Injector Sizing

[GeorgeRay]

Andy
I dont know of a full size locomotie that has injectors that are deliberately set differently. As you probably know they will feed from 250 psi down to about 50 psi if left alone. Ie from the boiler pressure of a West Country down to the last knockings when disposing at the end of the day. I doubt if the injectrs were changed when the boiler pressure was reduced from 280. Certainly in my time none of the locos on the BLuebell had different sized injectors although there was talk of changing one of the Terrier injectors for one of the P tanks so that the fill ate was reduced. As far as I am aware it never came to anything.

[spurley]

Hi there

From my experience George is right about full sized injector deliveries. However I remember that, on the Bluebell engines, the fireman's side injectors were usually easier to start and operate than the driver's side (nothing to do with the driver getting in the way!!) on most engines. I do remember that both the Adams and 323's injectors were able to operate down to 15psi if you kept reducing the water delivery to suit the pressure! Having said that I once had both safety valves up on the Adams with 170psi (red line was 160) on the clock with both injectors on after putting on a real good fire before departure being delayed! The end result was a very full pot and a rather sedate ascent of Freshfield before we got sight of water in the top of the glass again and the regulator could be opened with some confidence of not priming! Injectors are definitely an art to operate and need cold or cool water to operate correctly, once mastered and understood there is no real problem as long as the inlet filters are kept clean and the cones are regularly descaled. The lifting injectors fitted to the North London could be obstinate in hot weather and a bucket of cold water was kept in the cab (by those in the know) for dousing down if things got a bit hairy!! This generally happened when you most needed feedwater; either when a departure was delayed and the fire got going or up the line at the top of a bank with the water near the bottom nut! I'm sure George has vivid memories of these things too?!?

Cheers

Brian

[NarrowGauge]

Thanks to everyone who has responded on this. The replies have been most interesting, especially the 1:1 stories.

I certainly hadn't thought of fitting two injectors, each capable of delivering at different rates. However, I do note the reservations by some, regarding the use of these devices.

Not sure which way I shall jump, still have time on my side, so many pros and cons. Will no doubt be a case of adopting a solution that matches my ME skills!

My thanks to all
Dave.

[greasemonkey]

Hi All
If I remember correctly from my footplate days, the S15 number 506 on the Watercress line had two diffrently sized injectors. The small one could easily be fired against when climbing the alps leaving Alton. It was put on as we crossed Butts junction at the bottom of the hill and forgotten about until just before the top when it was switched of.
Following this idea I fitted a small 14oz injector to my Nigel Gresley in August when I took part in Guildfords OMLEC competition. Worked a treat, I put it on at the start of the half hour and forgot about it till the end with supply meeting demand easily.
Andy

[andrewtoplis]

Hi Greasemonkey,

Really? Thats the first engine I have ever heard of with different ones. I think Spurley's point about the firemans side being easier to operate is because they get far more use, we lazy b*ggers being loath to walk across the cab! Thus they are well worn in.

Some classes have either fast or slow jacks, Brighton Terrier ones work like demons, and I know one fellow who put on the injector then ran to the loo on the platform. The rest of the crew suddenly realised everything had gone all too quiet...

[ewal]

I would recommend a No 6 injector for a 2 gallon boiler & an axle driven pump. The No 6 will supply 4 pints per minute. My track is quite steep so I open the bypass valve when climbing & close it on the way down when it also acts as a brake. I once had a gallon a minute injector on my Tinker Belle but it wouldn't work so I swapped it for a No 6. I fill my boilers through the blow down valve this is better than removing a safety valve.

E.W.

[chris vine]

Hi,

On the subject of injectors, there is an old trick which I am sure everyone knows already but.....

if the injector won't work at the highest working pressure, which is a pain because you want to use it to quieten down the safety valves, you can move its operating range up a bit by moving the steam cone back a fraction. This is only a few thou and can be done with a shim washer just behind the flange of the cone.

It works a treat. I found it useful this summer when the feed water was a little warm and the injector would not function at full boiler pressure. 10 thou shim and the problem was solved.

Chris.