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MMD > Tech > AeoW > rv_216

Orchestrelle, Chapter 21.6
Rebuilding the Æolian Orchestrelle
58-Note Player Reed Organ, 1912 Model "W"
by Richard Vance
Copyright (C) 2002 by Richard Z. Vance
rev. A, 6 October 2002

Chapter 21.6 Functional Test of the Rank Chests

    Install the lids on the tops and bottoms of the chests, as they are done.  The lids are made of quarter sawn fir, only 1/4" thick.  Although this is very good, stable lumber, some of it is very soft.  In the case of one of the ranks, this wood was so soft that the little No. 6 flat head screws had pulled right through, crushing and pushing aside the wood around some of the holes. The ranks are so close together vertically, that there is not enough room to replace these screws with round headed screws and washers.  I finally puzzled out a solution, as shown below:

    Working from the bottom rank, remove the tape from the manifold board holes, and install the rank chests one at a time, for the initial functional test.

    Looking from the rear, one can see the 168, 2" No. 10 RH woodscrews, that attach all the ranks, and the secondary valve rail, to the vertical manifold panels.  My instrument came with heavy chest springs under all the screws, similar to the springs used on Aeolian player piano separable tubing joint blocks.  These springs were rusty, so I made new ones by cutting up the heaviest 3/8" diameter coil springs from McMaster-Carr.  The earliest Orchestrelles did not use springs here, but I think it would be a good idea to use them in any rebuild.  They have two advantages; first of all, they insure that all the gasketed joints between the vertical channels, and the holes in the pouch boards, remain tight.

    Just as important, one can see the springs going shut as one tightens the screws, and stop turning the screws before one inadvertently over tightens them.  Since I had to take the pouchboards on and off several times during the preliminary testing, I used a power screwdriver.  These critical screws are driven into maple cross-dowels in the soft pouch boards, and would be hard to strip;  But I wouldn't want to run that risk.  Thank goodness for the Black & Decker "PowerDriver"; I've worn out two so far, but they are only nineteen bucks.  A good investment, considering that an orchestrelle must have at least 2000 woodscrews!

    One little problem occurred on a few of the chests, as I first turned on the wind.  A fart noise came from the slef-energizing gaskets (see Chapter 2.3).  To compensate for the widthwise shrinkage of the manifold panels, I had spaced them a little bit away from the end wind towers.  I suppose the gap between the wind tower and the chest end was a bit too big to allow instant inflation and complete sealing.  Also, some of the chests were perhaps sanded a bit short.  Some of the chest ends originally had squares of leather glued on, to lengthen them.

    The problem is not that the gasket "diaphragms" are too tight to fill the gaps; there is plenty of slack in the middle of the leather squares, which can expand up to 1/4" outward.  Rather, it must be that the leather must start out fairly close to the chest end, so that when the pressure is turned on, the gasket is instantly and firmly inflated, and pressed against the chest.

    I tried an idea and it worked every time.  I made a square of felt with a 1-1/2" hole, and tucked it inside the loose part of the gasket.  I used cheap polyester "craft felt"; useless for most organ work.  But it is quite elastic and not very dense.  It compresses easily, so any of the chests can slide in easily.  But the felt presses the gasket against the chest end, so that it inflates quickly and firmly, with no perceptible leak even at turn-on.

    For each rank location, there were two 3/16" wooden dowels driven into the ends of the outermost channel panels.  It is important to allign the rank so that the mounting screw holes and the channel holes line up accurately.  But the rank chests are very heavy, and almost all of the dowels were boken off.  I replaced them with long #8 woodscrews with the heads cut off and the shanks ground to a smooth, rounded tip.  The matching holes in the chest backs were countersunk so the new metal dowels would center to them easily.  Now, when the heavy and awkward to handle chests were set into thier spaces, they could be firmly pushed into thier correct place against the boards with no problem.

    Now for the functional test of the pallet action, which can not be easily pictured, so I will describe it.

    When the wind is first turned on, there may be ciphers.  Where they occur, tape over the sound outlet hole to mark that note for further attention.  Try each note from the keyboard.  Some of the reeds will need attention later, and not speak now, but one can hear the proper flow easily, especially if the offending reed is pulled out.  Using a stethoscope, check each reed sound outlet for a leak noise when the note is supposed to be off.  On the larger reeds, there can be a slight cipher, not enough to sound the note, but easily heard with the 'scope.  Mark these locations with tape as well.

    In spite of all the care I took in connecting the pallet wires,. four of the six ranks had a few ciphers.  Significantly, none of the pallets failed to open enough to furnish plenty of wind to the reed.  So there was nothing for it, except to take the offending rank down, opening it up, and checking inside.  In each case, the marked, offending pallet was found to be visibly not fully seated.  In some cases, the wire was too tight; in others the wire loop around the staple was too tight, the springs were too weak, or the slots in the ends of the pallet were a bit tight.

    This was discouraging and tedious work, but I kept at it.  I finally reached a state where every one of the 348 pallets opened properly, and closed perfectly tight, on command from the keyboard or test roll.  I don't want to take a rank chest down, ever again!

    By pedal stroke counting, I determined that the closed pallet leakage averaged 0.94 CFM per rank.  A pretty good recommendation for Leather Supply House CGD-Sueded Goat, considering that the valve overlaps the seat hole edge by only 3/32", and there is about 236 linear inches of total valve edge outline per chest.

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