Drawing 17 - Cab Fittings, Clothing
1. False Backhead    
I have made the former for the backhead cladding in a similar fashion to the other firebox formers, using an offcut of 40mm solid oak kitchen worktop. The backplate is not flat, there being a fifteen degree change of angle about in line with the lower water level bushes and a return change near the bottom. After cutting out the basic shape with a jigsaw, I mounted the former on the mill table and set up to flycut the first angle. The nails are to prevent the wedges wandering downhill due to the slope. I have set the plate at ten degrees for this cut as it is the shortest distance and will leave the greatest thickness of material. The flycutter is a home-made affair with a boring bar in it.
This is the first section finished. Each depth of cut was 100 thou, four passes being needed to clean the top section. The small boring bar has one of the very sharp, polished carboide tips loaded. I needed the top to be square to the newly-created face and this was milled with a long-series 5/8" dia end mill, finishing at 2.15/16" from the bend line. A quarter-inch allowance had been left on the height specifically for this.
Then the work was set up at five degrees in the other direction to get the planned fifteen degree face. This one was more of a challenge to set up because the clamps have to be between the two bearing points of the former. To stop the workpiece rolling away, a cheap, rubbish square was clamped down to act as a fence where it overhung the edge of the table. The final setup was to create the 3/4" wide section at the bottom and for this the former was clamped flat to the table and the tool height set to just kiss the scribed line.
The backhead former has now been shaped and had the radii filed on. I tried to use the linisher but my belts aren't coarse enough and I was scorching the wood. The former was laid onto a sheet of 20 swg brass and the basic shape marked out with 3/4" allowance on each side for the returns. A fifteen degree fold was put into the workpiece and this was then clamped to the former and flanging began.
I annealed the material about four times and the next photo was taken after the second annealing. Because of the fairly tight bends at the top, the material was creasing quite considerably. After the fourth annealing, it became obvious that I would not be able to eliminate the creases. Unlike the copper for the boiler where the material was able to fatten up and flow, the thinness of the brass meant it was easier for it to deform rather than flow. Therefore, a pair of triangular sections were removed at each corner and the material beaten over in separate sections. These were then silver-soldered together prior to further melding.
Once the final shape had been achieved, the flanges were trimmed back to about 5/8". Then the backhead was offered up and the height set with packing. The bar across the top is to check that the top is about level with the bush for the steam manifold. Then it was just a case of marking out the various cut-outs for the boiler bushes, the firehole and the platform support blocks.
I marked the position of the gauge glasses by blue-ing the bush faces and offering the plate up. After drilling the four holes at 1/4", I checked the position of them and eased them to the correct positions with a rat-tail file. Then a step drill was used to open them up to the nearest clearance size. Next, I made up some spacers and washers to hold the backhead in the correct place using the blanking plugs I'd kept from the pressure test. I was then able to mark out the firehole from inside the firebox. This was set up on the mill to remove the waste.
Who needs CNC? CHC will do. Careful hand control enabled me to cut the waste out freehand using a 1/8" slot drill. The slot on the side is where my blower pipe comes out and should be almost invisible when the cab is built. As can be seen, the workpiece is clamped down onto a piece of timber and everything done by eye. Quicker than chain-drilling is one is careful.
2. Firehole Door Rails    
The backhead was replaced on the loco and the firehole dressed with files. Attention then turned to the firedoors and rails which are made from 3/16" square brass. These were cleaned up, followed by milling the door channel and drilling the mounting holes. For the lower rail, a pair of bosses from 3/16" plate were silver-soldered on and the holes for the bushes marked out. A pair of bosses with 3/16" dia spigots were also made up and these were soldered into 3/16" dia drilled holes. This provides a little mechanical strength as well, although I expect it's not needed. Ive also cut the material for the firehole doors from 16 swg brass sheet but I'm making these an 1/8" shorter than specified on the drawing because the oversize gauge glass assemblies would otherwise make it a bit cramped-looking.
3. Firehole Doors    
The firehole doors are more than just flat plates, they have some sort of baffle on the front. A piece of 16 swg brass was bent around a 5/8" diameter bar and two firedoor fronts cut from it. The sides were marked out by tracing from the drawing, then cut and linished to shape. As noted on the drawing, a spacer was used to help hold things together during silver-soldering. I made a pair of 3/16" dia rods drilled and tapped 8BA each end, then drilled 8BA clearance holes in the sides, a pair together each time. The small drilling fixture was particularly good for this.
The rods held the side nice and square and also acted as a clamping point. 1mm silver solder was laid inside against the corners and heat applied from below. Between the screws of the clamp the second one can be seen waiting to be soldered. The bottom was milled top size next; I removed the screws but left the spacer in place for rigidity. I scribed a line at 1.9/16" and set this, by eye, level with the vice jaw. Exact size is unimportant.
To solder the two parts of the door together, I put the screws back, just in case the second heat-up softened the earlier work, and made a horseshoe of silver solder to rest around the baffle. Heat was applied from below until the solder melted and flowed into the joint. One hand for the torch and one for the camera here. Last operation on the doors was to add the bosses for the operating levers. I made up a pair of 5/16" dia brass bosses that went right through to the door plate and step-milled holes to suit. This makes the boss stand vertical to the back face and saves having to make an angled face on the bosses. They can be soldered on the inside, too.
4. Firedoor Handles    
Before making the firehole door handles, I fixed the rails to the backhead so that I could check all the hole positions. The backhead was clamped onto a lump of 20mm MDF and the six 8BA holes drilled and tapped. The handles were cut from 16 swg mild steel sheet, then bent at the appropriate positions. The pivot bosses, as drawn, are on the wrong side of the handles. I silver-soldered mine on the outside, the bosses having a 3/16" diameter locating spigot. The slots for the door pins were done after bending.
The drawing shows the linking bar as a fabrication of three pieces but I made mine from 3/16" square brass bar and, after facing to length, drilled the two holes for the cotter pins. Then I milled the two slots using a 65 thou slitting saw. Then I milled away the top of the centre section to more closely resemble the prototype. I put some 1/16" packing pieces in the slots and dropped the bar into the vice. I'm only holding on 1/16" but it's enough for this.
To make the clevis pins, I used 1/8" diameter iron rivets, holding them in a collet and threading them 5BA. Because there is practically no head to hold on, I loaded them into a block with a 1/8" drilled hole through it, then offered it up to the collet. That's good enough to set them square and run a button die down.
After making the pivot pins, I assembled everything to check it all worked as it should. However, I didn't like the look of the handles, I felt they appeared too wide and clumsy. I decided to thin them down to 1/4" wide and also dress the heads of the clevis pins. I also made the brass top for the handle, which is soldered into place, and the door latch.
5. Dummy Gauges    
There are five dummy gauges to be made from brass bar. These were made in a single operation, drilling and boring the minor diameter through for either two or three parts per size, then boring the othr inside diameter for a depth of 5/32". The o/d's were skimmed and the smaller diameter turned behind with the parting tool. The brackets for the gauges have also been made from 20 swg brass offcuts, hacksaw and files being the main tools of the day. This one carries the main pressure gauge with the dummy steam heat gauge above.
6. Front Throat Cover    
I have made the front throat cover as three sections because it was easier to adjust for a good fit and because none of the joins can be seen when the loco is assembled. The material is 1mm galvanised steel with the galv dissolved off in the pickle tank. A 1/8" joiner at the bottom acts as a packing strip to space it forward to the correct distance and a single screw (not in this picture) into the foundation ring holds the assembly in place. The top will be held by two grub screws in the barrel ring: the two screws at the 4 and 8 o'clock positions are temporary. This needed quite a lot of fiddling around to get a nice fit at the sides and barrel.
7. Firebox Cleading    
The cleading for the firebox was cut from 24 swg brass sheet after first making up the sides in cardboard. To keep things manageable, I went for a join in the middle using a couple of pieces of 14 swg brass for joining strips. I started using 12 BA screws to fix the cleading but stripped a couple of threads. I then discovered that my small-head 10 BA screws were made from the same hexagon-size as the 12 BA screws so opened all the holes out to the new larger size. Having it in two halves also made it easier to mark out the position of the steam manifold and much simpler to put the bends in using the club's bending rolls. I will put a few more screws in later but they wont be trying to represent the spacings of the prototype.
8. Dummy Mud Rings    
There are four mud rings on the top of the firebox and two near the front of the boiler barrel. To make these, I started by parting off a load of 15mm copper tube into 5mm long rings. These were then squashed in the vice to form the oval shape and reformed at each end around 3/8" dia bar. A piece of 20 swg brass sheet was coated in flux, the rings rested on top and a piece of silver solder rested inside each ring. Heat was applied from below the sheet until all the solder had melted. It naturally flows to the edges of the ovals and penetrates underneath. The picture shows the assembly a minute or so after the heat was removed.
Each of the mud rings was then cut from the sheet with a junior hacksaw and the edges linished. Meanwhile, a start was made on the mud hole bridges, with a pair of 2mm channels being milled into a length of 1/2" x 1/4" brass bar. The outer wall thickness is about seventy five thou. To make each bridge the end of the bar was first cleaned up in the lathe followed by drilling the bolt hole on the mill. These were then cut off with a hacksaw and put to one side.
Once they were all finished, they were set in the milling vice and finished to 3/16" thick. Then they were loaded back to the vice and the legs formed by milling away the outsides as shown. This method allowed them to be upended and the other side done at the same settings, leaving the legs 1/16" thick. I kept the cutter at the finished depth and milled with the side of the cutter, 25 thou per pass. Back with the soldered parts, an 8BA hole was drilled and tapped in the centre of each dummy mud ring and a bridge screwed to each. I haven't bothered to completely clean up the outside of these because they are never seen once they are soldered into the cleading.
9. Dummy Washout Plugs    
Because I decided to do away with the square-ended stays at the top of the firebox, I needed twenty-one dummy washout plugs and I have made these from 1/2" dia brass bar. First operation was to turn the two outside diameters, drill a 6BA tapping holwe and part of to length. I have made mine a little shorter than drawing to reduce the chance of fouling on the cross-stays, with 5/32" under the head and a 1/32" thick flange. For the second operation, I changed over to an ER25 collet and plunged the bore with a small HSS tool. Because one cannot control the depth with collets like this (except with a backstop bar), after tightening I touched the tool on and wound the compound eighty thou to set the depth.
The square plugs were made from 1/8" square brass, held in another ER25 collet. Because it is an eight-segment collet, it held perfectly well in the 3mm-4mm dia one. They were turned to 110" diameter by 3/32" long and threaded 6BA then parted off with the square section finishing at 0.105" long. These were then screwed into the plugs and pulled tight, followed by linishing the backs flat. The one at the bottom is finished. The holes were marked out on the cleading and drilled next, using a stepped hole drill to make the 3/8" dia holes. A length of 4" x 2" was clamped to the table and a 1/2" hole drilled quite deep. The sides were then rested on the timber and the holes drilled freehand. It is worth mentioning that these type of cutters cannot grab because of their geometry and also that the top of the cleading acts as it's own fence, resting against the side of the timber.
I drilled and shaped the mudrings at the same time and then soldered these to the cleading, setting them about 1/8" below the surface. I've rested a horseshoe of solder on each one prior to heating. The dummy washout plugs were soldered in next, remembering that there are six high-level ones on the driver's side and only five on the fireman's side, offset a little forward of the others. This is what they look like on the driver's side although I have not put the mudhole door handles back in yet.
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