Gulbransen player

[Ron Nossaman]

>
> List
> I've got a Gulbransen player in the shop to clean up for sale, recently
> rebuilt by the late William Gilstrap (passed away about a year ago).
> Beautiful work! Very clean and neat. I don't know what has been done since
> the rebuild. Everything appears to be in order: cut off and accelerator
> valves working, motor running as smooth as possible, hoses tight. But, low
> volume and slow speed. A suction unit was added and works but sounds like
> it's working at its max. Pedaling fast barely turns the roll. Check valve in
> the suction box is in place and working. Reservoir bellows are completely
> collapsed. I have not done any work to this instrument yet. Everything was
> done before it came in. I'm the only one in this area to show any interest in
> working on players, so there are no resource persons near by. Any volunteers?
> I have some back ground in player service, and enough foresight to ask first
> before making things worse. I've subscribed to the MMD and hopefully getting
> some instruction from them. For those on the list who wish to respond may do
> so privately if they feel other members may not be interested. I await your
> reply(s)!
> Thanks!
>  
> Paul Chick



Try tightening everything you can find first and hope you get very lucky,
because it sounds like valves to me. Gulbransen had some good design features
that make them very efficient while they worked, and unusually touchy to
rebuild. The original pouches were pneumatic cloth. That means the dip was
shallower than would have been the case with leather, since the cloth won't
take the necessary compound curve without wrinkling. Replacing these with
leather, the rebuilder finds that the pouch well in the pneumatic leaf isn't
all that deep, and if he trys to dish pouches by "thumb", they will likely not
be dished enough, especially after he installs the fiber disk and valve stem.
The original valve stem was of a length that the pouch was almost lying in the
bottom of the well when the valve seated on the inner seat. That's not enough
margin for error with leather pouches, since they shrink with age and dryness,
and will float the valve above the inner seat. If you lightly touch the top of
a valve at rest and not under vacuum, and can (again, lightly) push it down a
little before it seats, that's the problem. I trim the stems so (with new
leather pouch and that little leather universal joint between stem and valve)
the pouch dish will be level when the valve seats. Even if the pouch shrinks up
like a drum head (which it won't if you make a dishing tool that dishes to the
perimeter of the well) there's no way the pouch will float the valve off the
inner seat, and playing vacuum will still seat the valve on the outer seat. The
proportion of pouch diameter to valve diameter is about 2.5 / 1 in these
actions, where more like 2 / 1 is the norm, so there's plenty of power
available for overcoming any minute resistance during the power stroke, but
very little tolerance on the return. When they are right, the Gulbransens are
just about the most efficient player actions made with wood and leather. That's
why they have the littlest pumpers in the industry, and why it doesn't take
much of a leak, or leaks to kill them. Also, you'll find that the sustain
pneumatic has all the power in the known universe, but doesn't lift the dampers
enough unless it's already floating them to where they don't work well. They
need a little leverage re engineering with rebuild too.

What to do about it? If this proves to be the problem, you have one chance
short of tearing down and doing the whole stack over. Pop off the valve covers.
This will probably destroy them, so plan on buying or making replacements. Pull
the valve off the stem, trying your very best to not pull the disk loose from
the pouch, for obvious reasons. With luck, that little leather universal joint
may be thick enough to clip shorter with toenail clippers and get enough slack
to work. If not (probably not) you'll have to make tools to hold the pouch disk
down while you pry the valve stem loose - all while working through a 7/16"
hole nearly 3/4" deep. Then you clean up all the stems, recover the inner seats
of all the valves because they were trashed during disassembly. Establish the
proper length for the stems by trial fitting and eye balling throw limits when
you work the pouch up and down with a piece of tubing to mouth. Trim the stems
to length, install a new little leather punching to the top, glue the stem to
the pouch disk, and the valve to the stem, and gap the valve when you glue the
new outer seats on. Then walk away smiling. That's the easy way. The hard way
gets considerably more involved.


Ron N