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Balancier Motors


Colin Harvey
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Guest Geoff McMahon

Let's look at how it works first and without drawings it is a little difficult to explain, but I will try.

 

The key action is attached to the pallet in the normal way with a so-called "pull-down" connecting the pallet to the action below the soundboard. This is usually a wire of about 2mm diameter. Between the pallet and the bottom of the soundboard (i.e. inside the pallet box) there is a small pneumatic motor (like a very small bellows) with a fork on the end of it which rests on a button on the pull-down wire. From the small motor there is a tube which goes to the note bar of the soundboard. As long as the pallet is closed, the motor is effectively exhausted to outside the soundboard, so the wind pressure inside the soundboard causes the motor to exert a small downward pressure on the pull-down effectively trying to open the pallet, but clearly not strong enough to do so. This means that the pallet is easier to open when the key is depressed. As soon as the pallet is open however, wind goes into the bar and through the tube also into the small balancer motor, so it no longer exerts any downward pressure ensuring that it does not retard the pallet once the key is released. Often the balancer will have a small spring which returns it to its starting position. Once the pallet is closed, the bar exhausts again so the motor exerts a small pressure on the pull-down again ready to assist the organist the next time he plays the key.

 

When was it first used? Well in modern times it was probably first used by Beckerath, although others have claimed to use if before him. The story is that Beckerath mentioned his idea in a moment of incaution and that it was leapt upon by somebody else who then claimed to be the inventor of it. However, there is some (I believe slightly circumstantial) evidence to suggest that Hill used it in the 19th century. Stephen Bicknell has mentioned this on occasion, but I don't remember exactly what the details were.

 

Properly designed and set up, balancers work very well, but if not set up properly or too large (Beckerath's first ones were too large and had to be altered) they can be a disaster as they impede repetition. Variations on the principle have been applied such as the piggy-back motors on some of Larry Phelps organs where there is a motor on the back of the pallet with a hole through the pallet to exhaust it to the wind bar. A nice piece of engineering and lateral thinking, but notoriously difficult to set up.

 

We only use them for the lowest 6-18 notes if we use them at all, but some builders carry them up into the middle octave.

 

John Pike Mander

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Thanks for that! After thinking for a couple of minutes, plus a piece of paper, I think I've got it. It is quite neat.

 

Yes, I too have heard of some (possibily circumstantial) evidence that some Victorian builders used balancers but not from Stephen. Nicholas Thistlethwaite's book on Victorian organs sketches a type of relief motor in the bottom of the pallet box as used by Hill but I think this works slightly differently as it simply has a tube leading to the atmosphere outside the pallet box.

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Guest Geoff McMahon

That is quite correct. The difference is that the motor in the example in Nicholas Thistlethwaite's book exerts a downwards pressure all the time and can be seen as a forerunner to the balancer. If you omit the connection to the atmosphere through the grooving in the bottom board to the hole for the pull-down (the seal for that is not shewn in the drawing and would have been on the inside of the bottom board) and instead imagine a tube connecting the motor to the bar channel somewhere behind the pallet, you have the balancer.

 

If you go to:

 

www.trierer-orgelpunkt.de/orgelphysik.pdf

 

That should download a .pdf file which if you scroll down you will come to a drawing of a balancer. The article is in German and you need to look for "balancier".

 

John Pike Mander

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This system seems to be quite interesting. Does it have drawbacks? I understand that if the leather of the pneumatic motor does leak, we may end up with a cypher -or a kind of "half-cypher" according to the size of the leakage-.

 

Best wishes,

Pierre Lauwers.

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Guest Geoff McMahon

Absolutely correct. If the motor gets perforated, a cypher or murmur will occur. That is the main disadvantage as you are introducing elements which might require periodic replacement just as if it were an electro-pneumatic organ, but generally there are not very many such motors, so their replacement is not as costly.

 

In addition, if not set up correctly, they can impede repetition. That is why in our design, the motors have their own independent return spring which is not connected to the action at all in any way. This ensures the motor snaps back to its start position as soon as the key is played.

 

John Pike Mander

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Guest Geoff McMahon

For those who are interested, here

 

balancers.jpg

 

is a picture of our balancers. The adjusting wire can be seen projecting from the bottom of the soundboard with the loop on the end. What is less clear is that the bit that looks like a cylinder above the fixed collar just inside the soundboard is in fact a coil spring. The strength of the spring can be adjusted by turning the adjustment; the stronger the spring, the weaker the effect of the balancer. Above the fork which pulls the pull-down wire down is a rail which stops the balancer off in the up position. The strength of the balancers can be regulated globally by adjusting the position of this rail (followed by adjustment of the adjustable collar on the pull-down wire).

 

John Pike Mander

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