Model Engineers' Workshop issue 4729 FREE 20 PAGE PREVIEW

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THE ORIGINAL MAGAZINE FOR MODEL ENGINEERS Vol. 231 No. 4729 3 – 16 November 2023

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Buckeye Coupling

Rob Roy Rally We report from Bromsgrove

Prototypical coupling for an A4 and Pullman cars

Explosions

The dangers lurking in apparently benign substances

B1 BOILER

For Thompson’s LNER loco

637 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

616

EDITORIAL Editor: Martin R. Evans 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 advertising manager: Sue Keily Advertising: Craig Amess camess@mortons.co.uk Tel: 01507 529537 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

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Vol.231 No.4729 3 –16 November 2023 608 SMOKE RINGS News, views and comment on the world of model engineering.

for details.

629 RADIAL VALVE GEARS AGAIN Duncan Webster explores the subtleties of valve gear operation.

609 A FIVE-INCH GAUGE 0-4-0 PADARN RAILWAY TENDER LOCOMOTIVE

633 A METHOD OF MANUFACTURING PISTON RINGS OF THE CLUPET STYLE

Luker presents Fire Queen, a Welsh slate quarry locomotive.

Martin Gearing exposes the secrets of making Clupet rings.

614 ROB ROY RALLY 2023 SUBSCRIPTION Full subscription rates (but see page 606 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.

Rex Hanman finds a healthy turn-out of Rob Roys at the Bromsgrove SME.

637 GOING WITH A BANG Roger Backhouse recalls some explosive experiences at the York SME.

616 BUCKEYE COUPLING FOR 5 INCH GAUGE Jonathan Buck creates a set of fully working buckeye couplings for an A4 locomotive.

641 LNER B1 LOCOMOTIVE Doug Hewson presents a true to scale five-inch gauge model of Thompson’s B1.

618 BOOK REVIEW Roger Backhouse catches up on mediaeval metallurgy by reading The Perfect Sword by Paul Gething and Edoardo Albert.

619 A MODEL ENGINEER’S CLOCK Jim Clark uses modern methods to make a skeleton clock inspired by John Wilding.

646 A NEW WORKSHOP Peter Seymour-Howell takes a break from building Flying Scotsman to build a new workshop.

648 PERCIVAL MARSHALL Ron Fitzgerald examines the life story of our

624 A PEEK BEHIND THE CURTAINS Steve Goodbody reveals the principles behind, and practice of, adaptionism.

founder and first editor.

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

628 OBITUARY Ken Wood remembers Nigel Thompson, former secretary of the Northern Association of Model Engineers.

THE ORIGINAL MAGAZINE FOR MODEL ENGINEERS Vol. 231 No. 4729 3 – 16 November 2023

655 CLUB DIARY Future Events.

ON THE COVER...

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Buckeye Coupling

Rob Roy Rally We report from Bromsgrove

Prototypical coupling for an A4 and Pullman cars

Rex Hanman demonstrates the steaming up process to Jack Irvine at the Rob Roy rally (photo courtesy of Rex Hanman).

Explosions

The dangers lurking in apparently benign substances

For Thompson’s LNER loco

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£4.95

B1 BOILER

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Midlands Show

MARTIN EVANS Editor

DIANE CARNEY Assistant Editor

I write this having just returned from the Midlands Model Engineering Exhibition at the Warwickshire Events Centre ( The osse ). or the first time, Model Engineer had a stand at the show, next to our stable-mate the Society of Model and Experimental Engineers (SMEE) who, along with us, were celebrating their 125th anniversary. It was very good to meet so many readers over those four days and I hope you enjoyed the show as much as I did.

For me, of course, the main attractions were the various locomotives on display. The most impressive, perhaps, was the 10¼ inch gauge LNER 2001 Cock o’ the North P2 locomotive, which currently lives at Stapleford Park. This is a model locomotive on a huge scale and was built by John Wilks, whose day job was as an academic and conductor of operas a fine example of the great diversity in the followers of our hobby! For me, perhaps, the locomotive of the greatest interest was Alan rossfield s latest, a inch gauge GWR pannier tank. This is because, of course, I have a nearly complete pannier tank in my workshop at home with its plumbing hanging out and Alan’s work is an inspiration.

I am mildly disappointed that it is BR black rather than GWR green but, as Alan rightly points out, this is correct for the prototype he is following, no. in the late fifties.

On display on the SMEE stand was the Duke of Edinburgh trophy, formerly

5-inch gauge GWR pannier tank 7713 (photo by Alan Crossfield).

608

Cherry Hill visits the Midland Model Engineering Exhibition (photo by John Arrowsmith). competed for in the Model Engineer Competition by previous gold medal winners.

The SMEE stand was visited

by Mrs Cherry Hill, nine times winner of the trophy, who was able to inspect some of her prize-winning models, displayed alongside the trophy.

IMLEC 2024 As I reported last time, next year’s IMLEC will be hosted by the Southport Model Engineering Club, with the support of the Leyland Society of Model Engineering. The dates for the event have now been decided – it will take place from Friday July 19th to Sunday July 21st 2024. So – get that locomotive ready and start practising! More details about the rules and about entering the competition will appear here nearer the time.

over 60 engines now joining the range alongside the Burrell traction engines, fastenings and materials already available.

‘EKP Supplies are the largest manufacturer and stockist of BA fastenings in the industry. Following a move to larger premises in 2021, the expansion of the company is going from strength to strength.

‘For any questions of requirements, please contact us on 01271-346441, sales@ ekpsupplies.com or visit our websites www.ekpsupplies. com and www.kennions.co.uk ‘ This is very good news, in my opinion. Kennions is, I believe, the oldest model engineering suppliers and it is good to see it continue in business. I remember visiting the old shop when it was located in Hertford, just across the road from the Hertford East railway station, and presided over by Mrs Kennion. The business seemed to specialise, at the time, in many of the older designs (not surprisingly) by Charles Kennion, Keith Wilson and LBSC. I wish Kennions all the best in its new lease of life.

EKP Acquire Kennions EKP Supplies have contacted me with the following.

‘EKP Supplies, based in Barnstaple, North Devon, are pleased to announce the purchase of Kennions Locomotives in September, allowing the continued supply of these locos for the future.

‘Company director, Alan Pocok, comments “Kennions has been a brand name in the model engineering world since the 1950’s and it is an honour to be able to ensure the continuation of these models for the future. These locomotives, alongside our Burrell traction engines, provide plenty of options for the model engineer to build and enjoy for years to come.”

‘This move will allow EKP to become a one stop shop for model engineering needs with

EKP Supplies

Kennions

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

Model Engineer 3 November 2023

A Five-Inch Gauge

0-4-0 Padarn Railway Tender Locomotive PART 15

151

between 65-70psi. Mr Lander did some interesting load tests on the springs which showed that the actual working pressure was closer to 50psi when aligned to the wear marks on the actual spring gauge (ref 3). The safety valve cover for the Fire Queen’s sister loco, the Jenny Lind, had the hole for the Salter valve closed off neatly. There were two additional holes that looked like the regulator rod went through the safety valve cover instead of around the cover like the Fire Queen, possibly between two standard safety valves?

For the model I used the more conventional model engineering type safety valve (fig 30). With the stainlesssteel boiler, I needed a safety valve that could handle a slightly higher heat removal rate. I also wanted the top

Luker builds a five inch gauge model of a Welsh slate quarry locomotive.

Continued from p.586 M.E.4728 October 20

The safety valves under the ornamental cover at the museum. Note the substantial ring, probably to prevent condensate from damaging the lagging.

The safety valve

(photo 151). The working pressures quoted by the ‘internet experts’ range from 60-100psi but the wear marks on the Salter gauge are clearly

7/16 x 32 ME

12.7 sq.

M3 - oil before steaming

2 8

8 15

M2 M3 lock

Ø16

Blower Valve Coupling

M2

11

20

Ø6.8

Ø2.5 Break corner

26 16.2

Ø6

2

Ø10.1

3/16 x 40 ME

x M 8 deep comp. union

10°

For packing to hold safety valve cover

Ø3

25

1.5

. sq.

35

Ø2.5 2 sq.

Ø7

10

6

5

Ø3

1

The large-scale Fire Queen had two distinct safety valves, the normal spring type and the Salter type safety valve

Mat’l: Brass

5

Ø1.5 5/16 x 32 ME

Blower Valve

Ø5.5

Tolerance takeup 7 for orientation

sq .

Silver solder

2

7/16 x 32 ME

Ø3.6

Ø6.4

10

Mat’l: Body brass

Ø4.5 2 Ø3.6 Ø6

Safety Valve Springs Mat’l: SS316L Wire Ø1.2mm Ø2 8 holes Active coils 6.5 6.6 PCD Free length 17.5mm Ø4mm mandrel

13.2

2 5

4 20

Ø8.5

4

90°

15.5

Blower Spindle

1 r2

Mat’l: Stainless Pilot hole Ø3.5mm

Safety Valve

3

Blower Lever

Stopping Plate Mat’l: Stainless steel or bronze

Mat’l: BMS

Small gap to pull down onto lagging Ø55.2 4

Ø5

Ø3 Ø50 Ø3

Ø42

8.2

Ø35

Blower Assembly

32.5

9.8

Locking nut

Fig 30 >>

Safety valve and blower.

www.model-engineer.co.uk

609

152

153

Machining the step on the inside to make sure the spring does not close any of the steam holes. of the safety valve to lie just below the ornamental cover with a sealing ring between the two to prevent unnecessary condensation from falling onto the boiler lagging.

The safety valve is incredibly simple to make and requires little description, other than the top adjustment nut. Some designs have the springs cover the holes which limits the flow of steam from the boiler. If a step is cut on the inside, the spring can rest on the step and the flow area is increased to the sides solving this problem without drastically changing the design principle (photo 152). I normally drill the holes around the periphery using co-ordinate drilling and a split square nut. 4 holes are drilled on the PCD, the nut released, turned 45

Fig 31

Steam regulator flow path and features.

610

Drilling the steam exhaust holes in the safety valve nut using a split square bar for alignment and clamping. degrees, and the remaining holes drilled. Turning the nut can be done by eye, which is probably better than trying to work out angles on a rotary table, which invariably results in the last hole looking far out (photo 153).

The regulator The original steam regulator had a two-valve system (one to each cylinder) with each valve having the radiation-symboltype (sic) port face, activated by a common lever (a picture was shown in the very first part of the series). This would be very difficult to balance properly on scale, so the model

regulator has a completely different slide valve system that is inherently balanced. The original also has a perforated steam pickup pipe that runs along the length of the boiler with a common collector pipe to the inside of the regulator.

This pipe was omitted in the model to improve the live steam volume and water level range. The steam flow is a little difficult to visualise in the drawings with fig 31 doing a better job explaining it than I can in words!

The regulator assembly for the model (fig 32) was broken up into sections with the dead steam volume kept

to a minimum to prevent unnecessary condensation and priming. The bottom piece of the puzzle (photo 154) required a few drilled holes, lapping the sealing surfaces and a little soldering. The hole positions aren’t that critical and just need to match the boiler mounting flange bolts to get the assembly to align with the boiler and the cylinders.

Each section was drilled using the drilling jig (first used for the boiler flange) but misalignment is inevitable due to the material and the depth of the holes. Two holes were conveniently picked and the assembly bolted together with a drill run through each hole to open them up to match the whole assembly.

The gland piece of the regulator puzzle was a simple casting with the gland sporting an extended spigot to help with alignment in the lathe (photo 155). The casting was clocked at the outer gland extrusion surface, using my touch and engage method, but the spigot got me off to a good start. A tightly fitting centre spacer is probably a good idea to prevent the jaws from crushing the casting or, even worse, causing the tool to bite and ripping the job from the jaws because of the geometric flex in the system. Machining the gland and casting is all done in one go and requires little description (photo 156).

154

Valve ports and lapped valve surface with steam pipe flanges ready to be silver soldered. Note the Tippex to prevent the silver solder from flowing onto the lapped surface.

Model Engineer 3 November 2023

FIRE QUEEN

Fig 32 58 Circumference = 167.5 6 M2.5

M3

42

38.4

Ø2

Regulator Mount 3

Ø4

Mat’l: Stainless steel

r7.5

2. 6

Ø2

9 7

Regulator Rod

Regulator Ring Rod

Ø2

13.2

4

Ø2

148.5

r2

3

2

2.4

4

Ø2

16.7

Ø26

3 6

M3

2 42.1

4

r2.5

Ø48 61 r22.2

Safety Valve Cover

Ø7

Ø3

Ø1.2 M2

Ø51.3

Mat’l: Brass 11

Ø3.1

13.9

Regulator Handle Mat’l: BMS or 2mm stainless steel

5

16.5

Ø4.5

5 r2

Ø2

6 9

Ø3.5 4.2

15.8

4.5

3

6.5

3

12.2

Ø32 Ø16

5

Solder

M3 1.6

36.1

1.3

13.9

9 Ø5

Regulator Dome Gland

To mechanical lubricator 6

Ø41 Ø45

M2.5

Mat’l: Brass

2 1

Mat’l: Brass

Regulator Dome Section Ø22

Ø8

6 2

Ø35

Ø35 M2 Ø3

16.7 11.1 min

Ø6

Valve Buckle

4.3 Ø5.6

Ø6

Ø3 for ball & spring

M3

5.4 Ø11 4

2.4

8

1 1

Ø11 2

Steam Dome Cover

Mat’l: Bearing bronze

5 1

Ø5

Mat’l: Brass, painted red

4 6

Ø1

9

4

Ø5.5

Ø5

Regulator Rod Guide

Ball & spring not shown

2

0.5

Ø4

Same profile as gland

17

Regulator dome gland Regulator steam flange

9

5 6

6

8

Slide valve Valve buckle

Ø3 Ø5

3* 4*

Mat’l: Bearing bronze

4

4

Regulator seat bottom Regulator casing

14

1 2

7.5

Item no. Part name

Slide Valve M3 6 deep

2

Ø2.5 3/16 x 40 ME for oil line to lubricator comp. union

Ø5

9

5

Regulator steam flange to match valve chest, 5mm thick piping to have loose flange comp. union Lap surface

Ø23

Regulator Seat Bottom Mat’l: Bearing bronze

Ø23

Regulator Casing Top & Bottom Mat’l: Bearing bronze

Regulator assembly and parts.

155

Using the casting spigot to align the gland section of the regulator with the four-jaw chuck.

www.model-engineer.co.uk

156

Machining the gland before parting off and finishing the female part.

611

>>

157

158

The safety valve cover and steam dome cover cast from the parting line to limit the effect of gas entrapment on the outside surface.

159 Simple bars and pointers are used to align any as cast surface to get the best position for the studs. This is preferable to following the drawing dimensions blindly.

The gland is finally drilled and tapped for neat little studs using the drill or milling machine. Because I was dealing with as-cast surfaces the use of geometric aids to line up everything was necessary. For example: a threaded rod with a sharp point held in the drill chuck will align the casting to the spindle; a round bar with a similar radius to the outer flange can be used to align the drill-chuck to the best-looking position of the gland (photo 157). I tend to follow any stud dimensions with a pinch of salt (even my own!) because there is no guarantee that the casting came out perfectly or that the first machining operation was perfectly aligned. If the previous centre line is followed as gospel, you may end up

612

with the studs exaggerating any misalignment, making the part look terrible. It’s incredible how the eye picks up tolerance stack-ups!

The steam dome and safety valve ornamental covers The safety valve ornamental cover on the large-scale Fire Queen has four parts which were soldered together. The joint lines for the ‘parts’ ran vertically down which indicates the parts were made around a former before final joining, rather than rolling. Incredibly it takes a keen eye to see this join at the museum; I could not pick it up on any of the pictures I had at my disposal, which just goes to show the level of workmanship in those days.

The cast, machined and polished safety valve cover.

Model Engineer 3 November 2023

FIRE QUEEN

160

161

Blower valve cover (machined) casting. Wooden cladding still needs to be fitted.

The steam dome cover for the model. Interestingly enough the steam dome fitted to the Fire Queen at the museum is actually for the Jenny Lind, with the original damaged in storage.

I wish I could say my cover was made in a similar fashion but I’m lazy! All three of the ornamental covers were 3D printed and cast. Interestingly enough, because the covers needed to have a good surface finish (and polished to a perfect shine), they were cast on the split line (photo 158). In doing this, all the surfaces at the bottom of the mould end up much cleaner because the gasses or slag float to the top and any draw will be from the top of the mould down the middle. If these were cast in the conventional manner any gas or slag would end up on the highest rim of the cast component i.e. one side will be perfect and the other side poor.

All the castings had convenient spigots to make machining easier, with only simple boring and polishing required to finish them off nicely (photos 159 and 160).

The steam dome cover has a central screw that holds it in place, making it easy to remove for a little buffing before a steam day.

www.model-engineer.co.uk

The regulator handle and rods The regulator handle was made from a sliver of plate, the holes drilled in the correct position and the bosses around the holes filed using radius guides.

This is one of the components that weren’t included in the original laser cutting order and is probably left for the workshop experts instead of the industrial professionals to get the job looking good. After all, it is the centre piece of the top backhead. The handle is a simple turned component with a small dimple left to align with a tiny hole drilled in the plate for final soldering.

The handle needs to be bent slightly backwards, in an arc, around a piece of scrap bar.

With everything assembled and the regulator fully closed the handle should stand upright.

The couplings are one of those items that, when first made, is difficult. Once you get the hang of it, it becomes one of those run of the mill machining jobs required on any build. The rods are

a little trickier for this build and need to be made rather accurately for the regulator to open properly without clashes. For the most part it is a soldered assembly with the circumferential length of the oval piece given in the drawings. I rolled the circle, soldered the ends together and squashed it until it matched a scale printout. Once the loop is finished then the rest can be bent, cut and soldered into place, with small screws holding the lot in place for soldering.

The blower valve and cover The blower valve is a taper cock valve with a much larger spindle to prevent unnecessary leakage onto the wooden lagging. Another alternative that I considered was modifying a ball valve but, in the end, I went for this simple design. The spindle and seat need to be lapped properly to prevent leakage but with such a large contact surface area this should pose no problems.

The top screw is designed to be periodically removed for squirting a little steam oil into the valve after a day’s

steaming. Interestingly, any dry steam taper valve does need to be oiled periodically to prevent cold welding under the high steam temperatures. I’ve even had dissimilar materials i.e. brass and stainless cold weld on one of these taper cocks which prompted the periodic oiling.

The blower cover was a single casting and required only the slot and a hole to be drilled (photo 161). My pattern for this casting was a single piece with a green sand core rammed the usual way. The internal surface had a liberal draft angle but the outside had none.

This allowed the pattern to be removed without breaking the core because the outer sand kept it straight. The bottom of the cover is clad with wood and painted before fitting to the boiler.

To be continued.

REFERENCES Ref 3

Notes on the Fire Queen sent to the author, Eric Lander, 2007.

613

Rob Roy Rally 2023 1 Rex Hanman reports from the Bromsgrove Society of Model Engineers.

The revamped steaming bays. ow! What a difference a year makes. Following last year’s rather quiet rally, a dozen complete locomotives and chassis gathered at the Bromsgrove society’s lovely setting - a setting further enhanced by the new steaming bay canopy, built by

W

a dedicated group of members, and a fantastic job they have made of it (photo 1).

They say ‘never judge a book by its cover’. First to steam up under the new roof was Paul ootton from hesterfield (photo 2). With peeling and nonexistent paint, it must be one of the most tatty Rob Roys. But

2

Showing its best side, Paul Wootton’s engine wasn’t the prettiest!

614

there was nothing shabby about its performance! Trevor stormed around the track, completing lap after lap (photo 3). The author has seen and driven numerous ob oys since the first rally a decade ago but he has never seen one go so well.

As well as a Rob Roy rally, it was also something of a

3

As performances go, Paul’s took the biscuit.

Model Engineer 3 November 2023

ROB ROY

4

7

Trevor Wootton enjoying his run.

Jack Irvine studies the steam up process.

5

Will Taylor’s double header.

‘Wootton’ rally, as also running was Trevor Wootton from Rugely. No relation to Paul, Trevor’s black liveried example was soon running nicely (photo 4). Trevor’s water tank was well admired. Made from

6

Bryan Mellum polishes Haggis.

www.model-engineer.co.uk

an inexpensive stainless-steel money box, it was just the ticket.

A double header arrived from Worcester. Will Taylor brought both of his engines along (photo 5). One of them, started

when he was 15, is currently undergoing a repaint. Neither engine was steamed on the day.

Unable to attend the rally for a few years, it was good to see Bryan Mellum who brought Haggis from Wales (photo 6).

With appropriate Scottish roots, Jack Irvine, now from Oxford, is just embarking on a Rob Roy build. Eager to learn all he could, Jack had lots of questions, and was keen to observe the steaming up process as the author’s cheap paraffin once again smo ed out the steaming bays (photo 7).

A small display included Rob Roys from Gerry Annett, Mike Forman and Martin Sheridan

(photo 8) - one was for sale, for £1500. Peter Greenhaigh is about half way through his build. Will we see it in steam next year?

As usual, the day wasn’t uneventful. Host club member Dave Palmer suffered the same problem as the author did last year… no blower! Also from romsgrove, an orsfield lost his fire somewhere between the steaming bays and the station. A search party was unable to locate it and Ian returned to the steaming bays.

The date of next year’s gathering will be announced in due course.

ME

8

Rob Roys and friends on display.

615

Buckeye Coupling for 5 Inch Gauge

PART 1

Jonathan Buck equips a 5 inch gauge A4 locomotive with prototypical couplings.

616

noticeable recent trend in the model engineering world is the offering of highly accurate small components to give authentic detail to model steam locomotives. Several suppliers have diligently created various items, usually lost wax castings, that strike the useful balance between being functional, accurate in appearance and not too time consuming to add to a model.

Brake valves, manifolds, roller bearing covers, spring brackets, crossheads; the list goes on and, li e all apparently infinite lists, one will invariably find that the item really desired for a particular model isn’t on it, or isn’t readily available at the time it is wanted.

So how easy is it to make these things to your own requirements? This article will cover the construction of a couple of drophead buckeye couplings, using some modern manufacturing techniques, a Myford ML7-R lathe, Tom Senior E-type milling machine and assorted hand tools (photo 1).

Around the later part of 2017, my father’s 5 inch gauge LNER A4 was nearing completion. As No. 4497, Golden Plover, to be correct it was going to need a 1935-pattern corridor tender and for that to be complete it would need a Pullman gangway and drophead buckeye coupling.

There is nothing very novel about either of these. Dave Noble had been offering buckeye couplings for years, but around this time he was indicating a desire to run down his operation and we assumed

A

we wouldn’t be able to get any, so somewhere along the way I made a slightly rash offer to design and make one myself.

The offer was accepted so armed with a copy of the 10A nuc le coupler profile and a lot of carriage photos, I set to in CAD. After a few unproductive evenings, I decided that I had underestimated the task.

Part of the problem was that couplers tend to live in the shadows and only get photographed from one angle.

The other part was that they are really quite complicated. I needed better information.

As a slight historical digression, the drophead buckeye coupling has its roots in the US in the 1870s.

At the time, US railroads used link and pin couplings. This mode of coupling is extremely dangerous for anyone having to work with it, requiring the shunter to go between moving vehicles and persuade the link pre-attached to one coupling into the waiting pocket of the other.

The credit for devising an automatic coupler, which

would couple without human intervention when two vehicles were propelled together and could be uncoupled safely from beside the vehicles, is usually given to one Eli Janney of Alexandria, Virginia (a nice place to stay not far from Washington, should you be passing by), who patented one in 1873. This coupler evolved into the Master Car Builders Association (MCB) and Association of American Railroads (AAR) standard coupler which, on being made mandatory in US service, effected a vast reduction in the number of injuries on US railroads due to coupling accidents. This coupler has acquired various names down the years, the ‘Buckeye’ name common in the UK apparently coming from the Ohio rass oundry, who first marketed them.

When the Pullman Car Company introduced its luxury coaches to the UK in the late 19th Century, it also imported its system of gangways and automatic couplers wholesale from the US, at a time when corridor

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Two 5 inch gauge drophead buckeye couplings.

Model Engineer 3 November 2023

BUCKEYE COUPLING

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4464 Bittern and its 1928-pattern corridor tender (converted in preservation from a non-corridor original). connections between coaches were largely unknown in the UK. ‘Pullman gangways’ were subsequently adopted by the LNER and the Southern Railway for their corridor stock, while the GWR and LMS went their own way with BSI gangways, which had the advantage of working with screw couplings and conventional buffers but required manually clamping together before use. British Railways adopted the Pullman gangway as well, for its Mark 1 to Mark 3 standard coaches and they can still be found in diminishing numbers between vehicles on HST sets.

Corridor tenders, with a passage through the water tank and the same gangway connection as the coaches on the back, were introduced by the LNER on Gresley A1 and A acifics in , to allow crew changes mid-journey on non-stop London to Edinburgh services. The later A4s had some new corridor tenders built (the 1935 pattern) and the earlier tenders were transferred to them in due course, being modified to suit their streamlined profile (as shown in photo 2 behind preserved A4 4464 Bittern).

They remained a limited fleet many A1s, A3s and A4s ran with conventional tenders, but as previously mentioned Golden Plover had a corridor tender all its working life.

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The buckeye coupling is an integral part of the Pullman gangway system.

The gangways have a large sprung buffer plate at the bottom (known as the vestibule buffer) and a face plate round the circumference, with secondary springing at the top. Once compressed to a distance set by the coupler, the gangways are closed with no additional coupling required, as the vehicles move laterally through curves the faceplates and vestibule buffers simply slide across each other. hotogr ph 3 details these components on the tender of 4497. The model buffer beam is rather less busy than that of 4464’s tender, which carries air-brake and water connections added in preservation to facilitate main line operation.

Anyway, to run their Pullmangangway, buckeye coupled coaches in the UK, the Pullman Car Company had to provide a means of coupling to locomotives and coaches with conventional drawgear with side buffers, a coupling hook and chain. Thus was born the drophead buckeye coupling, in which a conventional coupling hoo is fitted with a coupler mounted on an horizontal pivot pin. A support pin passes through the body of the coupler and sits in the eye of the hook to hold the coupler

in the raised position; when the support pin is removed the coupler swings down out of the way, allowing a conventional screw link coupling to be placed over the hook. This is the form of coupling that appears on the corridor tender of an acific.

Some diesel and electric locomotives without corridor connections have been fitted with drophead buckeyes (usually those intended for push-pull services with the locomotive spending a lot of time propelling trains). The vestibule buffer has the useful benefit of pre loading the

coupler in tension to take out the slack in the coupling and damping sideways movement between vehicles, so on most British diesel and electric locomotives so fitted, you will see the vestibule buffer even though no gangway is present.

The rapidly disappearing Class 91s are a good example of this.

The swing-head buckeyes fitted on ex lass 66 diesels are a different proposition and will not be covered in this piece, but are basically a way of fitting full si e US buckeyes for block freight workings while also retaining conventional draw gear. No vestibule buffers are fitted in this case, since none of the stock to be hauled has them.

At some point in my quest for further information, I found the National Railway Museum’s drawing list for Pullman Car Company drawings in their collection. Main works drawing collections can often be rather sparse in their details of proprietary items like injectors and air pumps.

The main railway works often didn’t make these items, they bought them. But since the Pullman Car Company was a major customer for automatic couplers, it turned out that they had a significant number of drawings concerning the automatic coupling and draw gear.

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[1] Drophead buckeye, [2] Vestibule buffer, [3] Face plate, [4][5] Screw coupling (to be placed on drawhook) and buffers for coupling to non-buckeye stock, [6] Vacuum brake hose, [7] Steam heat hose.

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With so many drawings of potential interest (and potential uselessness), getting prints of all of them was financially unattractive. However, you can arrange a visit to the NRM’s Search Engine facility and request in advance the boxes of drawings to which you would like access at no cost at all. A ticket to York for the day and the opportunity for a wander around the museum afterwards seemed like much better value than trying to guess in advance which sheets would be most useful.

In late September 2018, I paid a visit to York. The facilities for examining drawings are excellent: good lighting, large tables, a variety of soft weights for holding drawings open and

small platforms from which to take an elevated view. As it turned out, the catch was very good. There were some ancient blueprints (yes, real blueprints) so delicate and crumpled I didn’t dare unfold them, but there were two well detailed sets of drawings for the coupler, draw gear and gangway arrangements for a Pullman car, one from circa 1925 and the other circa 1959.

The two good sets of drawings showed slightly different variants of the coupler body. Couplings have changed over the years on the surviving tenders, with lower shelf brackets added to reduce the risk of overriding in a collision, but there exists a fine photograph of the bac

of a 1935-pattern tender in grey, ma ing it either an official works photo in photographic grey, or from one of the ‘Silver’ batch of A4s. Either way, the date is likely to be close to the introduction of the tenders.

This shows a coupler with features more like those of the 1925 drawings, so I chose that set as the basis for my design.

With a good set of drawings to work with, I set to work in CAD once again. My intention was to model as close to scale as possible so for the main castings I modelled at 1mm to the inch to begin with. This was particularly convenient; the dimensions from the drawings simply went straight into the keyboard. Once a part was finished, would apply a scaling

factor of 2.25 and adjust any holes needing subsequent machining to a suitable round number size (2.25 mm/inch is the same to three significant figures as the conventional inch-and-a-sixteenth to the foot scaling for 5 inch gauge).

At this point I should probably make a quick disclaimer regarding units. Professionally and in all my CAD work, I use metric units. All the machinery used in making parts at home is imperial, while the measuring equipment and assorted drills and cutters provide a mix of both systems. I will reference whichever unit system is most relevant to the operation or dimension being discussed.

To be continued.

Book Review

The Perfect Sword: forging the dark ages Paul Gething and Edoardo Albert odel engineers have wide ranging interests so this fascinating book should appeal to many. Archaeology, historic metallurgy, Anglo Saxon history and military re-enactment are all included in a wide-ranging work.

The story starts with pieces of an Anglo-Saxon sword found at Bamburgh Castle in the 1970s. Put to one side, it was years before their significance was appreciated.

Careful examination showed that the sword was a prestige item, perhaps given as a gift, demonstrating highly skilled workmanship.

The book details some of the metalworking techniques employed. As steel billets

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were not of consistent quality several were forge welded together, folded over and reforged giving an interesting pattern on the blade. As with heffield made scythes many years later, Anglo-Saxon smiths knew the technique of sandwiching a steel edge (for sharpness) between iron pieces (for flexiblity).

Whilst metallurgical science contributes to the understanding of these weapons, what is also interesting is the role played by re-enactors. Those who re-create historic armour and weapons are often ready to develop metalworking skills in the pursuit of accuracy.

By using weapons, even in

dramatic conflict, they soon understand the need for different types of sword for varied battle scenarios. That understanding has helped expand our knowledge of Saxon and other historic era weaponry.

This readable book by two acknowledged experts abundantly confirms that the Dark Ages were not so dark when it came to metalworking.

Roger Backhouse

Published by Birlinn 2022, www.birlinn.co.uk ISBN 978-1-78027-784-4 £22, 264pp, hardback

Model Engineer 3 November 2023

A Model Engineer’s Clock

PART 4

Testing the Clock Jim Clark makes a skeleton clock making good use of modern manufacturing methods.

Continued from p.590 M.E.4728 October 20

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inally, all the essential components were together in the test frames (photo 21) and the moment of truth arrived would it wor nitially, the answer was o.

After the first few moments of disappointment, some investigation with the pallets removed from the test frames showed that there was too much friction in the drive train for the escape wheel to be driven freely by the spring, except at its fully wound state. emembering a warning read in one of the cloc boo s that the fits of pivots and bearing bushes in cloc s must be to cloc ma er s tolerances , not model engineer s tolerances, revisited all the pivot bushes with a tapered broach to ensure that each pivot contacts its bush only at the narrowest point, not all the way along. also re chec ed the burnish on the pivots and generally made sure everything was as free as possible, with a little side play and plenty of end play.

After doing all this, a further test showed that the escape wheel would now spin freely under the lowest spring power, and its momentum continued to drive the whole train for several seconds after the spring reached its stop point, until everything slowly coasted to a halt. This loo ed a lot better. ith the pallets re installed, this time the cloc sprang into life immediately. A little twea ing with the escapement engagement and the beat seemed to be even and stable.

A quic chec over about half an hour showed that it was running a little fast, which was adjusted via the pendulum rating nut. After running overnight, it was minutes fast by morning a pretty good result for a first run

21

The test clock ready to run. was very pleased and relieved that theory was borne out in practice. espite all the calculating and chec ing, and the fact that was following in the footsteps of many before me, there was always the possibility of some error or fundamental oversight on my

part that could have brought the whole project undone. ow to the fine tuning. tems to be looked at were: Performance under various spring power settings The main spring needs to drive the escapement through

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This chart shows the amount of pendulum swing recorded either side of zero, for each wound turn of the main spring, across the whole range of the spring. the drive train so that a good, reliable pendulum swing is maintained (photo 22 and fig 4), without over driving the pendulum to the point where the pallets might bottom out on the escape wheel.

At less than about turn of the main spring, the spring force is insufficient to sustain pendulum action, which commences at just over degree swing (this is also dependent on the adjustment of the escapement pallet depth).

Minimum spring force for reliable operation is between one and two wound turns. nterestingly, at between and turns (spring is fully wound) the pendulum swing action starts to reduce slightly perhaps the extra friction in

the gear train under these high torque conditions becomes a problem owever, in previous spring tests and calculations, we determined that we would select the required wor ing turns (as limited by the stop wor ) commencing from either three, four or five wound turns. The orange dotted line in hart shows how the pendulum will perform if we use the optimum range starting at three wound turns. This selection avoids the low torque area as well as the high torque area above nine turns. n summary, the current main spring will easily provide all the power we need.

The original design for the escapement assumed a

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This photo shows the 9-tooth pinion that meshes with the great wheel.

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A simple test rig was used to measure the amount of pendulum swing in degrees.

pendulum swing of degrees with a maximum deflection of degrees, so the actual performance is well within these parameters. The selected optimum range should give a pendulum swing of . degrees at minimum, up to . degrees at maximum. ote To minimise the effect of circular error (which will be discussed in more detail later), the variation in pendulum swing needs to be as small as possible in our case it is about . degrees between operationally wound and unwound states.

Great wheel pinion - excessive side play The great wheel pinion teeth are very thin in section, especially

at the base where they are only . mm thic . There is a lot of force applied here up to gf depending on the winding of the main spring, so long term wear and potential failure of the teeth are both of concern.

There is quite a lot of bac lash between the great wheel and its pinion about . mm, which could be reduced by thic ening the pinion tooth profile, which would both strengthen the pinion tooth and provide a longer service life (photo 23).

Ma ing such a small pinion for such a high load duty was always going to be a challenge.

Older cloc s often use a lantern pinion in this situation, comprising a circle of round rods held between two collars

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A typical lantern pinion.

Model Engineer 3 November 2023