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!
