| Merddin and the Injectors | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Merddin Emrys has different
injectors to all our other engines. When they are working well they are
a delight to work but they do need a certain knack. The injectors are
now becoming more troublesome as they are in need of overhaul making the
knack much harder to acquire.
One of the problems we have is that we don't have the info we need to
overhaul them so read on and see if you can help To go straight to how you can help click
Merddin's injectors are lifting injectors [What is a
lifting injector?] and both are mounted on the drivers side of the
loco. Two are fitted, each with different feed rates for putting water
into the boiler. They are cunningly described as the "Big Feed" and, you
guessed it, the "Little Feed". In ideal operating conditions when
pulling a train the little one is on most of the time adding water to
the boiler to replace that used to pull the train. For potentially ancient items of equipment they have many features to
be found on the modern photocopier or computer An
Urgency Detector,
there is absolutely no way they will ever be rushed. If you need
them on in a hurry you have screwed up. Basically the pause is all
important and if you rush it the injector has too much steam in it
before the water lifts, gets hot and fails. You need to plan ahead
all the time. An Idiot
Detector, the
idiots can’t work them. They have no feel for the pause nor can they
sense when the injector is lifting. It makes subtle noises to tell
you what its doing and if you don’t have the feel for them you are
screwed. A Rough
Driver Detector,
they are prone to knocking off if you brake to harshly as it makes
the water surge, then they knock off, get hot and you’re screwed. The basic problem is they don't like getting hot and being fed hot
water and as they have aged they have become more fussy. They didnt used
to be so its time to fix them. Over the years they have been maintained without drawings by making
new bits like the old bit but hopefully with the wear taken out. Over
the years this has led to creeping variance from the original
specification. We need info and we think it must be out there somewhere as I'll
explain below For many years it was thought that the injectors on Merddin Emrys
were Whyte Patent Injectors but this has turned out to be folklore as
there is no evidence to support this. It has certainly been a commonly
held belief that has been repeated for as long as i have been involved
in the FR. Trouble is there is no evidence to support this view. Searches for equipment by Whyte reveales no records of injectors but
they did make water lifters for traction engines which is a similar
product and probably the origin of the misunderstanding. So I started a quest for the information we needed the first item
being what are they? I started with pictures of them which I e-mailed to a few well placed
sources.
Injector Identified This image was found in some ancient
tombe on injectors which identified it as a Holden& Brooke
Single Action Injector which was marketted as an improvement on
the original Giffard injector. This drawing is very very similar to our
injectors with the exception that the inlet and outlet positions
are different hands. This isnt a suprise as the construction
and application suggest this would be adapatable to the
location. Now we were getting somewhere but its
still not enough information to make or repair one. NEXT -
A BREAKTHROUGH
Soon a new drawing pinged in to my inbox This identified the injectors as Holden &
Brooke Sirrus or S pattern injectors. Better still it further identified Holden
& Brooke and their whereabouts. Even better news, they still exist
although not doing injectors these days. The are part of the
Armstrong Pumps Group of companies.
The drawing is printed on page 109 of Wallace Bentley's
classic "Sketches of Engine & Machine Details" - eighth revised
edition (first edn. 1898). Its still not enough information to
reconstuct an injector to its original spec as, whilst some
dimensions are shown, some critical ones are not The present day Holden & Brooke were
contacted and they have been very helpful and have supplied some
scanned documents they have but they do not have any drawings in
the archives. Company History
Robert Brooke originally worked for Sharpe Stewart & Co. Ltd.
When he first left them to go out on his own he founded
Broughton Manufacturing Company, which later became Holden &
Brooke Ltd. when he partnered with his friend Henry Holden also
from Sharpe Stewart.
H&B didn’t register until around 1887 after around five years of
trading. Rumour has it that they split from the company they
were working for and possibly with a few of their “intellectual”
designs in hand.
What I mean is, if the engine is circa 1870 it would not have a
H&B stamped injector. That isn’t to say that it wasn’t replaced
with the exact item but stamped H&B later on in service.
Add to that that Holden & Brooke made essentially the same
injector right up to when they stopped in 1960. The S pattern
injector is still in their 1958 catalogue. The interesting
comment being., “the S class just worked”.
It is therefore possible Merddin was built with pre H&B versions
of the injector which were later replaced with H&B ones, they
could be the originals as there are no H&B markings on them or
equally they could have been fitted anytime up to 1960.
This suggests two things: - They
aren’t some 130 year old design that's crap and should be
replaced but something that given some TLC and maybe new
bits to the original spec should work as well as they did
before they got old and grumpy and,
If
they were still making them in 1958 finding more detailed
info like a cone drawing should be a lot easier than finding
the 1880 version An injector on a steam locomotive is a
gadget that uses some of the steam in the boiler to take water
from the engines tanks and to force it into the boiler
overcoming boiler pressure in the process. Its function is to
replace the water used as it is boiled into steam and used. There is an
even more basic explanation
here Simplistically there are two sorts, a
flooding injector and a lifiting injector The lifting injector is located above
the water source and has to "lift" its feed water from the tank
to the injector before forcing it into the boiler. A flooding injector is located below the
water supply and the water is fed to it by gravity. A lifting injector can work as a
flooding injector but the converse isnt neccessarily true.
Merddin's operate as both flooding and lifting injectors as they
are mounted halfway up the tanks. When the tanks are full they
act as gravity fed flooding injectors but once the level in the
tanks falls below the level of the injector its first function
is to creat suction to lift the waterup to itself. They will do
this right to the bottom of the tank on the bottom of the foot
well. To operate them in lifting mode you
crack the steam on to create the lifting force - how much is a
subject of "feel" too little no lift, too much no lift before
the inector is too hot to work. At this stage you pause whilst
the water lifts, the pause varies with how far its got to lift
the water and is the subject of "feel". Once the water arrives
and is seen at the overflow you open the steam further and it
starts injecting water into the boiler. As they have aged they have become less
tolerant of error and warm water and some of their behaviour
suggests that the cone dimensions or locations has wandered from
specification The clue
is in the statement above "A flooding injector is located below the
water supply and the water is fed to it by gravity" On Merddin that well under the cab is solid and
is the well of the water tank. The lifiting injector feed pipes go right
down to the bottom of this well and will extract water until the tanks
are very close to empty. You will also note, if you look at a side view
of the loco, the bottom of the tanks aren't very far above rail level. A
flooding injector would have to go below the tank and would get knocked
off by the rails. And before you say "the other two have flooding
injectors" please note that the thing that looks like a tank below the
footplate is nothing more than a valance and is not part of the tank so
there is loads of room behind it relatively speaking. I have added this section, starting the day
after i published the main part of this page, as it was pointed out to
me that it would be handy to know where we have looked already and what
information we have to hand Info to hand when this page was first
published...... The engraved drawings shown in the waffle
above came to me via Roy C Link whom I asked for info knowing he has
an extensive collection of historical books and magazines such as
"The Enngineer". My photos of the actual injectors on Merddin were
used as the comparison for the pictures. Roy found the engravings
printed on page 109 of Wallace Bentley's classic "Sketches of Engine
& Machine Details" - eighth revised edition (first edn. 1898). He
also noted that Google alledged Holden & Brooke still existed. Amazingly
www.yell.com provided a phone number which in turn led to
contact with Micheal Heaton in the
Aftermarket Sales & Technical Support section of Armstrong
Pumps, the parent of H&B. Micheal provided the company history of
H&B during an exchange of e-mails. It seems Micheal is interested in
the history of the company and has been scanning items he finds to
create a bit of an electronic archive. This has produced two documents which you can
access on the links below In this single page document you will
see a drawing with the familiar injectors mounted on a
Lancashire Boiler with them collecting their water from sumps
below requiring them to lift the wate This is the drawing that makes me think
the stationary boiler plant field may be where we find more info The 1958 brochure repeats the connection
to Lancashire boilers but interestingly provides a table of cone
sizes available and the feed rates each provides at certain
boiler pressures. What suprised me for a 1958 document was
that the nozzle sizes are metric
Micheal also provided a link to a
digitally archived book which makes interesting reading from
around page 22 The book is "Injectors: Thier Theory,
Construction and Working" by W.W.F Pullen. The digital copy is
the 1906 third edition but the preface suugests the first
edition was in 1893 The 1893 edition is now
available as a reprint from Camden Miniature Steam Services. I
know someone locally with a copy [Tickle] and someone [Bear]
sent me a scan of an H&B advert in that edition. [rep alongside
A booklet
entitled -
“Injectors for Locomotives. A short account of the "Sirius" patent
Combination Injector for Locomotives" has been ordered from the
British Library. A search for the original patent is also to
be undertaken when someone can go and do it in person. A drawing of a H&B injector is being sent
from Australia We' have been contacted by a gent in NZ who
has a nearly new #5 injector and we are discussing getting some
measurements from it Contact has been made with
from
Museumstoomtram Hoorn – Medemblik as they have been making new
injectors directly from 3D solid model drawings. Not of immediate
use but info stored for the future. Links to a load H&B patents in the USA
provided. None of the S pattern but they are being studied to see if
there are common elements to our injectors. I have e-mailed Alan McEwan on the grounds
he is involved with mending mill boilers and the like but have not
yet had a response.
No response yet I e-mailed the International Stationary
Steam Society secretary from their contact details -
No response yet I have had a quick look at the search engine
at the NRM. It was only a brief look as I had a guest with me but
that revealed two key things: - Searching through masses of records be they
online or on paper is not my thing and, The NRM archive is arranged by railway
company so we would really need to identify a standard gauge loce
fitted with this injector to get us to something more focussed than
blind luck. Since I brought this up on the FR Yahoo
discussion group the following has been suggested or actioned
The extract of one of the main engravings shown to the left details the
cones for the injector but critically it only shows the external
dimensions, and not all of them. A detailed manufacturing drawing for these would make us very happy Note - on the second page referring to the S class injectors in the
1958 brochure note the section entitled "Instruction Booklet"
A booklet giving full information on the installation,
operation and dismantling of the injector, as well as what to do in the
case of difficulty is sent out with each injector. The made thousands of injectors therefore thousands of booklets
- someone must have one It occurred to me
that there are some who will come to this page and be wondering what an
injector is and what it does. What follows is a very simplified
explanation of what and why which takes some liberties with the laws of
physics to keep the explanation simple and something that can be
followed by the non technical
An injector is a device which uses steam
from the boiler to move water from the tanks into the boiler to
replace the water used in making the steam. So what is the problem? The boiler is pressurised to 160 psi [in
Merddin's case] so this has to be overcome to get water in. The steam taken from the boiler to power it
will be at a lower pressure so it can't simply push water in. Some magic is required Its all a game of pressure [Force] and
velocities [Speed] with a little help from the venturi effect. Venturi effect -squirting water through a small hole is a good
analogy for this crude explantion In an injector there are three venturi which we call cones. There are
three: - When working steam is squirted through the steam cone. This converts
pressure to velocity so the steam coming out of the steam cone is going
like the clappers [clappers - scientific term for pretty
fast] In the next section water from the tanks is dumped on to the quick
moving steam. The effect of this is that the steam is condensed and its
velocity is transferred to the water so we now have warmed up water
going like the clappers [or a bit slower due to losses] Next our fast moving water gets squeezed through another cone, the
combining cone, this gives it all another speed boost so we now have our
combined fluids going like the clappers towards the delivery cone ready
for the last bit of magic. You will notice the delivery cone points the opposite way to the
other two. This one works in reverse to the other two and now it
converts the velocity back to pressure -and here's the clever bit -
because we've added two fluids, steam and water, together we;ve
increased the volume so when its done with this speed to force
conversion our combined fluid is at a higher pressure than we started
with and, crucially, a higher pressure than the boiler so it can force
open the non return valve [clack valve] and enter the boiler. OK, so the above has taken some real liberties in making the
explanation simple. I am sure there will be those who say "no thats
wrong" but to them I would say please remember its aimed at those who
may have never seen an injector let alone worked one |
