Cookie Alert. This web site uses cookies. Information gathered is not shared and is only for pages used information.
Back to Top ▲

ROTARY BLOWING

Mr. F. E, M, Ducker B.A. A.M.I.M.E.

I accepted your invitation with pleasure. Then I found I was committed to a nice wide title and a span of minutes not so wide. Imagine that one of yourselves had undertaken to give a talk on organ building in forty minutes or so, and before this assembly! You will see the point. It means that I shall have to break with what I gather is the normal custom.. Usually, I think, some one aspect or topic is taken from your craft and gone into fairly thoroughly with exhibits and diagrams. I have had to give up this idea and am obliged by my title to give a broad sketch. No doubt it may be welcome news to some who have borne the heat and burden of the day to know that I have nothing headachy to put before you.
I want to begin with a little sympathetic touch. Organ blowing is very much behind the scenes, reticent, retiring, neither seen nor heard-or that is what it tries to be--and then the outsider thinks it must be a dull business, that there cannot be much in it, certainly not real engineering. But he is wrong; it can be very interesting. Nevertheless, a keen young engineer starting in this line of work has to overcome this despondency if he is to stick to the game.
Now, if my title had been" Organ Blowing," that nowadays would have meant the same thing as the actual one, but it was not always so, of course. I am sure I do not know when power was first used to replace human labours at the bellows, but fortunately that is outside my present task because all the early efforts at power blowing of organs were on the displacement principle. In fact, power blowing was well established before rotary blowing, as it was called, came on the scenes. The working of feeders by water engines was the most common form of it, but there were some examples of the use of proper blowing engines of the type used in heavy industry at the time--large reciprocating pumps.
The term "Rotary Blowing" has been in use from the beginning, but it is not altogether a happy one from the engineering point of view because it covers types not in general use for organ blowing. "Centrifugal Blowing" would be correct, and at the risk of seeming pedantic, I propose to use this term this evening to save ambiguity.
The word, of course, properly describes the principle involved. Pressure is developed inside a casing by whirling air at a high speed so that it presses outward by centrifugal force.
I believe this system was first tried round about the turn of the century and in this country, but things were going on also in America and I cannot be sure. In the first instance, and appropriately enough, centrifugal forge blowers were tried.
I say appropriately because one may reflect that while we associate bellows and wind with organs, they pertain, or used to pertain, at least as, much to the smithy. Centrifugal blowers had been applied successfully to the forge, so why not to organs?
But the job is a different one, and they were not very successful. Noise was the chief trouble.
I regard the five years 1902-1907 as the chief formative ones in purpose designed centrifugal organ blowers. The first firm date I know is 1902, when a British patent in the joint names of R. H. & L. B. Cousins was first applied for. Reduction of noise was a main object, and the sound principle of raising the pressure in a series of stages seemed to be covered. A number of fans (or impellers) were mounted on one shaft in separate compartments. Each fan fed into the next so that they acted in series. It was also provided that air could be taken off at intermediate pressures.
I feel sure that the multi-stage principle could not have been new at the time. I know of other patents about then relating to centrifugal pumps and high pressure blowers, which imply that the principle was already in use. The novelty must have rested in the application to organs.
A strong point was made in this specification of the shape of the casing (which was rectangular) in reducing the heating of the air and it also emphasised the preferability of wooden construction for the casing.
L. B. Cousins followed with another British patent in 1904, and there is an American one on similar lines in 1906. These later patents are interesting because they give a glimpse of the difficulties encountered. The timber construction gave trouble with shrinkage and the patent covers some details of construction with the object of meeting this. Noise was troubling the inventor, and silencing boxes were introduced in the outlet system. There was still the heating of the wind.
The blower casing was an elaborate affair with intermediate compartments through which cool air was to circulate on natural draught principles and certain features of the shape of the casing were again emphasised as important in reducing the heating. Much of this, I fear, was anything but sound.
It is not necessary that an idea should be sound to be patentable. I have seen another patent for an organ blower in which the inlet air is drawn over the casing to keep it cool. I do not know where the inventor thought he was putting the heat.
These were high times for the inventors.
I have referred to these Cousins patents because they seem to establish him as the first pioneer in centrifugal organ blowing with purpose designed blowers, but I cannot be sure. I cannot profess to be very knowledgeable on this historical side, and I do not know exactly where Mr. Swanton came into the picture-or even for sure from where. He also did some patenting of an organ blower about this time-of the square wooden box variety.
I hope the pleasing picture I have in mind of this gentleman is reliable (it is from an eye witness). He must have been a decidedly colourful personality. I am told that he dressed astonishingly well and that he used to drive about in (or should one say" on" ?) one of those very fleet and lightsome carriages drawn by at least two horses, and under the seat he carried a Ross valve
blowing Engine Ross water engine
Installed and running in a church in Feilding (a small country town in New Zealand)
Click Icon
Photograph courtesy of The South Island Organ Company
hydraulic engine, which was an American competitor to ours over here. He was their representative.
He used to dump this engine and say: "There you are, gentlemen, all you need is a plumber and you can retire your old blower man." I take it this was an early example of American salesmanship.
Well, it appears that he dropped the American engine and joined forces with Cousins in Lincoln. Together they produced the
Kinetic-Swanton Kinetic-Swanton blower engine
Kinetic-Swanton blower engine
April 1902 R A and L.B Cousans built a prototype blower for which they took out a patent.
At that time the Newland Congregational Church in Lincoln, which housed a three manual Jardine, had been experiencing problems with their hydraulic engine. Cousans submitted an estimate for replacing this with a new fan blower. This was duly installed in 1902 for a trial period and proved a huge success.
In 1903 the Deacons agreed to purchase the blower, giving access to the company to demonstrate the blower to potential customers.
The blower was named the "Kinetic" and a company was formed to build these blowers from the organ works in Cathedral Street in Lincoln.
Large numbers of blowers were produced, and in 1903 Hugh Swanton of Stepney joined L.B Cousans and the company was named The Kinetic Swanton Company.

Click Icon
blower of the type described in the patents. "Aerometer " was another name associated - with this firm.
It is interesting that there is an American firm making a " Kinetic" organ blower to-day. In 1906 there is an American patent by
I. H. Spencer, Ira H Spencer submitted a further patent in 1912
Click Icon
no doubt an original principal of the Spencer Turbine firm who made, and still make,
"Orgoblos"Orgoblo organ blower
Spencer Turbine "Orgoblo"
installed to power a Skinner Organ
Click Icon
in America. This patent concerns multi-stage principles giving the reduction of noise as a main object, and constructional matters are also to the fore.
My own firm at this time were well established in organ blowing by means of hydraulic engines. Our late Mr. Watson and his partner had been feeling their way with forge blowers for some years, and in 1906 developed a purpose-designed, multi-stage organ blower employing a composite cast-iron and sheet-steel construction of cylindrical form with shrouded impellers. This flouted Mr. Cousins' ideas as explained in his patents, and proved much more successful. This was, of course, the beginning of the "Discus."
The impetus behind the centrifugal idea was undoubtedly the spreading of electric supplies. The electric motor was ideal for driving these blowers. The supply of power was a statutory obligation of the electricity undertakings, which was not the case with domestic water companies, and there was no remedy if the water pressure fell too low to work the engines.
A number of other firms sprang up in the centrifugal blowing business just before and after the 1914--18 war, and there was some successful litigation by my firm over patent infringements. The firms of
Rockingham Rockingham blower
Rockingham blower unit
Note the generator to the right of the motor used to generate operating power for the organ
and Midland originated about then. There were rises and falls and, later, new names.
Later also, centrifugal organ blowers began to be imported from the Continent, Switzerland and Germany more especially, almost always of the single-stage type, due probably to different traditions and practices as regards the pressures required in the Continental organs.
I do not want to pursue development further than this, because to do so involves present day comparisons, and you know what comparisons are supposed to be
I should, however, perhaps mention (anonymously) that round about 1925 there was a sharp improvement in this country in almost all respects. Quietness, efficiency, reduction in size, and better engineering construction, followed a few years later by the introduction of the very small, high speed, enclosed blower. This latter, though very tiresome to develop, was later to be highly successful and revolutionise organ blowing for the small or moderately small low pressure instrument.
I would now like to run over some of the facts and principles regarding centrifugal blowers.
Almost the first thing is that, considered as a machine, a centrifugal blower is very simple. That is one of its merits. The broad principle of action also seems clear enough. If one spins a paddle wheel, one expects a draught. If one surrounds it with a casing, one would expect to collect some pressure from the centrifugal action, but it sometimes happens in engineering that the simple things are hard ones to fully understand. I could mention several examples. No doubt that is an attraction for some of us.
At any rate, centrifugal blowers and their applications can 'be very interesting. When it is a matter of covering a wide range of industrial and other uses, the solution of the problems met with is sufficiently elusive to have kept the work mainly in the hands of comparatively few large firms. They are not at all apt to communicate the knowledge and experience they have built up. So, a new firm either has to decide to copy some good selling lines, or do its own research, in which case, in this wicked world, it too tends to keep its knowledge to itself.
In organ blowing, we have not the wide range of conditions to fulfil that there is in general work, but to cover the whole organ blowing field we do have a fairly wide range and, then, of course, we have some nice problems all to ourselves.
Suppose now we take a brief look at the compression of air. Trap air in a cylinder with a piston in it. Reduce its volume, and the pressure increases. That is universally appreciated. But by how much? Halve the volume, double the pressure? Well, that's not a complete statement. There are three variables, not two. Temperature comes into it. Any altering of volume and pressure of air involves changing mechanical work into heat, and vice versa. But, very roughly, by and large, halve the volume, double the pressure, and, by the same token, expand to half the pressure, double the volume.
So if, say, your organ wants 1,000 feet (we say "feet " when we mean " cubic feet per minute," of course) mainly at 5 ins., and a spoonful, just a spoonful, as the saying goes, at 10 ins., why then, order your blower for 500 feet at 10ins., take out your spoonful, and then expand down to 5 ins, and get your 1,000 feet-eh! Dear, oh dear, something has gone wrong! Fancy a blowing engineer falling into that trap, and it is so tempting too! I have completely forgotten that we are living at the bottom of the ocean--the ocean of the atmosphere, of course. The weight of all that air up aloft, pressing down, makes a pressure of some 400 ins. W.G. So the blower would be taking in its air at 400 ins., compressing it to 410 and then we expand it to 405. Not a big expansion after all. One would get about 506 c.f.m. instead of 1000. I am sorry. The water gauge measures differences of pressure only. The difference between the pressure in a reservoir, for example, and that of the atmosphere outside.
It is worthwhile comparing the displacement method of compression with the centrifugal one. Feeders are our familiar example of the displacement (or positive) method. Imagine feeders connected to a wind chest with a hole in it, and a slide over the hole. Open the slide and begin to pump-one feels a certain resistance. Close the hole and one is brought to a stop at once--stalled. By pushing hard one can produce more and more pressure in the chest, limited only by one's avoirdupois, but the motion is locked. Suppose the side of the chest blows off. Then at once one can rattle away at the handle, experiencing little or no resistance.
This state of affairs is common to all reciprocating pumps, bellows, and positive rotary blowers. With the centrifugal blower it is exactly the opposite. Close the outlet and the motor driving the blower will have the lightest load it will ever have while connected to it. Open the outlet fully, and it will get the heaviest. With nearly all centrifugal blowers of organ blowing types the motor will then be overloaded, perhaps very badly.
Why does the centrifugal blower behave in this contrary way? I have known people refuse to believe it until it was demonstrated with an ammeter.
With the outlet closed, the air remains in the impeller and is simply whirled at high speed. Pressure is produced, but no flow. We know- that it takes little to keep a flywheel going at a constant speed, but it is hard to get it up to that speed. The air is simply adding to the weight of the rim of the flywheel. When the outlet is opened, it is as though the substance of the rim flew off, taking its momentum with it, and then it is replaced by air from nearer the centre which has not been whirling so fast. Thus, with the outlet open, air is continually being accelerated, and acceleration needs power, as we know.
One of the difficulties of appreciating the action of a centrifugal blower is that air seems so unsubstantial and light. Actually, a cubic foot of air as it is around us weighs a good ounce. When whirled at the sort of speed used in an organ blower, particles near the periphery of the impeller press outwards with a force equal to 500 or more times their own weight.
A centrifugal blower is essentially a constant speed machine, and for this reason the so-called constant speed types of electric motor are ideal for driving them.
Thus driven, a centrifugal blower will produce a certain maximum pressure and no more. This is one of its important characteristics. At any given pressure less than this,. it will deliver a certain limited volume. When delivering its maximum possible volume, there will be a high speed of air in the outlet, but it will be under no pressure at all.
One cannot have the maximum pressure and the maximum volume at the same time. This sometimes puzzles people. They will say: "But the blower gives, it may be, 6 ins. pressure-I have measured it, but it won't keep it up on full organ. It wants a more powerful motor." Generally speaking, this diagnosis is wrong. It may want a more powerful motor, but also something must he done about the blower.
The reason for the misunderstanding is again probably based on the displacement type of pump. If you drive such a pump at a certain speed and maintain that speed constant, you displace a certain volume per minute. The pressure can be made to be anything within the power of the motor to cope with by simply throttling the end of the supply pipe-and, in doing so, one does not diminish the volume per minute, so long as the motor is not stalled. If it is stalled, then you can increase the pressure still further at the same volume, with the same pump, at the same speed, by fitting a more powerful motor. This is strictly true for water, which is more or less incompressible. For air at organ pressure, it is still practically true, but for air at really high pressures, it would not hold.
A useful analogy to the volume and pressure given by a blower of organ blowing type is a car battery (provided we do riot take it too far).
Switch on the interior roof light of a car and, if the batteries are properly charged, it will burn at normal brightness showing, say, 12 volts. Next, switch on all the headlights. The roof light will dim somewhat, and the voltage drop to, say, 10. If we then try the engine starter, the lights will nearly go out, with the volts down to half or less.
Finally, if we were to bridge the battery terminals with a stout piece of wire, the lights would go right out and there would be no voltage at all. The wire would at once get red hot showing a very great current to be flowing but without appreciable voltage.
The voltage is the analogy of the water gauge, and the amps, the cubic feet per minute. The analogy of bridging the battery terminals with a stout wire is running a blower with free inlet and outlet. It should not be done.
The efficiency of centrifugal blowers at their best is apt to be less than that of a good displacement type, but whereas it is relatively easy to get a good efficiency with the displacement type, centrifugal blowers vary enormously in this respect. It depends, of course, on the excellence of the design, but it also depends fundamentally on the machine being proportioned to the job. I know of no other simple machine (unless it be a centrifugal pump-or a ship's propeller) which it is so necessary, for efficiency, to proportion correctly for the job. There is more than meets the eye in transferring a blower from one job to another, especially the larger ones. The same applies to increasing the speed to get more out of a machine. The horse-power demanded can pile up at a great rate, and likewise the tendency to heat and dry the air.
Great care and not a little knowledge and practical experience is necessary to measure with good accuracy the output of a blower, and it so happens that the snags nearly all have the tendency to flatter the blower.
I have had many makes and types of blowers through my hands-not only organ blowers-which I have been able to test, and I have been astonished at the number of times I have found really substantial discrepancies between my figures and the makers' claims.
This can be awkward, and years ago a Committee sat to try and straighten things out, but their efforts are not considered successful. I once heard the chief engineer of one of the big fan and blower manufacturers speak very scathingly of it, and it was quite evident he worked on his own lines-and there is some justification for this.
Another thing is that it is usually impossible to test the output of a blower satisfactorily once it is installed. If the output has been specified to the manufacturers and things do not turn out right, it can be very difficult to settle the responsibility. It is generally better for the blower manufacturer to make his own estimate of what is required, and stand by the results. It should, however, be noted that a blower which has too big a capacity will be inefficient for its work, and to say of an organ blowing installation that there are " bags of wind" is not necessarily a compliment.
Taking a broad glance over organ blowing to-day, it seems quite evident that the centrifugal principle has fully established itself as the practical best system of organ blowing, not only in this country but wherever there is an electric supply -and even where there isn't.
But in this interesting world of imperfections it cannot be ideal. In fact, the best organ blowing installation embodies the best adjustment of conflicting factors. it is naturally in the equipment for large organs that great care in working out the design shows to most advantage, and where close liaison between organ builder and blowing engineer is most required, but it is always an advantage : and the blower for a fine instrument, I submit, should be something to take some pride about-even if it is wholly behind the scenes. Just as one cannot have smoke without fire, anyone listening to the majesty of a good organ must realise that its power must come from something important. . .
But perhaps, to keep a sense of proportion, I should end where I began. There are those (outsiders, of course) who would regard an organ blower as a rickety box of paddles for putting wind into a dusty box of whistles. But you will gather that I don't hold with them.


Extract from :- Journal of the Incorporated Society of Organ Builders. Published 1947