SHM 26

Superstructure - The cab's roof

	There's always something that you won't find in any manual. I wanted the roof to be removable. For two reasons the roof needs to be soldered from the outside. This is in itself a tedious job to work neatly. But this is complicated by the need to distribute the overhang (fore/aft, left/right) evenly over the roof's halves. I want to be able to decide later to construct the interior after all and in that case I need to be able to get to into the cab again.
	Like a number of other parts the roof shows etched rims that are not found on the protoype. So the first job was to file them flush. Sometimes I doubt my sanity, so much effort has gone into etching this detail. It was after all the reason why this part was etched in the first place! If not soldered to the cab's sides this roof will not hold its form accurately enough, so I needed to make two roof supports, that also keep the roof exactly in place.
	I drew the curve of cab's rear on a 0.8 mm brass sheet and sawed and filed it to shape.
	Once of the correct form and size I solderwd this piece on the brass sheet from where it came...
	...and sawed and filed the second piece to match
	I often use Blu-tack as a placeholder during the soldering process. It stick the parts together while I can still adjust them. With some care it enables me to work far more accurately than using the traditional clamps. Blu-tack has the drawback that is is sensitive to heat, so keep it well away form the soldering iron's action. WARNING: Wikipedia states The material has a flash point of 93 °C / 200 °F, at which it releases carbon dioxide, carbon monoxide, water vapour, oxides of nitrogen, and toxic fumes. It is not necessarily dangerous, but apply it with prudence
	Note that that I scribed several lines: lines on the fore and aft rims of the roof to mark the outer contour for the roof supports. The inner line at front was a miscalculation, only one line is need at each rim. There's also centre line.
	In the setup in the previous photo the idea is that the Blu-tack will hold the two pieces together until a first tack solder is done in the centre with a quick a quick pass of a hot iron. If you don't linger it won't hurt the Blu-tack. Note that the roof support also has a centre line which accurately determined with the caliper. Both centre line of roof and support are carefully matched
	Centre tack soldered in place
	Check if the support is exactly on the cribed rim line. I made some adjustments after this photo. In the upper right of the photo you can see the scribed line appearing, so I pushed the support a tad more forward.
	Then, one piece of Blu-tack is removed. This side is carefully pressed to the roof's sheet, thereby giving the roof it final shape, and tack soldered. That is repeated with the second piece of Blu-tack. Finally the whole edge is soldered in two strokes from centre, allowing the heat of the first to dissipate before the second is done
	The whole process is repeated for the second roof support. Match the roof on the cab after every single step, starting with Blu-tack. Make all necessary adjustments to ensure a good tight fit. If you work carefully you can a achieve a perfect match.

Done! The roof fits tightly with no play yet comes off easily with some careful effort.
From here I continued with adding some detail to the roof