Injectors v pumps

I have recently come back to driving at our local track with a recently acquired 5" Manor. This is very nicely made with an injector and crosshead pump as well as a hand pump in the tender. I am getting used to setting the pump feed and seeing a nice steady level in the glass remaining while driving, using the injector while standing.

However in some ways pumps are horrible things being the first to leak and accessibility can be a problem. I am building a 5" Claud for which two injectors are specified and no pump. Any such pump if fitted would have to be between the frames.

I wonder what others experiences are of running with injectors and no pump? Is it possible to set an injector to run continuously under club track conditions?

Opinions would be welcomed.

Regards

John B

Hello John,

I drive full size traction engines, Fowler, Aveling and Porter, Alchin and find it is much easier to use a mechanical pump. Just turn one valve to supply water to the boiler. Injectors are a bit more finicky. And yes, there are problems with air locks and leaking seals. Good maintenance required !

With injectors, you turn the water on and carefully throttle the steam valve to inject the water. Often does not work the first time. Some injectors also work best at different pressures. Sometimes there is a low pressure and a high pressure injector. If the injector is too hot it will not pick-up. Injectors require a steady steam pressure and if you are rolling you have to back off on the throttle or the injector will drop out.

I doubt if you could use your injector to run continuousy for a track run. They are sized to deliver a set volume of water, normally much more than a pump and cannot be throttled. A pump works continually and dumps the water back into the tank when not required. When you turn the pump valve, water is diverted from returning to the tank and is fed to the boiler. It is possible to throttle this valve and only divert some of the water to the boiler.

I am building a 6" Ruston Proctor which only has an injector and a steam operated pump to supply boiler feed water. Others that I have seen in steam articles have a mechanical pump. But i intend to add a mechanical pump to my engine because it is easier to operate.

I need a drawing for a mechanical pump suitable for a 6" Ruston Proctor (10" dia boiler) if anyone can assist.

Regards, Paul.

Dear Paul

Thank you for your comments. I have plenty of experience of road steam too, primarily on ploughing engines. Some were fitted with pumps but most had just one injector which was usually very reliable. It had to be. Usually a pump was noisy and leaked. On most road engines pumps run off the crankshaft which in reality is probably too fast in many conditions.

I have no trouble with the 5" Manor injector.

The Claud design is by Martin Evans and I assume he knew what he was doing omitting the pump. Also Don Young, another prolific designer of small engines, was not keen on pumps.

Perhaps some club loco drivers can share their experiences?

John B

John;

Once I ran a 3-1/2" gauge LBSC designed locomotive, the builder only had an injector and handpump on it. It was fantastic, worked every time. What an eye opener.

I hope it makes sense, but I have a 3-1/2" gauge Shay loomotive 90% complete, and hope to have the injectors built (not purchased) in the coming months. No axle pump.

I used to do lots with full sized steam; the injectors generally worked flawlessly; they do take some maintenance, but what doesn't?

Anyway, my money is on the "injectors only" camp - we'll see in the future if my bet is correct or not!

Another JohnS.

Personally I'm a belt and braces man. I prefer to to have as many different methods of getting water into a boiler as I can. The only time I have problems with pumps is at the beginning of the season where I might get a stuck ball. This usually cured with squirt of water from a syringe into the inlet of the the pump, if then having to undo the bottom the pump and giving the balls a poke. Both of my locos have axle/crosshead pumps as well as two injectors.

On my Maxitrak Ruby I do have a small injector which I can run whilst driving without losing too much pressure.

Even though the design of your Claud does not include a pump I would include one paying attention in having access to the balls as I mentioned above.

Regards Luigi.

Thanks Luigi. Much appreciated.

To get back to the original questions - (a) what are the experiences with (hard) club running with two injectors (only) and (b) is it straightforward to set an injector on a 5" loco to run continuously? (without overfilling the boiler of course or losing boiler pressure)

Kind regards

John B

John,

I too am building a Martin Evans Claud, mine is on it's wheels, cylinder block done now doing the valves (for which Don Ashton prepared an improved design). I asked exactly the same question about lack of a pump on another forum, lots of useful advice the most popular of which is to put a small bore pump on one of the tender axles. The alternative would be a little weir type pump sat up on the running board ticking away contentedly, I quite like that idea.

Cheers

Julian,

Dear Julian

I have started a new thread on building a Claud to which I have taken the liberty of copying your reply.

Kind regards

John

Back to injectors/pumps

On the track - injectors every time. Preferably two, high and low pressure. Whereas a pump is purely mechanical, injectors work by magic, as we all know.

In the Sentinel in the road ... well, both. 'Pump on' for the long downhills and injector for when standing at signals or parked outside the pub. However, a traction engine on the road... usually pump as nothing ever happens very fast (or it doesn't on the one I know best). Injector for when parked outside the pub.

Edited By Diane Carney on 23/01/2013 01:15:49

I have not driven a loco so can only talk about experience with injectors and pumps on traction engines and road rollers. Often we tow a heavy trailer loaded with water, wood and coal and find that the injector is temperamental about changes in steam pressure when going up and down hills. The injector normally is reliable when the engine is stationary. (like outside the pub).

I too am a "belts and braces man" and prefer at least 2 different ways to get water into the boiler. The Ruston Proctor which I an building is designed for an injector and a Moore pump (like a Weir pump) but I want to add a mechanical pump as well.

Regards, Paul.

Could be a waste of space post but will post anyway

Petrol car injectors are electronic but diesels have had mechanical injectors for decades, and vary their throttle accordingly

Perhaps the principles of a diesel injector system might give rise to a solution

(I lack the in-depth knowledge to say either way)

Dear Andy

The principle of internal combustion injectors is quite different where by a mechanical/electronic system puts the fuel into the void of a cylinder at high pressure. A steam injector puts water into the boiler using its own pressure - takes a bit longer to exp[lain how!

Regards

John B

John,

I've been building and operating model locomotives for over forty years. I've never put a pump (hand or mechanically operated) on any that I've built. I've had few failures attributable to the injectors except in the early days when I quickly learnt a lot about them, but with two to work with I never got into any real trouble.

Looked after injectors are very reliable. With check valves that seat properly, and that's just one per injector, and adequate steam and water supplys with good fine filters you should have no problems. Don't be lead by anyone into believing that they need to be removed after every outing to be cleaned in acid. I only do this if an injector shows signs of misbehaving, and after checking for dirt in the cones, and I only use citric acid - never vinegar. I once had a loco laid up waiting for mechanical repairs for two or three years. When I eventually got the work done and the boiler tested, both injectors worked flawlessly although they hadn't been cleaned in years.

Always make sure there's no water lying in the injector when the loco is out of service. If not then the cones are subject to de zincification and will quickly be eroded. A squirt of WD40 after running is over ensures they are dry.

Don't oversize the injectors. They need to be operating for long periods. If you have injectors that are too big they will fill the boiler too quickly and you will be forever turning them on and off. 11ounce per minute will suffice on even large 5" gauge locos. You just turn one on when you set off and use the other to top up if you need to. The more you use them the better they get.

And a word of warning. If you have a pump and an injector the injector will give you problems because it won't get used enough, and if the pump suffices then you will neglect the injector and it won't work when you need it.

Finally lifting injectors operating in the submerged position are the best. It doesn't matter if you turn on water or steam first, and if the water suppy is interupted they will restart automatically.

Hope I've convinced you. Good luck

Eddie

Edited By 61962 on 24/01/2013 22:44:38

Edited By 61962 on 24/01/2013 22:45:09

Dear Eddie

Thank you for your posting. Yes, that is what I thought - no pumps for me though I will put a hand pump in the tender to satisfy our club boiler inspectors. I was concerned about forever turning an injector on and off but I think that you have answered that.

Kind regards

John

Thank you Michael. The Claud design I am following has clacks low down on the backhead. From what you say not ideal though this follows full size practice. The earlier Belpaire D16/2 had a top feed on the dome though this would conflict with the original I am trying to represent.

Kind regards

John B