TANGLEY CALLIOPE RESTORATION PROJECT (part 16)
by Dr. Bill Black
RESTORING THE VALVES
Last month we took the valve units apart. In PHOTO A, the metal valve casting has been removed from the pneumatic and we have cut the pneumatic open. The old covering will be removed, the wood sanded to remove the old glue and new pneumatic cloth and hinges applied.
PHOTO B shows the internal movable portion of the valve. This consists of a fiber disc, covered with a leather facing on both sides. A small wooden block is glued on the lower facing. This serves to contact the fiber disc lifter which is glued on the pouch. When the pouch inflates, the lifter pushes up on the wooden block and valve to allow vacuum to flow into the pneumatic. After disassembly, the metal valve units are cleaned up and the old pouch leather removed. The under side of the metal valve casting is gently sanded to true up any warped areas. This is done by placing a sheet of very fine emery paper on a sheet of glass which gives you a flat surface. The casting is then gently rubbed over the emery paper which will reveal any low spots from the surface being warped. This is done till the surface shows a flat surface.
PHOTO C shows the stack valves with new leather pouches installed. The fiber disc lifters are not visible as they have been glued on the underside of the pouch. The pouches are then sealed. PHOTO C also shows the pneumatics which have been recovered with new pneumatic cloth.
PHOTO D shows the finished valve and pneumatic unit. The small wooden fingers have also been removed and reglued. As mentioned before, this design is very nice in that the valves or pneumatics can been individually removed for servicing. There is one drawback however. As a result of fluctuation in humidity and the resultant expansion and contraction of the wooden portion of the pneumatic, the joint between the metal valve body and the pneumatic tends to fail. When the joint fails and loosens, a vacuum leak is created. In this case, hot glue has the disadvantage of hardening to become brittle. This glue tends to break loose from the metal valve body and allow leakage. To minimize this problem, we will use a glue which has some flexibility after it has set. Fabric stores sell a glue which works well for this purpose, SOBO Craft and Fabric Glue (PHOTO E). It is sold for use on surfaces like paper, ceramics, ribbons, silk flowers etc. It dries to a clear flexible joint.
Also in PHOTO D, note the top plate on the valve. As there is no means to adjust the valve clearance on the internal movable portion of the valve, this adjustment is made by rotating the top plate. The body of the valve casting has an inclined ramp to match another ramp on the underside of the top plate. So , by turning the top plate one way or the other the ramps will cause the top plate to be raised or lowered. To glue on the top plates we want a material which will hold them in place but allow for their removal in the future. For this, we use INDIAN HEAD GASKET SHELLAC COMPOUND (PHOTO E). This material can be obtained in auto parts stores.
They use this on gaskets for automotive applications. This material has enough body to it to hold the top plate in place as you position it for the proper valve clearance. It takes a grip on the parts rather quickly and holds the top plate in position nicely. However, you have to let the valves sit undisturbed for a few weeks for it to harden enough that the top plate can not be moved. Later, the top plate can be easily removed if necessary by warming the top plate gently with a heat gun to soften the gasket compound.
In PHOTO F, we are mounting the restored valves on the stack.
Dr. Bill Black is one of the nation's most knowledgeble Wurlitzer band organ experts. He has made recordings of many band organs and other mechanical music machines which are available for purchase in our CarouselStores.com website.