Welcome to
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 E4- Brakes, Buffers etc.
  1. Buffers and Stocks  
The buffers stocks are comprised of two parts, the main stock and the mounting plate. On the prototype, the backplate was a noticeably larger diameter than the base of the stock but, nowadays, they are both pretty much the same diameter. I'm modelling Calbourne as she is at the present time and have made the parts to represent this. Billets were cut from 1.1/8" dia stock bar for both items and also the buffers. I started by facing and lightly skimming all the billets for loading to soft jaws. I decided to make the buffers first and machined them in various operations; first the length, then the stem diameter, then the radius in the root etc. Soft jaws are excellent for consistent reloading with practically no runout.
I also made the buffer stocks in a similar fashion, forming the shape one step at a time. First by roughing out the o/d, then drilling and boring the buffer guide, using a radius tool to finish the o/d and form the root radius and then finishing the nose detail with another special tool. The base for the stocks were also machined in a similar fashion. The chuck was removed from the lathe and remounted on the mill table. Once centred, all the holes were drilled and tapped, as appropriate in both the stocks and the bases. The picture shows the modified bases that I have made to suit the different orientation of the stocks.
The red arrow is pointing at the fixed pivot and the blue arrow at the driven point. Both pegs are 5/16" diameter. The drawing shows the radius of the buffer faces to be 3.250" and this is the spacing between the two reamed holes in the bar that drop over the two pegs. This second picture shows the position after the cross-slide has been wound to the mid-point when the bar is parallel to the bedway. The facing tool is set so that it hits centre at this point and adjustment of the tool is made using the compound slide. Here is another view of the bedway clamp which has a myriad of uses from backstop to tailstock buffer to fixed steady, the list goes on. I also (incorrectly, as it happens) marked the connecting bar with the distance between the pivot holes.
The facing tool is set so that it hits centre at this point and adjustment of the tool is made using the compound slide. Here is another view of the bedway clamp which has a myriad of uses from backstop to tailstock buffer to fixed steady, the list goes on. I also (incorrectly, as it happens) marked the connecting bar with the distance between the pivot holes. I've set up the camera to record the operation. This video shows me winding the cross-slide to the middle, backing off again, adjusting the compound slide for another twenty thou and taking a second cut. One last job was to drill and tap holes for the buffer retaining pins and I managed to drill mine without breaking out the front of the buffer face. The chuck went back to the mill with the soft jaws loaded and the holes were drilled to depth using my fancy new depth-stop. I have also swapped 5BA for M3 in this instance. These are the finished components.
  2. Brake Rods and Adjusting Bottles  
The adjusting bottles were made from 5/15" square mild steel but, not having any in stock, I used door-handle spindles instead. They are about fifteen thou undersize but makes no difference to the job. Drilled and tapped in the lathe, then parted off to length. The longer open slot was milled out by keeping the open end intact during the main part of the work, then cutting away with a hacksaw. It was then returned to the vice with a piece of packing in the slot and the end milled out to size.
The front brake rods were made from 3/8" x 3/16" flat mild steel, milled to thicknes first and the offset formed next. The holes were drilled next, done back-to-back in pairs and pinning the first two before moving along the vice and drilling the second pair.
The outer shape was formed in the same manner as all the other rods, on a fixture with spacers made to suit the offset. The rear brake rods have forks at the ends so a different approach was used for these. The main section of each rod was cut from 2mm sheet steel, the shape marked out and then milled to the scribed lines. A couple of different arrangements were needed to get these right.
The fork was made by milling out a short slot in some square bar.
I drilled and pinned these to the end before silver-soldering. A pair of 4BA studs were made for silver-soldering to the opposite ends and I turned a 1.3mm dia stem on these for locating in a drilled hole in the end of the rods. These haven't yet had the final shape of the fork machined and I marked the drawing to remind me that the forks are offset a small amount.
The cross-hole in each fork was drilled first, followed by shaping the back with an end mill and, lastly, cutting the slot with a slitting saw. These are the finished brake rods, complete with their adjusting bottles on the ends.
  3. Brake Trunnions  
These two trunnions support the main brake shaft that carry the bellcranks to the air cylinder and the handbrake. Some 1" x 5/16" black bar was cleaned up to give two billets 7/8" wide by 1.11/16" long and 1/4" thick. The three fixing holes were drilled 6BA clear and a 13/32" diameter hole drilled and reamed to take the boss. The oval-shaped hole was milled in each and, over on the lathe, a pair of bosses machined for silver-soldering into place.
The next job was to mill the upper back part away where the trunnions bolt to the frames. Then they were flipped over and the lower front section milled away. The packing at the back of the vice brings the top level and the packing adjacent to the moving jaw is not actually doing anything, the workpiece resting on the top of the vice jaw.
To get rid of the milled edge I used a 16mm ball-nosed cutter. After this, the workpiece was turned over and the other side milled to leave the thickness a bit over 1/16". The boss was soldered in next and, once cleaned up, the final shaping done. Using a 2.9mm drill in the small hole and offering up fifferent drills to the large hole, I was able to get the cutter to just touch the boss and run out at the shoulder at the other end. I've just noticed that I need to radius the top of these trunnions but, apart from that, they are finished.
  4. Brake Hangers  
These have been made from 10mm x 6mm flat mild steel and, as is usual, I started by drilling all the holes. Then a simple fixture was loaded to the mill and two 2BA holes drilled and tapped to hold the hangers. 2BA fits nicely through 3/16" diameter holes. I also made four filing buttons, two of which are being used as washers and act as a visual guide when milling. The fixture was then moved to a tilt-and-swivel vice and the angle set for shaping the sides. All four filing buttons are in use here and act as limiters. After doing one side, the work was simply flipped over and the other side machined.
The other ends were done in the same manner but with the vice set to a slightly shallower anlgle. Then the vice was set back to zero and the arms thinned to the required thicknesses. The DRO was centred on the brake block pivot hole, then working either side of zero along to the respective buttons. I could have filed the bosses to shape but I was feeling lazy and made a simple mandrel to hold them in the lathe and turned the bosses to shape. A left-hand tool mounted in the front of the toolpost gave me access without clipping the protruding bits. The drawing shows the upper boss to be 9/32" thick but I have made mine 7/32", same as the lower one, and compensated by making four spacers to fit on the brake hanger pins.
  5. Brake Blocks  
The last few days have seen some milder weather and I took the opportunity to spend a little time in the workshop making the brake blocks. Like others before me, I have cut some blanks from an old brake disc which is a source of high-quality cast iron. The blocks are an awkward shape so I cut a rough cardboard template to act as a guide. The material was faced on both sides to bring them all to the same thickness although it's a little under the size specified on the drawing. A 20mm diameter back-stop behind the workpiece keeps it flat and level.
These are the four blocks with the outline marked in felt-tip pen. I also marked the pivot-point and these holes were drilled and reamed 4mm diameter. To start the clean-up, a 5/32" diameter pin was pushed through all four and used to support the blocks in the vice, aligning the first edges by eye. There's quite a lot to come off in this first milling operation, needing about a dozen 25 thou cuts to get to 3/32" above the top of the pin.
Once that was complete, a clamp was used to keep them together. The angle over the back of the blocks is 120 degrees so the assembly was rotated and set against a 30 degree angle gauge, this being held in place by the magnetic stand. This is where an extra pair of hands would be useful.
These edges were also reduced to 3/32" above the support pin, leaving the back of the brake blocks complete. The heel of the blocks were a little more difficult, needing to be at 112 degrees to the adjacent edge. Because they are being held against the right-hand edges of the vice jaws, I used packing at the other end to ensure that I could get the vice really tight. The protractor (or whatever it's called) is set to 68 degrees.
The toe-end was done in similar fashion but resting on a parallel and with a short pin keeping them aligned. The basic shape has now been achieved, leaving the circumference of the wheel to be machined. I don't have a faceplate for my lathe so an old fixture was pressed into service. I won't bother to describe the maths involved but each block is clamped, in turn, to one side of the fixture with a pair of anti-rotation pins to the back and a packing washer to lift it off the plate. The lump on the other side acts as a counter-balance and a means to measure the diameter
I wanted to use a 5/32" thick slitting saw to create the slot at the back and had to devise a way of holding the work. I modified an existing fixture so that I could bolt my small milling vice to it. With the moving jaw at the bottom, it's much easier to load the work and see what you're doing. Also, no large overhangs anywhere.
After a bit of linishing all round, these are the finished blocks. And this is one mounted on the brake rigging. I haven't yet machined the relief on the front face of the blocks because I want to get to Havenstreet and see if that feature still exists on the current brake blocks. If it does, it's a simple matter to skim a few thou off the faces. If not, then they will stay as they are as I'm modelling the loco in it's current form.
  6. Brake Cylinder  
The brake cylinder on Calbourne is air-operated and is quite noticeable under the right-hand running board. The drawing shows quite a basic affair so I have tried to make mine look a little more like the prototype. I machined the cylinder from 1" dia brass bar, reaming the bore at 5/8" diameter and turning a pair of external spigots on the ends. Two end-plates were made from 1/16" brass sheet, bored to fit the cylinder spigots, and a backplate (not in the picture) from 1/4" thick brass plate. I also drilled the various holes in the three plates to get the correct orientation; four in the top, six in the bottom and four in the backplate.
After some time in the citric acid pickle, the parts were assembled together, well-fluxed and snippets of silver solder placed at the joints. Two horseshoes of solder were laid over the cylinder ends, then heat applied from below until the solder flowed. When the lower joints flashed, heat was directed down the bore of the cylinder and, moments later, the two horseshoed melted in. The top cover was made from 1.1/8" diameter brass bar, turning a spigot on the front to suit the cylinder, then parting off to size. The air inlet pipe sits on top of this and was made from 3/16" diameter brass rod. The 3/16" x 40 thread was cut first, followed by drilling a 1.5mm hole down the centre for about 5/8" and finally parting off 1.1/4" long. A radius was linished on the end, a thirty-thou flat milled on one side and the two parts silver-soldered together. The air inlet was finished by drilling from the underside for about 1/8" and redrilling the hole in the pipe until the two holes met.
The bottom cover was turned from 1.1/8" dia brass bar, drilled and reamed 5/16" dia, and a 3/8" diameter boss turned for about a quarter-inch, then parted off. The six bolt-holes were drilled on the mill but I forgot to take a picture of this part. I did want, however, to reproduce the four webs on the plate but didn't fancy trying to solder individual wings to it. Instead, I made the webs as a single item starting with an offcut of brass bar that I drilled and reamed 3/8" to fit the boss. A 1/8" end mill was used to take a series of back-and-forth cuts across the billet until I achieved the shape shown in the right-hand photo.
The corners were then knocked of with a larger endmill to leave what looked like a flat-bladed pump impellor. After cleaning up, the "fins" were set on the bottom cover and the parts soldered together with silver-bearing soft solder. The next two photos are before and after.
The front of the soldered assembly was turned away on the lathe, then the end-cap loaded to a 5/8" collet in the square block and the shape of the webs milled using gentle plunge cuts.
The piston was made from 5/8" diameter brass bar, lightly polished and about three thou under nominal, with an "O" ring groove cut to suit whatever I found in the box. I wasn't worried about a tight fit of the piston to the bore, that's the job of the "O" ring. This is the collection of parts that make the finished article. After a session in the shot-blast cabinet, this is the finished article ready for painting and assembly.
  7. Handbrake  
The two bell-cranks had to be fitted to the brake shaft and, once again, the designer had made a pig's ear of things. The bellcrank for the airbrake on the right side of the loco was fine but the one for the handbrake on the left was drawn completely wrong. To the left is what he drew and to the right is what he should have drawn! Both arms need to be outboard of the spacer piece, not either side. I unsoldered the two arms and remade the boss to allow both crank arms to fit on one end and spaced correctly, then silver-soldering the parts together again. The handbrake adjusting bottle has been fitted to the lever arm with a clevis pin and the winding bottle to the lifting arm, with the winding shaft temporarily in place.
The handbrake pedestal has been made from a piece of bronze plate, milled all round to produce a regular block at the maximum dimensions. After setting up on two parallels, one was removed and the other moved to the centre to allow drilling of the four mounting holes. The sides were milled away next, using a 3/16" diameter end mill.
The upper catchplate was made next from 1/8" x 1/2" brass bar and the three holes drilled. The handbrake pedestal was held vertically and matching holes drilled and tapped, as appropriate. After taking this photo, I milled the counterbore which I had forgotten to do before. The catchplate was bolted to the pedestal with 10BA bolts and a 4.1mm drill dropped through for alignment, The the top outer edges were milled away.
The assembly has a curved outer face of about a 3/4" radius and the lower section tapers inward towards the top before returning to the original size. I made a carrier from a piece of 1" x 1/2" steel bar, drilled and tapped 8BA, to hold the workpiece. Nowadays, I tend to use these carbide PCB drills for shallow holes up to 3mm because they don't need centre-pops first. The four holes are 1/4" deep. I'm getting clumsier as I get older and find free-hand tapping of these small holes more difficult than before so used a small home-made tapping fixture to carry the tap.
The assembly was bolted to the carrier, mounted in the 4-jaw chuck and clocked reasonably true. The compound slide was set round to 1.5o for turning the tapered section. The diameter was turned in stages until the last hint of witness disappeared, then the tapered section cut in using the compound slide to back-cut.
The left-hand picture shows two views of the finished pedestal, although a fair bit of polishing is still needed to make it pretty. The handbrake shaft and handle had been made previously, the handle being made by silver-soldering a bent piece of 3/32" diameter mild steel into a 1/4" diameter rod. The shaft was 5/32" diameter material with a stop-collar silver-soldered on part-way up.
And this is the complete assembly bolted to the end of the water tank, with the full-size version afterwards.
  8. Vallances  
Starting with a 10 foot length of 1/2" square brass tube, I promptly converted it to 20 foot of brass angle by hacksawing it diagonally throughout it's length. Two pieces were cut off at 24.5/8" long and the edges milled down to create some 3/8" x 3/8" x 3/64" angle, milling along the length of the vice jaws, stopping the machine, rewinding the table and sliding the work along for the next pass.
The top section of each end was milled away to clear the buffer beam, then three holes drilled and countersunk each end for 8BA c/s screws. 20 swg brass plate was used to create four end-pieces for soldering to the main vallance. They were cut as oversize rectangles, a small lip milled away on the underside, then jointed with silver-bearing soft solder. Shaping was done afterwards.
On the mill, some angle plates were set up, the buffer beams clamped in place and the fixing holes for the vallance drilled and tapped 8BA. There are two centre supports between the drivers and the rear bogie that are made from 1.2mm steel sheet, These were cut and bent to suit, then bolted to the frames. Difficult to see but one side is bolted on and the other side is resting, inverted, on the frames.
  9. Main Spring Brackets  
Don Young never drew any part of the authentic main wheel springs for this loco, relying on a single coil spring below each axlebox. However, one model engineer, Nigel Bennett, drew out the various components to make the traditional leafspring components for his very nice model of "Ashey" and kindly sent me a set of his drawings so that I could make the same for "Calbourne". I started with the spring brackets, cutting eight pieces from some 25 x 10 black bar and milling all round to get blocks at the maximum dimensions. Then one side for reduced to 17mm for about 20mm length. These drawings are in metric so I decided to work in metric, complete with metric cutters, without converting anything to imperial, just to remind myself that I could!
One change I made is the frame bolting arrangement, opting for three M3 screws instead of five M2.5 screws. The three holes were drilled through 2.5mm diameter, then tapped M3 freehand in the bench vice. The DRO was zeroed on the fixed vice jaw and the middle hole. Next, the root of the inside shape was cut, plunge-cutting with a 6mm diameter end mill.
Three more operations were done with the same setup to produce end-points for shaping the sides of the vertical component, working plus or minus either side of the centre-line. The same cutter was then used to reduce the leg to 12.5mm. These are the eight brackets, starting to take shape.
To do the rest of the machining, I made a fixture with three bolt holes from a piece of 1" x 3/16" flat bar. I drilled the holes 3mm diameter for a good fit on M3 cap screws and fixed each bracket from below. After milling some soft jaws to take the fixture, I had to clock the tilt-and-turn vice in the "tilt" plane to compensate for jaw-lift. Then the vice was set round to 23 degrees to form the foot of each bracket. The DRO was zeroed on the inside of the ankle and the 6mm cutter was worked round in conventional mode to form the shape.
Once all eight were done, they were remounted and the cutout for the spring support pin plunge-milled with an M5 cutter. That completed all the work in the T&T vice so that was taken off the mill table and replaced with my main vice. The fixture was clamped in the vice, set at 67 degrees, and the holes for the spring pins drilled 3mm diameter. These were then widened and elongated with a 3.5mm dia slot drill. I modified the fixture plate for the last couple of operations; counterboring the screw holes, shortening the front end and cutting off the corners. This was to allow a 12mm endmill to cut the big radius on the back of the spring brackets. The fixture was clamped to the rotary table after carefully working out where to position it. The spring brackets were then screwed in turn to the underside of the fixture. The extra fences are to prevent the fixture rotating about the single clamping screw.
For the final operation, they were mounted to the fixture one more time and the section where they bolt to the frames milled away.That completes all the machining on these and, once they've had a bit of a clean-up and an hour in the phosphoric acid, they will be ready to fit to the loco.
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