What is the best flap valve material for a Wurlizter band organ
vacuum pump? Explained below is why I think they need to be replaced
(or improved).

The City of Binghamton, New York, asked me asked to look at a Wurlitzer
146-B that is not working. The organ was restored 10 years ago and then
put in indoors storage. The city wants to get the organ back on the
carousel.

What I discovered was no vacuum. I disconnected both outputs and plugged
them. The reservoir would not close more than an inch. I took the pump
home and expected to find some kind of big leak but found nothing.

The restoration is well done. The leather on the bellows and gaskets
are well made and the finish on the pump is well done as well.

What I suspect is the flap valves are causing the problem. They are
about 0.050" thick with a shiny finish (see photo). I don't know if
they have hardened from no use over 10 years, or are just the wrong
thing to begin with, but I don't think they are sealing well.

I suspect they are made from something like Columbia Organ Leathers
"Flap Valve Leather". In a discussion on a reed organ forum recently
it was suggested to use Columbia Organ Leathers "CPL Valve Leather".
This material worked well in a reed organ I restored but I'm not sure
if it will hold up on a band organ that plays 8 hours a day all summer
long.

My personal 153 band organ has a very thin leather flap valve but then
it has a metal backer plate. This organ has springs to hold the leather
tight on the outside valves but they are just tacked on the inside.

One other question is on the inside valves. They leather valve is almost
the same size as the enclosure they are in. I am not sure if this
impedes the air movement or not (see photo).

I have no experience on what these valves looked like originally. Any
help would be appreciated.

Dave Clark

 [ Wurlitzer Outside Flap Valve
 [ https://www.mmdigest.com/Attachments/23/05/15/230515_063801_IMG_1771_50.jpg 
 [ Wurlitzer Inside Flap Valve
 [ https://www.mmdigest.com/Attachments/23/05/15/230515_063801_IMG_1772_50.jpg