Model Engineer issue 4740 **FREE 20 PAGE PREVIEW**

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BUILD A TWIN COMPOUND WINDING ENGINE Join our online community www.model-engineer.co.uk

Vol. 232 No. 4740 5 – 18 April 2024

Crossness Adding glamour to the pumping of sewage

THE ORIGINAL MAGAZINE FOR MODEL ENGINEERS

Ruby Swann takes to the road

Cornwall

LNWR single wheeler is ready to roll

Radio Control Where steam and electronics meet

Rust

Where it comes from – how to stop it

513

523

Published by Mortons Media Group Ltd, Media Centre, Morton Way, Horncastle, Lincs LN9 6JR Tel: 01507 529589 Fax: 01507 371066 © 2023 Mortons Media ISSN 0026-7325 www.model-engineer.co.uk 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.co.uk Investment Manager: Chris Jeffery By post: Model Engineer advertising, Mortons Media Group, Media Centre, Morton Way, Horncastle, Lincs LN9 6JR 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 486 for offer): (12 months, 26 issues, inc post and packing) – UK £128.70. 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.232 No.4740 5 –18 April 2024 488 SMOKE RINGS News, views and comment on the world of model engineering.

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

492 IMLEC 2024

for details.

512 POSTBAG Readers’ letters.

513 MERRYWEATHER SELF PROPELLED STEAM FIRE ENGINE Werner Schleidt finds an old boiler and is inspired to construct a fire engine around it.

Rod Ainsworth invites you to compete in this year’s efficiency competition at Southport.

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

500 G1 OR 16MM LOCOMOTIVE RADIO CONTROL Malcolm Batt uses BBC micro:bit computers to add radio control to a 32mm locomotive.

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

523 A TWIN TANDEM COMPOUND STEAM ENGINE Graeme Quayle presents an interesting design for a compound winding engine.

525 BOOK REVIEW Henk-Jan de Ruiter reads about the restoration

504 GRINDING THE TARCUTTA CAMSHAFT Gerard Dean needs a pair of camshafts for a V12 motorcycle engine so decides to grind them himself.

of antique toys.

526 THE AMERICAN LOCOMOTIVE David Rollinson takes a look at the classic and ubiquitous 4-4-0 locomotive.

506 THIXOTROPIC METALS – ‘ALLOY 14’ Geoff Theasby strays into the cutting edge of metallurgical science.

507 SMEE NEWS

529 A VISIT TO THE CROSSNESS ENGINES Robert Hobbs visits a rather grand and ornate pumping station in South East London.

Martin Kyte reports from the Society of Model and Experimental Engineers.

508 RUST FORMATION AND PREVENTION IN THE WORKSHOP Neil Raine looks at the causes of rust and how it may be prevented.

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

535 CLUB DIARY Future Events.

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BUILD A TWIN COMPOUND WINDING ENGINE Join our online community www.model-engineer.co.uk

Vol. 232 No. 4740 5 – 18 April 2024

Crossness Adding glamour to the pumping of sewage

http://www.facebook.com/modelengineersworkshop

ON THE COVER...

Steve Goodbody’s 3 inch scale Allchin ‘Royal Chester’ traction engine Ruby Swann (photo Steve Goodbody).

THE ORIGINAL MAGAZINE FOR MODEL ENGINEERS

Ruby Swann takes to the road

http://twitter.com/ modelengineers £5.10

Cornwall

LNWR single wheeler is ready to roll

www.model-engineer.co.uk

Radio Control Where steam and electronics meet

Rust

Where it comes from – how to stop it

This issue was published on April 5, 2024.

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483

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s I write this, the weather has turned positively spring-like and model engineers are beginning to come out of hibernation, blinking in the unaccustomed sunlight.

Where I live, it is clear there has been a change in the weather as there has been no rain now for over 24 hours, for the first time, it seems, in several months. Temperatures have also managed to haul themselves into double figures so everything is looking very promising.

There are plenty of events to go to over the next few weeks, to make the most of the improving weather, and here I have listed a few of them.

A

MARTIN EVANS Editor

Parklands Railway Week

2½ Inch Gauge Rally

The annual Parklands Railway Week at Hemsby, Norfolk is a very popular event amongst the 7¼ inch gauge fraternity but, sadly, this year’s is to be the last. It is to be held during the week from May 25th to May 31st. If you wish to bring an engine you need to notify leighsteamer@ btinternet.com and further details can be found at www. sevenandaquarter.org

No need to feel left out! There is a 2½ inch gauge rally at the Cheltenham Society of Model Engineers on Sunday May 12th, from 10am to 4pm.

Register Parklands

Bassett-Lowke Rally 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.

07710-192953 MEeditor@mortons.co.uk

The second Bassett-Lowke Rally will be held at the Northampton Society of Model Engineers track on Saturday May 18th. Visiting locomotives are welcome in 7¼, 5 and 3½ inch gauges to run on their raised and ground level tracks.

There will also be Gauge 1 and Gauge 2 running in the marquee and the 45mm and 32mm garden railway will also be available.

To register please contact Kevin West on westkev58@ gmail.com

Kevin West

Details Parklands

3½ Inch Gauge Rally If you are into 3½ inch gauge and are based not too far from the Midlands then you may be interested in the 3½ inch gauge rally at Rugeley Power Station.

The rally is organised by the Rugeley Society of Model Engineers and takes place on the weekend of May 18th/19th. If you are interested you will need to book in advance (secretary@ rugeley-sme.org.uk) and bring the usual paperwork (boiler test certificate and insurance documents). Food and refreshments will be available both days. For accommodation, both Travelodge and Premier Inn are situated nearby.

Engineering in Miniature I was very sorry to hear the news that our rival publication, Engineering in Miniature, is to close after the May issue.

Perhaps you think this odd, coming from the editor of this magazine. However, many of our readers may remember that I was for a while editor of Engineering in Miniature (EiM) so I am (if you like – or even if you don’t like) ‘family’.

I followed Chris Rayward as editor (a hard act to follow) and was given a one-day crash course in putting together a magazine by him and proprietor Chris Deith. Chris then shepherded me carefully through the process over the subsequent year or so until he passed the magazine over to Warners. Chris was an excellent manager and I am very grateful to him for the guidance he gave me. I am glad though that he did not see the demise of his magazine, which he started back in 1979.

The two magazines provided two distinct styles in their presentation – a good thing for the readership. I hope that former readers of EiM may find the style of this magazine tolerable. I read in Facebook recently that our style is considered by some a little ‘pompous’ – so I shall endeavour to be a little more ‘umble in future, Master Copperfield!

Another commentator on Facebook made the very apposite remark that life will become progressively more difficult for printed magazines, as the future is digital. That is quite right and so, as well as being a little more ‘umble, we shall have to try to adapt to the changing modus operandi of the publishing industry. Our survival surely depends upon it.

Details 3½ Inch Gauge

488

Model Engineer 5 April 2024

The View from Butterside Down

Part 8: Third Hand Transportation, Part 4

Steve Goodbody takes a random walk through model engineering.

Continued from p.451 M.E.4739 March 22

ith all other possibilities exhausted, with a dead fire and a cobbled together manometer as evidence, the author concluded that Ruby Swann’s Royal Chester based design as producing very little of that most desirable commodity for a lively firebo draught nd that raised t o good uestions hy and hat could be done about it

W

Disclaimers and denials ver the years, ith the rise of the nternet and an evolving plethora of model engineering forums and ebsites on both sides of the tlantic, have noticed there is one topic hich, despite all reason and rationality, seems to provo e much angst, ire and gnashing of teeth amongst a portion of the message typing populace and that sub ect is draughting, so, ith a sense of trepidation, here is fair arning that am about to touch on this dangerous sub ect and strongly advise sensitive readers to

www.model-engineer.co.uk

cover their eyes and s ip for ard to the ne t article if they ant to avoid the potential fallout o ever, in the fervent but probably naive hope that this ill help s eeten the pill, let me admit right up front that am most definitely not an e pert on draughting no very little of the or s of reenly, ll, ylala, Chapelon, iesl, orta, e aitre and others and have underta en no original research can honestly say that have contributed absolutely nothing to the global body of no ledge on the sub ect and don t intend to start no hould you feel strongly about anything that follo s, therefore, am sure you are in the right and you ill receive no argument or complaint from me n short, everything hich follo s is simply a report of my first hand e periences ith a three inch scale single cylindered llchin traction engine named Ruby Swann, a doubled up version of ill ughes s Royal Chester design and hile strongly suspect that some of these findings

may be broadly applicable to other engines, especially as the supply of decent coal becomes more and more scarce and may therefore be of interest to other engine o ners especially traction engine o ners ho are rarely considered hen draughting is discussed, have noticed am not claiming this for a fact o there! onestly, you can t be too careful these days, can you

Running the numbers o , ith that behind us and for any brave souls ho may still be follo ing along, let me cautiously add that hile not an e pert on the sub ect, as an avid reader of this magazine for rather a long time have noticed that the draughting arrangements of many of the popular locomotive designs published in these pages over the years seem to follo a broadly similar set of guidelines, possibly originating from enry reenly in the s but really don t no and hich, if the reports are to be believed, seemingly result in steaming success Table 1 is included here as a reference for

Approximate Guideline last nozzle area

of the grate s surface area

enturi cho e area

of the grate s surface area

enturi cho e height above the blast nozzle

ased on a in cone of steam emerging from the blast nozzle

inimum chimney height and ma imum chimney diameter above the blast nozzle

ased on a in cone of steam emerging from the blast nozzle

Table 1: The approximate draughting guidelines, discerned from miniature railway locomotive designs.

489

>>

what will follow; it summarises those approximate ratios, at least as discern them, but have no idea if these ratios and arrangements are any here near the best that can be achieved and ma e no claim, recommendation or comment regarding their accuracy, relevance, efficacy, degree of perfection, or ability to histle the arseilles in the ey of ma or ut thin you no this by no tepping bac and applying a bit of logic a dangerous thing, no , ho ever, certainly li ed the fact that these ratios too the grate s size as their starting point because, to me, that made intuitive sense s reasoned it, rightly or rongly, a ell designed boiler ould sensibly be based upon the needs of the cylinders and, if so, then the size of the boiler s fire and therefore the size of the boiler s grate, must have been determined by the heat needed to produce sufficient steam from that boiler to feed those cylinders nd ith the grate s size so determined, then the ashpan and ues should also have been designed, respectively, to allo sufficient air into the fire and to enable the resultant gases to efficiently escape, all to eep the ames merrily burning o bring this train of thought to its conclusion, if the boiler as thus ell designed and the grate, ues and ashpan ere properly proportioned in turn, then the sole purpose of the draughting as to produce

sufficient vacuum inside the smo ebo to dra enough air through the fire bed to ma e it all or ince the appropriate amount of air is determined by the size of the fire and since the size of the fire is substantially determined by the size of the grate, then the grate s size seemed to be the appropriate starting point for the draughting design s say, this train of thought made sense to me earteningly, ob anderson s article, Front End Design, appearing in the une , 4 edition of Model Engineer, also used the grate s size as the basis for its front end calculations and seemed to support my supposition o ever, hile the blast nozzle size calculated using r anderson s formula agreed closely ith the roughly ratio to grate area hich seemed typical, his appro imately 2 ratio for the venturi cho e as far smaller than the hich appeared more typical and decided to stic ith the latter o complete the picture, hile ne that cylinder bac pressure as also an important factor, decided not to orry about that too much unless the guidelines suggested needed a considerably smaller blast nozzle than Ruby Swann’s current fitting to get the fire burning

the root of my troubles, no had the ability to generate a set of theoretical dimensions as a guideline against hich to compare Ruby Swann’s actual details o ever, to add one further un no n into the mi hich is more of a caveat than a disclaimer, given that the guideline dimensions ere presumably based upon the needs of a t o cylinder rail ay locomotive had no idea hether they ere e ually applicable to a single cylindered traction engine ith no other information or guidance available, ho ever, had to start some here and these ratios seemed to be as good a place as any here o, ho did Ruby Swann’s details compare ith these figures ell, after assembling the relevant formulae into a spreadsheet to perform the necessary calculations ithout repetitive effort, it certainly appeared that her front end dimensions deviated significantly from the guideline ratios, especially hen it came to her chimney n fact, the chimney, ith its lac of a venturi to help dra air from

the smo ebo and its large and increasingly larger diameter as it tapered upwards to the top, seemed to miss the mar by a significant margin in all respects and Table 2 shows ho the numbers stac ed up ssuming the guidelines represented reasonable if appro imate targets, then hat did these figures suggest et s ta e each in turn, starting ith the seemingly over large diameter at the top of Ruby Swann’s chimney and see s imagine it, as a steam engine or s harder, the et of steam e iting the blast nozzle speeds up and causes the cone of e panding steam hich is shooting up ards to correspondingly narro the faster the et, the narro er the cone and vice-versa nd this, it seems to me, is the li ely reason behind the in and in cone ratios in the guidelines the former representing the et hen the engine is or ing lightly and the latter hen the engine is or ing hard nd from hat can recall from many hours spent unravelling the mysteries of uid dynamics at

Compare and contrast t this point, convinced that inade uate draughting as Guideline Size Ruby Swann’s Actual Size

last nozzle diameter

inches

inches

inch

inches

ver 2 inches

enturi cho e height above a inch diameter blast nozzle

inches

o venturi

inimum chimney height above a inch diameter blast nozzle

inches

inches

a imum chimney e it diameter for a inch diameter blast nozzle and a inch high chimney

2 4 inches

Cho e diameter for a diameter blast nozzle

2

inches

Table 2: A comparison of Allchin Ruby Swann’s actual details against the Table 1 guidelines.

490

Fig 3 The 1-in-3 and 1-in-6 cones emerging from Ruby Swann’s blastpipe, drawn to scale.

Model Engineer 5 April 2024

BUTTERSIDE DOWN

Fig 4

The top of the chimney depicted in fig 3. The chimney’s diameter is too large to be filled by the 1-in-6 cone of steam, possibly allowing air to enter her smokebox through the annular gap. university and beyond, thin that my imagination is on the right trac , but m sure that someone ill let me no if m rong o ever, it also seemed to me important that hen an engine is or ing its hardest, the chimney s diameter must be sufficiently small for the in cone to fully fill it before e iting out the top because, if it does not, air may creep do n the annular gap bet een the steam et and the chimney and deplete the smo ebo vacuum nd in Ruby Swann’s case, the calculated numbers in able 2, hich are also sho n pictorially and to scale in figs 3 and 4, suggested that, ith its inner diameter of 2 inches, the top of Ruby Swann’s chimney as roughly of an inch too large, implying that the cone of e hausted steam may not be filling the chimney hen the engine as or ing hard n short, the guidelines suggested that improvement might be had if the chimney s overall diameter ere reduced by at least inch, but preferably more e t on the list, hen or ing lightly, although the in cone of steam ould certainly fill the chimney,

www.model-engineer.co.uk

the chimney s large overall diameter, fully 2 inches at its smallest point, meant that it ould do so at a much greater elevation than if the chimney contained the venturi cho e suggested by

the guidelines nd, hile believe that a venturi is not a common front end design feature for a traction engine, it certainly seemed plausible that adding one ould help mi the smo ebo gases ith the exhaust steam, draw those gases from the smo ebo and reduce the smo ebo pressure and create more draught in the process n short, the guidelines suggested that adding a venturi ith a inch diameter cho e at a height inches above the blast nozzle, thereby reducing the chimney s diameter by roughly inch at that point, ould represent another possible area for improvement inally, hat about that blast nozzle diameter ith a guideline of inches versus the actual diameter of inches, it certainly appeared that Ruby Swann’s blast nozzle as slightly undersized o ever, if increased, ould that resolve the problem hile the spreadsheet suggested no her chimney ould still be too big even ith a larger blast nozzle this as an easy e periment to perform and so,

after half an hour of lathe or , repeated the manometer tests ith a selection of larger nozzles and confirmed that, as far as could detect, they made not a hit of difference to the smo ebo vacuum hich, in all cases, remained undetectable n conclusion, ere to believe the guidelines, then they ere telling me that a narro er chimney, together ith a proper venturi to help dra the gases out of the smo ebo , ould be avenues orth e ploring ut ho to achieve these t o goals ithout ruining Ruby Swann’s other ise attractive and true to scale appearance photo 16 ell, that s a very good uestion but see that our editor is pointedly tapping his atch and so the ans er ill have to ait until ne t time m afraid To be continued.

16

A narrower chimney would certainly spoil the elegant appearance of an Allchin traction engine, in the author’s view!

491

IMLEC 2024 Rod Ainsworth, chairman of Southport Model Engineering Club, invites entries for this year’s IMLEC.

he 54th International Model Locomotive fficiency Competition is to be held at Victoria Park, outhport on th 2 st uly 2024.

The members of Southport odel ngineering Club, assisted by members of the eyland Club, are proud to be the hosts of the 54th anniversary event of C Our club was formed in 1978 and has currently over 2 members who range from raw novices to professional engineers. The club has extensive and attractive grounds and a clubhouse situated at the southern end of Victoria Park, Southport with access off Rotten Row. We have two raised tracks each catering for 3½ and 5 inch gauge locomotives he first of these tracks also has a 2½ inch gauge track and is 640 feet long and the second track is 1733 feet long. We also have a gauge 1 and 32mm track of and feet respectively The grounds have been judged to be utstanding by the oyal orticultural ociety s t s our Neighbourhood’ scheme.

Southport is a delightful Victorian seaside resort, no n as he Classic esort Southport is renowned for its gardens, sandy beaches and

T Southport Model Engineering IMLEC

492

many golf courses, including oyal ir dale here the pen olf Championship has been held on numerous occasions.

Its elegant town centre provides a vast array of shops and a wide selection of restaurants.

Lord Street is the main street ith many pavement caf s situated under a glass and cast iron ictorian canopy Visitors to the event will be required to purchase a ticket hich ill provide entry to the club grounds and the event itself. The cost will be £5 per day or 2 for the three days of the event. There is ample on and off-street parking available for both entrants and visitors.

There will be spaces available close to our grounds from hursday till onday th 22nd uly for tents, camper vans and caravans. These

will be under our control for which there will be a nominal charge r en avier is in charge of our caravanning and camping arrangements and visitors wishing to make use of these facilities on the weekend should contact him. here is also a Caravan Club site, for members of the caravan club, within a few minutes’ walk, but pitches here have to be booked well in advance as it very popular location! Visitors will be responsible for making their own arrangements with the Caravan Club outhport is a popular seaside resort and has ample hotel, guest house and bed and breakfast accommodation and again visitors will be responsible for making their own arrangements in this respect.

Model Engineer 5 April 2024

IMLEC

ithin easy travelling distance of outhport is the fine market town of Ormskirk and if the event at the club and the attractions in Southport are not enough to retain your interest then a visit on aturday to the open market is well worthwhile.

There will be a dedicated area for trade stands and if any traders are interested in having a spot over the weekend please contact en as soon as possible The Southport Club has a ebsite southportmodelengineering. club This website will be kept up-to-date with information about the competition and the main point of contact ill be en avier by e mail ublicity southportmodelengineering. club or mobile 2 259845).

The members of Southport odel ngineering Club would like to extend a warm

www.model-engineer.co.uk

welcome to new and past entrants of C as ell as all spectators. We look forward to meeting you over the ee end and to having a really great, mutually en oyable ee end Our main aim is to provide all entrants and spectators ith a thoroughly en oyable competition. Refreshments, including alcohol, will be available throughout the weekend with an evening of live music on the aturday night. There will also be an opportunity for visitors to run their locomotives on our trac s on riday and aturday evenings, subject to the usual paper or but e cluding any entrant who has not completed their run! or any competition to run successfully and be fair to all entrants there have to be rules.

This event is no exception and the following paragraphs outline the basic rules which apply over the ee end he

competition will take place over three days ith the first run starting around mid day on riday, depending on the number of entrants.

The competition will be run on our 5 and 3½ inch gauge dual gauge raised track and will be open to applicants on a first come first served basis by application form only he forms should be completed in full in order to be considered and accepted. A strict time line will be observed on all entries. The competition will be restricted to a total of 28 measured runs using the usual practice of the driver sitting on a dynamometer car, loaned to us by eyland Club, coupled to the engine. No initial circuits will be allowed prior to the run and a full fire at the start of the run will be observed. A set of the rules will be sent to the successful entrants.

The coal supplied for the event will be anthracite in a

choice of two sizes, grains and beans.

If more applications are received than can be run as planned then a list of reserve engines will be considered from the applications in order of receipt. The applicants will be informed if they are to be placed on the reserved list and they can decide hether to partake or not. If not the next one on the list will be offered a similar option. The number of reserve entrants will be limited to six and there will be a tick box on the application form where applicants can indicate their interest in a reserve place very effort ill be made to find a slot for the reservists to run over the weekend, but we cannot give any guarantees Prizes will be awarded to the competitors finishing in first, second and third places in the competition for the Martin vans Challenge rophy plus a prize for the best performing 3½ inch gauge locomotive. f you ish to enter the competition you should apply for an entry form via the ebsite or from en avier ll application forms will be sent out by email to the prospective entrants at the same time, as soon as possible, and the closing date for the return will be th ay The request for an application form will not guarantee entrance into the competition. A form will be sent to all potential applicants at the same time, and acceptance into the competition ill only be considered after a completed form is submitted. A brief description of the entrant’s locomotive and a short history of the driver will be required and a photograph would be appreciated ny previous C inners should declare the year and details of their inning entry ll successful applicants ill be notified by post and they ill be sent copies of maps, rules and local information. Reservists and unsuccessful applicants will also be notified ME

493

BUILDING 3020 CORNWALL

in 5 Inch Gauge

PART 3

Fig 8

11 11

20.1

Ø4 2

38

8

2 Ø3 26

Oil spigot 13

Boiler

Ø34

Ø32

Ø110

5 offset

10

Split line

Expansion link CL

Split line

3

32.5 Ø1 6

Axle Pump Eccentric Mat’l: Cast iron (can be split as shown or solid)

10

Pump Rod Plate (1 required)

Axle Pump Eccentric Strap Mat’l: Bronze (1 required)

5.5

6.4

38 20

8.3 6.3

8 Ø3

6.55 offset

Ø5 0

Jim Clark builds the famous LNWR 2-2-2 – the first locomotive earmarked for preservation.

Oil spigot

Cylinder

Continued from p.459 M.E.4739 March 22

Fwd Ecc.

Pump Ecc.

Rev Ecc.

13

Ø38 Ø40

31.6

Cylinder

Fwd Ecc.

Split line

Ø1 5.9

8

Valve Eccentrics

Rev Ecc.

6.2

Eccentric Rod Plates

Mat’l: Cast iron (4 required) (4 required)

Valve Eccentric Straps Mat’l: Bronze (4 required)

Inner Frame

Eccentric positions indicative only Shown at maximum vertical throw to demonstrate clearance from boiler

3.9 3.8

12.3 4.3

Inner Frame Thread 3/16 x 40

Ø5

117.6 100

Valve Rod Clevis Pin Offset 4.15

Outer Frame

Outer Frame

Braze rod into plate, then set up assembly on jig and braze rod end into clevis to ensure exact eccentric rod length

14

116

Mat’l: 4140 steel (4 required)

13 Ø5 Ø10

Valve Eccentric Rod Assembly 16 12

(2 left/right pairs required)

Valve Eccentric Rod Clevis Mat’l: Steel (4 required)

Eccentric design details.

Eccentrics The eccentric straps for the valves ere another significant design challenge. These have to be mounted on the centre axle and, as the boiler sits right above this axle, there is very little room. Figure 8 shows the eccentrics and a cross-section

17

This shows most of the component parts for the eccentric straps.

494

through the main axle, which demonstrates the problem and details my solution.

I resolved this problem by splitting the eccentric straps horizontally instead of vertically, as is usual practice (photos 17 and 18). The centre eccentric is the smallest, with

only a 5mm offset giving a 10mm stroke and this is used for a water pump. When the various eccentric straps are fitted to the eccentrics, they ust clear the bottom of the boiler at their highest point of rotation.

The eccentric strap bodies were fabricated from slices

18

ere is one complete eccentric strap, valve rod and clevis, finish machined and sitting on the jig that was used to ensure the correct valve rod length.

Model Engineer 5 April 2024

CORNWALL

630.0 28.0

33 6 7

7

26

39 95

192

118 7

33

72 4.5

Mat’l: 5mm mild steel plate

34 33 33

Mat’l: 3mm mild steel plate (2 required)

7

42

10 7

6

Outer Frames

6 32

212

22

20 12

Mat’:l 3mm MS plate

50

Rear Buffer Beam

7

Front Buffer Beam Inner

98

8

122 31

8 4 7

40 D PC 20

7 6 33

19

31

68

D & T 4BA Front

12 P CD D&T 8BA D&T 6BA

Mat’l: 3mm mild steel (2 required)

148 39

20 Location of axle pump

65

93

29

64

Mat’l: 12mm close grain hardwood Varnish or clearcoat

Rear Buffing Plates 194

127

Ø6

Front Buffer Beam Centre

56

12

14

53

205.0

6

36

30 205.0 Notch out to clear exhaust port as req’d 244

63

18

D PC

25

63

15

14 32

12

3

20

55

9

Front

8

34 8

5

9 148

20

6

107.0 Csk from behind and braze in long 8BA screws to secure buffers 210

10

Fig 9

20

42.5

35

38

8

5

88

Inner Frames

86

Location of vertical & horizontal frame stretchers between inner frames

9

9

Mat’l: 5mm mild steel plate (2 required)

135

31

Top view

12.5

4 7

Mat’l: 1.6mm MS

4.9

20

Front Buffer Beam Outer

630

Frame End Channels Expansion link CL

Braze plates together to form cyl. bracket Notch out front outside frame channel to clear cylinder

Cylinder Bracket

Fabricate from 20 x 20 steel angle welded edge to edge & then machined to size (2 front & 2 rear required)

2 required

60

100

31

11

Boiler firebox

192

Location of axle pump Horizontal frame stretcher

Backhead

Weighshaft

32.5

Valve CL Expansion link r127

Screw stretchers to inner frames then braze

Locate these holes from tapped holes in inner frame during assembly 65

Vertical frame stretcher

210 186 100

50.1

4BA screws to back of cyl. fixing block

86

17

Cylinder CL 4BA screws to inner frame

Horizontal Frame Stretcher

130

Mat’l: 6mm steel plate

Inner Plate For Cyl. Bracket 205

Plan View Showing G.A. Of Frames And Location Of Main Components

26

205 Drill & tap frame channel 6BA Secure outer frame with 6BA screws Rivet through buffing plate then braze outer frame & frame channel to buffer beam

16

14

56.5

8 5

17

8.5

65

20

r26

7 17

11 39 31

50 Rivet then braze inner frame & frame channel to front buffer beam inner

100

Drill & tap frame channel 6BA, secure outer frame with 6BA screws

Mat’l: 3mm MS plate (2 required)

112

Vertical Frame Stretcher

18 20

Sides For Cyl. Bracket Mat’l: 3mm MS plate (4 required)

Outer Plate For Cyl. Bracket Mat’l: 3mm MS plate (2 required)

Front Buffer Beam Hook Plate

Front Draw Hook

Mat’l: 6mm MS

Mat’l: 5mm MS plate File to shape

Mat’l: Fabricate from 6mm steel plate Screwed and brazed together

Design details for the chassis components. of the same phosphor bronze hollow bar that I had used for the cylinders, with ‘ears’ of brass silver soldered to either side. These were split through the middle ith a fine slitting sa and machined up to fit the eccentrics.

Photograph 19, taken much later in the build, shows the finished eccentric straps in place and connected up to

the valve gear. The boiler will sit between the wheels immediately above them. The space limitations are obvious.

The small brass spigots sticking out the right-hand side of each eccentric strap are for e ible silicone lubricator pipes that will bring oil down to the eccentrics from reservoirs on the running boards. The eccentrics are otherwise quite

inaccessible once the boiler is in place.

The chassis In the meantime, I had detailed out the frames and plates (fig ) that make up the chassis to a point where these could go

out for laser cutting (photo 20). bit of filing, some riveting and a little more silver brazing and the kit of parts turned into the basic framework (photo 21).

The two inner frames and the front and rear buffer beams are riveted and brazed together

20

19

A kit of mild steel plates ready to be put together.

21

Looking straight down on to the main axle between the driving wheels.

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>>

Frames partly assembled.

495

Ø16

Fig 10 Ø12

Ø1 8

Ø12

42

Mat’l: 4140 steel round bar Ø16mm

Outer Frame

18

14 inside

10 7

3

22

Outer Frame

Driving axle CL

9

5

Ø14

30

3

Axle Bush

38

Mat’l: Bronze

2

Leading/trailing Axle Horns

26

24

Mat’l: 5mm MS plate (4 required)

12

4

28

10

10

8

Braze small plate on back of horn to provide extra material for suspension pocket

8

18

Coil spring suspension pocket milled in horn/frame

69

18 5

42 54

Ø18

8

Rivet horn to outer frame with 3/32” steel rivets then braze

116 200

Leading/Trailing Axles

34 22

Leading/trailing Axle Keeps

18

2.0 Ø1

22

Mat’l: 3mm steel (4 required)

Axle Box Cover

Leading/trailing Axle Box Assy

Mat’l: Fabricated brass

Mat’l: Cast iron body & bronze bush 116 186

Part Cross Section Ø25

15

Outer Frame

Outer Frame

15

4

15 16

47 63

Through leading/trailing axles 70 40

1

Ø25 Ø16

110

14

40 36

Oil pocket

Inner Frame

Mat’l: Bronze

Driving Axle Keep And Frame Stiffener

Inner Frame

100 Eccentric positions are Indicative only

3 5

Mat’l: 5mm steel

Rivet horn to inner frame with 1/8” steel rivets then braze

50

Outside face of inner frame

6

Ø20

Axle Bush 2

63 15

25

D&T 4BA into frame/horn

8

6 Ø1

D&T 4BA

12

83

Ø2 0

36

Driving Wheel Axle Boxes 8

70

Driving Axle Horns Mat’l: 5mm steel plate (2 required)

116

D&T 6BA for locating pin

Part Cross Section Through driving axle

27

13 10

Ø16

Ø14.5

Spring Suspension Plate Mat’l: 3mm steel (2 required)

8

5

10

Spring Buckle (2 required)

Ø4 Braze hanger rod into clevis, thread & screw into spring pin Ø6 .5

Spring Hanger 19

(4 required)

116 154

Ø3 .2

88

Ø6.5

Locating hole

8

GA Of Driving Axle Suspension

13 9

Braze suspension rod into buckle & suspension plate

8

Ø3 .6

5.5

35

15

34 25

Detail Of Top Spring Leaf Spring leaves: 0.8mm spring steel 10mm wide, cut length to suit.

Substitute tufnol for some leaves to adjust spring rate if req’d

Driving Axle Mat’l: 4140 steel round bar Ø16mm

Axle and suspension details. to form a rigid central core for the chassis. In addition, there is a vertical and a horizontal frame stretcher that is screwed then brazed across the inside of the inner frames ust behind the cylinders, to add even more rigidity. The horizontal stretcher also provides a convenient place to mount the axle water pump. This core part of the chassis is never disassembled again; however, the outer frames and other components are screwed on to it and they are all removable.

The wheel sets had already been completed, so no ust needed to machine up the axle boxes, fabricate two large springs and hangers for the main axle boxes and sort out a fe other minor fi tures and fittings fig ).

496

This was quite an exciting part of the build, because it seemed to go from a lengthy period of head-scratching, problem solving and fiddling with drawings on the computer to something that began to look like a real locomotive surprisingly quickly (photo 22). did have some difficulties fitting up the cylinder assemblies which had also been made earlier. As these are turned inwards so the valve chests sit at an angle facing in towards the smokebox, it as a little difficult getting the cylinder mounting blocks silver soldered at exactly the correct angle during initial fabrication.

The error I made during fabrication came back to bite me during assembly of the chassis, as the two sides ended

up being slightly asymmetrical and things like the valve centres and the connecting rods did not quite line up as they were supposed to.

o ever, some udicious fiddling and application of shims in appropriate places eventually sorted the problems out, and the front view of the

22

A rolling chassis!

Model Engineer 5 April 2024

CORNWALL

Fig 11

(Check valve centre dims from job) Linkage to 86 machanical lubricator (one each side) Valve 50.1

65.5

Driving axle CL

Cylinder longitudinal CL

280

114.5

50 stroke 175

Cylinder vertical CL

25

Engine vertical CL

Rocker

Valve CL

30.3

ec

arm

nn Valve co

Valve rod

vertical CL

tion rod

Driving axle CL Part inner frame LH side shown

Part outer frame LH side shown

Outer Frame

Side View Of Cylinder Crosshead & Connecting Rod Assy

To machanical lubricator

Mat’l: Steel (2 required)

Cross Section Through Cylinder Crosshead Assy

13 10

Top View Of Valve Crosshead And Connecting Rod Assy

3

Mat’l: Phosphor bronze (4 required)

175

12

19 13 12.5

11 Thread & pin clevis to connecting rod

14

30

Braze big end on to connecting rod

2

Connecting Rod Assembly r33

3

Press bushes into clevis

Crosshead Slipper

Inner Valve Crosshead Guide

30

Ø14

Mat’l: Phosphor bronze (4 required) 6

Mat’l: Steel (2 required, LH & RH) 32

Drill, tap & fit oil cup for big end

Drill oilway through to pivot

(2 required, LH & RH)

Section Through Valve Crosshead Assy

10 20

Ø11

Ø9 .5

Clevis Bush

Mat’l: Steel (2 required)

Bore recess Ø10 2mm deep

Secure with collar & pin Locate holes for valve crosshead guides from holes in inner frame during assy

Mat’l: Steel (2 required,)

Crosshead Body

Fix with 8BA screws

Check height of slot from job

Connecting Rod Big End

12.5

2

8.9

40 25

Ø14 Ø8

Pivot Pin Mat’l: 4140 steel (2 required)

Mat’l: Phosphor bronze (2 required)

Ø1 0

Mat’l: Phosphor bronze (2 required)

2.5 Ø1

12

Press bush into big end

Big End Bush

Ø14

Outer Bush

Mat’l: Phosphor bronze (2 required)

4 3.25

30 8

2.5 Ø1

16

Valve Rod Bush

Mat’l: Phosphor bronze (2 required)

3

Inner Bush

12.5

24

6

6.5

Ø5

5Ø

9 2 Ø6 Ø5

6

6

Ø12 Ø10

Ø14 Ø11

0 Ø1

6.25 3.25 2

28

9

22

16

Rocker arm

Ø6 Ø5

36

22

Crosshead Body Pin

38

Ø12.5

Valve connecting rod

Valve rod

3 12

Inner Frame

Side view of valve crosshead & connecting rod assy

Ø1 0

Fix crosshead support with 6BA screws

Locate holes for valve guides during assy, D&T 8BA

19 Check height of slot from job

5

40 25

Connecting Rod Clevis

Oilway

Mat’l: Steel (2 required)

38

6 10

20.5 Dimple for retaining grubscrew Ø8

13 20.5

Crosshead Pivot Pin

Mat’l: Steel (2 required)

Mat’l: 4140 steel (2 required)

Valve Crosshead Clevis Mat’l: Steel (2 required)

Cut out to clear leading wheel Locate from holes in guides during assy D&T 6BA

Locate from holes in guides during assy, D&T 6BA

35

6

Outer Valve Crosshead Guide Press inner and outer bushes into valve crosshead clevis

80 Locate from frames D&T 5BA

Upper Crosshead Guide Support Channels 7.5 3.5

6

Braze end to valve rod

Valve Rod End Mat’l: Steel (2 required)

Locate from holes in frames during assy, D&T 6BA

Press bush into clevis

12 12.5

Valve Connecting Rod Clevis Mat’l: Steel (2 required)

Thread & pin to piston rod (LH/RH)

Crosshead Body Sub-assy Fabricate, braze & bore cross-hole for pivot

Lower Crosshead Guide Support Channels Mat’l: Fabricated 20 x 20 steel angle welded edge to edge & machined to size (2 required, LH & RH)

6

34

Press valve rod bush into valve rod end

20 3

5

Location of oilway (top guides only)

30

Ø8

Braze end to connecting rod

3 5.5

80 2

11

90

30

Ø5

38

20

(2 required, LH & RH) Drill & tap for retaining grubscrew 30

Crosshead Guides Mat’l: Steel (4 required)

Crossheads and connecting rods.

23

24

ront view with cylinders fitted. locomotive now looked as shown in photo 23. finished the crossheads and connecting rods (fig ), which I made as close as I could to the details I could see in the photos, as these are very prominent and visible features of Cornwall (photo 24).

e now have a rolling chassis with cylinders fitted and pistons that go back and forth as the wheels go round. rogress indeed!

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497

>>

Fig 12

6

Spacer

6

Mat’l: 3mm steel (2 required)

Lifting Link Top Bush

Mat’l: Phosphor bronze (4 required)

Mat’l: Phosphor bronze (2 required)

Lifting Link

Ø5 Ø4 Mat’l: Phosphor bronze (2 required) press into die blocks

Mat’l: 6mm gauge plate (2 required)

Ø1 3

6.0

Lifting Arm Bush Mat’l: Phosphor bronze (3 required)

(2 required)

Mat’l: 5mm steel (2 required)

18.6

Ø1 0 Braze reach rod arm into reach rod bush 10 15

Reach Rod Bush

Secure with collar & pin

Ø8 Press lifting arm bush into reach rod arm

Reach Rod Arm

Reach Rod Arm Assy.

Lifting Link Assy Expansion And Lifting Link Assy (2 required)

Mat’l: 5mm steel

(2 required, LH & RH)

Axle & eccentric CL

100

Mat’l: 4140 steel (2 required)

Front Braze lifting arms to weighshaft

Ø12 Ø6

Valve CL Valve rod

64 38.1

Rocker secured with collar & pin

Side view

Weighshaft And Lifting Arms Assy

Lifting arm

86

Rocker pivot (fit through hole in inner frame)

Ø8

Die block secured Braze die block with 1mm split pin pivot into rocker Die & thin washer block

4.9

Weighshaft 124.1

Setout Of Valve Gear On Inner Frames

Ø6

25

Front Fwd

117.6

Lifting link

Rev eccentric rod

Mat’l: 12 x 3mm steel

Bend rocker to align with valve CL

90 °

Rev

2.5

Axle CL

Reach Rod

Press rocker bushes into rocker

Valve CL

43.1

43.1 arm Rocker

nnectin g rod Valve crosshead

70

Reach rod to reversing lever in cab

Ø8

20.9

17.5

Pin reach rod arm assy. to weighshaft View from above

Valve co

Inner frame

Rocker pivot

Mat’l: 4140 steel

Mat’l: Phosphor bronze (2 required)

Ø6

Mat’l: Phosphor bronze (2 required)

117.6 Fwd eccentric rod Crank

Reach Rod Pin

Rocker Bushes

Weighshaft Bush

LH eccentrics only shown Reach rod to reversing lever in cab

127

13

17.5

Ø6 Ø4

6 3

Die Block Pivot 100

3

6

17.5

GA Of Valve Gear

Press lifting arm bush into each link

Ø

4 Ø1

.0 Ø4

Ø8

Mat’l: 4140 steel (3 required)

3.5

15.0 8.1

20 PC D Ø25

Weighshaft

Lifting Pin

38.1

6.

0

Rev Ecc.

38.1

Ø8

16

Press bottom bush into each link

Fwd Ecc. Rocker pivot

Fix with M3 high tensile cap screws

Braze top bush into both links

38.1

Valve CL

Ø8

6

2

Ø6

Expansion link CL

Ø1

Mat’l: Steel Inner Frame

12 PC D

Lifting Arm

View from front 32.5

Braze rocker pivot into base

Rocker Pivot

Die Block Bushes

Die Block

Ø1 2

38.1

Ø6 Ø8

6.2

8

Ø6

Mat’l: 6mm gauge plate (2 required)

Ø5

15

Mat’l: Steel (4 required)

Expansion Link

Mat’l: 3mm steel (2 required)

Ø8

Pivot Pin Base

Lifting Link Bottom Bush

Ø8

16.5

r123

Mat’l: Phosphor bronze (4 required) Press into expansion links

Ø8 Ø12

4

50.5

12

Expansion Link Bushes

3

10.5

Mat’l: 4140 steel (2 required)

Ø3

11.3

Pivot Pin

Ø3

Ø5

12 6

Braze pin into base

Ø6

6.2

Ø6

38.1

9 3

Ø5 Ø10

Ø6

3 D&T M3 19

8 Ø6 Ø8

Ø8 12 Ø

6 12

0.8

10.5

8.5

Rocker And Die Block Assy

Developed Rocker Profile

(2 required) check dims on job

Mat’l: 3mm steel (2 required)

Reach rod

Details of the valve gear.

Fig 13 T.D.C.

D&T 3/16 x 40 6

3.25

3.25 7.5

22

11.5

Fully open front + 6.55mm Fully open rear - 6.55mm 26.4 Exhaust port open

6

ic ntr 4° ce e 2 Ec angl tri Inlet port open

Cutoff = 75% B.D.C.

3

19.7

12.5

5.6

Valve And Drive Dog

24°

13.1 6.55

20

Valve And Port Dimensions 25

4.8

7

Zeuner Valve Diagram 3.35

3.35

26.4 12.5

Lap - 3.3mm Port opening - 3.25mm Valve travel - 2 x(lap + opening) =13.1mm Cutoff - 1 -(2 x(lap + opening)/travel)^2 =75%

Crank

Eccentric advance angle

Eccentric throw & valve travel

Valve timing.

498

Model Engineer 5 April 2024

CORNWALL

25

In late 2019 there was a disruption to progress caused by the arrival in my workshop of a certain Flying Scotsman locomotive, which diverted my attentions for some time. But that is another story!

The valve gear

Here is the almost completed valve gear seen from the front of the locomotive.

hen finally got bac to Cornwall after completing the Flying Scotsman pro ect, there were some fairly tricky details to be sorted out with the valve gear his all needed to fit in between the frames, and as previously mentioned regarding the valve eccentrics, the valve gear must not foul the bottom of the boiler, sitting between and ust above the main a le I drew up the valve operating mechanism in considerable detail and checked the design parameters against the formula and procedures given in Don Ashton’s book Design Procedures for Walschaert’s and Stephenson’s Valve Gear (fig ).

I also ran the design parameters through two versions of valve gear

26

A close-up of the reversing lever, fitted to the frame at the rear where it will be accessible inside the cab.

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simulation software, which are available free on-line from Charles Dockstader and Dr. Allan Wallace. I used the information obtained by fine tuning the simulations to determine the exact lengths of the pivot arms and the correct placement of the pivot points, and to determine the optimum advance angle for the eccentrics.

I even went so far as to draw a Zeuner Diagram showing geometrically the timing and cut-off I should expect, as shown in fig 3. The Zeuner diagram shows the relative opening of the ports (the hatched areas) as the crankshaft rotates through a complete cycle from top dead centre (TDC) to bottom dead centre (BDC) and back. This was a method of analysing steam valve gears developed

by German engineer Gustav Zeuner in the 19th century, nowhere near as sophisticated as more modern valve gear analysis and certainly not as useful or accurate as the software simulations, but an interesting exercise nonetheless.

In the centre of photo 25 is the small axle-driven water feed pump, with the left and right-hand side valve gear sandwiched in beside it. The motion for each valve rod is brought up from the die block down below via a cranked pivot arm.

Missing in photo 25 is the remaining connecting linkage between the rocker arm and the valve rod crosshead – this is still a work in progress.

The reversing lever, however ( ), was added at this stage.

The valve gear was probably the most difficult although not the most fiddly part of the locomotive. That was because I was trying to get a somewhat overscale design to fit into a very limited space between the frames and under the boiler. In the end, I think it has turned out to be quite robust and should provide smooth and reliable running (I hope!)

To be continued.

499

G1 or 16mm Locomotive Radio Control using BBC micro:bit Computers 1 Malcolm Batt shows that building your own radio control system need not be complicated.

oundhouse ate before fitting cab showing control servos fitted.

2

itronik ove robot.

500

Introduction This article describes a method of using a pair of BBC micro:bit computers to provide an economical radio control system for Gauge 1 or 16mm model steam locomotives.

The project started during lock down when I decided to build a 32mm locomotive to run on the track at the Wimborne Model Engineering Club. I started to develop a loco of my own design but being new to this gauge (my previous build was a 5 inch Sweet Pea) I soon realised the difficulties and comple ities of providing the mechanics at this smaller size, so I purchased a set of kits from Roundhouse

Engineering (photo 1). This picture was taken during the development phase before the cab as fitted lthough a lot of our members like to buy ready to run locomotives for each of the club’s gauges, I like the challenges and satisfaction of running something that I have built. So, when it came to providing a radio control system, the same challenge was there. s ell as being an active member of our model engineering club, I also help run an engineering club at a local school. Our projects, which we roll out to the students, include robotics which are based on the BBC micro:bit computer.

Model Engineer 5 April 2024