Anatomy of a WurliTzer Theatre Pipe Organ

Manual Chest.


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 another container.

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.

Top Boards.

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 Shell.

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 centre rails. 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 soulution.

Still to be done.....finish cleaning the bottom boards and then regasket and reassemble everything.

NEXT==>Coming Soon!


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