_THE WIND-CHEST._
THE somewhat wearisome task of boring more than 250 holes in the
sound-board being now assumed as accomplished, we may take the upper
boards and sliders apart, and retouch the holes here and there, as
required, with the hot iron. The apertures of the holes in the interior
of the channels must be thus attended to, as the boring-bit may have
occasionally torn the wood and left rough edges. Upon the faintest
suspicion arising in your mind of any flaw or crack set up in any
channel during the business of boring, smear over the whole interior of
that channel anew with thin glue, letting it flow as before into the
angles. A running of the wind from one channel to the next is, as we
have said, the most provoking of all defects, and might compel us to
pull the whole of the organ to pieces after it was set up.
The running of wind from one pipe-hole to an adjacent one, either under
the slider or between the slider and upper board, though very annoying,
is a much less serious evil. As a precaution against its occurrence, it
is usual to make little cuts or canals running tortuously all across
the table from edge to edge between the pipe-holes, and to make similar
canals or ducts across the under side of the upper boards, so that no
vagrant wind can pass from a hole to its neighbour in any direction
without encountering one of these little cuts, and being conducted by
it to the edge of the sound-board, where it will escape harmlessly.
If the planing of all the surfaces is absolutely perfect, these cuts
should be unnecessary, and we have seen highly finished sound-boards in
which they were omitted; but we must recommend their introduction by
all young beginners. They may be neatly and quickly formed by using the
=V=-shaped tool common among sculptors in wood, and procurable at any
good tool warehouse. Its two edges should be exceedingly keen. The cuts
may be about 1/8 inch in depth.
After this is done, the movement to and fro of the sliders should be
regulated by cutting a little slot in each of them, and letting a very
stout pin of wood or iron into the table within the slot, so as to stop
the slider at the exact points. Of course all your sliders will have
the same extent of play, say 1 inch, less or more, according to your
arrangement of the pipe-holes. You will probably have so far thought
over your whole work as to be able also to cut the openings or slots in
the projecting ends of the sliders by which the mechanism for drawing
them in and out will be applied to them. We shall show, hereafter, one
or two different ways of effecting this movement to and fro.
After this, take some good blacklead in powder, and with a stiff brush
rub it over every part of the table until the whole surface has a
lustre like that of a well-cleaned boot. Treat the sliders and the
under side of the upper boards in the same way. This application of
blacklead greatly diminishes friction between wooden surfaces brought
into contact. Some operators mix the blacklead powder into a thick
paste with spirits of turpentine, or with water. We prefer using it
dry, but we heartily endorse M. Hamel's complaint that it is difficult
to procure blacklead of good quality. That which is sold for household
purposes is often little better than a gritty sand.
When the blacklead has been applied, the bearers may be pinned down in
their places with small brads. The holes which you have bored for the
screws will be conspicuous in them: over each of these holes, using
thin glue or paste, place a slip of paper, extending 2 or 3 inches
along the bearer on each side of the hole. The use of this is to hold
up the upper board, in order that the slider may not be pinched so
tightly as to be immovable. The upper boards may then be laid upon the
bearers, with the sliders in place, and the screws turned until the
sliders can be made to glide to and fro with smooth and easy motion.
Our bench, let us assume, has been swept and cleaned up after this
blacklead rubbing, and now we turn over our work and proceed to a new
class of operations.
We have to attach to this lower side of our sound-board a shallow box
of the same length, and about 3 inches deep, called the wind-chest,
which is to contain the apparatus by which the admission of compressed
air to the channels is governed, and which is in direct communication
with the bellows by means of a wooden tube called the wind-trunk.
We are mindful, of course, in drawing up this account of organ-building
operations, that the majority of our readers stand in no need of
definitions of these common terms. To such readers it is superfluous
to explain that the valves by which the channels are kept closed while
the keys are untouched by the fingers are called "pallets," and that
these pallets are slips of wood a few inches in length, planed to a
triangular prism-like section, faced with soft white leather, and held
up against the channels, so as effectually to prevent the ingress of
air, by springs. When the keys are pressed, the pallets corresponding
to them are drawn down or opened by wires called "pull-downs," passing
in an air-tight contrivance through the bottom of the chest.
Fig. 13 is a transverse section of the wind-chest, in which _a_ is the
pallet, held up by _b_, the spring, and drawn down by _c_, the wire.
Part of the sound-board is shown above, also in section, as will be
easily comprehended; and Fig. 14 is a view of part of the interior of
the wind-chest when the front board is removed, four of the grooves
being shown in section.
We proceed by sections, with intervening remarks, as in Chapter III.
[Illustration: Fig. 13.]
1. Seven inches will be an ample length for the pallets in our
organ; and as our channels are about 12-1/2 inches in length (inside
measurement), there will be between 5 and 6 inches of the channels
uncovered by the pallets, and closed permanently in another way.
_Remark._--We take 7 inches as the length of our pallets on the
assumption that the widths of the channels are proportioned to a
sound-board about 4 feet long.
[Illustration: Fig. 14.]
2. Between the bars of the sound-board, at a distance of 6-1/2 inches
from that side at which you mean the movable front board to be, glue
pieces of thin wood about 2 inches long and fitting nicely, and when
the glue is dry dress these over with a fine plane truly flush with
the edges of the bars and of the cheeks. You have now a firm wooden
surface to which you will glue, by-and-by, the little flap of leather
which forms the hinge of the pallet.
3. The width of the wind-chest will be governed by that of the space
covered by the pallets to be enclosed within it, in our case about 8
or 9 inches. 3 inches will be a sufficient depth. Make the two ends or
cheeks of stout stuff, and face them up to correspond with those of
the sound-board, with which they will be flush, taking care that their
thickness is not so great as to prevent the leaving of an ample margin
to the two extreme channels for the pallet to rest upon.
_Remark._--In one of these cheeks a trunk-hole may have to be cut
for the entrance of the wind. We ourselves greatly prefer making the
trunk-hole in the bottom board of our chests. Your plans may not admit
of this, and you will act accordingly.
The back of the chest, called the "wind-bar," _d_, Fig. 13, should be
of strong and sound stuff, oak or mahogany, as it greatly helps to
strengthen the whole sound-board and to bear the weight of the pipes.
The corners should be dovetailed, or otherwise well and firmly jointed.
These three pieces, the two cheeks and the back or wind-bar, will now
be attached to the sound-board with glue and screws, to be separated
from it no more; but the bottom, _e_ (of 1-inch pine), will be fixed on
with screws only, strips of soft white leather being interposed between
the surfaces to ensure air-tightness; and the front board, _f_, will
be similarly fitted with an eye to occasional removal.
_Remark._--All such screws should be dipped in melted tallow, or
otherwise well greased before use, that they may not rust in their
places.
4. Prepare the pallets from clean and very dry pine. Every pallet
will be at least 1/4 inch wider than its channel, that it may have
not less than 1/8 inch of overlapping or margin on each side, and
it will have more than this space to spare at each end. The pallets
will be separated from each other when finally put in by stout pins
of iron or brass, driven into the bars _g_, Fig. 13 and Fig. 14. Two
such pins may be necessary between many of the pallets if the plan of
your sound-board has given unusual thickness to some of the bars, and
therefore unusual spaces between the pallets.
5. The pallets are to be faced with white sheep-skin, and it is usual,
but not absolutely necessary, to give two layers of it to each pallet.
About an inch of surplus will be left at one end to form the hinge;
and this hinge should be stiffened by gluing a slip of thinner leather
upon it and upon the sloped-off end of the pallet. The quality of the
facing leather is of the highest importance, and we must counsel the
reader to procure it from a builder, or from one of the shops which
supply builders' materials. The price of such skins is between three
and four shillings. If an inferior leather is used disappointment is
sure to ensue; and though leather of very promising appearance may
be bought at the fellmongers' or shoemakers' in your town, you will
only be put to new expense and additional trouble in the end by using
it. In putting the leather on the pallets, a common plan is to pin
down a sheet of glass-paper of medium roughness on a board, and to
scatter a little whitening on it. The face of each leathered pallet
(when the glue is dry) is gently drawn across this whitened surface.
If, however, the leather is of superior quality in the first instance
the glass-paper may be omitted, and a little whitening rubbed upon the
leathered face will suffice. Even this may not be essential.
6. In working the pallets in take great care that each channel is
covered by its pallet with an equal margin or surplus on each side
of it. It is well to trace pencil lines on the bars as a guide. As
you glue down each hinge give a little tap with a light hammer to the
pallet, and satisfy yourself by inspection that the impression on the
leather is equal and similar in every part. Allow no defect to pass.
Rectify, for instance, the slightest bruise or depression in any of
the bars at the points covered by the pallets. See, also, that all the
pallets play easily between their guide-pins. Finally, a slip of wood
about an inch wide may be bradded down upon the hinge-pieces. This is
not essential, but it is a protection against possible straining and
injury to the hinge by incautious treatment hereafter in cleaning the
surface of the pallets.
_Remark._--Organs have been constructed in which the pallets were made
to play upon a pin at the hinder end, and not upon a leathern hinge
glued to the bars. Such pallets could be taken out one by one at any
time for repair or cleaning. But repairs and cleaning, if the original
workmanship is good, become necessary only at extremely rare intervals,
and these removable pallets may be ranked among the mere curiosities of
our subject. They are described and figured, however, by Seidel.
7. The springs, see Fig. 13, are now commonly of steel, which has
extensively superseded brass, in consequence of the deterioration to
which the latter metal is subject. We are bound to say, however, that
we have used springs of best brass wire, even of late years, without
any disappointing results, and that sets of such brass springs are,
to our knowledge, as efficient as ever after thirty or forty years of
constant use. But it is undeniable that the brass wire now procurable
is subject to a change under the influence of damp and (it is said)
under that of the fumes of gas, which renders it brittle and quite
useless for purposes which require flexibility. Springs certainly
cannot be made from wire so spoilt; but, as we have said, when once
made from new wire, they may continue in use for periods practically
unlimited.
_Remark._--The store of brass wire should be kept wrapped up in brown
paper. This applies also to brass plate.
Whatever the wire, the springs may be quickly fashioned by using a
board, Fig. 15, in which you have fixed a stout wooden peg, _x_, and
two pins, _y_ and _z_. The wire, if brass, should be about No. 17 or
No. 18 of the gauge. The formation of the spring, by twisting the wire
round _x_, _y_, and _z_, is too obvious to require further remark. The
arms of the spring maybe about 5 inches in length, and they are curved
outwards (see Fig. 16) by drawing them between the thumb and fingers.
When so curved, and left uncompressed, the gape or distance between the
extremities will be 7 or 8 inches.
[Illustration: Fig. 15.]
[Illustration: Fig. 16.]
_Remark._--The strength of the springs must be regulated by your plans
in other respects. We ourselves like strong springs, even if the manual
touch be in consequence a little heavy.
8. The two extremities of each spring are bent at a right angle
or nearly. One of these will be inserted, but quite loosely, in a
small hole or punch-mark near the middle of the back of the pallet;
the other, also quite loosely, in a similar hole or depression in a
wooden bar extending the whole length of the wind-chest, and screwed
down within two notches made for it in the inside of the cheeks.
As the united pressure of the 54 springs will certainly bend this
bar, it is well to introduce a long screw at about its middle point,
passing through it, and biting well in one of the sounding-bars. The
spring-bar has a slip of wood, cedar or mahogany, about 2 inches wide,
glued or bradded to it along the side which is to be nearest to the
back of the chest. The springs will be held parallel to their pallets
by playing loosely in cuts, about 1/8 inch wide, made in this slip of
wood (Fig. 17).
[Illustration: Fig. 17.]
The socket, or punch-mark, upon which the pressure of the spring is
exerted, should be a little in advance of the middle of the pallet, so
that the latter may be held up against the bars throughout its extent.
The spring, be it carefully observed, is loosely held in place by the
sockets and by the rack in which it plays, and it can be removed at any
future time by the aid of the little clever tool which we have figured
in Fig. 18, and which you can make for yourself.
[Illustration: Fig. 18.]
When all this is done, furnish every pallet, if you have not already
done so at an earlier stage, with a little ring or crook, by which to
draw it down. This ring is best made by bending one end of a bit of
suitable wire, and thrusting the other obliquely into the pallet (see
Fig. 18_a_). This is better than driving in a little staple vertically.
The rings may be in a line drawn across the pallets about 1-1/2 inches
from their extremities.
[Illustration: Fig. 18_a_.]
_Remark._--But it will be convenient that the rings to which the
pull-downs will be hooked should be quite clear of the guide-pins.
9. The bottom board being now put in its place for the moment, draw a
line upon it from end to end exactly above the line of rings on the
pallets, and draw lines at right angles to this corresponding with
the centre of each channel, and therefore of each pallet. At each of
these points a pull-down will pass through the board, and it is plain
that it must be made to do so without allowing the wind included in
the chest to escape. This was formerly effected by "purses" (French,
_boursettes_), little leather bags, tied or otherwise attached to the
pull-downs. We have seen this method successfully tried, but it is now
so completely superseded by a simpler and more effectual plan that we
do not think it worth our while to say more of it.
The arrangement now invariably adopted is thus made:--Procure a strip
of brass plate, or several strips, equal in the aggregate to the length
of the chest, and about 1-1/2 inch or 2 inches wide. In too many organs
this plate is poor stuff, not thicker than a visiting-card, sometimes
even of zinc only, but in our opinion it should be at least as thick
as a shilling. Drill holes in this plate near the edges, and pin it
down for the moment on the bottom board, so that the lines of holes
for the pull-downs may run along its middle. Mark on the brass the
intersections of the lines as before. Having previously chosen the wire
for your pull-downs (of which more directly), take a fine drill, with
your breast-plate and bow, and on a bit of waste plate try the size
of the hole made by it, altering it on the oil-stone until the hole
receives the wire with the nicest and most accurate fit.
_Remark._--It will be well to store away the drill afterwards, with a
bit of the wire as a specimen, and to use it for no other purpose.
This drilling is not a difficult operation, and only requires care
and delicate manipulation. Of course, however, any clockmaker would
drill the holes for you. Assuming confidently that you will drill them
yourself, we recommend you to hold the bottom board, with the plate
on it, in the screw-clamp of your bench, or in a similar vertical
position, so that as the drill penetrates the brass it may be received
by the soft wood of the board. This will diminish the risk of breaking
it.
_Remark._--Those who have a light handy lathe will know how to utilise
it in drilling the holes in the brass plate apart from the board.
When all the holes are drilled, remove the plate, and clean off with
a fine file the rough projections thrown up by the drill. With a much
larger drill, twirled gently between the thumb and finger, smooth the
edges of all the holes on both sides of the plate. Try a bit of the
wire in every hole, and draw it to and fro, when necessary, until its
passage is perfectly smooth and easy. Grease should not be used; or, if
a little tallow is rubbed over the wire, it should be wiped off clean.
The holes in the bottom board itself may be of any size we please,
since they have nothing to do with keeping in the wind, and merely
allow a perfectly clear passage for the wire pull-downs.
It is plain that if we now pin down the drilled plate in its place, the
arrangement will not be complete without some provision for preventing
the escape of wind in large quantities, and with an intolerable hissing
noise, at the edges of the plate.
The builders prevent this escape and hissing by fitting two long slips
or tringles of wood (see _h_, _k_, Fig. 13) along the two edges of
the plate with glue and brads, or screws. These slips press the plate
closely to the board throughout its entire length, and they protect
from injury at the same time the rings of the pull-downs, which might
easily be bent and distorted.
Using thicker plate, however, we ourselves greatly prefer to glue
a strip of white leather, of the same width as the plate, over the
holes in the board, piercing it with a sufficiently large awl at the
centre of each hole, and we screw down our plate upon this leather,
using numerous short screws, placed only 4 or 5 inches apart, passing
through holes drilled near the edges of the plate, and countersunk in
the usual way. All escape of air is thus most effectually prevented,
and the slips or tringles of wood become unnecessary, except, indeed,
in their secondary character as protectors of the rings.
The bottom board may now be put on, and strongly secured by plenty of
screws, well lubricated with tallow. Prepare the pull-downs, of uniform
length, each with its little ring neatly formed; pass each through its
hole in the plate, and with suitable pliers form the top of the wire
into a hook, which takes hold of the ring of the pallet.
_Remark._--Or you may pass all the wires through the holes, and form
the hooks upon their ends before you fix the board in its place.
The builders often muffle the hook or ring with silk thread, or a
morsel of soft and thin leather, to prevent a slight clicking noise
which might be heard of wire against wire. This, however, is really not
essential. It is, or formerly was, very common also to interpose an =S=
of wire between the hook of the pull-down and the ring of the pallet.
These connecting links are unnecessary, and are better omitted.
According to strict rule the pull-downs, passing through holes in
brass, should themselves be of iron or steel; but we have always used
brass wire, and we must refer our readers to what we have said of this
material in treating of springs. They must judge for themselves. The
essential thing is that the wires should play easily and smoothly
through the holes, drawing down the pallets with perfect freedom, and
allowing them to return, when released, with a pleasant smartness. If
a single pull-down fails in these respects remove it at once. Perhaps
it is a little bent or bruised; possibly the hole in the plate may have
been inadvertently left with a sharp edge, which has cut a notch in
the wire; possibly, also, the pallet-ring may not be quite in a line
with its fellows, and therefore not quite correctly above the hole in
the plate, throwing the pull-down out of a right line into an oblique
one. Rectify all defects of this kind at any expenditure of time and
patience.
We have left all this time several inches of each channel open or
uncovered, since the wind-chest closes in only that portion of the
channels to which the pallets are applied. We may now finish our work
by gluing white leather, or parchment, or even only stout paper, over
the open part of the channels, taking care that it adheres well in
every part.
We may add that it is sometimes, or often, convenient to place the
wind-chest under the back part of the sound-board, and not under the
front; or to place it midway between the back and front, or a few
inches from either. This is done with an eye to arrangements connected
with the action or movement, which will be described in detail. When
the wind-chest is so placed care must be taken to provide for the
complete closing of the front board. A ledge of wood should be glued
and pinned to the bars in such case, to afford a bearing for the front
board and to receive the screws which secure it; or the edges of the
board may be leathered, and it may be thrust in, with a tight fit,
between the under side of the channels (roofed with wood at that point
for the purpose), the cheeks, and the bottom board, cut an inch wider
accordingly. Wedges are sometimes used, driven in behind clasps or
hooks of iron, to keep it in its place. But in truth, when the organ
is once well built and finished, several years may elapse without a
disturbance of the board.