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Steve's Britannia
5" gauge Adams O2 - Calbourne
Drawing E1(a). Drawing E1(b). Drawing E2(a). Drawing E2(b).
Drawing E3. Drawing E4. Drawing B1. Drawing B2.
Drawings S1 and S2 Boiler Assembly Assembly and Alignment Errors and Ommissions
Drawing S1- Running Plate, Tanks, Cab etc.
  1. Sole/Running Plate  
I was in the mood for a bit of tin-bashing so decided to make a start on the platework. This is mostly specified as 16 swg brass sheet but I shall be using 1.2mm steel sheet throughout which comes from the skip of a local fabricator (with their permission, of course) and is galvanised. I do all my marking out, cutting drilling etc first, then get rid of the zinc by pickling in citric acid before final clean-up and assembly. Paint does not adhere well, if at all, to galvanising even though it appears to be one step backwards with regards to rust prevention. I'm making a few changes here because the rivet detail on the drawing is wrong and the base of the side tanks are the actual running board. First job was to calculate the actual rivet spacings - 515 thou instead 0f 500 thou - and I also added some extra rivet detail not shown on the drawing. This is a top view of the latest "00" gauge version of the "O2" from Bachmann and this malachite green livery is only available from the Isle of Wight Steam Railway. I've checked the rivet detail at Havenstreet and it is very accurate.
There are six pieces in all, two from the front buffer beam to just short of the tanks, two to the centre of the cab doorways, one piece for the rear footplate and bunker combined and, finally, the small front central panel providing access to the oil reservoir. These are the first two sections cut and drilled. I've made the separate running plates for the sides and the cab footplate as well, once again spacing the rivets to match the prototype. There won't be many pictures of this work, it's just simple cutting out and drilling of holes. The tanks will be stand-alone items that fit to the soleplate. This overview shows the first five panels bolted together and sitting on the frames.
The final panel is the front cover and I've made this as a single panel as per drawing. In real life, there is a hinged section that gives access to the ends of the cylinders but this isn't large enough to get to the oil which hides below so a deep scribed line will mimic the join. It has a couple of tight bends in it to match the shape of the frames and these were formed by bending around some 5/8" dia bar for the first one, then around 9/16" diameter bar for the second one. I don't have a bender so this has to do.
When it comes to simple drilling, I don't always bother to clock out the component accurately. I just load against parallels and wedges set in the table slots, then set up the DRO by eyeballing a scribing needle held in the drill chuck. Within five thou is plenty good enough for decorative rivets. This is the front panel nearly complete. I can't set the finished depth until the smokebox is made and will put the lifting knob in once the final size is known. All the rivets will be fitted when I'm happy there is no further work to be done to any of the panels but, for this front panel, two of the rivets will be soldered in with tails underneath to act as locating pins into the top of the buffer beam. All the others will be cut and hammered flat underneath.
  2. Side Tanks  
Although most people seem to make their water tanks from brass for obvious reasons, I'm staying with the steel sheet. The Britannia tender was drawn as a sealed-for-life tank under the coal shute so that had to be rust-proof but there is full access to the inside of these side tanks because of the removable tops. Therefore, I'm going to try and line the inside of the tank with latex or similar when the panels are fixed together. Most of the panels are straightforward rectangles but the outside panels curve upwards towards the roof for a short distance. I used the boring head set at the correct radius to form these curves as I think it's easier this way but they could have been cut freehand because there is beading to be added later which would hide imperfections.
I'm using 8BA countersunk screws to fix the tanks together and now everyone can see where all that brass angle I made was used. I have made a separate inset panel for the bases so that the tanks can be removed intact from the loco if ever needed. The first tank is built up and the parts for the other are in a heap on the bench. To fix the tanks to the soleplate, I have silver-soldered three 2BA screws, with most of the heads removed, to the baseplate so that the tanks can be nutted from below. Matching holes were drilled in the soleplates.
The tank tops needed the filler pipes fitted and these were made from mild steel bar, turned with a locating spigot and silver-soldered to the lids. And, finally, a couple of pictures of the tanks sitting on the soleplates, the last one with the filler caps rested in position. There is a lot more work to do on the tanks but this is a good start.
  3. Front Splashers  
The front splashers include the leading sandboxes and I'm planning on making these functional. I've made a couple of changes to the sand valves but that's for later. The main part of the fabrication consists of four pieces, the curvy bit which runs from the back to the underside of the top panel, the top and end panel with the bend and the side and inside panels which are both the same. I'm really annoyed with myself because I accidentally deleted four photos of the individual parts and the set-ups for soldering so the first couple are the panels silver-soldered together.The two side panels were clamped around two spacers to hold them square and the curvy part, made over-long at both ends, was soldered first. Then it was dressed flush with the top and the bent section, also overlong at both ends, soldered on and dressed back when cool. The inside panel is recessed so that they fit up against the frames although there is a cutout needed at the front. The large hole is for the filler pipe to be fitted to and the smaller one the top of the valve assembly. There is also a hole shown on the drawing for the feed water pipe but I won't put this in until the boiler is done.
There is a floor piece to separate the sand hopper from the wheel splasher which is shown brazed into place. I'm going to keep mine unsoldered but a good fit because, once soldered, there is no further access to the sand valve. The floor piece is screwed to the soleplate to locate the main assembly over but, now that I've tested it, I'm going to solder a lug on at the front to hold the sandbox down onto the soleplate. Two screws already hold the back end in place. After that, I made all of the small parts assocciated with the sandboxes and fixed the filler pipe to the top with silver-bearing soft solder; I didn't fancy bringing the assembly back to silver-solder temperatures again. The last picture shown the filler caps and the top of the sand valve but I haven't fitted the spindle yet.
  4. Bunker  
Continuing with the platework, I have made some of the bunker and cabin parts and the first part to be made was the rear spectacle plate. Most of these items are simple marking-out followed by cutting and filing to shape and this one has to follow the underside of the roof. I used my Abrafile to cut the shape, then cleaned it up with sanding drums and files. The windows were cut out with a hole saw, then finished with the boring head. I get a couple of free penny washers as a bonus. The sides were next, the rectangle just sawn to size and two of the curves formed once more with the boring head. There is a cutout where the panel that spans the doorway fits and this was milled out with a small cutter to ensure a nice square corner.
The bunker rear panel was a little more difficult because of the two bends and me not having a bender / folder to use. A variety of clamps, vices, metal bars and large hammers were all used to beat the thing into submission. Suprisingly little swearing for this one, I must be getting the hang of this lark. Here, it sits between the two side panels. The various holes for the lamp irons and number plate were drilled, along with all the fixing holes for the jointing angles. More of my home-made brass angle was cut to suit and the three components fixed with 8BA countersunk screws. These allow me to assemble and disassemble at will, but will be filled with putty before any painting starts. The grey finish is where I have dissolved away the zinc in citric acid, followed by soaking in phosphoric acid for the protective layer.
The two pieces that bridge the doorways were made next and have been joined to the rear spectacle with brass angle. I'm planning on making this whole section removable so there will be some changes to how DY has drawn this area. For the moment, it just rests in place with a couple of clips to get a visual. And, finally, a view from the rear quarter showing how the basic shape is coming together. I never used to like tin-bashing much but it's quite satisfying when so much comes together in a relatively short space of time.
  5. Bunker Bulkhead  
I've now made the bunker forward bulkhead along with the two seat boxes, the shovel plate, coal hole door, door rails and the ledge which extends back to the rear spectacle plate. As can be seen, it's all simple cutting and drilling. The brass angles are riveted to the platework with the heads on the inside. On the visible side, they have been hammered flat into decent countersinks and filed flat. I've added extra angles around the base so that the bunker assembly can be screwed to the rear soleplate. This is the bunker assembly screwed together with the coal hatch sitting in the runners and the top ledge attached to the bulkhead.
With the rear spectacle plate set in position, I can now mark out and fix the other angle to it. The angle will rest on the ledge when in display mode but will not be fixed to it. The spectacle, door arches and roof will be removed as a unit when it is on the track. I can also replace the two temporary side angles with narrower ones to match the crossways angle. I wasn't happy with the spectacle plate - it was a little out-of-square - so I've remade that. The replacement angles have been made and are mitred to the crossways angle, and this time I've riveted them to the spectacle plate. This is a simple setup for creating mitred ends.
I've also made the locating arrangement for the fronts of the doorway panels. A section of plate has been silver-soldered to the inside of the panel and a catchplate made for the lower section, held in place by the fixings for the exterior handhold. It's basically an adaption of the permanent fixing that DY had drawn. The tabs need to be marked and cut to fit the slot milled in the back of the catchplate With the tanks and the bunker bolted into position, I was able to make the tab to size and there is also a little movement available in the catchplate holes to allow for fine adjustment. And one more photo showing the bulkhead with the coal plate and hatch in position. The spectacle plate looks better now, as well, with the narrower angle. I just have to drill a couple of holes and solder some a pair of locating pins to the crossways angle.
  6. Window Guards  
Calbourne has two protective covers over the rear spectacles to stop coal breaking the glass. There are a couple of ways one could make these but I chose to make mine from a solid billet rather than try to solder bars onto the cover plate. DY suggests the same in a note on the drawing and Nigel has made his in a similar fashion. Two billets were cut from 2" diameter mild steel bar, each about 5/16" long. This is a job that lends itself pefectly to soft jaws and a set were machined to suit. The jaw recess is only 45 thou deep but plenty enough to get a good hold on the material. The billets were faced on one side and the o/d turned to 1.850". Then the billets were reversed and the other side faced to leave them 1/4" thick. Again, the o/d was turned to 1.850". Next, the inside of the billets were bored using two different boring bars and finishing with a third boring tool with a large radius.
The billets were reversed in the chuck and the outside turned first, followed by the external radius which was blended in by eye. The flange thickness is 1/16", hence why the jaws are only bored 45 thou deep. From here, it was over to the mill with the chuck and the waste milled away to leave the protective bars. The drawing is wrong because DY shows six bars over the windows but Calbourne only has five. It may have had six in earlier times but that's not what I'm modelling, I'm representing the loco in it's current form.
Four slots were cut using a 1/4" diameter end mill, working down in 25 thou passes until the cutter just touched the flange. By moving over 5/16" on each slot, I finished with bars that were 1/16" thick. The final two sets of passes on the outside formed the outer bars. Some additional filing was required because of the underside radius but they've come out looking not too bad. These will be cleaned up properly later and, once painted, should look quite respectable.
  7. Footsteps  
There are four sets of steps on the loco and they are all the same so four pieces were cut from the material and also a piece of MDF to act as a support. I've sawn out the shape on the MDF because I've found that the milling cutter speeds I use for the steel are too high for the MDF and it scorches, overheating the cutter. The dust is pretty awful also and I usually wear my respirator mask when using this material but it is nice and flat and takes good clamping pressure so I'm happy to use it.
I thought it easier to do all four as a stack and put the single bend in later on. After working out where the centre of the radii were, I used a 12mm end mill to rough out the waist / waste (both being appropriate here) followed by the boring head which had been preset to cut 1.250" diameter. A third clamp was added near the middle before removing the right-hand one to allow acces for drilling the rivet holes. The two steps will be fixed with 1/16" diameter iron rivets after the zinc is removed.
Eight treads were made next, four of each, bending the backs first followed by drilling the rivet holes and, finally, curling the ends upwards. The top of the steps were bent but the fixing holes will be drilled once I decide how to fix them to the underside of the running boards. The parts were pickled in citric acid before riveting together. These are the four steps ready for fitting.
  8. Air Reservoir  
Calbourne has air brakes and the air reservoir is a prominent tank on the left-hand side of the loco. A piece of brass tube was purchased for this which was cleaned up with emery cloth and faced to length. A pair of bungs were made for the ends from some 1.1/4" diameter brass rod, skimming the o/d and forming the front reccess with a special radius tool. A 7/32" diameter hole was also drilled for the air inlet. The front was further reccessed with the same tool and the air connection point tapped 1/4" x 40 tpi before the cap was parted off. Two were made, one for each end, and will be silver-soldered into place.
I wanted a decent-sized chamfer on the backs because these will be soldered from the inside and this will keep the solder in place during the heat-up. These are the parts, ready to solder together. A pair of rings, from 1mm silver solder rod, were made a nice fit to the bore of the tube. One of them is in the tube already. The ends of the bungs were coated with correction fluid to stop the solder wandering away.
Flux was painted on the inside of the tube and around the perimeter of the bung, then the solder ring inserted into the tube a short way. The first bung was pushed into the tube until flush and then set up in the hearth. The bung was a nice, sliding fit and I'm doing one end at a time. All the flux and the solder is inside and heating was done from the outside. I've kept the tube as upright as possible to encourage the solder to flow all round, rather than pooling at the lowest point. It's not a very good picture but I can see that the solder has melted and flowed into the joint.
The other end was set up in a similar fashion but, this time, I wasn't be able to see the melt and had to rely on watching the colour of the tube to know when I had reached temperature. The workshop lights were doused and I heated until the tube was a little past dull red at the bottom. This was taken after I had put the torch down. It was impossible to tell if I had full penetration from sight alone so, after giving it a good soak, then cleaning up all round, I hooked it up to my hydraulic test kit. The drawing calls for testing at 100psi but I've pushed it up to 200psi and it held this for fifteen minutes before I let it down.
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