Welcome to
Steve's Britannia
5" gauge Britannia
Assembly & Alignment Drawing Errors 1. Mainframes 2. Pony Frames 3. Main Axles 4. Coupling Rods
5. Bogie 6. Pony Truck 7. Brakes, Sanding Gear 8. Cylinders9. Link Motion 10. Oil Pumps, Saddle
11. Smokebox 12. Boiler Detail 13. Boiler Fittings 14. Superheater, Ashpan 15. Valves, Pipework 17. Cab Fittings, Clothing
18. Cab & details 19. Footplates & details 21. Tender Frames, Axles 22. Tender WPU, Brakes 23. Tender Body 24. Tender Body, Filter
Drawing 18 - Cab and Details
1. Cab Floor Supports    
The five cab floor supports were made from 1.1mm mild steel sheet, bent to create the angle-iron shape and the end folded in and silver-soldered. I made mine at right-angles to the spar rather then angled and filed the anchor blocks on the boiler backhead to suit. I managed to get one of the blocks in the wrong place and had to modify the spar to suit. After drilling the various holes and milling the slots, they were pickled in citric acid to remove the galvanising to allow the primer to adhere properly. After assembling the floor and cab, it became obvious that the holes for the handrails were incorrectly dimensioned on the drawing and will need to be redone.
2. Cab Floor    
The cab floor was marked out then finished to shape with hacksaw and files. Holes for the fixing screws were marked out, drilled and countersunk to accept 8BA c/sunk screws and finally spotted through to the support brackets. The timber floor boards will hide most of these. Other holes have been drilled as required including some tapped holes for the back wall. The angles to the sides are for fixing the side sheets to and there are a pair of small brackets for the angled walls at the front.
3. Cab Sides    
The cab sides have been made from the same material as all the other cab parts, scaling from the drawing where neccessary. To get the curved shape where the cabside meets the running boards, I set them up on the mill and drilled two 1/2" dia holes and finished with a 16mm end mill. The rivet holes were equally spaced around the perimeter, the ones at the base of the cab being for dummy rivets in the prototypical position rather that that specified on the drawing. I'm also fixing my cabsides using full-length brass angle instead of the method drawn. The four corners of the windows were also drilled prior to cutting out with a 1/8" dia end mill. In both cases, I'm doing both sides at once, clamped together.
Holes were also drilled for the windows runners, the windshields and the top gutters. A locating strip was also made which screws to the top of the cabside, held by two 8BA c/sunk screws, for positioning the roof. These screws are hidden by the gutter. Finally, 3/32" half-round beading was soft-soldered to make the window frames. I made them as four sections per window, clamping each section in turn, drilling three 1.1mm holes and fixing with fine brass nails. The sections were then gently eased to the exact position required, well fluxed and soldered. The window on the left needs a little more work but shows the finished job reasonably well.
4. Cab Rear Wall    
Cut and bent in the same way as all the other bits but included here for completeness. The angle brackets are home-made from offcuts of the same steel sheet and milled to 5/16" wide. They are fixed to the wall with 1/16" rivets and screwed to the floor with 6BA bolts. The shape was formed using the plan-view on the drawing as a template.
5. Cab Roof    
I've made the main roof section in three parts, mainly because it suited the material I had to hand. The two sides are mirror-images of each other and the shapes were cut before bending. The curvature of the roof has not been formed yet. Another offcut was shaped to give an approximate outline of the front facia of the cab, mainly to give the correct height above the firebox. This will be replaced later on with a more accurate piece.
The centre piece was then made to fit the gap, much easier than trying to get a single piece bent accurately in one go. Half-inch wide joining strips are fitted below and held with 8BA c/s screws and a removeable panel will be made to slide into the gap. The roof curve was formed around a gas cylinder. Finally, the gutter strips were fitted and the roof section primed.
6. Cab Fronts    
Getting the angled front walls of the cab required a lot of work with cardboard until I was confident enough to cut metal, both sides being very slightly different. A lot of trial and error and a whole cornflakes box needed. The two fronts were cut after marking round the template and individually filed to fit. Then they were covered with masking tape and the windows marked out. The four corners were cut away with a slot drill and the waste removed before finishing with files and sanding drums. The rivet holes were drilled using the DRO for accurate spacing and the hole at the bottom is for an 8BA countersunk screw, fixing to the tiny bracket at the front of the cab floor. Instead of using half-round beading, I am using 16 swg brass offcuts to make the window frames which should, hopefully, disguise the error in one of the lower corners (I filed them out too much).
The outside of the brass was worked until they were correct for the outside form of the windows, then very carefully postioned and held with clamps. Flux was liberally applied, lengths of soft solder cut and laid against the joins and heat applied slowly and carefully from below. The clamps lifted the assembly enough for the flame to go underneath. The windows were then chain-drilled from the back and the windows filed to shape. One of the frames was a little out of position so the assembly was gently reheated and the frame nudged over slightly to get it looking symmetrical. I shall round the edges off a little just prior to painting.
7. Cab Rear Screens    
The rear screen walls are different on either side, the driver's one being full-height with a window set into it. I am making both of mine to the pattern of the fireman's side for ease of access when driving. Once again, cardboard templates were made to fit the roof shape and two panels cut from 1.1mm galvanised steel sheet. I also made the angled pieces that support the two doors. The screen walls have dummy rivets for most of their height with a pair of 10BA bolts used to hold each of the angles. The angles on the upper sections support the roof. I haven't yet decided whether or not to fit the half-round beading.
8. Sliding Roof    
The removeable roof section also contains the two sliding panels that are, I think, fitted on all BR standards. Four thin strips of steel, 5/16" wide, have been placed two either side and fixed with 3/64" brass rivets to act as the guide rails. These were milled and drilled on a special fixture (described in the tools section). The sliding section was bent to shape and the rear gutter strip fitted. This extends across the fixed roof section and butts up to the side gutters, making it one less edge to catch a wrist on when driving and firing. The two pictures show the removeable section partially opened and fully closed.
The rails for the sliding panels are shown as a milled section but I have built mine up using three layers of the 45 thou steel with a narrower section in the middle of the sandwich. The holes are at 1" centres and the edge of the rails are at the edge of the cutaway. Because the roof was already bent, the fixture I made for milling the strips came in handy for drilling the holes. It was mounted into a tiliting vice to bring the drilling line level with the table.
I still need to make the handles for the sliding panels and these will be fixed with 10BA rivet screws. This will allow them to be dismantled at a later date, if neccessary. The final picture shows the whole thing assembled and ready for primer painting.
9. Windshields    
The windshields on either side of the cab have a top and bottom pivot block, the support bar and a perspex window. The blocks were made from 1/8" square brass, a 1/8" length turned to 0.067" dia, threaded 10BA then parted off 1/4" overall length. A 1.7mm cross-hole was drilled in the body of the blocks for holding the support bar. The support bar was machined from 1/8" dia brass rod, with a spigot turned on each end 1/16" diameter by 1/8" long. Over on the mill, a slot was cut with a slitting saw to squeeeze the perspex into. Although the drawing shows a 1/16" depth of slot, this would wreck the pivots on each end and a first pass was made at thirty thou depth followed by a plunge beyond the spigot to seventy five thou depth, along to the end and out again before hitting the spigot.
The perspex was marked out to the shape of the windshield, then cut out and filed to finished shape. A section was filed away at each end to clear the run-out of the groove and the perspex pressed into the slot. They are a tight fit and don't require any adhesive. I have made my windows 1/4" shorter than the drawing, more closely sized to the prototype, and the windshields are also a quarter-inch shorter than drawn. The final picture shows the driver's side in postition.
10. Cab Handrails    
There was some surplus 1/8" dia stainless steel tube in the stock drawer and this was used to form the cab handrails. Because of the three bends in them, I decided to do them in two sections with the join hidden in the doorway stanchions. Using tube meant I could easily drill and tap the lower section so that an 8BA screw could be used to fix them to the platform support. For the top, I made some 5/16" long blocks from 1/4" square mild steel with a 1/8" dia hole drilled for a 1/8" depth. These were then cross-drilled and tapped 10BA and bolted to the cab roof. The drawing shows a soldered fixing point but this is easier. I had to remake my platform supports because the holes were in the wrong place, though.
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