GWR saddle tank pipework

[Conory]

On the 1361 class and maybe others, there is an assembly of pipework on the footplate on each side of the engine just in front of the cab.

 

Can anyone tell me what it's called and what it's purpose is?

 

Was it a standard design or did it vary between classes?

 

Thanks

 

Julian

[R A Watson]

I suspect what you are refering to are the injectors, these are a very important part of the loco as it is the means of getting fresh water into the boiler.

 

Normally the water comes from the tanks through the top pipe via a valve in the cab into a space where steam from the boiler is fed from the end nearest the cab and out the other end into a pipe connected through a non return valve to the boiler itself. A very ingenious system of "cones" in the injector body, utilising the forces and vacuum created by the steam passing between them, picks up the water and carries it into the boiler. The bottom pipe is the overflow and water can be seen running out of here at the start and end of the the injector operation.

 

This is a simplified description of what happens but is a basic explanation of how the things work, I suspect others will elaborate on the subject in due course.

 

Wally

[Gordon A]

Julian,

 

The pipework is the part of the injectors, one each side, which inject cold water into the boiler from the saddle tank.

 

There is a clear picture in Russells GWR engines (Vol 2 if you have the two vol version.)

 

Gordon A

Bristol

[Conory]

Thanks, injectors it is then.

 

I've got both the Russell books and what was confusing me was that on the older photographs of saddle tanks the injector assembly seems a bit primitive, as if it was still being perfected. They seem to be left out of the scale drawings so the notion of fabricating ones in OO out of bits of brass pipe soon evaporated.

 

I need a pair for the Finecast 1804. Google tells me that Alan Gibson sells cast ones in brass so that's my likeliest option unless anyone knows of alternative sources.

 

I presume the cab on my model should have piping that corresponds to where the injector comes in.

[Gordon A]

I believe you will find that the fitting immediately below the saddle tank is the water on off valve, with an operating rod going back in to the cab which was turned to operate.

 

Similar injectors are fitted to the later 1366 tanks. Russel gives you a couple of small cab diags which may be useful.

 

Gordon A

Bristol

[Conory]

Thanks for the help on the 1361 injectors.

 

My more immediate problem is the Finecast 1804 which I am building as a 2721 class. There isn't room on the footplate for injectors because the toolboxes are in the way. The solitary rear 3/4 view in Russell doesn't help much and I'm wondering if it would have used some other system. Looking at the 2721 Pannier doesn't help because they moved the toolboxes out of the way to fit a normal injector setup.

 

I notice some of the other saddle tanks in Russell have much simpler pipework between tank, footplate and cab.

 

Can anyone point me at a more useful photo of a 2721 saddle tank.

 

Thanks

 

Julian

[Happy Hippo]

Julian,

 

You have hit the nail on the head with your comment about moving the toolboxes.

 

That is what they did! If the fitter couldn't erect an injector where it should be fitted close to the cab and under the water tank (it is a gravity feed), because the was a toolbox in the way, he'd move the toolbox!

 

The problem with slavishly following GA drawings is that apart from the wheel/cylinders/valve gear arrangement, everything else can be moved around a bit to accommodate mistakes in the drawing office. They were there for the guidance of the erecting staff who had to put these things together and make sure they worked, so they were well versed in moving things around to suit. Once delivered to their depots, fitters often carried out more local modifications to make thing easier to work on or to make life easier for the loco crews.

 

hth

 

Richard

[The Stationmaster]

The best drawings for pipework on GW locos (assuming the coppersmiths followed the drawing of course) are the Pipe Drawings (they also are quite handy as a GA drawing as well so I am told as they show the whole loco as it should be assembled ready for fitting the pipework).

 

I understand - but have never checked - that the GW Society at Didcot hold some Pipe Drawings and there might be others at York (and possibly copies at Swindon 'Steam'?). The chaps (volunteers) in the library at 'Steam' always seems a very helpful bunch and are gradually putting together photo files for as many classes of GW loco as the material allows - might be worth getting in touch with them and arranging to visit?