Pipe-Making Tips, Stoppers, Voicing Supply

by Tony Goldsworthy

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Pipe-Making Tips
I have found the following method to be a good way of building the smaller pipes with the 2 to 3 mm wall thicknesses. Lay one of the pipe sides on the work surface and glue the back and the other side together using the unglued front of the pipe as a removable spacer. To apply a good downward pressure I use small pet food cans with melted lead in them and place them along the length of the pipe. To even up the load I use a length of 'inch by eighth' mild steel strip and place the weights on top. When the glue has set you can insert the pipe end and mouth piece, taper the front piece, glue it and insert it. Usually it holds itself nicely in position with the pressure from the two sides. A little pressure from the weight cans ensures an airtight joint. With the thinner walled pipes there is always a tendency for water based glues to swell the wood surrounding the joint which can cause the wood to warp.  A solution to this problem is to seal the inner surface of the pipe with the PVA solution before assembly as this will minimise the rate the water will penetrate the joint. You wont get rectangular section pipes if the edges of the wood are not at right angles. I cut my wood (cedar - I couldn't bring myself to use balsa) a mm or two oversize and then cut back to the mark with a very finely set plane. I have made up a 'shooting jig' which is like an oversized bench-hook with a flat and level board attached below it. You rest the pipe side on the bench hook with its side parallel to and slightly overhanging the edge.  It is then easy to plane the piece back to the line using a small plane on its side and a nice right-angle results.

With regard to attaching the pipes to the front board I have successfully used self adhesive 'Velcro' hook and loop tapes to locate the pipes on other small organs I have made. I will assess using this method for this organ. I guess there could be a 'volume' problem as the pipe will be insulated from the front which will no longer be able to act as a sound board. It isn't a traditional material but I am sure the nineteenth century makers would have used it had it been available to them.

Pipe Fixing
Some time ago I made a portative organ with 'Velcro' brand adhesive hook and loop tape holding the pipes into the pipe rack. I was toying with using this approach on the Busker organ I am currently building. My concern is that without the back of the pipe being firmly fixed onto the pipe board the board would cease to act as a resonator/sound board and the organ would lose some of its volume. So I borrowed a Decibel meter from work and ran the following tests.  The 'executive summary' of the tests is that, if anything, the volume is enhanced when the pipe is secured with Velcro.

The tests were all done on a 'C' pipe with a Radio Shack dB meter with the microphone 500mm (20") directly in front of the mouth of the pipe and about 200mm (8") lower than the pipe mouth.
The background noise ie bellow and general clatter was 58 dB
With the pipe hanging free in the air on the end of the feed tube the pipe produced 74 dB
With the pipe clamped to the pipe board the pipe produced 71 dB
With the pipe secured to the pipe board with two pairs of 20mm (7/8") Velcro discs the pipe produced 75 dB.

Thus Velcro is a reasonable fixing material which will be much easier to use than attachments made out of wood. I will run a pair of strips (hooks) across the pipe board and stick the loop material to the pipe. The feed tube entering pipe will lend some rigidity too. I may need some timber 'fancy bits' to route the air into the left and right mitred pipes though. I know it's not a traditional material but I am sure that if they had access to Velcro in the past they would have used it!

With regard to the reduced volume of the clamped pipe it could be due to the clamp (a plastic thing you squeeze open and when released a spring pressure performs the clamping) was stopping the pipe from resonating. But I guess the act of screwing into the pipe to secure it to the pipe board wouldn't exactly enhance the resonance either.

While I had the test rig set up I ran a test on the volume of sound I was getting from the pipe while the pitch was being changed. C 75 dB, C# 78 dB, D76 dB. Raising the pitch of the pipe beyond these notes showed some interesting changes in volume. Again I think this was due to some of the tonally related notes resonating the pipe.

Pipe Stoppers
I have discovered that pieces of 10 mm (3/8 inch) closed cell camping mattresses (the sort you rolled up and carried when you used to hike) form excellent pipe stoppers. They can be cut with scissors, collapse nicely so as to form a good seal , slide in the pipes and can be 'superglued' onto handles formed from lengths of bamboo shashlik skewers. They weigh next to nothing and as they spend their lives trying to expand into the walls they don't readily move yet they can be repositioned with ease.

I find making stoppers from leather clad wood with card shims probably the worst part of pipe making and the camping mattress stoppers are a joy to make and apply. The only down side is the colour (mine are 'burnt orange') is decidedly non-traditional but not many people will see them.

Air Supply to voice Pipes
Use an air mattress/inflatable toy foot inflation pump to generate wind to voice pipes. (Don't use a battery one as you wont hear the note above the din!) These inflators have a conical connector which will slip into the PVC wind pipe. Use aquarium air supply or car windscreen washer 'tee' pieces so you can connect in a U-tube manometer and blow the pipe at a known water gauge. The advantage with using this method is you can actually see what you are doing and the wood of the pipe doesn't become loaded with exhaled moisture and swell out of shape.

 
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