| Drawing E4- Brakes, Buffers
etc. |
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1. Buffers and Stocks |
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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. |
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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. |
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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. |
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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. |
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2. Brake Rods and Adjusting Bottles |
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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. |
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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. |
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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. |
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The fork was made by milling out a short slot in some
square bar. |
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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. |
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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. |
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3. Brake Trunnions |
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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. |
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| 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. |
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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. |
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4. Brake Hangers |
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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. |
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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. |
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5. Brake Blocks |
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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. |
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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. |
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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. |
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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. |
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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 |
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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. |
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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. |
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6. Brake Cylinder |
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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. |
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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. |
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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. |
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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. |
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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. |
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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. |
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7. Handbrake |
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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. |
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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. |
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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. |
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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. |
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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. |
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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. |
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And this is the complete assembly bolted to the end of
the water tank, with the full-size version afterwards. |
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8. Vallances |
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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. |
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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. |
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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. |
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9. Main Spring Brackets |
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| 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! |
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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. |
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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. |
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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. |
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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. |
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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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10. Next Item... |
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