BLOWDOWN VALVE
I thought I'd start on something simpler. The original boiler has one blowdown valve on the back of the boiler just
beneath the firehole door.
I couldn't see an easy way to get at it so I've used two blowdowns, one on either side. There's not much to their
construction. The body being made from phosphor bronze and the tap, stainless steel. I've also fitted a brass
locking nut. I would have liked a longer exit pipe as I always fill my boilers by connecting with a pipe on to the water
hose. Unfortunately, there isn't much clearance when it's screwed into place. I have given it some deflection to send
the steam away from the bodywork.
SNIFTER VALVE
Starting at the front, I've begun with the snifter valve.
There probably isn't any need for one as I'm not using superheaters and the blast nozzle is quite high up, so there is
little likelihood of grit being sucked into the system. Still, better safe than sorry.
Its position is opposite the blower feed on the other side of the smokebox, although I did manage to slip and drill
slightly too high up causing the valve to be at an angle. I had to cure this with two wedge washers. The smokebox is now
complete inside, although it will require some joints to be sealed after the outside has been painted.
CLACK VALVES
Three clacks to be made for the water feed to the boiler. They are all the same except for the
size of the inlet pipe from the water pumps which is bigger than those from the injectors. The construction is much the
same as the snifter. I always make the valve seat removable in case it needs some attention. It also avoids having to
make different sized 'D' bits to make the seat. I've had to make an adaptor to fit the boiler to the clack as the hole
in the boiler is quite large. I've not made the nipples and nuts yet, as I'm not sure whether I'll be using imperial or
metric piping.
THE MANIFOLD
The manifold has seven take off points of which five are valves and two are feeds to the gauge and the whistle, plus one
inlet. I could have made the manifold with five valves in a row, but as I was using bronze bar with a hole down the
centre I would still have had to make a stop at either end. So, I'll make two large globe valves to go in the ends.
Much more time consuming but it should look nice. Ball turning is not something I do very often and it always gives
me problems! I could have bought the casting but this type of bar makes a neat job. I'm fortunate in that there is a
supplier quite near, so I can go in and see what he has on the off-cut shelf.
I've been a bit short on time lately what with holidays etc. so it doesn't look like I've done very much but it's surprising just how long some of the bits take to make.
MANIFOLD VALVES
One thing I forgot, and I've done this before, is that there are handwheels on the ends of the valves and they need
clearances!! So the manifold has put them a bit close to each other so I may have to stagger them.
There's a lot to make in each valve and the three front facing ones took a long time. The photo shows this and I've yet
to make the handwheels.
To make the exit pipe fit so that it points exactly vertical can be a problem. I've seen
people use shims and it's in and out a lot of times and even then it can go wrong with the final tightening just taking
it passed the vertical. Most people use a locknut, but this always creates a gap between the nut and the body; sometimes
a few thou but it can be nearly a complete thread width. I make a feature out of it. I use a larger nut and counter-bore
it. It only needs to be just wider than a thread in depth and the gap is hidden when the body goes into the counter-bore.
Next came the two globe valves; one on either end of the manifold.
I know they look nice but really, I have to ask
myself are they worth the effort. For such big valves the steam ways are still very small due to the way they are
constructed.(1/8")This is the bore size of the pipes supplying steam to the injectors. The first one took me a day and
half to make before I was satisfied. The problem is getting the valve to shut off. The screwdown part is easily made off
centre and then it leaks. However, the second one was finished much more quickly and is a better one of course. One
learns by practice. I won't mention the ones I threw away! I found that the only way I could be certain of getting the
valve hole in the exact centre was to bore out to the large hole and turn up another piece of bronze in the lathe with
the orifice drilled, the bit parted off and a good fit in the bottom of the bored hole. I then soldered it in place and
drilled through the inlet hole again. I say that with confidence, but I hope I've got it right!
These last two pictures show the completed manifold. I don't usually paint them but thought I'd tart this engine up a bit!
After all, the beauty of narrow gauge modeling is that anything goes. I've only painted the bronze parts as these are hard
to keep polished once they get hot. The brass work is only polished; I suppose I could lacquer them. I still have the
five handwheels to make and I haven't worked out just what I'm going to do yet. The large nut at the base actually only
has 4 threads as it's a locknut, the rest of it is counter-bored to make a feature out of it. I had to mill a flat over
the entire length of the manifold so that I could get a spanner on the valve locknuts.
I thought I'd better update the site because the next parts are again time consuming for what appears to be little done.
I'm a bit disappointed in my appeal for info on boiler tests in other countries. So far I've only had 2 emails and both
were about the way the Aussies do it.
HYDROSTATIC LUBRICATOR
I started with the easy bit first; the oil tank. The filler cap finishes flush with the footplate and the tank is underneath
at one side. The oil collects via a tube which is inside the tank and goes straight to the top. The theory is, the oil
floats on the condensed steam and goes down the open ended tube. It's always worked for me and I like them because I can
monitor the exact amount of oil.
As it's a pressure vessel, the tank is thick. It's left over from my clock making days
and is 3/16" thick as are the silver soldered endcaps which are let in. It will hold more than enough for a day's running.
This is the first time I've made a double sight glass and I could have got away with one if I'd fed the oil in in a
different place. This is quite a fiddly job to make, and I've never painted one before either. The brass nuts on the top
are 8BA re-threaded 7BA. This makes them smaller and neater. I'm reasonably satisfied with the end result although I did
make some errors. I didn't quite match the bottom left hand side exactly to match the top and so had to resort to some
fine filing. Grooving the bottom plate to take the two 'O' rings wasn't exactly accurate first time, so I had to
compromise by going up to a slightly larger 'O' ring on one side. It doesn't show, and at the moment both sides seem to
be air tight, although I haven't done it under any great pressure. Like a lot of things,I'll not know until it's under
steam.
The partially hidden tube, sticking out at the bottom is a clack valve with a spring to stop any back pressure
occurring. In the past, I have found that another clack is necessary next to the cylinder end as steam can leak back and
then a horrible, yellowish mass collects in the glass!! I'll have to make these later when I start to assemble everything.
I would like to have had longer glasses but they seem to come in only the one size. Maybe one day I'll find a supplier and
change them. When the time comes, I will fill the tubes with a mixture of 50/50 water and glycerine. Some people use salt
water, I've no idea of the theory behind that, but salt and brass is not a good combination I believe.
THE SAFETY VALVES
When I ordered springs for the Romulus safety valve (there was no drawing), the one I was sent was of a larger diameter
than my biggest tap and die.
In the construction the spring has to pass through the hole. My largest was 18mm. Not
wishing to go to the expense of buying a larger set, I phoned around for a smaller spring. The ones on my other 7-1/4
are 1/2" diameter.
This company thought they had one about that size and posted off two. So I carried on making the bodies
using the 18mm tap to thread the necessary hole. Being satisfied with my results, I had to wait for the post (weekend).
When they arrived I found they were an identical size to my first one and were 17.7mm in diameter which is just too big
to go through the tapped hole. To be fair, they were about 1/2" inside diameter! Rather than waste more money and time
waiting I did the best I could think of. The picture shows my solution. I made an adaptor ring with the outside thread
being my choice. Actually, it was 22mm and 20 tpi. A right mixture, but good practice in cutting mating threads. Cutting
metric threads on my lathe is no joke and would mean buying a special gear wheel.
I like to make my safety valves part
at the ball end so that I can get to the valve seat for maintenance. I've used one ordinary safety valve and one pop
valve on my other loco, and I might well do the same with this. It's quite easy to turn one into a pop type by turning
a ring which fits round the ball with the required gap.
This second picture shows the steam escape holes; more than adequate.
This third picture shows all the components. They're mostly made from bits in the cuminandy drawer. Copper water pipe
(I hope it's thick enough.) Some bits are brass; those which don't have direct contact with the steam, and stainless
steel ball and rod. The last picture is the completed valve but I'm hoping to find a decent piece of brass or copper
tube to cover them. I'll no doubt scrounge a bit from somewhere.
I've only got two main components left to make. The vacuum brake system and the whistle valve. The trouble with having knowledgeable friends is that they keep making suggestions! "You can't have fixed windows, they've got to open". Not a hinge but a swivel which makes fitting that much harder. Well I'm not in any hurry and it won't be ready with a driving truck before the season ends. Then of course the inevitable 'what sort of lamp'. Plenty of time to think about that.
THE WHISTLE VALVE
The whistle valve is quite conventional with the usual ball and spring arrangement. I've put the pivot at the back so
that the action is downwards. I could have put it on the front so that the action was upwards and operated the lever
with a chain, but I didn't want things dangling about the cab! As can be seen, the whole unit screws into the top of
the manifold. The spring is quite a strong one so that suddenly letting go will ensure a good seal.
VACUUM BRAKE SYSTEM
EJECTOR
One of the problems I've had with my last ejector was that when the boiler pressure dropped to 40-50 psi, then the vacuum
created by the ejector wasn't quite
enough and so the brakes gradually came on on the carriages. The pressure was quite
enough to pull the train though. So I spent a bit of time with this one testing and trying different settings. I
eventually got 15 inches on the gauge with about 40 psi on the air line. I know this isn't steam and might well produce
a different result, but I tried it against my old one and it is an improvement.
I've included the two 'D' bit tapered
reamers in the picture; one is 12 and the other 24 degrees. As can be seen from the photo, the whole unit is quite small.
I must confess I don't enjoy drilling holes 1/2 mm diameter!
BRAKE LEVER
The brake lever is quite a simple piece of equipment to make so long as you have some sort or rotating table for the mill.
The curved slot is 2.5 mm wide and 2.5 mm deep. The difference in the colour is because the back part is a lump of gunmetal
which I had and probably has a high copper content, whereas the front part is brass. I made this one in reverse to the one
on my Kerr Stewart as it will be on the right hand side of the cab. I found it un-ergonomic to push the lever forward to
apply the brakes. This one will be correct; pull the brake lever to apply the brakes.
Theoretically, I've finished all the parts for the engine, but in practice I'll have to make windows, a couple of in line
clacks for the oil line and no doubt other bits and pieces. However, I'll have a break and begin getting it ready for painting
so I'll have to strip everything off to get to the footplates which is where I'll start.