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MMD > Archives > March 1997 > 1997.03.25 > 10Prev  Next

Repairing Deleika 20-key Organ
By Craig Brougher

Mike, You posted this question regarding repairing Deleika 20-Key Organ:

> However, the organ has two related problems. First, the bellows
> reservoir is inadequate -- you have to crank at a pretty fast tempo to
> avoid sound gaps as the feeder goes through top and bottom dead center.
> As a musician I feel that some of the pieces on my rolls really should
> be played slower -- and my arms get tired!

If the organ isn't just "designed" poorly and the lower register isn't too strong, then your problem is the feeder system, i.e., pumping bellows and reservoir. First, check to see how far open your reservoir gets before it begins to spill. Maybe it never spills(?). If the reservoir doesn't spill, then you know you have a problem. The reservoir in a properly designed crank organ should be spilling practically all the time it is playing.

> Question 1: Are my bellows leaking, and if so, do I have to rebuild
> them or can I try to delay the inevitable by applying a coat of
> Neatsfoot oil to the white leather, or would diluted rubber cement be
> better (ugh)? This organ can't be more than a few years old, and I'm
> surprised that the bellows leather should be porous already. I should
> probably shellac the top board and maybe check the flap valves inside
> too.

Quick fixes won't work and you will just waste your time trying them. Neatsfoot oil doesn't air- seal anything. It just preserves leather that's exposed repeatedly to moisture. If this organ has just been built, I suspect that you may have an end-grain leakage problem or a cracked reservoir-- something like that. I can't see how it could possibly be cloth and leather this early in the game. Figure to find something that has broken.

Sometimes the bellows covering has come off the bellows. For example, if they have used quick tack fish glue (that's a glue similar to Lepages school glue), continual moisture in the air will take it right off the wood. If they have failed to size the end grain in their reservoirs before they glued the coverings on, just a couple of inches along that seam will render the machine almost useless. feel for and listen for air leaks along the covers. Any pipe you want to disable just slap some masking tape over its mouth somewhere. It will still blow air, but won't sound.

> Question 2: There's no "melody" and "accompaniment" division, but the
> scale divides into 9 (double) Dutch Bourdons for the top notes, nicely
> displayed, and 9 single Bourdons hidden under the case. The latter are
> voiced too loud for the solo pipes, and a bit too "tubby" also.
> Besides, they use far too much of the limited air supply -- one good
> "hoot" chord drains the reservoir.

Too-large a stop will drain the reservoir too fast, of course. You can probably tell by how far the mouth is cut-up. Sometimes you can "toe-voice" these pipes a little by just throttling down the air supply to them at the toe. Then you can re-tune them, but you already know that. The large ranks' air requirements are exponentially scaled to their position on the musical scale. Every few notes may literally double the air requirements. Voicing last of all will be the way to go.

> So I'd like to throttle them back somehow -- put a constriction on
> the plastic tubes that feed each accompaniment pipe from the valve
> chest, or maybe limit the travel of their valves (easy in theory, but
> hard to get to). As a pipe organ nut, my ideal solution would be to
> replace them with narrower-scaled Rohrflotes, but that's a tad
> extreme. :-)

Yes. You can do that. But first, isolate the feeder system from the pipes, and you should be able to tell exactly what your problem is. You may have to just cover the plenum hole to do that. You can also tape over the spill and pump up the feeders, then find the leaks by "feeling them blow." My bet is feeder cloth or leather covers that have come loose from either the bellows or reservoir wood somewhere. (Check hinges where weak gluing breaks first).

Craig Brougher

(Message sent Tue 25 Mar 1997, 14:04:03 GMT, from time zone GMT.)

Key Words in Subject:  20-key, Deleika, Organ, Repairing

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