Merddin and the Injectors

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.

  • Those with the knack want to see them fixed.
  • Those without want to see them replaced. [and demonstrate a marked lack of understanding of the loco in making such a claim  -WHY?]

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 HELP


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.

Top end Bottom end
the top end injector or  "Little Feed" the bottom end injector or  "Big Feed"

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.









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

 As it would seem there must have been thousands of them made I have asked Peter Johnson to put a note in Steam Railway asking for info and I will also follow up a few other leads.


Now we have identified what sort of injector they are and that they were made right up to 1960 there is every chance the information we seek exists somewhere in the preserved steam field or in some archive somewhere. The trick is going to be finding it and this is where I need help. Rummaging about in archives in not my thing. Can you

  • Offere any pointers as to where to look

  • Actually do the looking

  • Say, oh look what I've got and hand over a set of drawings for these injectors.

We have brochures that show they were marketed for static boiler operations as well as for loco's so does anyone have contacts with the mill engine fraternity? I will add the brochures and additional info that we have to this page as time allows in the next few days

You can contact me by e-mailing      Info - AT -        [replace  - AT -    with @ - i'm sure you know the drill]

Thanks         Paul Martin

What is a lifting injector?

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

  Why cant't flooding injectors be fitted?

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.

Updated 02/06/11 Information we have/ Sources we've explored

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  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

1930's Brochure 1958 Brochure

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

1906 Book

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

H&B Advert

  • 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.

Updated 02/06/11 Where else have we looked /asked for information
  • 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: -

  1. Searching through masses of records be they online or on paper is not my thing and,

  2. 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 request for info has been copied to a Yahoo group aimed at stationary steam   Many contacts made, no news as yet
  • It has been suggested that the appeal for info be passed to "Old Glory" magazine which I will do when I get a moment   E-mailed the editor but he's not replied yet
  • Preston Steam Services has been suggested as worthy of an enquiry. Again I will do this when I get a moment    Done, pointless! They replied in the vane of we know sod all about your injectors but ask us for a quote to fix them. At no point did i ask for a commercial quote
  • Someone suggested asking if any of the ancient loco's at the Bluebell have anything similar and they are going to follow this up.   Done, nothing relavent so far
  • A book has been indentified in Australia and I have sent an equiry  Orderd a copy
  • A traction engine has been identified with a H&B injector on the tractiontalk forum and an enquiry has been sent    No response yet
  So tell me what you want, what you really really want   apologies for the spice girl outbreak

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


How it Works

"Ye cannae change the laws of physics!"   Scotty, Star Trek


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

InjectorSo whats it do?

  • 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: -

  • Steam Cone:
  • Combining Cone
  • Delivery Cone

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