Downton Train Crash of 1884 in EM Gauge

[Stevers]

Well hopefully not, although it's bound to fall off YMRG's South Junction at some point if I can make it go fast enough. So no, this is a thread about modelling the vans and coaches of this ill-fated train in 3D CAD with a view to getting them 3D printed.

As a child I lived for a short time in Downton which happened to be after closure of the Salisbury & Dorset during the period when the track was being lifted, so I'd seen the track down from the bridge in Moot Lane and seen the smoke above the trees from the school playground from the demolition trains oblivious to what was about to happen to something so apparently permanent. However the urge to model this unfortunate train only arose after an impulse purchase of one of those K's Milestone Falcon Class kits on Ebay that was missing all the dodgy underpinnings that I would have discarded, making it a curiously attractive purchase. Although this feeling was somewhat tempered when I realised that the driving wheels originally provided had the 24 spokes not available commercially!

Falcon Class engines were used on the Salisbury & Dorset in 1880s and 1890s, and Siren (being a Bournemouth engine) was my initial choice. A splendid photo in Bradley from this period shows it shorn of almost all Beattie weirdness, with a purposeful looking stovepipe chimney, painted domes and modestly extended cab. Although as it happens Sirius a Salisbury engine might be a better choice for reasons outlined below.

So with a layout supposedly set in the 1950s, what sort of train could this late condition engine pull, for pull a suitable train it must? The latest products from Hattons and Hornby were quickly discounted as being too modern for the sort of train that I had in mind, and then I remembered the Downton Train Crash (actually across the river from Downton) and wondered if there was a BoT Accident Report online - and there was! It's a fascinating document giving a voice to all sorts of people who had been witness to that dreadful event that took five lives. From my point of view though it gave a lot of information about the vehicles in the train, including running numbers, build dates, lengths, braking and coupling arrangements, all of which I could cross-reference to drawings and photos in Gordon Weddell's LSWR Carriages Volume 1. From this I produced a montage of that fateful Salisbury to Weymouth train that included the close coupling of pairs of carriages for stability. My chimp brain liked what it saw and generated considerable enthusiasm for me recreating it as a good example of what an early train through Verwood would have looked like, albeit with a Salisbury engine hence Sirius.

On Christmas Eve I started on the 1865 Third Class coach by scanning in Gordon's drawing, then importing it into and scaling it in QCAD. From this I made a 'regularised' trace of it to winkle out any inconsistencies in the drafting, and then started to create suitable 2D drawings in QCAD ready to recreate the coach body in 3D using OpenSCAD. Some of you may know that I've previously generated a yard crane and LSWR Type 1 signal box using this method, but a whole coach body? Anyway, as there were three of these in the train, it seemed a good place to start. The body came out OK, so I gave it compartments, seats, a roof, then buffers, leaf springs and axle boxes to go underneath with some full length footsteps and Mansell wheels all following the Weddell Drawings. By News Year's Day the coach in 'late' condition with long buffer shanks and two full length footsteps each side was complete.


It's a simple little thing with conventional panelling and uncomfortable wooden seating. It is shown here fitted with my interpretation of the not very Continuous Newall Mechanical Brake that will be the subject of the next not very exciting instalment. As an aside all the coaches have similar springing arrangements, wheels, W Irons, lamps. and braking arrangements, so these items are created once and shared by the vehicles that need them, with any variations like wheelbase, brake standard positions, and control arrangements specified using input parameters.

 

[AJC]

I'll be really interested to see how these come out in the flesh, Steve. In terms I'm familiar with these are basically the normal size of fitted vans so really quite petite!

Adam

 

[Stevers]

Next up and the leading van of that fateful train was this 1864 Pass. Brake. No 167.

There should have the same style of brake van (No 191) at the the other end of the block set, but this had been substituted by an 1859 style van (No. 99) -probably at Salisbury. Both were boxy things, though very different in character. I soon realised 167 was not nearly as straightforward as it looked. On this one the framing was internal so the doors looked much like the rest of the sides, Close inspection of the supplied photograph showed that the bead half way up was rounded, something that was indicated on the drawing, but wasn't obvious to the unwary. The drawing and photograph also showed deep moulding round the non-door windows. Generally the approach adopted is all about capturing the 'look' rather than pin point accuracy, although having everything more or less the right size and in the right place definitely helps the 'look'. It's impossible for me to know exactly what form that deep moulding took, but I can make something up, of a traditional pattern, that looks much the same. A huge advantage of working in 3D CAD is that components can be viewed in place from the same angle as a photo and adjusted accordingly.

The framing has been accomplished by criss crossing horizontal and vertical drawn sections, this was the approach I used to put the chamfers on the panelling of the Third Class Coach. These sections are drawn in QCAD, imported into OpenSCAD. then extruded and manouvered into place by a string of appropriate commands in what is actually a text file. These shapes can be combined to make more complex shapes. This is done using set theory (think Venn Diagram). Mostly 'unions', both implicit and explicit, are employed, but to put the window openings in through the droplight layer a 'minus' operation was used (a 'difference' in OpenSCAD speak). Now OpenSCAD is a very robust and stable program, but this use had an unfortunate effect on the preview render when faced with a complex model like this, though happily not the final render which takes significantly longer to process.



As you can see OpenSCAD preview has rather lost the plot. In fact when I minused out ('pressed out') the non-door window mouldings I encountered a bug that stopped the preview dead in its tracks, one that should be fixed in the next release of OpenSCAD. The workaround for this was to add a parameter in my program that skips this step for preview as shown here, but allows me to reinstate it for the final render. Also shown are the red rods that minus out the holes for the handles and handrails along the side. For this a '#' in front of the command colours that component red and makes it translucent.


Armed with the experience I needed at the start of doing the 1860s coaches I managed to get OpenSCAD to preview my replacement AW diesel shunter body to its full potential, but only by almost completely avoiding minus operations. When setting the colour of objects in preview it's possible to set the opaqueness, so in this case the glazing pockets are implicit unions, coloured sky blue and set to be translucent. The handrails etc. are just set to be a light grey. For the final render all these will be minused out to leave holes and pockets using another parameter. My travails with the nominally 4mm scale Mercian Models kit will be covered in another thread, but I expect to reuse the etched running plate (via a 'cut and shut' to the correct size). This means that the running plate in the render is for presentation and context, although it will also be minused out for the final render to ensure a nice flat bottom to the print.


I had threatened promised to cover the not very continuous Newall Mechanical Brake this time, but I've rambled on rather too long about the joys of OpenSCAD, so this is an interior view of the 1864 Brake showing the Newall Brake Control Gear, Seat, Platform, Step and just a hint of Desk, all closed in as 'Dog Boxes'. The guard would need to be pretty athletic to gain his seat with that brake wheel and column in the way! The ripples visible on the insides by the windows is where the bars will be fixed, and whether those glazing pockets can be made to work remains to be seen!

To finish off I had thought that flaring a chimney or dome into a boiler would be impossible in OpenSCAD, but I now realise that a parameterised routine could be written with quite a bit of Trig to flare any cylinder into any other cylinder, and that would be called with appropriate parameters for the sizes of everything when needed. Having experimented with FreeCAD and Fusion360 (death by constraints), I'm increasingly convinced that at the very least I prefer the difficulties of OpenSCAD to a more graphical approach to CAD.

 

[Stevers]

I'll be really interested to see how these come out in the flesh, Steve. In terms I'm familiar with these are basically the normal size of fitted vans so really quite petite!

Yes, tiny troublesome trucks - and only about two foot of them! Hopefully the low roof line, all those footboards, and close coupling in pairs might mitigate the truck like look somewhat. The Falcon Class loco is pretty low slung too. The cast footplate of that pretty much sits on the rear driven axle meaning that hornblocks will not be an option for the twin beam compensation I shall be fitting to it. There's definitely room for the sort of High Level Gearbox and Mashima that I'd normally fit in the engine though.

The crane I designed in 4mm, looks more impressive in 7mm, and I've a hunch these could be the same!

 

[Stevers]

There's not a lot of information about Newall Brakes on the Interweb, but they do get a mention in another accident report far up in the Grim North where they were (if I remember rightly) described as powerful and were also not held to be at fault for the accident.

My interpretation of the Newall Brake follows on from Gordon Weddell's diagrams and drawings which very clearly explain how they work, but not how they looked, which for a mere railway modeller could be considered more useful. It's a complicated mechanism, and if the multiple bevel gears and the rack and pinion were exposed as I've modelled them they would have been a dirt trap with the regular lubrication that would have been essential.



We'll kick off with the curved spoked control wheel, this you would like to think was consistently turned in one direction to apply the brake and in the other to release it. It's mounted against the bulkhead and turns a shaft in a column whose form is made up. The brake was held on (or off) by either a rope or a catch. This configuration of bevel gears pretty much forces the brake standard to be offset from the wall in a very inconvenient position for the guard to climb into the seat provided to supervise the progress of his train from the caboose. The brake column for the 1859 brake is shown close up against the other side of the bulkhead. To me the clear implication of this is that as built the 1859 van was fitted with something other than the Newall Brake - something Jon Nazareth has correctly concluded. There is a tie rod between the W Irons, and that ought to be redundant if the Newall Brake Bar had always been present.


The brake standard emerges from the floor under the vehicle where another set of bevel gears transferred the drive to a shaft running the length of the van. Along this shaft was (surprise) another bevel gear set that transferred the movement, via a short cross shaft, to a rack and pinion that applied pressure to a lever on the V hanger. Also visible is a cylinder, and this was an optional feature of the Newall Brake. It contained a spring, and the brakes were released against this spring to aid any subsequent brake application. This feature would I assume, only be found on brake vans. The long shaft is offset from the centre line, and there is only just enough room to fit the brake actuator behind an EM wheelset. The actuator unit will be a separate 3D print and there is a cut out in the mount for it to clear the W Iron base. The long shaft will be minused out for the final print so a wire to simulate it can be threaded through all those bevel gears and brackets.


Lastly we come to what I suppose could be described as the sharp end. What appear to have been wooden brake blocks were bolted to a mounting plate that slid on a bar mounted between the W Irons. The drawing doesn't show how thick these bars were, but there's not a lot of room for them. and I've just set them at a thickness that fits and is potentially 3D printable. It's this bar that caused me to choose cosmetic W Irons. Originally the plate that attaches the brake block was just a rectangle, but this looked wrong so I chopped the corners off and they looked more credible after that. The push rods that activated the brakes were shown with long overhangs at the cross rod end, and I assume this would be where the wear in the brake blocks would be taken up in a way that is way too tiny to replicate in 4mm.

Both brake vans in the Downton Train Crash additionally braked the adjacent pair of close coupled carriages. For the brake vans to be at the ends of the block set there must have been a 'good' and a 'bad' end to brake from. Any continuously braked coaches would need to have the correct orientation in the block set with those at one end logically requiring an opposite orientation to those at the other end. If this wasn't the case surely there wouldn't be consistency in which way the control wheel should be turned to apply the brake. I'd like to know which way this might have been, but until I know better, I'm thinking that the train ought to be on the end closest to the brake wheel if only on the basis that the guard could reach to wipe the inside of the caboose glass to see where he was going.

With the Newall Brake fitted and being partially close coupled, one can certainly see the logic in running these coaches as a block set.


[Edit] Newall not Newell - entirely my mistake and not from Weddell. Spring assistance may have been on all vehicles according to Wiki.

 

[Stevers]

There were two First Class Coaches in the block set. They were close coupled in the centre of the train and not braked from the ends, thus I haven't provided them with brake gear. They are quite different to the Third Class coaches in not being conventionally panelled, and it seems likely that as built they were 'teak'. They bear a very strong resemblance to some Brighton coaches of the period and it seems likely that they are more of a Metropolition Carriage and Wagon Co. design than LSWR. Weddell One has a photo of a Brighton coach (in teak) to illustrate these coaches. There should be a second bead curving up the tumblehome at each end, but so far the exact trigonometry to achieve this in CAD has escaped me, and the assumption is that this bead will need to be added the old fashioned way. The drawings make these coaches look much more like something Maunsell would have produced. but this is less evident once the side windows are given bolection mouldings. As before these are in late condition with two full length footboards and long buffer shanks. There should by this point have been a roof ventilator for each compartment which looks to be the same design as that sported by the Hornby four and six wheel coaches that are also modelled as oil lit.


The drawings show comfortable looking upholstery, though not individual seats and I have tried to capture this in my design.

Although not labelled as such on a (Swiss?) website, Bradley states that this is 294 stopped for attention at the new Bournemouth loco shed in 1896.
ETH Zürich - ETH-Bibliothek - E-PICS - ETHBIB.Bildarchiv - Ans_05373-0769

Including a very sharp cropped version of the above there are two superb shots of Vesuvius Class 294 in late condition in the Bradley Beattie Book, showing both sides with domes painted and most likely in Goods Green. Having modelled the vans and carriages that came a cropper at Downton, it seems somehow remiss not to model the train engine involved, when dimensionally these engines are almost identical to the later Falcon Class builds and they have the same boiler. For the Vesuvius Class the rear splasher box is longer to cover the donkey pump originally fitted, and on 294 the front splasher is solid not pierced. One advantage of modelling the Vesuvius Class over the Falcon Class is that the bottom slidebar mount is much more robust giving more material to attach the outside leaf springs to in a model.

Although I'm sure both photos are later than 1884, it seems that all of the modifications in the pictures could have been made to 294 before this date so it seems reasonable to use these as reference photos for a model of the train engine in the crash. The Bradley Beattie has the GA for the Vesuvius Class and much larger prints of the GA are available from the Drawings Service of the South Western Circle. A bonus is that 294 was built with the Stirling type wrap over cab that I originally had in mind for my engine. I think those two photos, and the availability of a GA are extremely good reasons in themselves to model 294 from my incomplete K's kit rather than one of the Falcon Class that it was intended to be.

 

[Rob R]

Metropolitan tank sneaking into that photo on the left?

 

[Stevers]

Good spot. A passenger tank engine (apple green?) with bunker 'under the metal awning'. I can't think of anything else it could be!

 

[Tim Birch]

For those interested in the details of 19th century attempts to improve train braking, James Newall (not Newell) had his first patent for a brake patented in 1852 (patent 939), and a second patent on 16 January 1854. In the first patent, the shafting was on the carriage roof, and in the second patent it was underneath the carriage. He was carriage and wagon Superintendent of the East Lancashire Railway from (probably) 1847 until 1870. The ELR had steep gradients with some miles of its main line being 1:40. His design introduced improvements to existing slide brakes so a breaksman could apply the breaks instantaneously to several carriages. The manual effort of the breaksman was only required to release the brakes by winding a handle to compress a spring held in a 4'4" cylinder. When compressed the spring was held in place by a ratchet and catch. To apply the brake, the catch was released.

Some tests were carried out, supervised by William Fairburn. In one, the test train (composition not now known) was released down the 1:40 bank towards Accrington station. From a speed of 48mph, it was brought to a stand in 375 yards.

 

[Stevers]

The Weddell drawing doesn't show any form of brake on the First Class coach, but such a vehicle would be a liability to have around loose unless there was some form of hand or parking brake. Presumably the Newall (noted!) Brake could be wound down from the ends of the coaches as a form of hand brake. If all vehicles were sprung 'on' then the brake would need to wound 'off' to marshall them. The more I think about how this could been worked, the more I wonder about the practicalities of it!

 

[Stevers]

James Newall (not Newell)

Thanks Tim, now corrected.
There's more on the web about the 'Newall' brake. Let's hope I don't start referencing the work of Mr Weddall!

 

[Tim Birch]

Thanks Tim, now corrected.
There's more on the web about the 'Newall' brake. Let's hope I don't start referencing the work of Mr Weddall!

Happy to help.
The other name which crops up in association with Newall is Charles Fay; in fact there are some references to the Fay/Newall brake. Fay's break was similar but different and probably copied Newall's. However, when the ELR amalgamated with the Lancashire and Yorkshire, the two worked together to develop the brake which performed creditably at the Newark brake trials in 1873 (by which time Newall was dead).

I have found another reference to the effectiveness of the brake, when a train of seven carriages was brought from 35mph to a stop in 228 yards on a gradient down of 1 in 40.

 

[Overseer]

These may be of interest. Not Newall brakes but the same type of brakes. This is a Daniel Gooch mid 1850s design for the Geelong & Melbourne Railway, and built by Joseph Wright & Sons. Only second and third class carriages were fitted with brakes through the 1850s, first class passengers could not be subjected to the unpleasant motion and offensive noise of brakes being applied to their carriage.

Note that the bar the brake block slide on has a taper around the centre pivot, and no V hanger. A V hanger would prevent the suspension working - the brake beams were connected to the axleboxes on these ones.

 

[Stevers]

According to Wiki, in the Newall system the rods ran along the roof, and the Fay system they ran underneath. The Fay system though is supposed to have a worm drive in the system to slow an automatic brake application, and yes automatic brake application was a feature apparently. There's supposed to be a conical spring in each carriage to achieve this, but that doesn't sound like it belongs in a cylinder, so certainly some confusion. There is also the possibility that Weddell describes a uniquely LSWR version of the Fay/Newall brake!

 

[Stevers]

Following the two First Class coaches was a single Second Class coach, sufficiently closely related to the First Class coaches for me to share most of the code and drawings to create them. As with the First Class coach there is every reason to think that this is another 'teak' coach, though painted by 1884. It was close coupled to a Third Class coach that wasn't in the block set as formed at Clapham Junction. This was the longest carriage in the train and it had a longer wheelbase than the others, requiring a version of the Newall/Fay brake with longer slide bars and push rods. This render shows it with a single footboard and little steps, and for robustness I haven't fitted the very decorative footboard brackets that this and the First Class coaches had. Seating was upholstered, but not as plush, nor was there as much room as in First Class. Both First and Second Class coaches had loop door handles rather than T handles.


This is with two footboards as these coaches were normally photographed (later in life) and as I will have them 3D printed for my Downton Train. The bottom board isn't close to the ground, and the steps are about 9" apart so just about a normal step size. I think they must have been provided for safe (ish) passenger access from the original low platforms that would still have been in use at the time. The long top footboard seems a safer option for this than the little short steps. I still need to address the extra cylinder (ventilator?) that is seen next to each oil lamp on these coaches in late condition, and I am dubious at the lack of steps to access the roof on any of the coaches. As I've managed to source twenty Midland wagon buffers that are very similar to these buffers, the coaches will be 3D printed without buffers, and that will make it easier for me to organise the close coupling of the pairs of coaches to make up the block set correctly.

 

[Stevers]

Bringing up the rear of the train was this 1859 passenger brake van, in my case retro fitted with the Newall/Fay brake gear in the same manner as the 1864 Passenger brake that was on the other end. It's not specified what wheels were fitted, but it seems likely that they were spoked as shown here. It's a characterful little van with it's deep external framing, and ribbed roof, though the doors must have been shallow framed to accommodate the drop lights.


Internally the desk, seat and platform have been boxed in as 'dog boxes', and the desk has been given the ticket rack it's supposed to have had. Originally I was going to build the set with the extra third and two 1864 brakes, but I'm glad I did this little chap as he's now my favourite of the set. The plank walls are 0.6mm and the framing 0.9mm for a total thickness of 1.5mm. The internal partitions are 0.8mm, and no doubt it will take a couple of test prints to fine tune what can and can't be 3D printed. The voids under the desk and platform are open underneath, and that's really the only allowance I've made to 3D print them so far.

 

[Stevers]

This is the current (finished?) state of the Third Class coach. Earlier iterations of this coach had four oil lamps which were probably only correctly spaced for the Second Class Coach - a cut and paste error! It seems that the small cylinder adjacent to each oil lamp seen in later photos may have been an oil reservoir for the lamp. End steps aren't shown on the drawings, but are seen in later pictures. The ones I've added are of the pattern seen on coaches from the 1870s. The steps are overscale thickness by 0.2mm as they will be minused out for the 3D print. .005" nickel silver strip inserted into the printed slots will be used to form the steps. In the 1870s coaches were typically provided with short vertical handrails at each side and two short handrails on the roof. The long curved handrails seem to have appeared later. The ones on the model at 0.45mm are again overscale as they will be used to minus out holes for 0.33mm wire. Steps only seem to have been fitted at one end of coach so in my case at the outer ends of the close coupled pairs. The offset nature of the Newell/Fay brake means that I need both left and right handed Third Class coaches so that the brake rods line up. The easisest way to accomplish this is to change my code to optionally rotate the underframe through 180 degrees rather than to try to move the new steps and handrails.



The HMRS LSWR/SR Transfer Sheet No. 9 has transfers in a style that seems compatible with the limited sample lettering for the 1875-1900 period in the old HMRS LSWR/SR Livery Register. The 'SECOND' and 'LUGGAGE' samples are more compressed than the various examples for 'FIRST' and 'THIRD', but if they weren't, they wouldn't fit in the limited space of a door panel. The Weddell drawing for each vehicle shows a lettering layout that is of an earlier pattern than would have prevailed by 1884. I'm assuming that in my period the 1864 brake van with three sets of double doors and a lot of little panels, would have been lettered thus:


As can be seen above, the brake vans alone require a significant number of 'LUGGAGE' transfers, together with a couple more 'COMPT' transfers. In addition we'll need a supply of transfers for 'THIRD', 'SECOND' and 'FIRST', running numbers, and two 'L&SWR's for each vehicle. Examination of the HMRS transfer sheet shows that two sheets would be sufficient in all respects for the Downton train other than the crucial 'L&SWR' transfer since for reasons known only to the HMRS, just two are provided per sheet. As I would like to produce WD transfers for my AW diseasel disaster, it seems sensible to explore adding some L&SWR transfers to whatever I commission. In preparation I've traced the lettering in the Livery Register to produce a vectored image and above is a jpg of that. Someone has been lined up who can also produce the 'gilt' transfers needed for the coaches, but also potentially a Goods Green lining set for the Vesuvius/Falcon Class Loco.

 

[Stevers]

What seems like ages ago, this thread was kicked off by a slightly random and perhaps ill-considered purchase of a K's Milestone kit for a Falcon Class loco. This engine if built would require coaches not available ready-to-run. which thanks to a BoT Accident Report and the work of Gordon Weddell, now exist for a specific but unfortunate train - though currently only in a virtual world. On the day of the accident, the train engine was Vesuvius Class 294, which was a development of the Falcon Class, of similar size, yet differing in many details, so really I need to consider the work needed for the loco next.

With almost all of the crude K's underpinnings missing, the next task was to develop some sort of etched chassis that would enhance the kit and could be built to EM (or P4) Gauge. The original idea was to quickly knock up a simple Perseverance style chassis, but I very quickly established that this isn't the prototype for anything remotely sensible! So, using the Hollywood Foundry guidelines for dealing with cusp, and the PPD guidelines for colouring the artwork, I've used QCAD over the last three weeks to design several different sets of components - these being (so far):
- Smokebox Front and Cosmetic Frames
- Crossheads and Slidebar Assembly
- Loco Frames, Rods and Brake Gear
- Tender Frames and Brake Gear
- WG Beattie (Stirling style) wrapover Cab

Following tradition I thought I'd start with the tender and using a 'road kill' layout these are my plans for an etched chassis in 0.4mm nickel silver for the tiny Beattie 1950g tender. I'll be compensating it using twin beams with a trim screw above the trailing axle set in a dedicated frame spacer, with the wheels mounted in High Level Kits Miniblox - hence the 4mm wide half etched slots. These tenders have been photographed with large wooden brake blocks, but the brake arrangement shown here is a later development. The third layer of brake shoe is there as an option to add chunkiness. Hangers appear to be quite delicate in photos and drawings, and I'll be thinning mine slightly as on reflection I've overcooked them. It took me a while to get to grips with the guard irons, until I realised that they could only be an extension of the brake hangers. At the front I've provided something to hang the brake actuating shaft from and an operating arm to go below the brake standard. All of this fits inside the unmodified white metal tender body and I have had to move the top brake pivots forward slightly or the rear one would have been off the end of the frames and buried in whitemetal.

The mid-blue is half-etched from the front and will need to be pure blue in the final artwork. The red is half-etched from the rear. As a novice this colour scheme is something I can get my head around. Confusingly QCAD 'colouring in' is described as 'hatching', it's very sensitive to surrounding lines not being joined 'properly' leading to some rework. Sometimes the 'hatching' completes, but it is then lost (with an unhelpful error message) when the file is saved. This is also due to line intersections needing rework, and always in my experience where a curve joins a straight end on. All this is going to make adding the moats and tabs required for responsible chemical etching quite tricky! I hope to retain the 'road kill' layout as it makes the etch and required assembly easy to understand.

Currently each QCAD drawing for etching has five layers:
- Finished Size
- Cusp Allowance (added or subtracted)
- No Etch - Black
- Half Etch from Front - Blue
- Half Etch from Rear - Red

This approach allows me to keep tabs on where I am in making allowance for cusp as I can always see a 'before' picture when making any changes. I have also made a GA drawing where each logical set of components is on its own separately coloured layer. I use this to understand how the different parts relate to eachother as I can easily switch the visibility of sets of components and bitmap images in and out by layer.

Luckily the excellent Hollywood Foundry (HF) guidelines for etching had been safely squirelled away whilst still available. In my researches I'd seen guidelines that suggested adding 20% for cusp, but that seemed to be over egging it and I was thinking that in theory 15% might be nearer the mark. I was therefore reassured that HF did indeed suggest adding 15% (o.o6mm in this case) all round, apart from slots where to avoid the difficult task of opening out a slot you should remove 15% on each side, but not ends. It seems reasonable that holes could be a special case of a slot, and for the holes in the tender I've yet to make any allowance for cusp.

I'm new to this so correction on any aspect would be appreciated!

 

[Yorkshire Dave]

Metropolitan tank sneaking into that photo on the left?

Good spot. A passenger tank engine (apple green?) with bunker 'under the metal awning'. I can't think of anything else it could be!

LSWR 318 class LSWR 318 class - Wikipedia

 

[oldravendale]

I had no idea about that, Dave. Good engines no doubt - the Met/District had a lot of them - but obviously not suitable for the purpose for which they were purchased in this case.