Downton Train Crash of 1884 in EM Gauge

[Herb Garden]

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
View attachment 221472
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!

Your approach looks good can't see any faults as a someone who also designs etches.

I also have a Ks falcon that needs rebuilding so do let me know if you accidentally make a second set of etches and want rid of them....

 

[AJC]

Very interesting, Steve - I don't know much about artwork drawing (I just build the results!), but I can't see anything that would trip you up. Would a hole etched through the brake shoe overlay, in order that you could insert wire all the way through for location, be an improvement? I think it might. Obviously the fold-over tab does allow for that, but a hole through is belt and braces. I see that the actuation gear is hidden behind some convenient steps: even I would ignore that. Looks very positive.

Adam

 

[Stevers]

Would a hole etched through the brake shoe overlay, in order that you could insert wire all the way through for location, be an improvement? I think it might. Obviously the fold-over tab does allow for that, but a hole through is belt and braces. I see that the actuation gear is hidden behind some convenient steps: even I would ignore that.

In general it all depends whether I've ended up doing this for me, a few hardy and experienced souls, or a very secret army of Victorian era LSWR modellers. The two layer approach would suit the latter best, but I don't think that's something I need to worry about! When I hand fret brake blocks and hangers, I start by putting in the holes to line them up for assembly, so I'll make that change, as the hardy souls will like that too.

 

[Stevers]

The 'finished' tender chassis fret:

In a surprise development a 3D printed body to go on it. Jolly useful for a model of Lion Class Stour, or for anyone planning to convert a Beattie Well Tank to tender form, as the LSWR did when these tanks were retired from suburban duties.

I'd like to think I'm about half way through, but am only too aware that's not how it works. Interestingly the K's tender castings hold up well to scrutiny and I still plan to use them for 294. The K's rivets are a little bigger and a bit further apart and I'm in two minds as to whether that's better or not in a model where the prototype rivets are so tightly packed.

There's a vertical handrail on the other side that I may want to etch some brackets for, in which case I'll add those to my 'finished' chassis etch.

 

[Stevers]

We're at the point where I am starting to produce STL files that could be printed.



This is a view of the top with it's little shanty town of tool boxes. The tool box at the back is metal and has stops on the hinges to stop the lid from falling back. I'll probably organise an etch for these, with a recess in the lid to take the etch. There should also be a staple to secure the lid. Forward of this are two wooden chests that I've sized and positioned to match those on 294. On some tenders these were longer and of slightly different design. The lids on these were I think hinged, but I've yet to represent hinges or fastenings. In almost all pictures these boxes are partially obscured by a carefully constructed mountain of coal. Forward of that is a small wooden chest that appears to have a lift off lid that is flat or almost flat. This is rarely level front to back in photos, so I suspect this is just sat on a shelf. This one is positioned according to the photo of 294 and it was the resulting ugly gap between partition and box that first led me to think there must have been a shelf of some sort. I suspect that a shelf was both sides although a box was only visible on one side of the tender on 294. I've put some representative rivet detail on the tank top and into the coal hopper, and the flat filler lid has holes for a handle, there being no evidence that it was hinged.

There was a problem with the rendering process. This takes over an hour on my laptop, and about 25 minutes on our tower PC that has better graphics support. In order for the bead along the top of the flare to appear curved I'd set the facet number to 600 and the full render process didn't like this number to be above about 300 for this item. At 300 the very gentle curve was rendered as two straight rods. I changed the facet number to 20 and recoded the bead as a series of 10 straight lines that appear as a smooth curve. This allowed the render to complete without error, in less time, with reduced file size, and with a better fit to the flare - everyone's a winner! A major consideration in reducing file size and processing times is facet size, particularly for all those lines of rivets where the facet number used is 10. For comparison the facet number for the leaf springs is 120, and tank filler 60. There are facet size and facet angle parameters in OpenSCAD, but I've had no success with those with anything other than the most basic of shapes.


There is little information on the tender fronts, though I'm reasonably confident about the brake standard, and the sand hoppers with cranked pipes giving a straight drop to the rails. The GA doesn't show any kind of shelf below the coal hole, although there is a suggestion of one in a photo. It looked silly without one, so I've done the minimum and added a door and some rivets to give the whole a bit of life. The front handrails will be minused out for the print. This hole will be a nominal 0.65mm, but will print at about 0.45mm as represented here. The tender handrail brackets will also be minused out ready to receive the half etched brackets in the chassis etch. My plan for the brake standard is a handrail knob and bent wire to represent the handle. The wooden tool boxes and shelf components will be separate prints.



The original 3D model was based on the drawing in MRN from 1965, cross checked to photos. There is a GA of one of these tenders (as designed) in the relevent Bradley and this gave me the layout for the lamp brackets. I already had my doubts about the flare and was not too surprised when I overlaid the layout from the GA onto my 3D model that the top lamp bracket was only half way up the flare. Anyway a written measurement on the GA confirmed that the top of the tank in the MRN drawing was 1mm too high and the top of the flare a further 0.5mm too high. Photos could now be seen to support the GA dimensions. After a bit of rework, the top bracket was where it should be and the beads and rivet lines all tidied up again. The shunters handrail/water gauge is just a length of wire mounted on two long handrail knobs with an extra knob at the base to better represent the prototype detail. Visible underneath are the etched chassis frames positioned just to check fit.

Something I haven't considered yet is the drawbar. It should go through the dragbeam, but that's not usually very convenient in model form, so I'll run it just underneath the dragbeam, which I might fillet out a bit so the drawbar can be nearer to where it should be. Next step is to start separating out the different parts and complete all the minusing out that's needed for a 3D print.

 

[Stevers]

Some fairly serious upgrades have followed a lot of help from a friend. I'd traced the leading axlebox and hadn't realised that it had a 3' leaf spring, and the others 3'6". Quite clearly so on all my drawings and a howler that's now been fixed.

A photo of the front of the tender has now been seen, and I have been able to make mine look more like at least one example of these tenders. So definitely no shelf, big rounded sand hoppers (as also glimpsed on one of the Beattie Well Tank conversions in Bradley) and just room for a single step. The lift up door is so large that corners needed to be trimmed so they would be less likely to cause injury on any ascents of the coal mountain to reach the back of the tender. I've already enlarged the coal opening and am wondering if logically it shouldn't be a little larger at the expense of the door. I've only suggested the drag beam and buffer detailing as it will be below a fall plate. There are at least three sorts of sanding hoppers on these tenders that I would describe as 'narrow tapered' as per K's kit, 'wide tapered' and 'rounded' as this one is.


Models of the Ilfracombe Goods tend to show the coal hopper filled in below the forward tool boxes and it doesn't seem impossible that this somewhat dead area of the hopper might have been boarded in, giving somewhere for the tool boxes to sit on at least some of these tenders.

 

[Mudmagnet]

Test printed the tender today and works really well. Will post to Steve to evaluate.

 

[Stevers]

An excellent quality print - very pleased with it! All those rivets, the flare, the steps, the axleboxes and the spring detail have come out really well. There should be a second large tool box, and the axlebox retainers look a little awry. The latter doesn't seem unusual for the parts of a print nearest the plate. I'm thinking I need to add sacrificial rails along there so that the print can get going properly before it gets to the retainers.

 

[James Spooner]

View attachment 227945View attachment 227946

An excellent quality print - very pleased with it! All those rivets, the flare, the steps, the axleboxes and the spring detail have come out really well. There should be a second large tool box, and the axlebox retainers look a little awry. The latter doesn't seem unusual for the parts of a print nearest the plate. I'm thinking I need to add sacrificial rails along there so that the print can get going properly before it gets to the retainers. I'm thinking that needs a sacrificial rail that can be cut off to allow the print to get going properly.

That’s looking very impressive Steve! Can’t wait to see the rest of it!

cheers

Nigel