Entry posted by D869
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Progress continues on the class 22, but at a rather slower pace now that I'm working on the detailing of the nose ends. There's a lot to do here (and it still isn't finished) and it's definitely a place at which the Worsley Works scratch-aid kit becomes more scratch than aid.
The Prototype
The nose is another place on the class 22 where a lot of detail variations appear. I won't attempt to cover all of them here. The most obvious is the presence or absence of headcode boxes. These were not fitted to the earlier locos from new but were retro-fitted in the mid 1960s. This retro-fit also involved changes to the handrail arrangement, removal of the headcode disks (obviously), plating over some apertures and the addition of a few other appendages whose purpose is not readily apparent. The later locos had headcode boxes from new along with a different (and less cluttered) arrangement of handrails, lamp brackets and marker lights.
As far as I can tell, all locos seem to have left the factory with a pair of single piece gangway doors on each end. The locos that had headcodes retrofitted also received two piece gangway doors evident by an extra (strip?) hinge which is not quite central on each of the doors.
In addition to these main variations there are lots of detail differences on individual locos such as handrails being in slightly different positions, different bracket arrangements and so on, so again - get some good photos of your chosen loco. It is possible that some of these variations resulted from accident repairs, so I suppose that some locos may have had one end different from the other.
And so to do battle with the model?... not quite…
The Phoney War
I've chosen one of the 'headcode retrofit' locos which means that neither of the two alternative ends provided by the kit had the correct layout of handrail holes. This meant that there would be a lot of holes to drill and bits to attach. I thought that it would be quite easy to mess this up and get holes or headcode boxes slightly out of place which would result in something that would look obviously wrong and be very difficult to rectify. To try to avoid this I decided to make a jig to help me to get the holes and the headcode boxes in the right (or at least a consistent) place.
Before starting on the jig I took a look at the help provided in the kit for the nose detail, which is not a great deal - some detail is etched into the nose and there is also a set of etched headcode boxes. I tried the headcode boxes in place on the nose but quickly decided that they were too small and probably too thin as well. Their small size would also make it very difficult for me to finish the headcode boxes in the way I've done most of my other locos so they were consigned to the spares box.
Having learned my lesson by having to junk my first attempt at the roof overlay I decided to draw the nose detail using CAD to get the positions and dimensions right. The dimensions were scaled from a photo and transferred to the CAD drawing. The drawing is not intended to be a prototype drawing but rather a drawing of the model as I intend it to be, taking into account the sizes of nickel silver strip that I had available and my ability to mark out and drill to a certain level of accuracy. Once the drawing was done it was printed out to the same size as the photo and overlaid onto the photo to check the position of the various items. After a few minor adjustments the drawing was printed off to 2mm scale and stuck with Pritt to the front of the loco. I was really pleased with how it looked - I just wished that creating it in three dimensions without messing it up would be so easy.
I suppose I could have used the paper overlay as a template for marking out directly onto the ends of the loco but I was not confident that I could get the template accurately aligned with the etched detail nor could I see how this approach would help me with positioning the headcode boxes.
The jig was made from a piece of 20 thou brass (obtained for free from Allen's stand at a show). It uses the bottom edge of the nose as a datum to ensure that it is in the correct place vertically. For horizontal alignment I used the centre line of the nose by aligning by eye with the joint in the gangway doors. These datum lines correspond to two edges of the jig and all of the marking out was done from these edges. The jig has a cutout to fix the position of the headcode box and 0.3mm holes for each of the handrail holes and the marker light. The holes in the jig are intended to be used just to fix the positions of the handrail holes - the real end is drilled through the jig just enough to start a hole. The remainder of the hole is drilled after the jig has been removed. Most of the end detail is symmetrical, so the jig only covers half of the nose. It is then simply turned over to do the other half. Once the jig had been cut out and drilled a piece of nickel silver strip was soldered across the bottom edge to act as a guide to keep it in the right place.
I used a permanent marker to cover the whole jig in an attempt to prevent it from being accidentally soldered to the loco.
I tested the jig on one of the spare ends from the kit. This showed that the basic idea worked and also showed up a small error - one of the handrail holes was too high so the horizontal handrail wasn't truly horizontal. I tried the jig again on the opposite side but this time used a piece of paper to space the jig away from the bottom of the end slightly while drilling the hole with the error. This fixed the error and also proved just how small an error was noticeable with such a short horizontal handrail.
The photo below shows the jig (before the last modification) in place on the loco.
And finally…
The Model
The real ends went much the same way as the test on the spare end except that it was a lot easier to keep the jig in position because I had a whole loco to hold instead of just a piece of 10 thou sheet. Drilling the handrail holes was still a pain. My mini drill and flexi drive won't grip a 0.3mm drill so it all had to be done by hand so drilling the 16 handrail holes took forever. The upper holes need to be drilled through a 40 thou sandwich of nickel silver with a constant fear of breaking the drill (note to self: file a cutout in the backing pieces next time). I kept the drill lubricated and removed it regularly to clearing the swarf. Nevertheless I still broke several drills while drilling the jig and the real loco.
I'm quite pleased with the results so far. The accuracy is still not 100% perfect but I'm sure that it is a lot better than it would have been if I'd tried to mark everything out individually on the ends.
I made the headcode boxes from a piece of 10 thou nickel silver (another freebie from Allen), drilling a hole and opening this out to make a rectangle of the right size for the headcode box window, checking regularly with the vernier callipers and a square. Then I filed the frame to size around three sides of the hole, using the other side as a 'handle' (see the pic below). Finally the box was cut off on the fourth side and cleaned up. This is a time consuming job and I found it required a lot of patience and care to get an accurate result. Even so, I think that my efforts are noticeably less accurate than etched components.
I was quite careful while attaching the headcodes. First I tinned the back of the headcode and brushed the surface of the nose with Green Label flux. Then I put the jig into place and put the headcode box into the jig. I soldered just the free (outer) edge of the headcode box to the nose first with minimal (almost no) extra solder. Sometimes this took several attempts - it's quite easy to get a dry joint because there may not be enough heat going into the nose itself. Once the outer edge of both headcode boxes were attached and both checked for position I put the jig back on but moved it across to allow easier access to solder the inner edge of the headcode box. Once this was fixed I revisited the outer edge with more flux and a little more solder to ensure a good joint. Finally both boxes were checked by pulling them hard with tweezers to ensure that they were firmly fixed. I've found that once properly fixed these are very difficult indeed to shift - in some cases I wanted to move the boxes across slightly but I had to give up because I just couldn't unsolder them. Even unsoldering the headcode boxes after attaching them to the spare ends was quite difficult.
While attaching the headcode boxes I discovered another little error creeping in - even though I was very careful in aligning the jig to the etched centre line of the doors I still found that one headcode box was further out than the other. At first I thought this was just my mistake in aligning the jig but I had the same problem on the second end and I was sure that I had aligned the jig correctly. In the end I needed to deliberately move the jig across very slightly to correct this error. I still don't know where this error has come from.
After soldering the boxes into place on the second end guided by the jig I was not totally happy with how they looked - somehow they just seemed too close together even though the calipers didn't show any significant difference from the other end. I tried to unsolder them and adjust them but they wouldn't budge - the end of the loco is a very efficient heat sink. The next day I still wasn't any happier about the way they looked so there was only one job on the agenda - they were coming off no matter what. In the end I shifted them by adding extra solder inside the headcode boxes to allow more heat to be conducted onto the end from the iron. I also clamped a heat sink to the cab side in an attempt to reduce the risk of unsoldering the corner of the loco. I needn't have worried because I could actually see how much of it was hot enough to melt the solder - just a tiny circular area around the iron.
Anyway I got both boxes off without bending them too much and then cleaned the extra solder off the end. I then decided to modify the jig by making a small cutout below the inner bottom corner of the headcode box. This allowed me to see part of the etched oval line on the nose which turned out to be a better way to find the position of the headcode box. In the end I positioned the boxes so that they fully overlap the oval with about half the width of the etched line to spare. After removing the jig I was a lot happier with the result. I re-checked the other end and decided that I was still happy with it so didn't attempt any further adjustments
The circular openings near the top of the nose were made more three dimensional by making a couple of rings of fuse wire to fit into the etched circle. I found that coiling the wire round a 0.6mm drill was about right for this. These were attached with solder paste - not something that I like using because it always seems to fizz and leave a general mess to clean up, which is exactly what happened.
Lines to represent the extra fold in the gangway doors were scribed (carefully) with the craft knife. I don't know if this will be visible after painting - I'll have to wait and see.
The marker lights were drilled to 0.6mm and fuse wire rings soldered into place. These were then opened out slightly with a 0.75mm drill and lightly filed back. They should have a different appearance from the holes at the top of the nose even though they are made in more or less the same way. I'm not sure that this really worked - they still look pretty similar to me. On the other end I used a 0.5mm drill to make the rings and just cleaned the holes out back to 0.5mm after soldering. These seem to give a slightly better result. That does mean that my two ends are slightly different now but who can look at both ends of a loco at the same time?
I haven't yet added the remaining details to the nose ends because some of them will probably be quite vulnerable while I'm still building the loco. I have made a few sample handrails and brackets just to check things out. Positioning and holding some of them for fixing may prove to be a challenge. Here is a picture of progress so far. I hadn't intended to attach the handrails yet but while soldering the brackets this one decided to stay put. The photo has also shown me a few bits of stray solder that still need to be cleaned up. Try not to look at the 'N' gauge wheels - they aren't staying.
This is still an ongoing story -I need to make the holes in the headcode boxes go the rest of the way through the nose so that they can be backlit (one day). I haven't yet done all of the work on the other end of the loco and I also will need to come back again at a later stage to attach all of the more fragile bits and bobs.
I'm hoping that the valences will be rather more straightforward and that I can actually use the bits provided by the kit.
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