The roof detail goes on...
Choice of Prototype
So far I hadn't really done anything that had limited the choice of loco that I could build, but on reaching the roof that was about to change because this is one place where there were lots of variations.
The pilot scheme locos D6300-6305 were ruled out because they had a different layout for the louvres and doors on the sides and would need a different body etch. They also had a much simpler roof layout than the production series locos.
The roof detail differences appear on the train heating boiler roof (that's the roof at the end of the loco that has the little door high on the side for filling the boiler tanks from water columns). There seem to be two small raised panels on the exhaust side of the loco. Earlier production locos tend to have a grille opening in the upper of these panels. Later locos have the opening on the lower panel. The obvious conclusion would be to say that this variation depends on the boiler type - the books say that D6306-6325 had Clayton boilers and D6326 onwards had Vapor boilers. The snag is that the photos don't quite match this theory - D6326 has the grille opening in the upper panel and the switch to the lower panel happens from D6327 onwards.
Dapol seem to have made their opening cover both of the panels. For a while I thought that this was wrong, but inevitably I found a photo of D6311 that shows otherwiseâ€¦
Later locos (D6329 onwards?) also have an extra opening on the opposite side of the boiler roof.
To complicate matters further many locos had one or both of these openings plated over later in life. Possibly the boilers were isolated although I don't think I can remember seeing any sources that actually say so.
I also wanted to avoid having to reproduce the 'eyebrow' vents over the windscreens on some locos. These almost follow a pattern - D6300-D6312 have them D6314 onwards don't. I think that D6313 didn't have them but the only photo I've seen is not 100% clear. The fly in the ointment is D6333 which also has the eyebrow vents. Quite why this happened is a mystery to me. Like I said in another posting, class 22 variations are a minefield.
As ever, the story boils down to the fact that you need one or two decent roof photos of your chosen prototype at your chosen period to be sure that you've got it right.
So which one did I pick? As I said in Part 1, I wanted a green loco. My initial choice (in spite of eyebrows) was to go for D6309 because there is a very nice 1969 photo of it at St Blazey on John Chalcraft's site atâ€¦
I couldn't find any decent roof photos of D6309 so in the end I picked another green loco with no eyebrows which was known to frequent Plymouth and Cornwall - D6323. I have 3 photos of this which show the roof detail clearly. All of them are fairly distant and I don't have a really good close-up photo. One of them is hereâ€¦
... still if a photo of the roof of D6309 in the last few years of its life does materialise, I still might go back to that one... eyebrows and all.
I was originally intending to use the roof overlay provided in the kit but the more I looked at it the less happy I was with it. It correctly shows that the main grille is off-centre but I feel that the grille is too far off the centre line and loo large. I wasn't happy with the position or sizes of some of the other features either. I decided instead to make my own overlay from scratch using 5 thou nickel silver. This is half the thickness of the one in the kit, so should be better in appearance on that score as well.
I sketched out the features of the roof and then marked the whole thing out on the nickel silver sheet. After cutting it out and making the exhaust and fan grille holes I formed the curve (around the solder sucker again) tried it on the loco. The fan grille opening was in completely the wrong place because I'd made a mistake in my measurements somewhere along the line. Darn.
I scrapped the first roof and went back to the drawing board (or rather CAD) and did a proper drawing of the roof features. I was then able to print this out and try the paper roof on the loco to check that everything was in the right place. Of course I should have done this in the first place. I often spend way too long researching and planning instead of getting on with the job but on this occasion I cut metal in haste and repented at leisure.
Once I was happy with the paper roof I marked out the second attempt at the overlay onto the nickel silver and I cut out the overlay. I then offered it up to the main roof and marked the position of the grille opening onto the roof. This was then cut out 1mm oversize to avoid having a 15 thou edge showing and so that I could attach things directly to the underside of the overlay behind the opening.
The photos below show the roof overlay in place, the CAD drawing and my failed first attempt.
... plus a comparison between my CAD drawing and the interpretation of the roof in the kit
The fan grille is something that has been giving me some cause for thought. The easy option would be to take one of the spare grilles from the kit and attach it behind the opening in the overlay. At the moment, however my plan is a bit more ambitious - I intend to model the four walkway strengthening ribs which are visible in photos and to model the cooling fan beneath these. I don't have anything suitable for the grille itself, so I'm going to try leaving it off and see what the result looks like. I'm intending to glue everything together in this area so that I have the option to change things if it doesn't work out.
To make the walkway ribs I blu-tacked a couple of pieces of nickel silver strip to some wood so that they were parallel with a gap of just over 8mm between them. These were then fluxed and tinned. A piece of Eileen's 0.45mm brass wire was then soldered across them and snipped off with wire cutters. I then used a 0.75mm drill to space the next rib from the first, held everything in place (with my fingers), applied flux and quickly soldered each end in place. I managed to successfully repeat this process twice more so that I had four parallel ribs. I think that holding things with fingers helped here because it made me really careful not to dwell too long with the ironâ€¦ and as a bonus I didn't burn myself either.
The excess wire was then trimmed and filed off and the whole thing laid wire-side down onto a file and given a rub to flatten the top surface of the ribs. The photo below shows the finished walkway.
The extra panel on the roof of the engine room was the next job - this was marked out on 5 thou sheet and a small hole drilled to start the vent opening. Photos show a distinct 'lip' around this. My original plan was to use one of the small grilles from the kit but I think these are too big. I was thinking about making a lip with 5 amp fuse wire but then a much easier answer presented itself. I started using a tapered reamer to open out the hole and noticed the lip that it was raising on the reverse side. I filed this off and started reaming from the back of the hole instead. Once the hole had reached 2mm I then cleaned up the lip but left some in place. This left a nice subtle lip that I don't think I could have made any other way.
Finally I cut out the small extra panel for the boiler roof. I'd picked a loco that had all of the boiler roof openings blanked by the late 60s so I didn't have any holes to worry about.
The photo below shows all of the roof detail temporarily in place on the model. I will fix it properly later on when it is less likely to get damaged.