|Making Bellows the Easy
When I made my first bellows by following the John Smith video, it took me
a week and ended up being a total disaster! Glue everywhere, stiffeners
all over the place, and the glue had dried before I had even finished trying
to line everything up. I vowed to find a better method - One that worked!
Since then, I have made around 15 sets of bellows, either for organs or for
my various experiments and 'inventions', and I have developed lots of easy
tricks to simplify the job. I used to hate making bellows, now I quite
enjoy it! This is a collection of all these hints and tips:
If using blackout material for the bellows, make sure that it is airtight.
I bought some expensive 3-pass blackout cloth from ebay and, although
it was light-tight, I found that I could blow straight through it! So
don't think that the expensive stuff is the best.
MDF is perfect for the bellows boards - preferably 1/2" (12mm) thick. Seal
it with diluted PVA glue. Drill holes halfway through with a flat bit,
from one side then the other.
When cutting the cardboard stiffeners, allow a gap of 1mm between the edges
of the cardboard and the boards, top and bottom. This is to allow the
sides to fold inwards without being restricted. There is no need to
leave a gap between the upper and lower stiffeners because the cloth folds
in the opposite direction along the centre line, which moves the stiffeners
further apart. In fact, the lack of a gap down the centre will help
prevent the cloth from blowing outwards.
Cut away the corners of the front stiffeners very slightly where they butt
against the side stiffeners, to allow the cloth to fold 90 degrees around
the front of the boards.
I use duck/duct tape for the internal bellows hinge. It's much easier,
stronger, and sticks instantly. But beware that PVA glue won't stick
to duck/duct tape, so use cloth or leather for the outside hinge. Don't
mess about trying to fold the internal hinge in half, position the two bellows
boards together and stick the tape straight across the joint. Use a
strip of 3mm thick MDF to act as a spacer between the two boards when they
are closed. To be honest, I am not convinced that the internal hinge
actually does anything!
I recently tried this trick to simplify the task of making, cutting, and
glueing on all the cardbooard stiffeners. This is a fiddly job at best, and
accurate placement of all 6 pieces is not so easy.
Instead of 6 separate bits of cardboard, I made just 3 double-height ones
and scored them down the middle. This eliminates half of the marking and
cutting out work, makes it much easier to position them accurately, strengthens
the central fold, and prevents them from lifting off the cloth. Quite a lot
of advantages for doing half the work!
These bellows ended up very slightly stiffer than the normal method (as you
would expect) but the difference is negligible, and doesn't affect their
operation at all. I would guess that the score will eventualy separate after
prolonged use, but that won't matter. The idea is to simplify construction.
If you are using thick leather for the bellows, this idea probably wouldn't
work so well because the leather would try to pull the 2 halves apart at
the score line. The result would be a very stiff central fold. I
have tried it with leather up to 0.8mm thick and it works alright.
The three stiffeners, cut out and scored, ready to fit
Measuring and Cutting the Stiffeners
The middle stiffener should be equal to the width of the bellows, and the
height of the bellows minus 2mm. The cut-outs are not exactly 45 degrees
(although 45 degrees works). They should be cut away slightly more,
to make more room for the sides to fold in.
The side stiffeners should be the same height as the front stiffener, and
taper down to a point where the two boards meet at the hinge. The 1mm
clearance at top and bottom is produced automatically by the spacer between
the boards at the hinge. You could cut out one stiffener and then draw
around it to mark out the others, but I prefer to measure each one out
individually, as it is more accurate. Draw a line down the centre of
all the stiffeners and score along the line. Fold the stiffeners in half
and flatten out again. Before glueing on the stiffeners, you need to
cut the point off the side stiffeners (around 2" from the point) and trim
the 4 points off the middle stiffener.
Cut the stiffeners out with a sharp knife, then snip the points off
Marking Out the Cloth/Leather (Don't
I now save a large chunk of time by not marking out the bellows cloth at
all. I just draw a centre line. After you've cut out the stiffeners, they
can be lined up on the centre line and glued on, without any other markings
on the cloth. Then cut the cloth around the stiffeners, leaving
about 3/4" margin all around. This method is particularly useful for
leather, as the leather easily pulls and stretches out of shape during marking
and cutting, so the marks end up being mostly meaningless!
Apply glue to the stiffeners and carefully place them on the cloth, lining
each one up with the centre line drawn on the cloth. Start with the
middle stiffener, followed by the side ones. For extra accuracy, check that
the distance between the two side stiffeners is exactly equal to the width
of the bellows.
Wipe any surplus glue off, so that it will not ooze out onto the cardboard
stiffeners. When dry, trim around the cloth, remembering to leave about 3/4"
margin to glue the cloth onto the boards.
The stiffeners glued onto the bellows cloth, each one aligned with the
centre line. No other marks are needed.
Glueing on the Bellows Cloth/Leather
I found that the method of glueing on the bellows cloth by holding the bellows
vertically in a vice (as shown in the JS video) and starting from the front
was very fiddly and inaccurate. Accurate placement is rather hit and
miss because you are working from the outside and can't easily see the position
of the cardboard stiffeners in relation to the edges of the boards. It's
also slow, the glue gets in places it shouldn't, and the glue has started
to go off by the time you get to apply any clamps. As if that wasn't bad
enough the bellows are closed so the cloth keeps trying to pull itself away
from the boards and come unstuck. A complete disaster!
I found it was very much faster, easier and more accurate to do it
the following way, (and you don't get glue all over your fingers neither!).
PVA glue is alright for glueing leather, but not so good for glueing
blackout cloth. I use Copydex to glue blackout cloth.
Before starting, it is best to make sure that the front cardboard stiffeners
are exactly the same width as the bellows boards, and make the two small
cuts in the front corners of the cloth that allow it to fold outwards along
the top board (see John's video if you don't know what this means). It
doesn't matter if the front cardboard is not exactly the right width, as
long as you take this into consideration when positioning the cloth on the
boards in the following procedure.
Lay the bellows cloth flat on the bench. Apply glue along
one long edge of the bellows (both boards) and also along the front edges.
Place the long edge of the bellows carefully on the cloth, lining up
the cardboard exactly between the two bellows boards (remember the 1mm gap).
Check that the corner is in the correct position. Do not glue
the front on yet. Press down hard for a minute to press the boards firmly
onto the cloth/leather.
Now apply glue along the upper edges of the boards. Fold the cloth
up the front edges and check that the cardboard is sitting in the correct
position. Finally, fold the cloth over the top edges and line the cardboard
up with the hinge end of the boards. Pull the cloth tight and press
it well into position all around, then place a heavy book or clamps on it
and leave it overnight.
This method is very fast. I did a pair of bellows and a reservoir
in under 5 minutes, with no fiddling about at all. The weights or clamps
can be applied very quickly, leading to a stronger joint.
Note that the bellows remain fully open throughout the entire operation,
there is no need to close them or crease the cloth, as it tends to unstick
When dry, trim the ends of the cloth, fold them over the bellows hinge and
Leave for at least 24 hours for the glue to fully cure before testing the
bellows or putting any pressure on them.
Bellows placed on cloth and accurately positioned against the cardboard
stiffeners. Note the 1mm gap
Glue applied to the board edges
Wrap the cloth around the board in one go and pull it tight. Making
sure that the cardboard stiffeners are centrally placed. This method
only takes a few seconds!
Completed bellows. The spare cloth is trimmed off around the edges when
the glue has dried
If using blackout cloth, instead of trimming it off, it is a good idea
to fold it over the edges and glue it down onto the boards. Especially
on the corners, where leaks are more likely to occur
Rather than use weights or clamps, it is preferable to pin strips of wood
or MDF down the sides of the bellows to hold the cloth or leather firmly
in place. Use veneer or panel pins. This is a good idea anyway, as it prevents
the stiffeners from trying to force the cloth off during use. If you
are going to do this, it is probably a good idea to do it whilst the glue
is still wet, and prepare the strips ready.
To make your bellows more flexible, close them, clamp them up tight, and
leave them for a day. This presses the folds and sets them. You
may be surprised at the difference this makes.
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