I had wondered why you'd written on the drawing that you were going to make in two parts - now answered. But, forgive me for asking, I've a new question brewing: The drawing shows the clamping holes top and bottom, but none in the top-middle. I'd imagined this was because of the exhausts - but you have a hole in the middle. And yet your final picture shows exhausts - so why the holes?
Wilf
Very simple answer, Wilf, a cock-up on my part- blithely drilling away without concentrating on the drawing. However, because the hole is isolated from the steam area, it won't matter. Actually, there is no solder joining the upper and lower chambers between the two steam channels but the gaskets between the faces (not shown because they will only be used at final assembly) should prevent any steam loss through the hole. If it became a problem, I could soft-solder a plug into the errant hole. Even if high-temperature steam melted the soft solder, it couldn't go anywhere.
Regards, Steve
Chris, back in the workshop around Easter-time. I like to fiddle with my "OO" gauge loft layout in the winter quarter, it's a lot warmer indoors.
The milder weather has seen me returning to the workshop earlier than normal, so time to crack on.
Expansion links
I had some 3/16" thick gauge plate in stock so this was used to make the expansion links. After working out the missing dimensions, the two pieces were cleaned up at 1.11/16" x 5/8". Then the two holes for the link bracket were drilled and the two holes for the eccentric pins were drilled and reamed 7/32"
There are two different radii on these and a special carrier plate was made to hold them whilst on the rotary table. A pair of holes were reamed to take some locating pins, another hole tapped M8 to take the clamping finger and two reamed holes for dropping over a central pin on the rotary table.
The rotary table was fixed on the mill and the DRO zeroed on the centre of the pivot pin. The locating pegs for the link were pressed into place on the plate, which was loaded using the hole for 3.5/8" radius and clamped parallel to the table. I didn't bother clocking the plate square because the extremities of the slot will be set by eye.
The first link was loaded to the pegs and clamped down, using the other one as packing. Winding the table along until the DRO read 3.625" set the radius for the slot and a 4mm hole was drilled in two places where I guessed the ends to be.
A 4mm end mill was used to rough out the slot, eight passes at 25 thou depth of cut, stopping when I hit the back of the drilled hole each time.
The slot was then opened out using a brand-new 3/16" slot drill.
THe outer radius of the expansion link is 2" so the carrier plate was remounted on the table on the second pivot point. This reamed hole was set at 5mm less than two inches to compensate for using a 10mm cutter to form the shape.
The back end was machined next and I pulled the pins from the carrier plate and used them to support the work in the vice, thus ensuring everything stayed square.
The ends were linished around a filing button to give the final shape. A pair of phosphor bronze bushes were made and pressed into place with a drop of Loctite. Once dry, they were reamed 4mm and the ends of the slots were filed square with needle files.
The link brackets were made from 1/2" x 1/4" flat mild steel, milled down to 3/16" and drilled to match the expansion link. The hole for the pivot pin was also drilled at 1/8" diameter. The only variation from the drawing that I have made was to move the pivot pin forward so that the forward offset becomes 0.072". There will be a few other modifications that will be detailed at he appropriate time.
The pivot pins were turned to size and parted off, reversing to put a 1/8" dia x 1/8" long tail on them to set in the link bracket pivot hole. These were then silver-soldered into place. I've screwed them into a bar so that I can heat from below and gravity will drop them tight together.
The clearance for the valve spindle fork was milled away next, using a 4-jaw chuck to support the work.
The final shaping was done by holding the work on the pivot pin and one more support pin to get the angle, flipping over to do the other side. The packing under the pin lifts it to the correct angle.
To finish, the parts were all cleaned up and each expansion link riveted to it's bracket with two 3/32" iron rivets. These should be countersunk but I've chosen to use roundhead ones. Once painted, it will be very difficult to notice this departure from the drawing.
Regards, Steve
Last Edit: Mar 18, 2022 13:06:50 GMT by springcrocus
I like that sort of set up for a large radius, had to do the same but with a much longer overhang to get a 110mm radius ( my rotary table is only 125mm in diameter) on a pot handle. I was surprised how rigid I managed to get the support using 6mm steel plate. Mind you I was only machining aluminium.
The wise men don't know how it feels, to be thick as a brick!
I've made the valve guide from a couple of offcuts of bronze silver-soldered together. After milling all round to get a clean block at the maximum dimensions, I centred it up on the DRO then roughed out the back of the flange that bolts to the motion plate.
This was followed by drilling and reaming the two 5/16" diameter spindle holes, then using a 7/16" dia end mill to clear out the recess. I also started to centre the six mounting holes, then realised that I couldn't do the four corner ones until the circular shape had been made. That's what the two spots on the flange are.
The other side of the guide is not symmetrical because of the oil pocket so the block was roughed out in a different manner, mounting end-on into the vice and using a tipped boring bar to remove the waste. It's better this way, anyway, because I dont need to use the side of a long cutter.
Once the basic shape of the valve guide had been machined, I milled out the two pockets on the top of the guide, one an oil pocket and the other an access pocket for the top fixing screw. I drilled four corner holes for each pocket then used a 1/8" diameter end mill to clear the waste.
The cylindrical shape of the guide was formed on a rotary table. I made a mounting pin with an M6 tapped hole over which one side of the valve guide was mounted. A 1/4" dia long-series end mill was used to make a series of plunge cuts every three or four degrees of rotation before making a final pass at full depth and winding back round to the starting point.
The other side was done in similar fashion, then the valve guide upended and the flange milled to shape. Finally, the valve guide was reloaded to a vice and the six mounting holes drilled 6BA clear.
This is the guide mounted on the motion plate and assembled into the frames.
I must apologise because over the last few months I have been trying to find a particular notebook that I wrote up the Hall simulator results of the valve gear for 'Fishbourne' off the old now defunct computer. It had considerably more in it on other valve gears worked out, and I can't find it anywhere. It must be somewhere!
As I have previously posted, the expansion link radius is incorrect on the drawings for equal valve events and the suspension offset is also incorrect as it is in the centre of the expansion link slot.
The incorrect expansion link slot radius I can easily provide a correction for, but the suspension offset would possibly be 3/64ths to 1/16th.
Julian, I do hope you find your notes; it will be interesting to compare my own rudimentary adaptions to your obviously superior calculations. I have made some changes to the valve gear, the forward offset of the expansion link pivot being one of them. You may have overlooked my mention of this about half-way down the relevant post. In my case, I have made this 72 thou (unlike DY's zero offset) but, I have to say, I am muddling along with very little understanding of what I'm doing. It usually all turns out OK in the end, though.
Valve spindles
These have an offset portion that needs to keep it's orientation and the easiest way seemed to be to make them from square material. I started by machining some 3/8" square mild steel, turning and polishing the main body of the spindle to 0.312" diameter and leaving a section at the end for the bit that joins to the valve stem. This actually turned out to be a waste of time and was turned away later.
Then I made an offset sleeve to carry the spindle for the next turning operation. After clocking true in the mill chuck, the 5/8" diameter billet was offset by the required 1/16" in the "Y" axis and a 5/16" diameter hole drilled and reamed right through. Before removing from the chuck, a 3/8" diameter endmill was used to make a pocket for the end of the valve spindle to locate in.
Three slots were milled part-way through the sleeve using a slitting saw, the final slot being cut right through in the bench vice with a hacksaw. I chose to use a vee-block for this operation and the engineer's square clamped to the bed is just to help align the block on each cut.
Each spindle was loaded, in turn, into the sleeve with the square shank pulled tight into the pocket then turned to 5/32" diameter, finishing off with a radius tool to profile the shoulder. I also put an M4 thread onto the front on the spindles to take a threaded boss.
The spindles needed to be kept square whilst finishing the head end so, for this, I used a collet in a square block. These things tend to rotate the collet slightly at final tightening so I clamped the work to a 1-2-3 block to keep it aligned.
From there, it was quite straightforward to mill out the slot, relieve the sides and drill and ream the cross-hole.
Finally, a pair of 7/16" long bosses were made from 1/4" diameter mild steel, tapped M4 and screwed tightly onto the end of the spindles with the help of some Loctite. An hour later, they were loaded back to the sleeve and a 4mm endmill used to relieve the ends to 9/32" deep. These are the finished articles.
Regards, Steve
Last Edit: Mar 20, 2022 17:24:30 GMT by springcrocus
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.
Back on the lathe, it was time to turn the face of the buffers and I used the same technique that I used on the Britannia's smokebox door. This relies on the saddle being moved by a connecting bar rotating about a fixed pivot point. My bedway clamp becomes the fixed point and a peg in the cross-slide becomes the driven point. Here is the basic setup viewed from above. I couldn't find the original fixed pivot for the bedway clamp and made a new arrangement.
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.
I've set up the camera to record the operation. It 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.
And to cap it all, within hours of finishing the job, I found the original fixed pivot in the box where I keep odds and ends of tools and fixtures. Right under my nose and a classic case of not seeing the wood for the trees.
Regards, Steve
Last Edit: Mar 23, 2022 9:53:52 GMT by springcrocus
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. I will ream the 5/16" holes in the bosses after soldering.
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 square, 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 different 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.
Looking really good, thanks for posting so many photos I like the angled inlet pipe on the steam chest.
Could the reason for countersunk rivets on the link brackets be to avoid fouling whatever links are attached to them?
Credit for the angled steam pipe should go to Nigel Bennet who inspired it, not me. His drawing of the steam chest showed it straight up whereas DY's drawing shows it fixed to the front and angled. Nigel has very kindly supplied me with much information including some of his extremely-detailed drawings. As for the rivets, if they get in the way of anything, I will just grind them down. I think they are in fresh air, though.
Regards, Steve
Last Edit: Mar 27, 2022 15:32:08 GMT by springcrocus
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 angle. 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.
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 afterwards.
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. These are a slightly different form to the ones on the vertical actuating rods that were shown above.
My last visit to the Pumphouse saw me leave with a 10 foot length of 1/2" square brass tube, one of a few that John the Pump had been given by a colleague of his. Well, that didn't last long; 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.
John also gave me some engraved brass plates that were in his scrap box and one of these 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.
But that is because John knows that any material he gives me will get used to good purpose, not just squirrelled away and hoarded for the sake of having it.
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 horseshoes 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 next 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 although one is reversed on the round bar.
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.
To make these, I started with a couple of billets sawn from some 40mm x 10mm black bar. I'm not going to try and machine around the oil upstand, I will fit proper oil pots instead.
They were cleaned up all round to finish at 1.7/9" x 1.13/32" x 1/4", making sure that the big-end brasses fitted nicely to the thickness.
The position of four pilot holes were worked out, these holes drilled 4mm diameter, and the centre cut out with a 4mm end mill. I used 25 thou depth-of-cut on each pass, winding round in a clockwise direction. The thin section at the left-hand end is left purely to provide support for the billet.
After roughing out, a series of finishing passes were worked out to get the final size and shaping. The ends of the con rods are wider than the brasses and both these dimensions need to be as accurate as possible. I normally draw up a machining-steps list to ensure I don't mess up the workpiece, arrows showing where I'm going and the finishing dimension on the DRO. Here, Y0 is the centreline and X0 it the left-hand outer edge.
The hole for the stem of the oil pot was drilled next, followed by the outer form of the strap, reducing the width to 1.5/16" in a single pass of the cutter each side. Doing it this way gives the correct shape to the strap.
All that remained prior to assembly was to remove the support section from the front with a hacksaw and clean up the inside faces. I've used the con rods to support the strap whilst milling.
The big-end brasses were filed to make a nice, sliding fit on the forks. I added centre-pops to the inside of each strap and on the ends of the con rods to keep the parts matched as two sets, then assembled each pair and drilled the cross-screws. Because they can't be seen on the finished loco, I've followed the drawing and used 1/8" diameter pins with 5BA threads on them but the prototype would probably have been proper cotters. After drilling the first hole, the pin was inserted prior to drilling the second hole.
The pins were finished off with 6BA nuts overtapped with 5BA and a simple oil dashpot pressed into the top of the strap. Oil holes were then drilled 1.8mm diameter through both the big end and the small end bearings and the small end reamed to 1/4" diameter. The big-end bearings are already to size and need no further work. These are ready for the loco.
However, because the hole is isolated from the steam area, it won't matter. Actually, there is no solder joining the upper and lower chambers between the two steam channels but the gaskets between the faces (not shown because they will only be used at final assembly) should prevent any steam loss through the hole. If it became a problem, I could soft-solder a plug into the errant hole. Even if high-temperature steam melted the soft solder, it couldn't go anywhere.
I like the angled inlet pipe on the steam chest.
