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The Pitman Chest

by Mr. A. Thompson-Allen.



I have been asked to talk about the "pitman" chest. The "pitman" chest: why so called? What is it? Who uses it? And why? These are matters of interest to almost every organ-builder. I shall do my best to answer these points adequately.

The "pitman" chest has been known for over 50 years. I think I am right in saying that the name "pitman" refers in engineering practice to a certain pattern or type of connecting-valve known as the pitman-valve and here we have the association-hence "The 'pitman'-valve windchest".

To review the two principal forms of pipe-organ manual-chests, and the sub-division of these two forms. On the one hand we have the slider sound-board, shown here on the left-hand side of my column. For all practical purposes there is only one principle involved in the slider-soundboard that is-the slider and single pallet per note (not per pipe). On the other hand we have the sliderless windchest (shown at the head of the right-hand column). Now if we were to work out how many different principles in sliderless- chest design we could elucidate, I don't doubt that within half an hour or so a list of about 101 different known principles involving the ventil windchest alone, could be written down. But apart from a 101 different ventil chest designs which we may be able to resurrect, how many principles of sliderless windchest design other than the ventil chest could we think of? Personally, I believe I'm right in saying there are only three other principles, making a total of four main forms of sliderless windchest.

Here they are:-

Slider Soundboard Sliderless Windchest
1. The Ventil Chest: 101 types.
2. The Unit Chest (a magnet/or primary per pipe):
A Slider Soundboard or X types.
3. The Austin Universal Chest: i type.
4. The Pitman Chest: X types.


It is the last named of the right-hand column with which we are dealing to-night.

In the "pitman" chest, as with the Austin universal chest, the wind remains in it for as long as the blower remains on. This comprises one of the several features of the "pitman" chest: to get away from the grave disadvantages which we all know to be associated with the Ventil Chest. Just as the Unit Chest belongs to organs built on the "extension-system", so the "pitman" and all other types of Sliderless Wind Chest and the Slider Soundboard belong to the "straight" organ. A "pitman" chest would not, I think I am right in saying, be of any more use in an "extension" organ than a slider soundboard would be.

There are various claims alluding to a first use of the "pitman" chest, but nearly all statements I have come across to date are in my opinion suspect. Ernest Skinner, for one, claims it as his invention. Audsley tells us that the Hutchings-Votey Organ Company constructed an organ in 1899 for the Flatbush Dutch Reformed Church, Brooklyn, New York, containing the "pitman" wind-chest. The "pitman"-valve is referred to in his description and revealed in his drawings. But the design is unnecessarily elaborate and does not represent the "pitman" chest we know to-day. Incidentally, Audsley tells us that a patent, taken out by Charles Brindley of Sheffield in 1897, two years before, is practically of identical design and (to use Audsley's words) "leaving little doubt that the invention belongs to Charles F. Brindley". But, according to the latter's patent specification quoted by Audsley there is no reference in it of any kind to show that the stop-action was by a "pitman"-valve or similar.

From other sources we learn that the Art Organ Company of America were one of the first to use a "pitman" chest at the beginning of this century. Also, I am told, Mr. John Compton produced a chest on this principle in 1901. From researches I have made I am of opinion that the principle of the "pitman" chest was discovered long before 1897 by August Gern in 1883. But more of that later.

Let us take a glance at this modern sectional drawing of a "pitman" chest of the type used by Casavant Freres Ltd., the well-known Canadian firm of organ-builders. Casavants have used the "pitman" chest for well over 20 years now, and from conversations I have had with Mr. Stephen Stoot, their technical chief, nothing is likely to persuade them to discard the system after long experience of its use. As my drawing here indicates, the design and construction is very simple. As with practically all "pitman" chests of modern design, the table of the chest, on which the pipes stand, disregarding any expansion chambers, has a set of 61 or 73 transverse grooves passing through from front to back and staggered between the pipe wind-ways. These grooves convey wind at windchest pressure from the main set of 61 or 73 manual primary valves to the interior of the pipe-valve pouches or membranes. There is a membrane for every pipe on the chest and the full set of 61 or 73 membranes per stop is (in this example) contained in one membrane-rail as shown here in section. Attached to the under-side of each membrane-rail is a grooved piece of wood acting as the drawstop-action chamber. This groove runs the extreme length of the membrane-rail, so there is one such groove or chamber per stop. Usually, the pipes are planted in C and C "sides" and there is generally a passage way

sectional drawing of a "pitman" chest of the type used by Casavant Freres Ltd.
Click for larger image


in the centre between these two "sides". This fact of-course is taken advantage of to cut each membrane-rail per stop in the centre, in which case a conveyance or grooved connecting link is applied in the centre to join up the severed drawstop-groove from the C to the C# side. At the same time this gap in the centre is taken advantage of to split the underside face-boards into C and C sides, and to have the main wind-trunk brought up at this central point of the chest. The under faceboards usually cover two or three stops in width and, being only half the length of the chest, are easily removable. No pipework requires touching for access to the membrane-rails or action machine. Assuming that there is one chest per manual, there would normally be one action-relay machine per chest. Up to 10 or possibly 11 stops may be incorporated in one chest: above this number of stops, as with the slider or any other form of chest, one thinks twice and then has two chests.

Let us assume for the moment that this stop sectionalised here is "on". The drawstop-groove is then connected, by means of a small drawstop valve, to the free air outside the chest. When a note is played the corresponding transerve groove in the table of the chest is also connected, by means of its action valve to the free air. And so the pipe-membrane will then be collapsed against its individual spring, by the pressure of wind in the chest, enabling its respective pipe to speak.

So far, in this reference, I have not mentioned the "pitman"-valve as this simplifies matters for those not familiar with the "pitman" chest. The "pitman"- Valve is introduced to prevent the pipe-membrane from functioning when the note is played and the stop is not drawn. Suppose then we release the note sustained and start again. This time we put the stop in question off, and so charge with wind at chest pressure, by means of its corresponding drawstop valve, this longitudinal drawstop-groove under the membrane-rail. Now, here is the "pitman"-valve concerned, a disc of firm soft leather riding between an over and an under valve-seat. As there is wind at chest pressure on top of this "pitman"-valve when the note is off, and wind of the same pressure underneath the valve also (when the stop is "off"), the effect of gravity dominates and the "pitman"-valve remains upon its lower seating. But play the appropriate note (still with the stop "off") and what happens? The action channel A is exhausted and so the compressed air in the drawstop -chamber D instantaneously blows up the "pitman"-valve P, thus sealing the channel C and keeping the membrane M still inflated. And so, a note is played, but the pipe-pallet does not open for the reason just given.

If, while still sustaining the note, the drawstop is then put "on", thus exhausting the chamber D, then, in these circumstances only, the membrane will exhaust itself into the chamber after which the "pitman"-valve P will collapse.

But contrary to this description our friend Mr. E. M. Skinner has other views upon how the "pitman" chest works, with which I cannot agree: the reference is found in William H. Barnes' "The Contemporary American Organ" where a letter from Mr. Skinner on this subject is quoted as follows:-

Mr. Richards stipulates that only 8 stops shall be placed on any one chest, showing that he, along with the balance of those interested in the chest, does not know that the pipe pneumatic is not exhausted through the key-channel, but on the contrary, exhausts into the stop-action-channel when rush of air in the key-channel sucks the "pitman" over to the key-port, leaving the channel open for the pipe-pneumatic to exhaust directly underneath said pipe-pneumatic and out of the stop-action".

From the above description will he realised one of the most important characteristics of the "pitman" chest, that the drawstop attack, decay and repetition will be as rapid and as quiet in operation as the key-action itself. A very great attribute in these days of multi-console controls and slick piston actions, quick changes, etc., and especially where large organs are concerned.

Now where two or three of the stops on one chest are required to be on heavier pressure, and thus a partition is introduced inside the chest to isolate the heavy-pressure stops, it is frequently a wise precaution to see that the action-groove A also he isolated and have its own separate heavy-pressure relay. If only the one groove A is retained for both heavy and light pressure stops, then this groove must be charged with the heavier pressure wind. If not, the heavy-pressure membranes (supported internally only by light pressure) would collapse and cipher. But the point is, if for the sake of economy we only have one relay and one groove (instead of aseparate heavy-pressure groove and relay for the heavy pressure stops) we are then introducing heavy pressure into the light pressure membranes--a rather dangerous thing to do unless special precautions are taken: otherwise heavier pressure on the inside of the membranes would tend gradually to blow the membranes off. Also, the heavy pressure will try and seep through the leather of the hundreds of membranes in the light pressure side of the chest and so tend to build up a false pressure in the pipe-wind above the static one. In addition, the rapid attack of a light pressure membrane having to punch a heavier pressure of wind out of the membrane and through the action-groove, when a note is played, tends to cause the speed of the collapsing light pressure membrane or membranes to be reduced somewhat. And so we learn that it is better to have an equal pressure in action groove and chest where possible. The same applies to putting a heavier pressure in the drawstop groove.

But I don't want to detract from the simplicity of the "pitman" chest by dwelling too much upon the "don't's". For straightforward design as here indicated by the drawing, and similar designs as used by the old Skinner Organ Company, Möllers, Kimball, etc., and ourselves for some years before Casavant took it up and as still employed, in so far as I am aware, by the Eolian-Skinner Company to-day, also as used by at least one other well-known firm if not more in this country, the "pitman" chest presents a very attractive and workable proposition. Besides being less expensive, the advantages over the ventil chest are not really worth discussing at a meeting of experts, for there is no doubt that the "pitman" chest is incomparably superior to the ventil system, but the advantages over the slider-soundboard, where brand new organs are concerned, are also important. To-day, organs are built with different materials and for different conditions than the organ of the past. A new set of problems faces the

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modern organ-builder. One of these is that of modern church and concert hail heating. And so I suggest that unless one happens to have a stock of the suitable timber essential for slider- soundboards construction, the "pitman" chest provides a very favourable alternative. Only one kind of timber is necessary in the construction of the "pitman" chest and that is a good straight pine, sugar pine, white pine or the like. The design of the "pitman" chest should he such that the grain of the timber is all in one direction: again, an invaluable factor to suit extremes of climates, seasons and heating in modern buildings. (I am referring now to the manufacture of new organs and not the rebuilding of organs possessing fine old slider-soundboards already well seasoned and acclimatised.) A "pitman" chest should be dowelled to the chest rails at front (or back) only. The chest is then able to expand or shrink freely throughout extremes of seasons, winter heating conditions when the atmosphere of the church or hall is frequently parched and dry, versus the humid atmosphere of the summer months. I have observed a chest of some 8 stops at the extremes of these two seasons by noting a pencil mark made upon the chest-rail where the hack of a "pitman" chest rested in mid-winter heating conditions. In the summer, that same chest has expanded as much as in. because it is free to expand, not only through not being fixed to the rails, but because of the chest construction-grain all being one way. What would happen to a slider-soundboard with its right-angle opposing grains (bars versus table) in these circumstances? Admittedly, harder wood is used for a slider-soundboard, but the table would probably split and the consequences are only too well known to us.

Again, a small new organ, with a couple of slider -soundboards on a light wind-pressure, is a very different proposition from a large new organ containing perhaps a dozen manual soundboards, several of which require to be on heavy pressure for reed choruses, etc. The modern organ-builder is likely to find himself up against it if he decides to use new slider soundboards, especially in a larger organ: but if he chooses to employ "pitman" chests, whatever the pressures required, he has nothing to fear. No enmassed action thumps from a dozen slider-soundboard pallets, no runnings, no tight or loose sliders and escapes of wind in deepened scorings: no accumulated crash of 100 drawstop sliders being moved when a General Piston is touched.

I would like for a moment to return to the early "pitman" chest and the first application of a "pitman" or similar valve as a means of stop-control in lieu of the unhappy ventil. Besides the "pitman"-valve, the old Willis V Valve of 1856 would serve the same purpose-see diagram: so would the Gern rocking-valve of 1883 and it did. Here is a sketch of the Gern 1883 drawstop action performing on exactly the same principle as the "pitman" chest of the Hutching-Votey organ in 1897. And so in a sense we would not be wrong in suggesting Gern as the inventor of the Pitman Chest principle.

Now we come to The Duplex Pitman. (Here described to the audience with the aid of enlarged drawings).

An important point we have to bear in mind in voicing pipes for the slider or the sliderless chest: pipes intended for a slider sound-board should be voiced

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on a slider- soundboard voicing-machine and pipes for the sliderless- chest should be voiced on a sliderless- chest voicing-machine. Many of us know that this counsel is not always adhered to.

To conclude, I hope I may be pardoned if I refer to a little incident in connection with windchest design which happened when I was at the age of fifteen and a pupil of Mr. Henry Willis. It seems a long while ago now. I used to keep a leather-bound album in which I would make sketches of what I then thought were advanced mechanical designs connected with our art, my intention being to revolutionise the whole craft of organ-building within a couple of years. One day I hit upon a design (remember my youthfulness at the time, please) for doing away with the drawstop-sliders and key-pallets of a slider-soundboard. Instead, I would have one slider per note for the key-action only and no pallets. In theory, this seemed a very simple arrangement as one glance at the sketch on page 50 will reveal.

In went the album-sketch to the sanctury-office where at that time Mr. Henry Willis and Mr. G. Donald Harrison presided (circa 1922). I was expecting to see works-orders at once given out for no more of the old type of soundboards to he constructed, giving place to my new and revolutionary design.

But, instead, I received the album back on the following day as usual. Above my sketch of the proposed new soundboard I had written, "Nothing to go wrong, nothing can go wrong". Underneath this rather bold statement of mine the following words had been added by one of the two gentlemen concerned, " . . . . 61 slides". Ever since that time during the ensuing 25 years, whenever Mr. Willis pokes his head into some strange organ (not of our manufacture, of course) and perceives some wild and complicated piece of mechanism tried and used once only by some brave but unfamed individual, I hear him mutter sotto voce, " . . nothing to, nothing can ! "