|Drawing 10 - Reversing Gear, Oil Pumps, Saddle
|1. Smokebox Saddle
||The drawing suggests using 2mm copper or brass sheet to
fabricate the smokebox saddle but I had considered making it from mild steel.
However, I couldn't find a local supplier so bought a piece of 14swg brass
sheet at the Midlands MEX and used that. First, I cut out the blanks I needed,
remembering to cut the width of the main saddle piece to the development
length to accomodate the bending of the material. The four sides of the
saddle support will be riveted together before soldering the saddle in place.
The crossways pieces are cut to fit exactly in the frames and the lengthways
pieces are cut to the nominal dimension minus two thicknesses (0.160") and
will fit between the two crossways pieces.
||Next I marked out the cutaways and then stitch-drilled
them, removed the waste and cleaned up the shape will rotary burrs and sanding
disks. I also drilled and countersunk two rivet holes at each end for fixing
the corner angle pieces to and am using 3/64" countersunk brass rivets for
this. Once drilled, I clamped an angle piece flush with the end and drilled
through the existing hole, countersunk the opposite side and fixed the rivet,
repeating for each hole until both sides were complete. Finally, I clamped
the end pieces to the sides, drilled through and riveted these to produce
the box shape of the saddle support.
||To make the main saddle piece I calculated the spacing
between holes, as this is not given on the drawing, and marked them all
out before drilling for 10BA clearance. I chose not to remove the centre
section before bending because I would have ended up with a rather weird
shape. I also turned up a piece of MDF to the size of the smokebox to act
as a former since I don't yet have the smokebox material. I don't own bending
rolls but we have some up the club so Saturday morning I took the plate
and former along for the next operation. I have never used bending rolls
so a collegue kindly gave me five minutes tuition and then left me to get
on with it.
||About ten minutes work saw the job complete and I have
deliberately rolled the shape a little tight as it will be no trouble to
ease it back to the exact diameter of the smokebox material but not so easy
to go back and roll it through again. I'm also aware that it is normal to
allow extra material at each end because of the leading and trailing flat
spots but I've managed to get quite a good shape without this. After easing
the circumference back to fit the template, I marked out the ends of the
saddle support and then removed the waste to leave it ready for silver soldering
to the main saddle piece. Here it is waitng to be clamped to the saddle
prior to joining.
||The components of the smokebox saddle needed to be soldered
together and I had to decide how to keep the two parts together during the
soldering process. I decided that the best way was to drill a hole though
the saddle and fix a cross member across the saddle support with a nut and
bolt. The main advantage was that it kept the mass down and I wasn't wasting
all my gas heating up clamps. At this point, I undid the clamp and gave
the brasswork a really good clean-up.Then I mixed up the flux and put some
on the edges of the saddle support before locating the two parts together
and clamping down again. Following this, I fluxed the rest of the assembly,
placed my pieces of solder into the inner corners and then painted the rest
of the flux over the solder. Then I assembled my hearth from my fly-ash
blocks and placed the assembly inside.
|I was approaching this job with much trepidation
but took a deep breath and off I went, directing the flame around the sides
and underneath the assembly. After a few minutes the flux had turned to
a pinkish slag, bubbling away, but the solder wasn't melting and I started
to give the occasional blast of heat over the top. The mild steel clamp
turned cherry red but the solder still hadn't melted. At this point, I chickened
out and turned off the heat. I decided to mix another load of flux, a little
more watery this time, and applied this liberally around the area. A moments
thought made me realise that if the solder hadn't melted, then I couldn't
have got it hot enough. So this time, I took no prisoners and really blasted
the flame into the area and wached the whole assembly start to glow. And
then, as if by magic, the solder started to melt at the front and slowly
crept along the sides and across the back until it was all gone! I kept
the flame going for another five seconds or so until I was sure the solder
had all melted, then turned off the gas. This photo was taken twenty seconds
after removing the heat.
||Once it had all cooled down I gave the assembly a good
scrub in clean water but had to use an old sciber to get rid of the remaining
encrusted flux and had a good hard look to ensure that a decent joint had
been made. I'm pleased to say that the solder has flowed evenly throughout
and appears to be quite a good joint. It now needs a really good rub-down
to improve the appearance, and I have spent ten minutes or more with emery
cloth trying to clean it up but I will give it a few minutes in the shot-blast
cabinet later to see if that will speed up matters. It did, and here is
the final result.
||And to finish the job off, I loaded the assembly to my
large vice on the mill and removed the central area where the pipes come
through. I just need to spot through the frames to mark the boltholes and
this part is finished.
||There are commercial lubricators available but I thought
I would like to have a go at making my own and decided to make the tanks
first. I didn't have 18swg brass in stock so chose to use 20swg instead.
I started by making a hardwood former to bend the material around, making
the former a little larger to suit the thinner material and preserve the
outside dimensions. A pair of brass strips were cut 1.7/8" wide by 5" long.
I made use of my large milling vice to get the first bend square, positioning
the former level with the end of the jaws.
||With the first bend accurate, I was able to finish the
other sides using the bench vice, finishing with the final side overlaying
the first side. Before removing the waste, I removed the former, inserted
a junior hacksaw blade in the fabrication and re-inserted the former before
clamping up. The waste from the two overlapping sides was then removed using
a junior hacksaw, the packing blade ensuring that when the gap was closed
the tank would become square.
||The larger of the two offcuts was then cleaned up and
used as a soldering strap at the back of the tank. A recess was milled into
the hardwood former to clear the strap and pushed back into each tank section
in turn to enable milling the ends square and to finished length.
|| A pair of base plates were cut from 14swg brass sheet,
squared up and the centre section milled away by about twenty thou to create
a location for the tank sections, followed by drilling the mounting holes.
Then the bases and tank sections were soldered together, the clamp in the
picture being used to ensure the earlier solder didn't fall apart. The bases
had taken on a slight bend after soldering and each was reloaded to the
mill and skimmed flat. It was only a few thou but enough to cause rocking
of the assembly. To finish, the various holes were added to the tank sides
ready for the pump components to be fitted.
|| The body of the lubricator pump should be brass but I
have used a couple of offcuts from some bronze plate that I worked on recently.
The bodies are 3/8" thick so I was able to machine all round to get them
to size. I have added a clearance chamfer at the bottom because of the solder
in the tanks. All the drilling, tapping and reaming operations were done
on the big mill using co-ordinate positioning because all holes are on the
same centre-line so I only had to set the "Y" axis and leave it locked all
|| To suit my tooling, the 1/8" reamed hole has been made
as 3mm and the 5/32" holes as 4mm. Threads are all 40ME or 8BA, as specified,
except for one blanking plug that I drilled the wrong size hole so went
to 6BA instead. The one awkward hole was the inlet channel which is at twenty-five
degrees to the horizontal. For this, I used a slot drill to create a small
island to start the drill, and had a piece of sacrificial material in the
cross-hole so that the drill didn't wander as it crossed over.
|| The collection of plugs, unions and other assorted pieces
were all made from brass bar. The only part that was not straightforward
was the shuttle on the outlet side which required some grooves milled in
the sides to allow the oil to flow. After turning to size on the lathe,
the three grooves were put in using a dovetail cutter on the mill. A piece
of hexagon bar was used to index the three sides as it was quicker than
setting up the rotary table. Apart from the piston and the spring, these
are all the parts that make up the body of the pump.
|| Next up was the plunger. To make the plunger and collar
I started with some 5mm flat black bar intending to make the whole thing
in one go. Two are required and I cut material to make both by splitting
after milling. A pair of pilot holes were drilled first followed by milling
away the internal form with a 1/8" slot drill. The dimensions on my sketch
are the plus and minus co-ordinated from the hole centre for machining to
finish size. Moving to a larger cutter for more rigidity, the outside form
was produced next leaving a 1/16" thick wall all round..
|| Finally, the workpiece was held vertically in the vice
and the waste cleared away to leave the shape shown. This was then sawn
in two and then it was over to the lathe to turn the 3mm diameter using
the 4-jaw chuck and a small supporting centre. However, after wrecking one
of the pieces because of a poor setup, I decided to take a different approach.
The leg was sawn off, a small boss milled and an M3 hole drilled and tapped
into the end. Into this was screwed a length of 3mm stainless rod of the
appropriate length. Even this was too restrictive and the boss was cleared
away just prior to assembly.
|| I made the eccentric from phosphor bronze although the
drawing calls for mild steel. I think it will wear better but may be wrong,
easy to replace if neccessary. There are different ways to produce eccentrics
including independent four-jaw chucks but I chose to use an offset bush
because it is repeatable without clocking up the workpiece. First I turned
the main boss, holding the 9/32" dimension to within a thou for a good fit
in the bush. I also drilled and reamed the hole 3mm, which I'm using instead
of 1/8" dia. The parent material is 5/8" diameter because the workpiece
will clean up with about ten thou to spare. Next I made the offset bush
from a piece of 3/4" diameter mild steel, turning the O/D to 11/16" dia
and leaving a shoulder for butting up against the chuck jaw, then reversing
and facing to length. The offset hole was made on the mill by holding in
a table-mounted chuck, clocking true then offsetting by the given throw
dimension of 3/32". The bush was drilled and reamed 9/32". I also made a
small brass plug to fit in the other end of the bush to ensure it didn't
distort when clamped up in the lathe chuck.
|| The eccentrics were then loaded to the chuck and pulled
up really tight, and I mean REALLY tight, otherwise the intermittent cut
could have moved the workpiece round in the bush and ruin it. All turning
here was finished in the one visit, using the compound slide to control
lengths. To drill the locking screw hole, I made a simple drill jig from
some hex mild steel as I find this easier than trying to set up fiddly components
in vee-blocks and vices etc. I've used M3 rather than 8BA because I have
a load of M3 grub screws in stock.
|| The drive shaft was made using 3mm stainless
steel rather than 1/8" dia material solely because it was in stock. The
various bushes are as per drawing, except for the hole size, of course,
but the rear supporting bush has been made to solder in from the outside,
rather than the inside, because of the strap at the rear of the tank. The
other variation I made was the turned and threaded part of the shaft. My
8BA button die is in very poor condition and not up to producing a decent
thread on stainless but I have M2.5 available in both HSS split die and
spiral-point HSS tap, my favourite combination of threading tools. As a
long-time machinist in industry, I really don't like carbon-steel dies or
hand taps and avoid them where possible. The part called "adjusting bush"
with its locknut is straightforward turning and threading with tap or die,
as appropriate, but I'm not sure what it's meant to adjust - it bolts to
the tank and is simply a support. The priming handle has been made from
3/4" dia brass bar. The stem was turned, drilled and tapped first and the
handle created on the mill. A filing button was used to guide the shaping
near the stem. The picture shows the components loosely assembled in the
|| To make the ratchet, I started by skimming down to 7/16"
dia a short length of 1/2" dia bar which I aquired from a local factory
and is tough as old boots. It's BS S154 which is equivalent to EN25. I also
parted through part-way so that I didn't have an intermittent cut after
the teeth were formed. The bar was then transferred to the mill and the
teeth cut with a dovetail cutter. I have chosen to make 36 teeth because
that is ten degrees, and two turns of the handle on my rotary table and
anyway, I don't have a dividing head, I went round three times before I
was happy with the depth and then returned the bar to the lathe drilled
the hole and finished parting them off.
|| I've chosen to make the lubricator operating levers from
16swg brass because I have a box full of brass offcuts to use up. They would
just about come out from 1/2" wide strip but the holes would need to be
offset quite accurately to make it work so I used some 5/8" approx pieces.
Although they are left- and right-hand, they are symetrical so I made them
as a stacked pair, starting with the holes. These were co-ordinate drilled
using the DRO on the mill.
|| I then set up one of my universal milling fixtures and
drilled a matching pair of holes for clamping the work down with. The two
levers were bolted down using 8BA bolts and with small washers underneath
for some cutter clearance. It only needed a few thou. I then roughed out
the maximum dimensions at the head, tail and spring-mount positions. Once
I had those dimensions correct, I then needed to skew the jig over to form
the tapered shape. I don't have any slip gauges but an appropriate sized
drill was good enough to provide the correct offset.
|| I didn't want to unbolt the work from the fixture so
had to move the jig in the other direction also, just using a combination
of smaller parallel and drill to get the same amount of movement on the
other side. Here is the final side just finished. The rest was just filing
and linishing, a filing button being used at the head end and freehand at
the bottom. Four pivots were needed and these were made next on the lathe
using 3/16" dia mild steel, simple turning and threading, and then it was
onto the pawls. I have made these from 1/16" brass as a temporary item to
check "proof of principle" and to create a pattern. They will be remade
when I get some ground flat stock.
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