Newsletter No.55 September 2009

In this issue ...

What the President did on his holiday page 2

News from the Administrator pages 3-4

CAM pages 4-6

CAD pages 6-9

Gas Pump pages 9-10

Letter pages 10-11

Announcements page 11

This newsletter is published quarterly by the

INSTITUTE OF BRITISH ORGAN

BUILDING and edited by Geoff McMahon

Letters, news and articles to: Geoff McMahon

16 Chestnut Drive St Albans

Herts. AL4 0ES geoff@mcmahonfamily.co.uk

Opinions expressed by the editor and contributors are their own, and are not

necessarily those of the Institute

Photographic Credits:

Harrison & Harrison (pp.1, 7 & 11)

Doug Levey (p.5)

Anthony Hall (p.8)

Alan Taylor (pp.9 & 10)

A drawing produced for the workshops of Harrison & Harrison using Inventor, a 3D parametric modelling system, based on a 2D design originally created in AutoCAD. See pages 6-9 for further details.

2

I hope you have all had wonderful summer holidays and have re-charged batteries, ready for whatever is thrown in your direction. We managed a few days in Venice, which was even better than I expected. Hot, busy, full of tourists struggling to drag their cases over the bridges, and so nice to be in a city without even bicycles. A major part of that city’s success was due to sea power, and I was amazed by the size of the assembly line galley production that was at its peak four hundred years ago. When Henry III of France visited in 1574, one complete galley was built while he was being entertained at a state feast. Monteverdi’s tomb was visited in the Frari, and his place of employment at San Marco also viewed. As with many of the finest churches in southern Europe, the former glories of music have gone, and for now at least, any ideas of anything more difficult than a few guitar chords firmly stamped on.

It is a different matter in Cambridge, where you can’t move for choirs and organs. The IBO day there is reported inside, but I can give you the results of a little survey. It seems to me that organists are not quite sure about what sort of organ they really like, and that the

Festival Hall organ set things spinning, resulting in a bun fight between the progressives and the traditionalists. I thought it might be interesting to see what the present band of IBO-ers considered to be a good organ, and asked them to name three that came to mind that have been built in the last fifty years. The top two had equal votes, the next three were in second place, and the rest had a vote each, and are in alphabetical order.

Cambridge, Trinity (above) Metzler

Oxford, Queens (right) Frobenius

Birmingham, St Chad's Walker

Coventry cathedral Harrison

Edinburgh, St Giles Rieger

Bath Abbey Klais

Bridlington Priory Nicholson

Cambridge, Little St Mary's Tickell

Chelmsford Cathedral Mander

Dulwich, St Barnabas Tickell

Dunblane cathedral Flentrop

Eniskillen, St Michael's Wells-Kennedy

Glenalmond College Harrison

Kensington, Hyde Park Chapel H N & B

Liverpool RC cathedral Walker

Penn Parish church, Bucks

St Andrew's Holborn Mander

St Martin in the Fields Walker

Stoke D'Abernon Marcussen

Tewkesbury Abbey K Jones

Westminster, St Stephen's Drake

Worcester Quire organ Tickell

York Lyons Concert Hall (orig) GDB

You will all be aware of the Open College Network training that has been devised over the last few years, and implemented at Harrison and Harrison with good results. You may have forgotten that the IBO funds the setting up of the scheme, and it may not be clear that it operates regionally, so someone wishing to start their own training programme (using the existing blueprint) would need to go through the same application procedure in their area. Creative and Cultural Skills is a government organisation that is trying to set up training schemes for musical instrument making, which would include organs. The IBO are hoping that our units can be incorporated into their designs for National Occupational Standards in Craft. Those that have emails should have received an invitation to take part in an online consultation. If you have not already done this, do so now. The consultation can be found on the website: www.ccskills.org.uk It would be good to be able to move forward on this, not just because it means funding. A well-trained workforce can only be positive for our future.

Martin Goetze President

3

Administrator’s News

Business Member Survey Whilst several Business Members took advantage of the incentive to complete and return their forms in advance of the 4th September deadline, I am still awaiting forms from a few. Could you please take a few moments to return your form as soon as possible. Do remember to send supporting documents and photos via email. Professional Member Subscriptions I am pleased to confirm that the Board has decided to keep the rates for Professional Membership (Business, Supplier, Individual and Associate) unchanged from last year. As always, payment terms are thirty days, unless (as a Business/Supplier Member) you would like to take advantage of the interest-free quarterly payment scheme. Do contact me for further details.

IBO Website

We have recently added pages showing photos of recent IBO Meetings. Please do send me (by email) any photos you may have taken at this year’s meetings of the people, places, organs – in fact any memories you have of the day and these will be uploaded for you to share.

Asbestos

Whilst the IBO has a leaflet available on asbestos, its dangers and organ builders’ responsibilities, the Board would advise all those maintaining organs to visit the Health & Safety website and read up some more on this topic. The website is: www.hse.gov.uk/asbestos/index.htm If you suspect that you have found asbestos:

� wear appropriate personal protective clothing/mask when taking sample

� use tweezers to take a small sample of material

� put in a small self-sealing plastic bag and label where it has come from

� put inside another plastic bag � send in a jiffy bag to an appropriate

laboratory to test � Cost approx £10 plus VAT per sample

One such laboratory used by one of our Board members is: Linsch Consultants Culfin Ashley Road RYDE Isle of Wight PO33 4BD Tel 01983 811 134 Fax 01983 611 147

IBO Training We are currently putting together plans for courses to offer in 2010. Professional Members: don’t forget that there is a training grant available to help with the cost for you and/or your staff to attend a course. This grant could offset the actual fee for the course, the expenses in attending the course or, indeed, the cost of funding an employee’s absence from the workshop. Please do contact me for details. The Board considers all such matters in confidence.

Notes from Croner:

First-aid training From 1 October 2009, the Health & Safety Executive is introducing new arrangements to the first-aid training regime. These do not entail any change to the current legislation but will confirm that, to comply with the regulations, first-aiders provided by an employer in the workplace for the purposes of the regulatory requirements must hold a certificate of competence in either first aid at work (FAW) or emergency first aid at work (EFAW). The FAW qualification has been reduced from a four-day to a three-day course, and may be issued by a training organisation approved by HSE. The EFAW qualification is a one-day course, issued by a training organisation approved by the HSE or a recognised awarding body, to award an accredited qualification in EFAW applying a training standard set by the HSE. The new first-aid training arrangements have been designed to offer employers more training options for first-aiders. In addition, the training time taken to achieve compliance with the legislation will be reduced. Finally, more frequent training will be required through annual refreshers in order to improve the competency of first-aiders by maintaining their basic skills. The new training arrangements do not affect first-aiders holding a valid FAW certificate obtained under the existing arrangements. However, where a first-aider retrains on or after 1 October 2009, the new arrangements will apply. Health & Safety poster Following on from my piece in June’s Newsletter concerning the new Health & Safety poster, the HSE has urged businesses not to be duped into buying unnecessary and overpriced copies of the poster. There is some evidence of misleading promotions wrongly claiming that the old poster must be replaced

4

immediately and that the new law poster should be displayed on every notice board within the business premises. This is incorrect and employers could be led to believe that they are not meeting their legal requirements. As reported in June, you have five years to switch to the new poster and pocket cards (they must be replaced by no later than 5 April 2014). If you choose to continue to display the old poster you must make sure it is legible and keep the addresses of the enforcing authority and the employment medical advisory service up to date. You can check that your HSE law poster is genuine by looking for the unique, serially-numbered hologram on each poster. The HSE says: ‘If businesses receive any promotions relating to the law poster or pocket card and are in any doubt about their authenticity they should contact HSE on 0845 945 0055 before parting with their money.’ And finally… ‘If you’re 50 and you’re happy clap your hands!’ According to new research from Standard Life (based on a survey of 2100 adults), people feel most confident about their skills at work when they reach the age of 37, but fulfilment in the workplace does not peak until they are 50. The research also suggests that the trend for "olderpreneurs" is set to continue, with almost one in ten intending to start a new business in retirement. The survey also found that 33% of respondents want to continue in full-time work after reaching retirement age, while a similar percentage (31%) would like to carry on in a similar role but on their own terms. John Lawson from Standard Life said: ‘Quite simply, people do not get old like they used to. The Baby Boomers started a trend for redefining what is effectively their “third age” and these findings point to a continued trend for re-writing the rule book for younger generations.’ Having worked over 30,000 hours (at the age of 37) before feeling confident, and until age 50 to feel fulfilled, it stands to reason, he argued, that people will choose to continue to do a job that they enjoy and are good at…. Best wishes,

Carol Levey

Summer Meeting Renato Lucatello of Mander Organs travelled to Cambridge with more than a degree of broad-mindedness! It was fitting that this day had been scheduled so soon after the launch of iboTalk; once the initial on-line exchange of greetings had subsided, it was right down to business discussing the invasion of foreign organs. This I thought was a promising start to the site, a topic that generates genuine debate. The subject of organ projects not going to British builders is as contentious as ever, and a day in Cambridge was a perfect opportunity to ‘inspect the goods’ of two recent foreign installations, balanced by something home grown. First up was the Kuhn organ in Jesus College. Much has been talked about this organ, the first in this country from a very well-established Swiss builder whose profile has been raised of late with some rather ambitious European projects. The organ itself sits up beside the gracious Sutton case; is the distinguished great-grandfather looking pitifully down at his super-sized junk-fed distant offspring? Not at all, this is a neighbour it can be proud of. Yes, this is a much larger organ than the Mander that preceded it, but not in a big and brash sense. Tonally, this must have been a tricky one with much of the organ directly behind the choir stalls, leaving very little room for error regarding speech and balance in a relatively dead acoustic. It can be bold, but it has real warmth and above all clarity. I thought tonally it was faultless, and although the demonstration gave it plenty of opportunity to fall flat on its face, it didn’t. In fact, it exemplified the versatility needed in a college instrument to educate the choirs and scholars of tomorrow.

The case has come under heavy criticism and my initial opinion was that this was perhaps a missed opportunity. I gradually modified this view, however, bearing in mind that it really did have to be a complete contrast to the Sutton. It could certainly have been a little more elaborate without clashing,

5

and it could equally have been a caseless façade hidden behind a screen (which incidentally was one of Kuhn’s initial proposals). What we have here is a simple, finely-made modern case, which is completely representative of what a present-day Kuhn organ is. Most companies have a definitive style of voicing and design which tends to reinvent itself with each new generation. This is a typical Kuhn of the 2000s, just as it was a 1970s Mander which previously filled that very same space. The biggest disappointment was not being able to get into the organ for a good old crawl, something which we organ builders all love to do. I would have expected to find fine guts to this instrument, but it’s always interesting to see for yourself which materials and components are used for specific tasks. The console layout was comfortable, although the swell action seemed a little on the heavy/spongy side. The organ footprint is larger than you think and the run to the swell is probably longer than average, firstly having to turn ninety degrees, and then feeding a wind hungry division with generous pallets. I was wondering if we would see the ingenious Kuhn “mini barkers”, which are sometimes incorporated within the confines of the console chassis; however I know that this feature comes with a heavy price tag, and if it had been there, I’d have been asking why the key action of a two-manual organ requires assistance! Personally, I did like this organ. Yes of course I would have preferred the contract to have gone to a British builder, but in time we will appreciate that a Kuhn instrument of this era is a something special.

The next visit was to see the small Danish organ recently built in the beautiful chapel of Trinity Hall. I was really looking forward to this, as I was not familiar with the work of Carsten Lund, and was expecting a truly distinctive tonal style. We were warmly and entertainingly welcomed to the college by Dr Nigel Chancellor (who had acted as the college’s project manager), but once we had moved from the exquisite grounds into the chapel and the introductory talk grew ever longer, my misgivings grew with it! Tales of Danish oak floors, ingenious maintenance-

friendly devices, real live unsteady wind and a lead-lined swell box were suggestive of re-inventing the wheel, but I was determined to keep an open mind until I’d heard and seen up close for myself. The sound was not terrible and indeed lived up to its description of ‘sweet’, but it could have been so much more. Seventeen stops in such a wonderfully intimate and sensitive location: this organ could and should have impressed us with colour, brilliance, versatility and above all personality. I thought the case was disappointing, the chapel deserving of something more elaborate and eye-catching. As for its construction there were no great surprises, the familiar components, materials and layout all competently executed. Almost everyone building new organs today seems to achieve the same high standards of quality; what we are always looking for is something exceptional, and this organ just did not deliver that in any respect.

Last on the agenda was the Tickell organ in the church of St Mary the Less. If there was any anxiety about its status as the only British representative of the day, this was quickly dispelled as it performed in a way of which Ken and all of us can be proud. Of course we were all feeling content after a hearty lunch, and Gordon Stewart’s demonstration was both varied and entertaining, but the instrument itself is undeniably fine. The console layout is comfortable, the action crisp and responsive, and the restricted stop list offers surprising versatility. This was a project which warranted ingenuity, inventiveness and identity. The swallow’s nest location is a challenging one, and to extract enough sound out of twenty-two stops in a compromised position is always going to have its limitations. If full organ did sound a little unfocused at times deep in the body of the church, this is a minor observation of what really is a lovely instrument. Ken has done a remarkable job laying this organ out for maximum egression without its having to strain too hard. After the demonstration there were two presentations, one by Ken on the planning and installation of the organ, and another by Gordon Stewart on the subject of console design. This turned out to be a very

6

amusing discourse (sometimes bordering on frivolous!) on what we as organ builders should be providing to today’s organists. I am a great believer in technical advancements, but we are getting to a point where we demand too much out of an organ console just because it can be achieved. The more organists expect in the way of pistons, generals and levels, the less visible is the identity and personality of the individual organ builder. We only scratched the surface of this major debate in the discussion, but I was particularly pleased with the note on which it finished. Asked why he numbered his pistons right to left on this organ, Ken replied by saying that it was simply because he’d done it once before, liked it, and thought he’d do it again. Bravo - that’s how to hold on to your identity!

Renato Lucatello At Jesus College Chapel, organ scholar Tim Lambourn played: Prelude, Fugue & Chaconne in C, BuxVW 137 Dieterich Buxtehude Fantasia in C Minor, BWV 537a Prelude & Fugue in F Minor, BWV 534 J.S. Bach Master Tallis’s Testament Herbert Howells Recessional William Mathias Gordon Stewart’s Programme at Little St Mary’s was as follows: Four Movements from the Second Organ Book L. Marchand Prelude, Fugue & Chaconne D. Buxtehude Trio Sonata No.1 J.S. Bach Theme & Variations E. Bossi Impromptu in D (for Arthur Harrison) S. Nicholson A Good King Chills Out for Spring R. Cockroft Toccata in D Minor A. Renaud We are also most grateful to organ scholar Oliver Sullivan for demonstrating the organ in Trinity Hall chapel, and to all those who contributed to the day’s success.

The Death of the Pencil? Geoff McMahon investigates whether computers have taken over the world of organ designing In compiling the following article on the current status of computer aided design in organ building, I realise I may be in danger of preaching to the converted, so pervasive has been the spread of digital technology since the appearance of Ken Tickell’s article on the subject in The Organbuilder Volume Nine (1991). Even so, with the IBO having made design our theme of the year for 2009, it would seem an appropriate moment to take stock of goings-on in the nation’s drawing offices! Roughly a third of the respondents to my far-from-scientific survey named AutoCAD (or its slimline version AutoCAD LT) as their principal designing program, attracted initially by its position as market leader, and/or the quality and availability of local Autodesk representation in their particular region. The choices of the remaining two-thirds reflect the variety of programs currently available to suit different platforms and budgets; Ashlar Vellum was adopted by Mander Organs at the time of its development as a Mac-based rival to AutoCAD, whilst TurboCAD and Microstation have their own fervent devotees. There is clearly a base-level of functionality which all commercially available programmes can be expected to deliver, and the widespread adoption of data exchange formats (notably files with .dwg and .dxf suffixes) means that it is relatively easy nowadays to share drawings with users of different systems. However most users report occasional problems with importing text and dimensions from other formats, while architects’ drawings in particular can cause difficulties of scale where they have been produced relative to a particular plot-size, or in imperial measurements instead of metric (in the latter instance,

7

re-scaling by a factor of 1/25.4 usually does the trick!). In the early days, converts to CAD were quick to recognise the time-saving potential of developing libraries of standard parts which could be instantly retrieved and pasted into working drawings as required. (A particular boon for some organ builders has been the availability, initially in the form of CD-ROMs, of component drawings from the major German supply houses.) As much as organs consist of common components, however, it is in the fine-tuning of the variable factors that we seek to differentiate ourselves as individual builders. Accordingly, there has been a growing interest among organ designers in the development and application of the parametric features of their respective CAD programs. The term parametrics refers to geometric patterns (such as a pipe mouth) which can be redrawn by the software itself to suit varying dimensions. The illustration on the previous page (created using Graphite – Vellum’s counterpart to AutoCAD LT) shows a parametric symbol of a wooden pipe in plan view; the significant dimensions may be entered into a dialogue box (for instance when reading off a chart of measurements from an existing stop) to create individual templates for each note, or the values for a new stop can be read wholesale from a spreadsheet to generate all the required templates in one operation. The drawing below shows a Harrison soundboard end-section drawn with the help of AutoLISP (AutoCAD’s programming language), and requiring the input of only six variables (a datum point on the screen; the width of the grid; the depth of the grid; the width of the well; the distance from the front of the grid to the front edge of the pallet opening; and the length of the pallet opening).

With such powerful tools as these at our disposal, it is perhaps not surprising that there has been little or no apparent take-up of the soundboard planting programs that initially caused ripples of excitement when they first appeared in the late 1980s and 1990s.

Significantly they were each associated with the name of the continental firm in which they had been developed, and were inevitably geared towards the practices and “house style” of the firm in question. It was hard to justify the (not inconsiderable) expense of acquiring additional software when, to create finished working drawings of each soundboard, it was in any case necessary to export into your “normal” drawing program. Peter Collins’ experience is representative of many; having experimented with one such program, he ultimately decided he would prefer the freedom to use his own judgement. (In particular, he likes to exploit the smaller scaling of the sharp side of a soundboard to pinch a few precious millimetres from the rod in smaller instruments.) Many UK designers now input pipe scales from their own spreadsheets (which can themselves be tailored to produce any desirable variation of note-halving, addition constant etc.), so it is even harder to make an economic case for the stand-alone planting programs. The advent of CAD, and in particular its logical extension CAD-CAM, has significantly affected the way in which designers communicate with those doing the actual manufacturing. To begin with, the ability to print infallibly accurate drawings at varying scales was eagerly exploited by all parties; rollerboard, soundboard and coupler chassis layouts, in particular, could be issued as full-size templates on inert film so that centres could be pricked straight through onto the actual material. Increasingly however this sort of work is being automated by many builders; instead of being printed, the drawings are converted into code and sent via a computer network to a CNC router or similar machine. Harrison & Harrison are by no means unique in stating that all of their drawings for soundboard and action work are processed in this way. The pioneer for this form of production in British organ building was, of course, J.W. Walker & Sons, in the years after the company’s acquisition by Robert Penells and its move to Brandon (apparently the first computer which they bought was a Sinclair!). Many present-day designers are influenced by memories of the organisation of the Walker drawing office under Robert’s son Andrew, and the legacy lives on in the form of the impressive CNC plant at P&S Organ Supply Co. Commissions for new slider soundboards are drawn up in AutoCAD, exported as .dxf files and converted by an APS processor package into instructions for the router. Andrew Dolby also reports that a new CNC machine has recently been installed, dedicated to the manufacture of keyboards, for which the designs and codes can be directly generated using an integrated program called ArtCAM. Many continental firms are known for their reliance on well-developed CAD-CAM facilities, perhaps the most frequently cited being Rieger Orgelbau of Schwarzach, Austria. I myself visited Rieger in the late 1990s and was notably struck by the way in which their systems had been geared to assist with the racking in and staying of pipework. The diameter of

8

each individual pipe at its intersection with the rackboard and/or stay rail is pre-calculated and machined before the material reaches the workbench, where only minimal fitting is then required. Richard Bower’s CNC router will perform a similar operation once the pipes have been measured in a jig, but on the whole this would appear to be a potential efficiency saving that most UK companies have yet to exploit. An important recent development has been the emergence of a computer-literate workforce, meaning that designers are able to call on the assistance of competent CAD operators from other departments when the workload increases. There is also the option of making construction drawings available to a laptop or terminal in the workshop itself, in the spirit of the elusive “paperless office”. Many bench hands appreciate the freedom to interrogate and interpret the layout of the organ they are building at will, to the extent that requests for dimensions to be omitted altogether are not uncommon (‘the first thing they’ll do is go round and delete them all!’ I was told by one supplier). On the one hand it can be liberating to be relieved of what is still one of the more onerous aspects of designing by computer; on the other, it requires a considerable leap of faith on the part of an “old school” designer to cede so much autonomy to the shop floor! It also heightens the importance of “getting it right first time”, since dimensioning a drawing (when hitherto latent inconsistencies may first become apparent) has been an important stage in the quality control process up to now. As Andrew Pennells once wrote: ‘the mistakes are perfectly drawn, and don’t look like mistakes at all’! Another area in which CAD technology has moved on in recent years is in the field of three-dimensional designing and modelling. Readers may recall Ken Tickell’s demonstration at the Cheltenham meeting in October 2006 of SketchUp, a program which extrudes 2D geometry to produce convincing images of wooden pipes, building frames, complex joints etc. Most of the major CAD packages (at least in their more expensive incarnations) offer the capacity to create similar wireframe views of components, thus helping the workshop to visualise (for example) the layout of a winding system. At the very top end it is possible to render the surfaces of these elements with appropriate textures and colours, so that theoretically one could produce a realistic three-dimensional proposal drawing of an organ case in stained oak with polished tin pipes. That such drawings are not yet commonplace reflects the scale of investment in software and design time required, even the most experienced CAD users finding the necessary techniques to be located at the very end of the learning curve! In fact, although Ken Tickell finds SketchUp useful as a design tool in visualising the interrelation of three-dimensional objects, it is perhaps surprising to learn that the perspective proposal drawings for which his company is known are in essence the product of his

basic 2D CAD program. Once the front elevation of the instrument has been established, return panelling is drawn in at the appropriate angle to create the illusion of depth, and the whole drawing exported as a PICT file into a Photoshop image of the building interior. At this point a variety of finishing techniques is available depending on the desired appearance and ultimate purpose of the presentation; often Ken finds that a black and white treatment is most effective, with certain decorative details completed by hand. He concedes that this method is most successful in relatively straightforward architectural contexts where the vanishing point is easy to project (such as the west end gallery of a church). Where the angles are more oblique, and the background details more geometrically complex, the results are not always so convincing (as became apparent in the production of drawings for the twin cases in the Quire of Worcester Cathedral, which were ultimately executed by hand).

Anthony Hall of the Clevedon Organ Group agrees that CAD drawings of casework can appear sterile and devoid of artistry if not carefully handled. Judicious use of shading brings life to 2D monochrome drawings, while the closest that the CAD operator can come to holding a pencil is through mastery of the polyline function. This is especially useful for elements that would be carved on the finished case, and is well-illustrated by Anthony’s rendition of the casework for St Katharine Kree (above). If it is fair to make such a clear distinction between the decorative exterior and the functional interior, then it is perfectly exemplified on pages xx-xx of Organ Building Volume Eight, where Dominic Gwynn’s pen-and-ink drawings of Leatherhead Parish

9

Church sit alongside Martin Goetze’s TurboCAD soundboard plots. Martin seems a reluctant follower of CAD’s commercial imperatives, and stresses that most of the organs in existence today (including the joint winners of the IBO poll at Cambridge) were built, and continue to function perfectly well, without the intervention of a computer! Does all this mean that a threshold has been reached, beyond which mere machinery cannot hope to emulate the creativity of the human brain? Most of us are familiar with Aidan Nutter’s breathtaking hand-drawn casework proposals for Mander Organs (see for instance Newsletter No.49, pp.1 & 7); many may earnestly hope never to see the day when such artistry can be reproduced by a computer! Even so, most of Aidan’s proposals start off, like Ken’s, as front elevation views in a CAD file which are then printed off, stuck onto a drawing board and traced over. This process reminds us of the significance of the acronym: computer aided design – the computer can assist the development of the drawing, albeit by means of a spreadsheet to generate basic data, or a PDF file of a scanned sketch to send to a client, but it is still the human designer who calls all the shots! Geoff McMahon worked for thirteen years in the drawing office at Mander Organs alongside Stephen Bicknell, Didier Grassin and Aidan Nutter. He is now a freelance organ designer based in St Albans, Herts.

Gas Engines for Organ Blowing Applications (Part One) Summer is for jollies and the Anson Engine Museum at Poynton Cheshire should be high on any jolly list. Located on the site of the old Anson Colliery, Les Cawley and Geoff Challinor have assembled one of the largest collections of stationary engines in Europe. Engine enthusiasts come from all over the world to see the early gas and diesel engines. One such early engine was designed by Bisschop and listed Organ Blowing amongst its many applications. The engines were renowned for their simplicity and ease of repair and were considered the most successful of all so-called non-compression engines built.

The engine was patented by Alexis de Bisschop of Paris in 1871. The British patent rights were acquired by J E H Andrew & Co of Stockport, England, in 1878 who manufactured over 2000 engines before production ceased in 1894. The engine proved modestly successful in spite of its relatively high gas consumption and was more popular in England than in France, probably because gas was cheaper in England. The Bisschop engine did not suffer the noise and recoil of other small gas engines, hence its suitability for quiet applications such as organ blowing. It is

10

described as a non-compression engine since there is no compression of the air/gas mixture before its admission to the cylinder. The air/gas mixture is admitted early in the expansion stroke, followed by ignition of the mixture, with exhaust occurring during the return of the piston. The adoption of a slider-crank mechanism significantly reduced any noise and vibration. The engine’s small power output was rated in manpower rather than horsepower units, where one manpower is approximately 125 watts. The engine's output was two manpower, which is about 250 W or 1/3 horsepower.

The operation of the engine is very simple. When the piston is in its lowest position the pressure in the cylinder is below atmospheric. As the piston ascends during the first 40% of the stroke, gas and air are drawn into the cylinder through metering ports and past flat rubber check valves. A little before halfway along the stroke the piston valve exposes a gas pilot flame and the gas charge in the cylinder is ignited. The pressure of combustion closes the flap valves so that no flame escapes to cause a gas explosion. After the piston has passed its top position, the piston valve moves to expose the exhaust port. The inertia of the flywheel carries the piston downward and the exhaust gases are pushed out through the common cylinder intake and exhaust port. These early engines had a simple flame ignition system which would no doubt cause great concern with today’s insurance companies and Health and

Safety Legislation. However, I suppose the risk was no more than that of a tuner setting the organ on fire with a candle. How we have progressed! Whilst researching this article I spoke to a gentleman who can recall finding a small gas engine and proceeded to run it on the kitchen table. Normally the engines are fitted with a concussion unit to stop any pressure surges feeding back into the gas main. Unaware of this important fact running the engine blew all the gas mantles in the house. Not wishing to be caught out by his parents, he made a dash for the local shop where he found several of his neighbours also wishing to buy replacement gas mantles! Finally, to put the development of these early gas engines into some historical context, it is worth mentioning that the first street to be lit by gas in the United Kingdom was Chapel Street, Salford, in 1806. Initially, the gas was supplied by a certain Mr Lees who had installed a small gas production plant to serve the gas lights within his neighbouring mill. It was not until 1819 that Salford Gas Works was completed and the public distribution of gas commenced.

Alan Taylor

Letter to the Editor

Dear Sir, Reverberation Time William McVicker’s admirable and monumental exposition of the reverberation time at St Bride’s, occupying five pages of Newsletter No.54, may have alarmed many readers who fear they might someday need to perform a similar calculation. But I suggest that, for practical purposes, the following simpler method would suffice. Any calculation of reverberation time is essentially approximate, not least because we cannot know accurately the absorption coefficient of any particular wall, floor or ceiling. If you start by supposing St Bride’s to be a cuboid thirty metres long, sixteen metres wide and ten metres high, the calculations are simple, and at least as accurate, proportionately, as the uncertain absorption coefficients which must be used. The north and south walls of the building are rectangles of area 300m2, of which about 60m2 is window and 240m2 is plaster. The floor has an area of 480m2, of which about three quarters is covered with occupied seats. The west wall has an area of 160m2, and an estimated average coefficient of 0.2 may be assumed. The east wall has the same area, of which about a quarter is glass. The reredos must be treated separately, and both sides will absorb sound; take it to be rectangular, measuring eight metres by five metres. Treat the ceiling as a plane surface with the same area as the floor, and an average coefficient of 0.25.

11

The calculations are set out in the table below; the volume of the building works out as 4800m3, and the total absorption comes to 408 units, giving a reverberation time of 1.89 seconds (similar, as it happens, to the figure estimated in the building at the time of the experiment). Much of the arithmetic, except perhaps the final division, can be done mentally. Yours faithfully, Hector C. Parr Barnard Castle, Co. Durham 29th June 2009

Area coefficient absorption North Wall (plaster) 240 x 0.01 = 2.4 North Wall (glass) 60 x 0.18 = 10.8 South Wall (plaster) 240 x 0.01 = 2.4 South Wall (glass) 60 x 0.18 = 10.8 Floor (marble) 120 x 0.01 = 1.2 Floor (seats) 360 x 0.50 = 180.0 West Wall 160 x 0.20 = 32.0 East Wall (plaster) 120 x 0.01 = 1.2 East Wall (glass) 40 x 0.18 = 7.2 Reredos 2 x 40 x 0.50 = 40.0 Ceiling 480 x 0.25 =120.0 Total = 408.0

Total Volume = 16 x 30 x 10 = 4800 So Reverberation Time (at 125 Hz) = 0.161 x 4800

408 = 1.89 seconds

Announcements

David Hirst succeeds Mark Venning as Managing Director of Harrison & Harrison on 1 October 2009. Mark, who has held that position since 1975, will remain active as Chairman. Katherine Venning retires on 18 September after twenty years as the company’s Administrator. Her successor is Naomi Hirst. We wish Mark and Katherine every success in their future endeavours. We also extend our warmest congratulations to Laura Venning on her marriage to Simon Johnson on Saturday 18 July. Theirs may be described as a ‘tale of three cathedrals’: St Albans (where, at the time of their meeting, Simon was Assistant Master of the Music, and Laura a member of the H&H organ installation team); St Paul’s (where Simon is now Organist); and Durham (Laura’s home town, visible in the photograph, although the wedding itself took place in the more intimate surroundings of xxxxx parish church).

Star Organs of Britain Calendar 2010 is now available from Andrew Hayden price £14.50 incl. p&p to UK. Please also visit www.starorgansofbritain.uwclub.net for information about further offers. Organs featured include St Alban's Cathedral; Harlton, Cambs.; St Oswald's, Hartlepool; Our Lady of Egmanton, Notts.; Cawston, Norfolk; Hillborough, Norfolk; St. Paul's, Pilrig; Holy Ascension, Settle; Burnmoor, Co. Durham; St Vedast, Foster Lane; Yaxley, Hunts.; Framlingham Unitarian Suffolk.

12

THE INSTITUTE OF BRITISH ORGAN BUILDING PRESIDENT:Martin Goetze BOARD:Michael Blighton Andrew Fearn David McElderry Duncan Mathews Alan Taylor Kenneth Tickell David Wood

01909 485635

020 7739 4747 07776 307535 028 9266 4257 0191 378 2222 01706 826021 01604 768188 01484 533374

TREASURER:Rosemary Wakeford Canal Cottage Crofton Marlborough Wiltshire SN8 3DW Tel: 01672 870956 Fax: 01672 871352 pennysmilldesign@btconnect.co

ADMINISTRATOR & SECRETARY:Carol Levey, 13 Ryefields, Thurston, Nr Bury St Edmunds, Suffolk 1P31 3TD Tel/Fax:01359 233433 administrator@ibo.co.uk www.ibo.co.uk