Injector size

[Michael CallaghanParticipant @michaelcallaghan68621]

Hi. It’s come the time to think of injector sizes for my 5 inch gauge three cylinder royal Scot. The loco needs two injectors. There is no axle pump and the only other means of getting water into the boiler is by the tender hand pump. So my question is what size injectors do I need. Thanks

[Dave WoottonParticipant @davewootton]

I’ve used a 15 oz and a 22 oz to feed a 2 cyl Brit in 5″ gauge and it seemed fine, used the smaller to maintain a constant water level and keep the safeties quiet ( very free steaming!), and the larger if more rapid filling was needed under very heavy loading. I did try a 12 to run continuously but it was not very reliable. All were commercial injectors, bought from the old Hertford Kennions, and the late Fred Laroche, I seem to remember Fred’s were rated 16 and 25 oz. The Brit also had no axle pump fitted and these two sizes seemed to do the trick.  I recently purchased two injectors for another loco from Reeves 2000 and these work well. I did have a go some years ago at making some to the Laurie Lawrence design in M.E these did not work well! Royal Scot’s are lovely engines and seem to run very well.

 

[Speedy Builder5Participant @speedybuilder5]

+ 1 for Reeves injector.  You have to bear in mind the cold water temperature. I have a SPEEDY 5″ tank loco, but in summer (most of the time) the tank water was too warm to get the injector to work. Using water from the riding car is more manageable. I started off with a Mac Models 11 oz number 2 injector that would only work on the coldest days. I now use a Reeves 25oz injector that will pick up with tepid water and has proved quite reliable.

I have also installed a caravan high pressure 12volt water pump in the riding car which will pump in excess of boiler pressure but has a “fail safe” in that the rubber tube blows off the fitting at about 80psi. Ideal for initial boiler fill but can be used on the hot boiler if the injector fails or lack of steam!

Bob

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