per chest so the whole chest is done together.
Removing the top board intact is much easier than trying to remove the pallets and springs
from inside the chest. With the board on the bench it is easy to remove all the springs.
The pallets can then be removed, and numbered. The spring rails are then removed and all the
pallet guide pins pulled from the top board.
The pallets were all stripped of their leather and polished, of course, and then carefully
sanded flat ready to be releathered. They went into storage before being releathered to
prevent any possibility the new leather would be damaged or distorted before they were
reassembled with the top boards.
The bare top boards were now able to be refinished. "Dishing" is common and is the process
of the timber curving over time, particulary on the pallet side where a perfect seal is
required. In bad examples it is preferable to plane the timber flat but these were not too
bad and sanding and scraping did remove most of the curvature. On the wider boards not all
the curve was removed from edge to edge but the pallet area was made flat.
The top boards were then polished on all sides. A few days after this was completed this
became a topic on the WEB. All informed opinion was that the bottom, pallet, side of top
boards were never, and should not be, shellaced. It is believed that shellac here can cause
sticky pallets. I had seen that there had been something on these top boards originally. It
was visible on the surface and as runs down into the slots. Although it was only a thin coat
and not as shiny as the top side it was clearly shellac. Having always believed that any wood
should be sealed on all sides if it is sealed on any side, and as I was not inclined to sand
off the new finish the shellac was left in place. Time will provide the answer to whether this
is a good idea or not. It was during this process I added an air compressor to my toolkit.
Compressed air is a much more effective way of removing the dust from all the nooks and
crannys and holes when sanding down top boards. The compressor takes up some of the
limited space in the workshop but it is worth it.
The bare shell of the chest was now available to be prepared for reassembly to start. When the
secondary pneumatics were removed much of their gasket material remained in the chest so that
needed to be removed. This was another point of slight controversy as I had been told that water
should never be applied to the gasket leather in a chest as it will cause damage. This seems
to contradict the use of water soluable glue. I did use a little water to dampen the leather
and break down the glue. Careful and limited application ensured no water flooded the channels
in the wood which may damage the seal applied to them. With care the leather was removed and
most of the glue scrapped away. Most of the timber had an eneven surface before I started
and showed now ill effect from the water treatment. This did happen in the warmer part of
the year so it dried out quite fast.
The top and bottom gaskets were all removed next. This showed up how many of the
brass screw inserts
in the bottom of the chest had pulled or screwed out. More than half were faulty yet
there was little evidence on the gasket of leaking. It was clear that all off these inserts
should be fixed now so they were all removed at this time. Many had clearly pulled out and
others had unscrewed. The pins down the side of the inserts which are supposed to prevent
them unscrewing clearly did not always work. When I got to the last chest I discovered
that most of the inserts in the back wall and in the ends had had Helicoil inserts added
at some time. These appeared to be holding well. Enqiries could discover noone else who
had experience using these inserts in this application.
Now with the shell completely stripped to bare wood the pneumatic mounting surfaces
could be sanded flat. The positions of the pneumatics were originally marked out with pencil lines.
These lines were not always straight or in exactly the right position. These lines would be
expected to disappear when the surface was sanded down to remove the remaining old glue and
restore the surface to flat. To preserve the location of these lines a small indent was made
at each corner with the point of a small nail. These holes will not cause any harm and will
not be sanded away. They provide a mark to allow the lines to be replaced later in the
original positions. An alternative method is to make templates for each size pneumatic with a
peg to fit into the hole and use the templates to draw the lines around. This would also correct
any of the original errors.
After sanding these surfaces flat the lines were redrawn and then the timber outside of the
pneumatic areas was repolished and the chest turned over for the other sides to be done and
then the outside. As the inside of the chest was being shellaced extra shellac was run into
the joins at the ends of the chests and at the
In some cases the shellac ran out the other side. Repeated coats caused the leaks
to stop. The gaps were not large enough to allow glue to be forced around all the corners and
a leather strip around all the corners would be difficult. The shellac is liquid enough to wick
its way around the corners and will fill all the small gaps. It will shrink as it dries but
the next coat will have a smaller gap to fill until it forms a complete seal.
These leaks have no effect when the adjoining ranks are on the same regulator and trem system
but they are very important when the adjoining ranks are supposed to be seperate. A very small
leak will cause the trem from one chest to effect the other chest causing a rank with the its
trem off to have an unexpected trem. If both trems are on it will be impossible to get either
to behave properly as each will effect the other. If the chests are on different pressures
e.g. the Vox (6") next to a Flute (10") the higher pressure will slowly pump up the lower
pressure regulator above its correct pressure until the trem is turned on or some pipes are played.
All these problems can be very mysterious and confusing when there is no obvious way that the
two wind systems could possibly be joined, but quite obvious when you work out what is going on.
It is best to avoid confusion by ensuring that these problems do not happen.
All the valve boards, pin guides, spring rails and primary pneumatic
rails were also refinished during this time. The primary rails have a strip of rubber cloth
to seal off the holes bored where they are not needed but have to be done to get the holes
where they are needed. Istead of removing and replacing this cloth I tried a radical
approach. I supported each rail at 45 degrees, with the rubber cloth side down, and carefully
dropped PVA glue into the hole. With several small amounts added the glue ran down the
inside of the holes and was filled to the level of the pneumatic hole. This shrunk down as
it dried but there should be a solid plastic plug in each hole now and the rubber cloth is
purely decoration so any deterioration will no longer cause problems. The PVA plug should be
permanent while being invisible and it would be easily drilled out if anyone is ever so inclined.
The remaining problem before reassembly could begin was to do with the addition of the
seperate Tibia tremulant and regulator. The instrument was built with two trems, one for the Vox
and one for the rest. The manual chest had a manifold on each end. Each manifold was divided
into two sections, one for the Vox and the rest for the other four ranks. For the Tibia to
have its own wind system the manifolds would need to be further divided to isolate the Tibia
from the rest. The manifold on the "C" end of the chest
connected the Vox to the regulator and
the others to their trem and was only 40mm deep internally with both air lines connecting to the
front of it. The other end manifold was deeper, about 130mm,
with the Vox trem and the wooden
trunk from the Main regulator connecting on the bottom. If the Tibia chest had been the one at the
front or the back of the four rank group it woud have been simple to add another divider into
each manifold and connect an air line on each end but naturally it was not that simple. The
Tibia is the fourth rank sitting between the Salicional and the Trumpet. This means it is
neccessary to keep the Salicional, and Flute, chests connected to the Trumpet.
Replacing the manifolds and air trunking was one option but it was possible to keep virtually
all the original material and achieve the desired result neatly. The
solution was to cut a
block the same thickness as the manifold box and cut a hole for the Tibia feed. With this
block glued in place and gasketed the same as the rest of the manifold onto the chest the
Tibia would be effectively isolated, at this end. The top and botton of the block are rebated
to provide linking channels for the other ranks while keeping maximum surface area for the
gasket. These channels are not as large as might be ideal but are large enough to have some
effect on the Main Trem on the other ranks. The feed line for the Tibia will attatch to the
front of the manifold like the Vox line. At the other end the trem line needs to be brought
from the end of the Tibia chest to the outside of the manifold. Attaching a flange to the end
of the Tibia chest inside the manifold is simple but it could not be brought straight down
as this would be in the middle of the Main feed duct. There was space between the Vox section
and the Main duct for the Tibia trem line to be connected to the bottom of the manifold so
a simple PVC pipe connection was possible inside the manifold to join the end of the Tibia
chest to the new trem outlet postion. Having the trem line connect out of alignment with
its chest may be confusing for the casual observer but it is the simplest and quite neat
Still to be done.....finish cleaning the bottom boards and then regasket and reassemble