Repairing Deleika 20-key Organ
By Robert Linnstaedt
Mike Knudsen writes regarding his 20-note Deleika organ:
> Question 1: Are my bellows leaking,....
> Question 2: ...The [single bourdon] are voiced too loud for the solo
> pipes, and a bit too "tubby" also..... So I'd like to throttle them
> back somehow. ... my ideal solution would be to replace them with
> narrower-scaled Rohrflotes, but that's a tad extreme. :-)
Dear friends, "Extreme" is an understatement -- "uninformed" comes to mind. A finely voiced pipe organ is not a do-it-yourself job for an amateur. _However_, this situation (only 20 pipes) is very do-able. :-)
Each pipe can be individually adjusted for volume, tone, speech, and pitch. The down-side is that changes to any one of these also affects the others. With care, you can do it. But only one variable at a time!
1. Find the defect.
2. Remedy the defect.
(This is not a secret, but it's often ignored.)
First, check your reservoir for leakage. Do Not change the voicing on any pipes until you have an airtight reservoir. With the reservoir isolated from the rest of the system, inflate the reservoir until the spill valve opens.
Stop. Time how long it retains some inflation. If it's a minute or more, consider them airtight. If less than a minute, you may have a leak; the larger the leak, the shorter the time. Likewise, test the rest of the system. (You didn't say how the reservoir performed when new).
A quick-fix of rubber cement will only remedy porosity. It should not be used for re-gluing a joint; hot hide glue is the correct adhesive. If you use rubber cement, dust the cured cement _generously_ with baby powder so you don't glue your gussets together. (Quick-fixes are generally frowned upon). ;-)
Voicing is where artistry comes in, so humility is vital. Years of study and experience are needed. You don't have them. So,... proceed carefully. Do it in this order:
1. Inspect the pipes, pipe valves, tubes, spill valve, etc. for damage, kinks, slipped regulators, etc. Correct any defects before proceeding.
2. If your pipe valves are all opening properly and uniformly, look at the pipes. The "foot" of the pipe will have some means for regulating the wind supply: either a butterfly valve, a screw, a slide on the toeboard, or just a lead toe. Regulate the air supply to each pipe so that they speak fully and promptly. When done, go back through (at least once) the entire set of pipes so that the loudness is appropriate for each section, and uniform throughout the section.
3. Tuning. Do not change the windway, frein, bridge, upper lip, ears, etc. except in the most unusual of cases. (i.e., you know what you are doing, and know your craft as well as Deleika).
Just remember these important steps:
1. Find the actual problem.
2. Fix the problem. First.
Only Then Correct voicing faults:
1. Regulate pressure at the reservoir.
2. Regulate pressure at the pipe.
3. Correct the tuning.
Robbie adds,
>[ I tried throttling the short air-calliope pipes to tame the shrieking,
>[ but it didn't work well. Even after changing the "cut-up" (the big
>[ gap between the base and the resonator), it still didn't sound very
>[ good. I didn't try making a narrower wind gap, which maybe would
>[ help.... -- Robbie
All else being equal, reducing wind pressure to a labial pipe calls for lowering the cut-up. Slightly, if at all. High cut-ups permit pipes to be blown harder without over-blowing. That's why calliopes have such high ones.
One variable at a time. Go by small steps, as small changes have enormous effects. Caution: do not do anything irreversible unless you have knowledge and experience (and can easily replace ruined pipes).
Best wishes,
Robert Linnstaedt
The Organ Shoppe, Benbrook TX |
(Message sent Tue 25 Mar 1997, 17:40:22 GMT, from time zone GMT-0500.) |
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