Model Engineer issue 4745 **20 PAGE FREE PREVIEW**

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Vol. 233 No. 4745 14 – 27 June 2024

THE ORIGINAL MAGAZINE FOR MODEL ENGINEERS

Flywheel for a twin compound winding engine.

Tender body for Cornwall

Working lamps for a five-inch loco

A visit to a club by the Oxford canal.

High-pressure engine by Trevithick

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EDITORIAL Editor: Martin R. Evans MEeditor@mortons.co.uk Deputy editor: Diane Carney Designer: Druck Media Pvt. Ltd. Club News: Geoff Theasby Illustrator: Grahame Chambers Publisher: Steve O’Hara CUSTOMER SERVICES General Queries and Back Issues 01507 529529 Monday-Friday: 8.30am-5pm Answerphone 24hr help@classicmagazines.co.uk www.classicmagazines.co.uk ADVERTISING GROUP HEAD OF INVESTMENT – Lifestyle & Tractor Publications | www.talk-media.uk Mason Ponti mason@talk-media.uk A: Talk Media, The Granary, Downs Court, Yalding Hill, Yalding, Kent ME18 6AL Investment Manager: Karen Davies karen@talk-media.uk PUBLISHING Sales and distribution manager: Carl Smith Marketing manager: Charlotte Park Commercial director: Nigel Hole Publishing director: Dan Savage SUBSCRIPTION Full subscription rates (but see page 6 for offer): (12 months, 26 issues, inc post and packing) – UK £132.60. Export rates are also available, UK subscriptions are zero-rated for the purposes of Value Added Tax. Enquiries: subscriptions@mortons.co.uk PRINT AND DISTRIBUTIONS Printed by: William Gibbons & Son, 26 Planetary Road, Willenhall, West Midlands, WV13 3XB Distribution by: Seymour Distribution Limited, 2 East Poultry Avenue, London EC1A 9PT EDITORIAL CONTRIBUTION Accepted photographs and articles will be paid for upon publication. Items we cannot use will be returned if accompanied by a stamped addressed envelope and recorded delivery must clearly state so and enclose sufficient postage. In common with practice on other periodicals, all material is sent or returned at the contributor’s own risk and neither Model Engineer, the editor, the staff nor Mortons Media Ltd can be held responsible for loss or damage, howsoever caused. The opinions expressed in Model Engineer are not necessarily those of the editor or staff. This periodical must not, without the written consent of the publishers first being given, be lent, sold, hired out or otherwise disposed of in a mutilated condition or in other unauthorised cover by way of trade or annexed to or as part of any publication or advertising, literary or pictorial manner whatsoever.

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Vol.233 No.4745 14 –27 June 2024 8

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SMOKE RINGS

29 INDEX TO VOLUME 232

News, views and comment on the world of model engineering.

33 THE MAGIC BOLT

AN ENGINEER’S DAY OUT

Jacques Maurel finds a novelty bolt that will keep you guessing.

Roger Backhouse spends a day at the Whitchurch silk mill on the banks of the Oxford canal.

35 A TWIN TANDEM COMPOUND STEAM ENGINE

14 MINIATURE GAS TURBINES – AN INTRODUCTION Tim Coles explains the application of gas turbines to model engineering.

17 THE STATIONARY STEAM ENGINE Ron Fitzgerald tells the story of the development of the stationary steam engine.

20 LNER B1 LOCOMOTIVE Doug Hewson presents a true to scale fiveinch gauge model of Thompson’s B1.

24 ENGINEERING SURFACE FLATNESS Neil Raine explains the definition of surface flatness and how it is achieved in practice.

28 BOOK REVIEW Roger Backhouse reviews Peter Tuffrey’s picture book depicting the glorious years of the LMS.

Graeme Quayle presents an interesting design for a compound winding engine.

40 WE VISIT THE BANBURY SOCIETY OF MODEL ENGINEERS John Arrowsmith visits a long-established club near Leeds.

43 BUTTERSIDE DOWN Steve Goodbody returns with further tales of the trials and tribulations of a model engineer’s life.

47 BUILDING 3020 CORNWALL IN 5 INCH GAUGE Jim Clark builds a model of Francis Trevithick’s LNWR 2-2-2 locomotive.

52 CLUB NEWS Geoff Theasby compiles the latest from model engineering clubs around the world.

55 CLUB DIARY Future Events.

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Vol. 233 No. 4745 14 – 27 June 2024

Flywheel for a twin

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THE ORIGINAL MAGAZINE FOR MODEL ENGINEERS

compound winding engine.

Tender body for Cornwall

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ON THE COVER...

A tender tank for Cornwall, a five-inch gauge LNWR 2-2-2 locomotive (photo by Jim Clark).

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Working lamps for a five-inch loco

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A visit to a club by the Oxford canal.

High-pressure engine by Trevithick

This issue was published on June 14, 2024.

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Three GWR locomotives, all built by Tony Newbury. From left to right we have 6868 Grange, belonging to Stuart Duncan, 4202 a GWR 2-8-0T, belonging to Penrhos Grange John Painter and 1028 County of Warwick, belonging to Peter Lawson.

MARTIN EVANS Editor

DIANE CARNEY Assistant Editor

Martin Evans can be contacted on the mobile number or email below and would be delighted to receive your contributions, in the form of items of correspondence, comment or articles.

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Parklands Week Ends Writing this on a Bank Holiday Monday, I have just returned from the Parklands Holiday Centre in Hemsby, Norfolk, venue of the very popular ‘Parklands Week’, held every year at the 7¼ inch gauge railway which is a feature of the centre. Sadly, this year’s ‘Week’ was the last and, later in the year, the railway will be retired and the track will be gone, to allow redevelopment of the site.

The construction of the railway was begun by the late Don Witheridge, proprietor of

Pet, a 7¼ inch gauge model of one of the seven shunting engines built for the 18 inch gauge system at Crewe works, built in 1865. This engine was built by Eric Upchurch from measurements of the preserved locomotive. Bravery (or folly) is a necessary prerequisite for riding on this engine!

the holiday centre, in 1973 with the construction of a single ‘out and back’ line.

This was developed over the following several years into the approximately one mile long railway that now occupies the site. Tha annual ‘Parklands Week’ began in 1980 and has been repeated every year except in 2020, when it was cancelled because of the COVID pandemic.

The ‘Parkland Week’ plays host to a wide variety of 7¼ inch gauge locomotives, from all over the country, and here I have included a ‘picture gallery’ of some of the locomotives seen there this year.

If you are a club aiming to construct a 7¼ inch gauge railway, you may be able to acquire the necessary material from the Parklands Railway.

There is well over a mile of aluminium track, mostly of 32mm section, on plastic sleepers as well as several other items including rolling

A nice looking GWR Dean Goods, built

by Keith Wilson and belonging to James Duncan, having previously belonged to Ted Martin. stock and signalling equipment.

Any enquiries should be made to Brian Baker at leighsteamer@btinternet.com It was a Bank Holiday so did it rain? Yes, of course it did.

Brian Baker

Cock-up Corner Welcome to our now regular feature! This time I have to apologise for an error in John Arrowsmith’s report on the Llanelli Rally (issue M.E.4743, 17th May) in which I claimed that Llanelli was in North Wales. Of course it isn’t – it’s in South Wales, as I should well know, being Welsh myself. All the same, I blame Wales, which has far too many places whose names begin with ‘Llan…’.

A very fine LNER 25 ton breakdown crane built by Don Ketley and now owned by John Dalton.

Model Engineer 14 June 2024

An Engineer’s Day Out

Whitchurch Silk Mill, Hampshire Roger Backhouse visits a Regency mill still weaving silk on Victorian looms.

Whitchurch Silk Mill

Winchester City Mill

Watercress Line

Twyford Waterworks

Museum of Army Flying

Milestones Museum

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hitchurch Silk Mill on Hampshire’s River Test is one of the most attractively sited buildings visited in this series.

It’s an example of a small, rural enterprise that adapted to developing opportunities with national and international associations. Now it is the last remaining Regency era mill in the United Kingdom that still produces silk in the original building on Victorian looms (photo 1).

It contrasts with the more industrial Paradise Mill in Macclesfield (Model Engineer 4601, 7 December 2018) where steam power had been adopted, although still to be seen there are hand powered Jacquard looms that also produced complex patterns and even pictures. Unlike most Macclesfield mills, Whitchurch silk mill did only plain weaving and there were no Jacquard looms.

Water power was used in Hampshire from early times.

The 1086 Domesday Book lists over 300 watermills in the county. These were corn mills, of which many survive such as City Mill at Winchester. Water powered textile production is more associated with the northwest of Britain and Wales.

Rock Mill in Carmarthenshire and Quarry Bank Mill at Styal, Cheshire, survive as water powered textile mills.

Another industry to use the local water supply was at Portal’s Mill at Overton where

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paper for bank notes was made but, sadly, closure was announced in 2022 and the machinery was recently offered for sale.

Silk industry history The silk worm is native to China and was smuggled out, first to the Arab world and then, particularly, to Italy where silk production developed from the late 9th Century onwards.

Early attempts to start an English silk industry were unsuccessful until Huguenot (Protestant) silk weavers left France after the Revocation of the Edict of Nantes in 1685, an act of religious intolerance that caused economic chaos.

Many skilled workers came to England, often settling around Spitalfields in East London, which became a centre for hand silk weaving.

Weavers also moved out to Braintree and Sudbury in Essex and Suffolk. One was Samuel Courtauld who built up a large silk business before diversifying into other textiles.

The silk worm moth feeds on white mulberry trees only and does not generally do well in the UK climate. A silk worm chrysalis is surrounded by a long filament of thread removed by immersing the chrysalis in hot water. Silk has a triangular structure which acts as a prism, thereby giving it a natural shimmer. It is a light and versatile fibre.

English produced raw silk was not a great success, though a silk farm operated from the 1930s to 2011 at Lullingstone in Kent. Raw silk is now imported.

Many processes in silk weaving are similar to those

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Whitchurch silk mill on the River Test is an attractive building in this pleasant small town.

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involved in making other textiles but the terminology is different. The hank or skein in cotton manufacture is termed a slip in silk weaving. A cotton weaving pirn, holding the thread in the shuttle, is known as the quill among silk weavers, and a heald or heddle lifting warp threads alternately in the weaving process is known as the leash.

Whitchurch silk mill The mill originated as a development by local men, William and Henry Hayter around 1813 when they set up a manufactory with a foundry and joinery works on the site.

The business went bankrupt and the site was sold to William Maddick, a London based silk weaver who already had a Macclesfield silk factory. He commenced major alterations; inserting a third floor, bricking up central doorways, adding more windows and improving the water supply. Though Maddick retained ownership he may never have visited the mill and it appears to have operated under local tenants, known to have produced silk from 1820.

In 1844 the mill passed into the ownership of John Spencer and Alexander Bannerman from Manchester but a year later William Chappell took over, the first time a Whitchurch man had been the owner. The following years were difficult for the silk industry. Food prices were high and worker discontent was growing.

There were challenges from imported silks and tariff changes put home grown manufacture at a disadvantage.

The first free trade agreement between Britain and France in 1860 flooded the market with cheaper French silks and many silk mills closed, though the British cotton industry benefited.

This was a direct result of the ‘Manchester School’ of free trade, one of whose apostles was Richard Cobden, himself a cotton manufacturer. He wrote, ‘Let the silk trade perish and go to the countries to which it properly belongs.’ (King Cotton itself was to disappear later.

Similar arguments were used, in the 1970s and 1980s when the cotton industry and ready to wear clothing trade were being destroyed by overseas competition.)

Like most mills, Whitchurch employed child labour, some coming from parishes eager to find places for orphan children in their care. Thanks to research by Jacqueline Brown and others, much information about the workforce has come to light. Working conditions were poor but probably no worse than other mils of the same period.

A Whitchurch shopkeeper, John Hide, bought the mill at auction in 1886. The auction advert mentioned that ‘first class trout fishing’ was also available. His son, James devoted his working life to the mill. He introduced power

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The silk mill seen from downstream with the River Test to the right.

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Gear wheels and governor near the waterwheel. Drive to the machines was via overhead line shafts.

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2 Dyed hanks (slips) of silk are shown here on ‘swifts’ below ready for winding on to bobbins in a winding frame.

A waterwheel drives the silk mill Wider wheels like this are used on ast owing rivers with a relatively low head o water Wooden oats need to be renewed about every ten years.

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looms made by Smith Brothers and Hattersley, some of which survive today. The mill specialised in weaving silk serge, much used for lining men’s coats including, from around 1900, those made by Burberry. This product largely replaced the previous thread production.

The mill’s waterwheel is like others on rivers with a

comparatively low head of water; a wide, breast-shot type.

It was replaced around 1890 by one locally produced by Arnfield of Ringwood with a cast iron frame and elm floats (photo 2).

Later owners included Stephen Walters and Co., based in Sudbury, Suffolk, who ran it for fifteen years from 1956.

Besides the Burberry cloths

Model Engineer 14 June 2024

DAY OUT

they made Ottoman silks, a heavy weave, for the academic and legal outfitters, Ede and Ravenscroft. Eventually, in 1971, that firm bought the mill and silk production remained the same, continuing to be used for legal and academic gowns. (When a barrister becomes a King’s Counsel he or she ‘takes silk’ and wears the more expensive cloth.)

By the mid 1980s the mill was losing money and the owners obtained planning permission to put houses on the front lawn. This threat to an attractive building (photo 3) in the heart of Whitchurch roused local people - including former Master of the Rolls, Lord Denning - who worked with Hampshire Buildings Preservation Trust to raise funds to buy the mill. They were successful but it required extensive rebuilding and conservation works which were carried out by Whitchurch

craftsmen. It opened to visitors in 1990 (photo 4).

Silk processing In most instances of the processing of natural fibres, a number of short threads have to be combined together and twisted to form a suitable thread for weaving. Silk is different. It comes as very fine filaments from the silk worm chrysalis (or cocoon).

Filaments are between 500 and 1500 metres in length and traditionally came as hanks (slips) which were untangled with a parter.

Silk is usually dyed before other processing. Dyeing was once done at the mill but dyed silk is now bought in.

Slips are transferred to ‘swifts’ on a winding frame (photo 5) and pass through ceramic guides which move from side to side ensuring that the silk is wound evenly on a bobbin (photo 6). Whilst

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Silk passes through ceramic guides which move from side to side, thus putting threads on the bobbin evenly.

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Bobbin frame holds the hundreds of bobbins that may be needed to set up the warp threads.

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From the bobbin frame threads go to the beamer which winds thread on the weaver’s beam. That beam is out of sight to the left just below where the weaver is sitting. This is a slow and complex process. the mill retains this hundredyear-old equipment, which is sometimes used, most silk now comes on cones to be rewound on bobbins.

After winding on to bobbins comes the preparation of the weaver’s beam. This holds the warp threads - i.e. those that run lengthwise along the bolt of cloth. Warping (or beaming) is a time-consuming process.

In it threads are arranged in the warp pattern order as in a striped fabric.

Bobbins are arranged on a frame (photo 7). Threads are then taken across to the beamer (photo 8) to be arranged on the weaver’s beam. Once threads are wound on the beam is taken carefully downstairs to the weaving floor and the looms. Formerly a lift was used (photo 9).

The weaver’s beam is placed in a loom and the threads

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Lift formerly used to lower a weaver’s beam in a cradle to the weaving oor below drawn forward as the warp.

There are several looms in the mill, including a wooden hand loom used for demonstrations (photo 10). As with other looms, the healds (leashes)

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Simple hand loom set-up for demonstrations. The wooden pedals below link to levers to lift the healds (leashes) and create the ‘shed’ through which the shuttle passes.

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Healds (leashes) are wooden frames holding eyes which each have a warp thread. As a leash lifts it raises the appropriate warp thread to create the ‘shed’ for the shuttle.

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A loom set up to weave striped cloth

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Enoch Ruston maker s late on the acclesfield made loom

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Heald (leash) lifting mechanism. Although the mill has no Jacquard looms that can weave fancy patterns, this device can alter the way healds are lifted to help create patterns using a Dobby mechanism.

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Chain to operate the Dobby mechanism. Even simple words could be woven using a Dobby but there’s no evidence this was ever done at Whitchurch.

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A shuttle contains a pirn (quill) of thread which is paid out as the shuttle passes across the loom though the shed ometimes artificial ur is used in the shuttle to stop thread paying out too quickly.

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lift alternately to form a ‘shed’ through which a shuttle passes (photo 11). Healds (leashes) carry threads with eyes through which the warp thread passes.

One of the delights of silk weaving is the way different colour effects can be produced by changing the order in which leashes lift. For example a twill has diagonal lines across the fabric. A so called ⅓ twill is made by passing the shuttle under the first warp thread and then over the next three. For the second pass it goes over the first,

under the second and then over the next three.

Other effects are creating shot silk which is woven from weft and warp threads of two or more colours together giving an iridescent appearance.

Most weaving was done on power looms. These were made at Macclesfield, a major centre for silk production (photo 12). Once the weaver’s beam was in place and shuttles ready, weaving could begin and leashes lifted automatically according to the pattern of cloth being woven (photo 13).

Although the mill was never used to weave the fancy patterns and pictures possible with Jacquard looms, some patterns could be woven using Dobby mechanisms. They are controlled by a chain of bars, each one fitted to lift a particular heald (leash) thus creating a pattern (photos 14 and 15).

Shuttles were similar to those used in cotton weaving.

They were precision made with a pirn (or quill) inside holding the thread (photo 16). As weaving used lots of thread, pirn winding was automated and winding machines were a standard fitting in any weaving mill (photo 17). As the shuttle passes through the shed to form the weave, a metal beater comes up behind to press the just woven threads together thus consolidating the finished cloth.

Overview The mill is something unique.

There have been significant

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Shuttles used lots of thread so pirn (quill) winders like these mechanised the winding process.

Model Engineer 14 June 2024

DAY OUT

commissions for the National Trust, Winchester Cathedral and for many film and TV productions including Titanic, Sense and Sensibility and Garrow’s Law, branching out beyond the Ottoman silks into colourful fabrics of a type that could have been made in the 19th Century. The mill has also

produced silk ribbons, usually made as a wide cloth which is then cut into individual ribbons.

Weavers here are able to produce special commissions and can make shorter runs of specialist silk patterns.

What visitors see at the mill depends on the processes ongoing at the time. During my

visit in 2023 the weaver was preparing a weaver’s beam and there was no weaving going on. On other days there might be something else happening. However, the mill remains an attractive spot to visit with enthusiastic staff and volunteers.

Guided tours are

recommended where possible as these explain more but lone visitors will still find much to enjoy. There is a café and small shop. Besides the charms of the Test Valley there are several other places to visit nearby, proof that even in the most scenic areas engineering interest is rarely far away.

Visiting the mill Whitchurch Silk Mill 28 Winchester Street, Whitchurch RG28 7AL Tel. 01256 892065 W: www.whitchurchsilkmill.org.uk.

Parking and Whitchurch railway station are nearby. (Trains, London to Basingstoke/ Salisbury/ Exeter.)

Open Tuesday to Sunday 10.30 - 5pm (last admission 4pm). Also open Bank Holiday Mondays.

Further reading Winders, piecers, warpers and weavers. The story of Whitchurch silk mill, Jacqueline Browne. No bibliographic details. Obtainable from the mill.

Who stole the secret to the industrial revolution? Glynis Cooper, Pen and Sword 2023.

Early days of silk production in England, including the suggestion that technology was stolen from Italy.

Other places of engineering interest in the area Winchester City Mill (National Trust - free entry – photo 18) Remains of a corn mill, formerly used as a Youth Hostel. Built 1744 on a much earlier mill site. Partially restored in 2004 but then damaged by floods. Model of corn milling by water power.

Bridge Street, Winchester SO23 9BH Tel. 01962 870057 W: www.nationaltrust.org.uk/visit/hampshire/winchester-city-mill The Watercress Line (Alton to Alresford – photo 19) Ex-Southern Railway line with steam services and special events.

The Railway Station

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City Mill Winchester was one of many mills on the River Test; now owned by the National rust achinery is not resently unctioning due to ood damage but models show the working.

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West ountry acific Wadebridge at Alres ord during a driver e erience day on the Watercress Line hotogra hed th July 2 Alresford, Hampshire SO24 9JG Tel. 01962 733810 W: www.watercressline.co.uk Twyford Waterworks Edwardian water works with original boilers, Hathorn Davey triple expansion engine, water softening plant and 2 foot gauge railway.

Open 11.00am - 4.00pm on selected days.

Twyford Waterworks Trust Hazeley Road, Twyford SO21 1QA Tel. 01962 714716 W: www.twyfordwaterworks.co.uk Museum of Army Flying Well displayed history of army flying from balloons and man carrying kites to helicopters.

Middle Wallop Stockbridge Hants SO20 8FB Tel 01264 781086 W: www.armyflying.com Milestones Large museum including displays about Hampshire engineering firms such as Tasker, Wallis and Steevens and Thorneycroft. All under cover.

Basingstoke Leisure Park Churchill Way West Basingstoke RG22 6PG Tel. 01256 639550 W: www.milestonesmuseum.org.uk ME

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Miniature Gas Turbines – An Introduction PART 2

Turbine wheel Tim Coles takes us through the basics of model turbines.

Most miniature gas turbines use an a ial flow turbine wheel (photo 8 and this is universally produced as a lost wa casting in nconel alloy, to resist the heat and centrifugal loads on the turbine blades. That said, some real enthusiasts still like the challenge of making their own turbine wheels by hand. The cast wheels usually incorporate a ‘sacrificial ring’ in the hub, this being ground away as needed during the balancing process. The sacrificial ring is non structural and therefore parts of it can be safely removed during balancing without compromising the structural integrity of the wheel. learly, the turbine wheel, the robust shaft connecting the turbine to the compressor,

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A ial ow turbine wheel

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and the compressor wheel assembly need to be balanced to within uite close limits if the bearings are to last for a reasonable time. With the engine at full power, the e haust gasses leave the engine at around 600 degrees at a velocity of about 00 metres per second.

A small number of miniature gas turbines use a radial inflow turbine, usually sourced from automotive turbochargers, which all use radial inflow turbines. The main advantage here is that such turbines are readily available, with a lesser advantage of using a simpler V arrangement. These wheels are, however, uite heavy, although weight savings can be made in the V design and construction. They can be

a little less efficient than a ial turbines but, correctly set up, radial inflow turbines have a wider operating envelope and are generally more efficient than the e uivalent capacity a ial turbine in this si e range, which is why all turbochargers, at this si e, use radial inflow turbines. See the note about the T A engines at the end of this article.

Bearings The bearings used in these engines have a tough life as they spin at very high speed just how fast depends on the si e of the engine (photo .

The larger model engines run at around 100,000 rpm, but the smallest run up to an ama ing 50,000 rpm, over ,000 revolutions per second The front bearing runs in a relatively cool environment but the rear bearing is right up close to the hottest parts, the V and turbine wheel. Most engines now use cageless, ceramic ball bearings which seem to perform best in this application, with bearing life something in the region of 50 hours running time.

The lubrication system mostly used for these high speed bearings sounds a bit hit and miss, but works well.

A little like a two stroke petrol engine, typically three to five percent of lubricating oil is mi ed with the fuel, and a small proportion of this fuel lube mi is then fed to the front bearing from the main fuel line, via a flow restrictor from the fuel pump. When the mi hits the high speed shaft and bearing, it atomises and then passes, as a fine oily mist, down the shaft tunnel to the rear bearing, after which it burns off, as it passes out through the turbine.

Model Engineer 14 June 2024

TURBINES

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ha t attached to turbine wheel and com ressor

The control of gas turbines As in full si e, the power of the engine is governed by the rate at which fuel is pumped into the combustion chamber. A gas turbine is auto governing, based on the amount of fuel supplied. As the pump speeds up, the flame becomes rich and develops more heat in the combustor, e panding the air and making the turbine spin faster. This causes the compressor to draw in more air until the fuel air ratio matches and the engine settles to the higher rpm where the fuel air mi is stable. onversely, as the fuel pump slows down, the flame becomes leaner and develops less heat in the combustor and therefore a lower e pansion of the air in the chamber this then causes the turbine to slow down, which

results in less air being induced by the compressor until the fuel air ratio matches and the engine settles to the lower rpm where the fuel air mi is again stable. f, on the other hand, fuel is pumped in too uickly, then the compressor will not catch up uickly enough and the flame will become so rich that it will e tinguish through lack of o ygen. onversely, if the pump is slowed too uickly, then there will be too much air and not enough fuel and again the flame will e tinguish due to being too lean a mi . n early manually operated engines this was overcome by winding the pump rate up and down slowly, so that the rotor simply responded to the heat delivered. Modern engines use an ECU (engine control unit or more properly, a A E ( ull Authority igital

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odel turbine control system

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Engine ontrol . This clever device is fed with data on the speed of the rotor, the e haust gas temperature and the throttle setting, computing these signals to control the fuel pump speed, to ensure the engine reaches the power setting demanded by the pilot in the shortest but safest duration. The pilot has a simple power lever on the transmitter.

However uickly the power lever is moved by the pilot, the engine only responds as fast as the A E will allow.

Apart from controlling the running of the engine (photo 10 , the A E also automatically controls the startup se uence, as well as the shut down and cooling se uence. Most manufacturers supply a remote display unit which monitors the performance and condition of the engine in operation, this being disconnected from the aircraft before take off, although more recent A E Smart displays are designed to remain connected at all times, recording flight data as a bonus. All of this electronic wi ardry makes operating a gas turbine in a radio-controlled model aircraft pretty simple. n many cases, to start the engine, the throttle trim is moved from minimum to ma imum which has the effect of enabling the start se uence.

The throttle stick is then moved from minimum to ma imum and then back to minimum, which then begins the actual start se uence, controlled automatically by the A E and remaining under the control of the A E until the engine is running at idle speed, at which point authority is given to the pilot to use the throttle control to alter the engine power setting as desired.

After landing, the pilot will command the A E to shut the engine down, probably by moving the throttle trim from ma imum to minimum.

The fuel supply to the engine will then be stopped and the engine will spool down to ero, at which point the A E will start a cooling se uence, drawing air through the

engine to cool it down from its operating temperature. This ensures good bearing life by preventing heat soak from ‘cooking’ the bearings. nce the engine reaches its preset stop temperature the A E will deactivate.

The combustion chamber in a gas turbine is like a primus stove and re uires pre heating to vapourise the kerosene fuel so that it will burn. Early miniature gas turbines had gas start, with propane used to pre heat the combustion chamber, this being ignited by a standard model glo plug.

However, most engines now feature ‘kero start’ in which a small electrical heater burns a supply of kerosene to pre heat the chamber. The earliest engines also used compressed air to blow the rotor round on starting, but now an electric motor spins up the rotor, under the command of the A E .

Turboshaft engines As mentioned, gas turbines can be used to produce shaft power by adding a further turbine stage. n miniature jets, this consists of another larger power turbine, known as a free turbine, mounted downstream of the primary turbine, and running on its own shaft. This then delivers shaft power to a gearbo , driving the rotors of a helicopter or the propeller of an aircraft (photo 11 . A cast stainless steel duct, with an e panding cross section, takes the fast gases coming off the

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odel aircra t turbo ro system

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gas turbine owered locomotive

onstructing a model turbine primary turbine and e pands them before delivering to the power turbine, this usually being a lost wa nconel casting. After passing through the power turbine, the e haust gasses are led away by a large cross section duct, often split in two to pass either side of an aircraft, for e ample.

The gearbo es are usually uite simple affairs with spur gears but they do have forced lubrication, directed into the mesh of the gears. Helicopters are now regularly powered by turboshaft engines, and some turboprop aircraft are now seen at shows, but the turboshaft is an e pensive bit of kit to put on the front of a model aeroplane

combustion chamber on this engine is rated at 18kW. This is e uivalent in mechanical terms to about 5 H . f this figure, some 18 H is delivered to the compressor, running at 160,000 rpm that’s ,700 revolutions a second.

At full power, the engine pulls in around 150 litres of air per second, e uivalent to an average dustbin full. The engine will run with an e haust gas temperature of up to 700 degrees Centigrade but it is better to keep down to around 600 degrees. uel consumption is, not surprisingly, high at about 5 ml per minute on full power but, when set against the power produced, the consumption is not unreasonable.

Some statistics As an e ample, for the purposes of this article, ’m going to use the Wren MW 5 engine, a well known design originally producing ten pounds of thrust but in later models developed to produce nearly twice that figure. The

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The Gas Turbine Builders’ Association Miniature gas turbines are commercially available with thrust ranging from a couple of pounds through to 50 or more pounds and most flying enthusiasts will simply go out

and buy one of these. They come complete with all the ancillaries such as a A E , fuel pump, fuel valves, starter and a digital display. However, some individuals may want to build their own engine, perhaps partly to save money and partly as a challenge. This is where the T A comes in (photo 12 . nitially established in 1995

by Tom Wilkinson, the T A started out as a contact group to link jet home builders to share information on designs, construction methods and materials. nterest in home building waned for a time as commercial jets became available but the organisation is still thriving to cater for those who still wish to have a go at building a gas turbine themselves, or who want to gain a better understanding of how they work. To make this easier, the T A has designed a range of four engines especially for the home builder, with outputs of 15, 0, 5 and 0 lb static thrust. n each case, the compressor wheel and the turbine wheel are available commercially from turbocharger suppliers.

The turbine wheels are of the radial inflow type, unlike the majority of commercial engines

which have a ial flow turbine wheels. These engines have been designed specifically for model engineers to make in an average model engineering workshop (photo 13 . The prototypes have been made using a standard Myford Super7 lathe. Even the milling operations were undertaken on the lathe with the use of a vertical slide. A number of jigs have been designed to simplify operations, such as machining the vanes on the side of the diffuser, as well as producing comple profiles such as those of the intake. urther information about the T A can be found via their website www.gtba.co.uk.

as urbine uilders Association This article first appeared in the ritish Model lying Association newsletter.

ME

Model Engineer 1

une 0

The Stationary Steam Engine PART 58 –THE COALBROOKDALE ENGINE AND THE INTRODUCTION OF THE ENGINE TO LONDON Ron Fitzgerald takes a look at the history and development of the stationary steam engine.

Continued from p.692, M.E. 4743, May 17

www.model-engineer.co.uk

he dates given by John Vivian for his recollections of the Stray Park combined cylinder and boiler steam whim engine vary between 1800/1801 and 1801/2. This would suggest that the engine was built before the Trevithick and Vivian patent was granted and as Stray Park was one of the mines managed by Andrew Vivian it is reasonable to suggest that he was providing a facility to enable trials to take place. The known mechanical details of this machine are confined to Vivian’s statement that the cylinder was contained in the boiler and the piston rod worked horizontally. In the latter respect it differed from the stationary engine contained in the patent which showed the cylinder as vertical.

At about the same time that the Stray Park whim engine was proving itself, another experimental engine was being built by the Coalbrookdale Ironworks. Richard Trevithick’s connection with Coalbrookdale was initiated by his father who was ordering pipes for Dolcoath in 1775. Trevithick junior had continued the relationship and by the summer of 1802 the Dale had completed an engine. It is possible that plans were being prepared in January, three months before the patent was sealed (ref 305) and the engine was operational by 22 August when Trevithick wrote to Giddy from Coalbrookdale. This letter is worth quoting in its full vernacular:

T

Shod have writ to you some time sence but not having made ufficient trial of the engine heve referd it until it in my power to give you an agreeable information of its progress. he boiler i ft iam the Cylinder inche in iam, feet stroake. The water piston n. drawing and forcing feet perpendr, e ual beam fir t et it off with abt lb. on the Inch pressure against the team valve without it Load before the pumps were ready and have sence workd it everal time with pump for the inspection of the engineers abt this nibeourhood. The steam will get up to lb or lb to the inch in abt one hour after the fire i lighted the engine will et off when team i abt lb to the inch, abt troke per minute with it load. here being a great deal of friction on uch a mall engine and the team continue to ri e the whole time it i worked it go at from lb to lb to the inch in fair working ... troake pr mt it became o unmanageable a the steam encreased that I was obliged to top and put a cock in the mouth of the dischardging pipe and leve only a hole open of by of an inch for the steam to make its escape into the water. he engine will work troake pr mt with a pre ure of lb to the inch again t the team valve and keep it con tantly weming with wt (3 cwt.) of Coal every four hour . have now a valve making to put on top of the pump to load with a teelyard

so to try how many pounds to the inch it will do of real duty when the team on the valve i lb to the inch. cannot put many more pumps (lengthen the standpipe hence the head) as they are very lofty already . he boiler i inch thick and think there is no danger in putting it much higher (ref 306) Trevithick’s letter describes an engine with a four feet diameter boiler, the shell of which was 1½ inches thick (certainly cast rather than wrought iron) and a cylinder of 7 inches bore by 3 feet stroke.

It had been tested working a 10 inch diameter pump with a beam connection between the cylinder and the plunger pump. The water was pumped into a stand pipe 35½ feet high. Steam pressure varied between 50 p.s.i. and 145 p.s.i. and the reference to the exhaust escaping into the water probably indicates that a feedwater heater was used similar to that included in the patent.

There is another description of what is undoubtedly the same engine. Simon Goodrich’s Journal records in somewhat more elegant prose: 2. Wedne day 2 rd ebruary . Coal rook ale. reakfa ted early and then went over the ale companie work along with r. homa . aw r. revithick engine which works by the force of steam without condensation. t had worked a double inch pump feet troke troke per minute raising the water >>

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feet which wa uppo ed to con ume cwt of coal per hour. This engine was erected under the direction of r.

Trevithick for an experiment. he team cylinder in which the steam was made to act both way wa placed within a ca t iron boiler, the pi ton rod coming through the tuffing bo at the top-----round thi boiler was another case of cast iron at a ufficient di tance from it to allow room for the fire place and ue the fire wa made on a plate at the bottom of the outer ca e and circulating between the outer case and the boiler, entered by a hole through one side of the outer end a chimney of brickwork carried up a ufficient height to produce draught. To prevent the outer case from burning away or conducting the heat off too fast it wa lined on the in ide with firebrick .

Much of the content of Goodrich’s diary entry can be identified with Trevithick’s letter to Giddy but it adds several salient points. The cylinder is stated to be doubleacting and is inserted into the boiler vertically. There was no condenser. The boiler had a double shell of cast-iron, the hot gases circulating in the space between the shells. The fireplace was underneath the inner boiler and, to prevent the casing burning away, it was lined with firebrick.

A third source of information is to be found in the Coalbrookdale Ironworks ettling Journal (ref 307) that records charges to…..

Richd Trevithick & Co.,…. which may be taken as referring to the then partners in the patent, Trevithick, Vivian and West.

The heading is sub-titled …. or Castings for Experiments---now at the ale . The list of items includes: boiler at cwt 2 tr . lb ca e for do. 22cwt. tr 2 lb . cost £48. 3. 7d. cylinder top and pipe cwt tr. lb and tuffing bo lb .. charged at £18. 7. 8d. otably, the first two items on the list specify a …boiler and a…. case…. for the boiler.

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This indicates double shell construction similar to that specified in the patent with an inner water and steam vessel enclosed by a cast–iron outer casing. Together these descriptions suggest that the Coalbrookdale experimental engine was virtually identical to the patent drawing of the stationary engine.

The total cost to the partners was £205 5s. 10½d but there were further charges which were debited on the 18th October 1802 including …. itting attg. ngine boiler etc., making oint putting up pipe etc., men in all day at per day and 2 men imilarly employed for day at 2 - per day.

The Coalbrookdale engine may also have served as a demonstrator (Goodrich’s inspection of it was doubtless intended to persuade a prospective customer). That a demand existed for a cheap, compact and fle ible engine of less than 15 horse power had already been demonstrated by the smaller engines recently produced by Boulton and Watt, Murray. Trevithick’s engine had the additional advantages of not requiring cooling water for the condenser and a much

higher potential specific output due to the raised steam pressure. All of these factors must have been thought to give the engine a strong appeal for London with its multitude of small trades.

Even before the patent was applied for Trevithick had apparently supplied an engine to London. Francis Trevithick, based upon an extract from Trevithick’s account book under date 1800, records a payment to Arthur Woolf: …. o Arthur Woolf going to London a engine fireman with the helland engine at per year.

The biographer elaborates later on the same page: . .. in a high pre ure portable team engine wa was sent to London in charge of Arthur Woolf, the well-known engineer. (ref 309) In Volume II of the Life this has been expanded into: n Woolf, who had been a mine carpenter went to London with the fir t high pressure steam engine which Trevithick had sent beyond the limit of Cornwall ---probably to eu rewery--- , for he wa there in and in the receipt of a year from revithick a engine fireman. rom the

date of Woolf patent in his payment from Trevithick cea ed ...

Francis Trevithick’s footnotes: n . revithick account book ol . p. n. Capt. John ivian recollection ol. . p. 2. (ref 308) By this time Woolf was no longer employed at the Hayle Foundry. Following the trade of carpenter, he moved from Cornwall to London and after a brief period with Bramah he applied his skills to engineering. This led to an involvement with Hornblower and Maberley, building their patent engines and it was the installation of one of these engines that brought him into contact with Meux’s riffin rewery in ondon.

Hornblower’s engine for Meux was built in 1796 and as a result Woolf was appointed as the brewery engineer, a post he held from April 1797 until October 1806, initially paid £2 per week, later raised to £3 per week (ref 310).

The statement in the second volume of the Life seems to be Trevithick’s attempt to reconcile the entry in the account book with Woolf’s

Fig 187

John Farey’s 1804 drawing of the London dyehouse engine.

Model Engineer 14 June 2024

THE STEAM ENGINE

Fig 188

John Farey’s 1804 drawing of the London dyehouse engine cylinder. employment at Meux’s Brewery but the suggestion that the Trevithick engine was intended for this customer is conjecture on Francis Trevithick’s part.

For a number of reasons this is difficult to accept. irstly, if the engine was intended for the brewery, the question arises why Woolf, who already held a responsible salaried position at that establishment, should be paid a further £2. 10. 00. per week by Trevithick to act as a fireman Secondly, the account book explicitly describes the engine as the helland engine. As the Suffolk place name carries no identifiable significance, Shelland seems to be a personal name but there is no known connection between such a person and the Meux establishment.

Finally in discussing Meux’s Brewery, Peter Mathias, in his authoritative history of the eighteenth and early nineteenth century brewing industry ( 311), considers the possibility that a Trevithick engine was installed whilst Woolf was machinery superintendent but concludes that this was confusion with an engine of Woolf’s own design.

As further evidence he points out that when the brewery was offered for sale in 1809, the

www.model-engineer.co.uk

catalogue makes no reference to a Trevithick engine. Nor does Rhys Jenkins mention such a Trevithick engine at the brewery in Woolf’s time ( 31 ). f Meu ’s riffin rewery is unlikely to have been the location for this first Trevithick high-pressure engine outside Cornwall then it remains to determine the relevance of the name Shelland. Accepting that Shelland’s business was entirely independent of the brewery then the possibility arises that Woolf was acting for other parties whilst he was employed by Messrs. Meux, effectively following the role of consulting engineer. The term fireman at that time referred rather to engine man than it did to stoker.

Within the next twelve months John Farey saw several more Trevithick engines working in the metropolis. He made a detailed drawing of one such machine which was in use at a dyehouse in 1804 (ref 313, 1 ).

Although there are a number of similarities with the design shown in the patent drawing the differences are notable.

Most obviously, the cylinder has been repositioned from the vertical to the horizontal

( 1 ). This allowed the somewhat vulnerable framing carrying the crankshaft, flywheel and the outer ends of the slide bars shown in the patent to be replaced by a sturdier timber trestle. In both the patent and in Farey’s engine most of the length of the cylinder barrel was enclosed within the boiler. The valve operating mechanism is more robust in the London engine; a simple reciprocating rod with tappets trips the swinging valve rod arm replacing the delicate cam ring and roller with its unexplained linkage.

Farey’s drawing of the valve chest shows a more elaborate arrangement compared to the patent design with two plug cocks, one above the other.

The upper cock controlled the steam admission and exhaust, the lower valve acted as a stop valve intercepting the steam port that led into the outer end of the cylinder. The exhaust from this end of the cylinder exited through a separate port but inlet and exhaust to and from the other end of the cylinder was by way of the elongated port that ran down side of the cylinder.

The complex double-skinned boiler of the patent with its baroque feet was abandoned in favour of a simple tun boiler, familiar from the earliest days of the Newcomen engine.

Entirely made of cast iron, the top was hemi-spherical but the sides were a tapering cylinder, narrowing as it approached the fire setting. The fire grate was built in to a brickwork cylinder which enclosed the cast-iron boiler shell. Above the fire, the base of the boiler was domed. A dead-weight lever safety valve was mounted on a manhole cover at the highest point of the domed top of the boiler.

To be continued.

NEXT TIME The London road coach.

REFERENCES Ref 289 Ref 306 Ref 307 Ref 308 Ref 309 Ref 310 Ref 311 Ref 312 Ref 313

Dynasty of Ironfounders. The Darbys and Coalbrookdale.

Arthur Raistrick. Pub Longmans. 1953. P. 161 Quoted p. 163, Dynasty of Ironfounders. The Darbys and Coalbrookdale. Arthur Raistrick. Pub Longmans. 1953.

Dynasty of Ironfounders. The Darbys and Coalbrookdale.

Arthur Raistrick. Pub. Longmans 1953. Appendix 5 Life…. Vol II, p. 112 Life. .Vol. I. P. 90.

A Cornish Engineer: Arthur Woolf, 1766 – 1837 Rhys Jenkins. T.N.S. Vol. XIII 1932-33. P. 55 et seq.

The Brewing Industry in England 1700-1830. Peter Mathias.

Pub. C.U.P.1959 p. 96 A Cornish Engineer…. Rhys Jenkins op.cit.

A Treatise on the Steam Engine, Historical, Practical and Descriptive (1827). John Farey. Vol II. P. 14.

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LNER B1 Locomotive PART 47 – AWS GEAR AND LAMPS

Doug Hewson presents an authentic 5 inch gauge version of Thompson’s B1 locomotive.

Continued from p.771, M.E.4744, May 31

irst of all, I would just like to touch on the AWS (Automatic Warning System) gear which is quite visible on lots of later locomotives. It is more or less identical on most locomotives and sadly I have no drawings of the gear. However, I did take lots of photographs of the gear on a Black Five at Llangollen which was being steamed by the late great Bob Maxwell. I had a most delightful morning couple of hours chatting to Bob as he wandered round the engine oiling all round and he gave me free access to take lots of photographs. The engine was 44806. hoto ph 33 is the shoe on the bottom of the plate which is bolted to the back plate to retain the lower link of the screw coupling to prevent it from unscrewing. hoto ph 33 is the top of the plate bolted to the bottom of the buffer beam. hoto ph 33 is the mounting for the transponder shoe (if that is what it is called!) and the bracketry supporting same. These are mounted on the front cross member of the bogie and on my 4MT they are mounted on the pony truck.

The transponder is quite easily spotted, like a small upside-

F

338

Top of the retaining shoe.

339

Transponder shoe mounting.

337

Screw coupling retaining shoe.

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down dome. hoto ph 3 is a closer-up view of the mounting gear.

I promised that I would come back later and describe the lamps on my engines. One thing I found most valuable - and I would not like to be without it - is my gauge glass lamp. fitted these on to all on our locomotives when I was building the railway around my new house. This was so that we could work into the night and we did, sometimes until almost midnight. It is lit by a 5mm LED when they were a new idea. All

we could get at that time was red, yellow and green, I think.

When the high brightness white ones came on the market, we thought that they were amazing.

However, I thought that they were a bit too bright for me, so I stuck with my yellow ones as they look far more like paraffin lamps. All you need to make these is a double AA battery holder which you can hide somewhere on your engine, like inside a tool box or under the cab floor, some very thin T E coated wire, some 10 thou nickel silver sheet, a switch, a

Model Engineer 14 June 2024