Some say the injector is probably the most mysterious part engineers have ever come up with.

In this article I’m not going to cover the technical details and functionality of an injector, as others have already covered this subject very well. I’d rather like to share my experiences with them, specifically on the Feldbahn, so you get the chance to experience a much quicker start than I did.

The cover image shows an Injector No. 5 – two of them are fitted on the Feldbahn.

Trivia

Usually I’m not the type of person who reads manuals before dealing with the subject itself – but this time I did… and not only once! Well, what can I say, unfortunately it did not help me at all. At least not in terms of how to operate the Feldbahn’s injectors.

So which manual did I read? As the Feldbahn is a very similar engine to Station Road Steam’s Stafford 0-4-0, and to my knowledge there is no operation manual explicitly for the Feldbahn, I went for the Stafford’s manual. I followed the instructions in section 4.4. Injectors closely and failed miserably at starting the injectors.

What did I try in my first attempts to get the injectors started?

  1. Open the water valve fully
  2. Wait for the water to run out constantly from the overflow pipe
  3. Slowly, but steadily, open the steam valve
  4. See the water run faster (water/steam mix)
  5. Open the steam valve fully
  6. No change compared to step #4

If I initially opened the steam valve too quickly (after step #2), only steam was spat out of the overflow pipe. It also might be worth mentioning that I tried these steps at various boiler pressures, starting at 110 psi all the way down to 70 psi.

After two steaming attempts with no ’luck’ feeding water into the boiler (and successfully but unknowingly performing the End of Day test), I went back to research. This time I crawled the internet like a madman.

Gaining Knowledge – Things to Check

I found out that my main problem must have been a wrong assumption combined with, probably, outdated information from the operation manual. Maybe other injectors are fitted now than when the manual was written.

Also, I found good indications that the statement from Station Road Steam in their operation manual

The injectors are reliable devices, if they fail to work check that […] the injector itself is clear and clean.

should be taken seriously, as I found a tiny metal chip stuck in one of the injector’s cones when checking them. It’s needless to say that this might have caused problems on top of the operator’s inability.

One video on YouTube (I have no idea how I managed to find that) helped me a lot to understand the parameters of an injector in action. You’ll see why later.

After my research, I combined the gathered information, which key elements were:

  • Probably the bends directly after the delivery cone might cause some problems? (Most found suggestion, also by tales) – Unlikely. Why should Station Road Steam ship a non-functional design?
  • Do I have air leaking into the water feed line? Probably. I ‘seated’ the fittings and made sure to tighten the nuts adequately when reassembling the lines around the injector.
  • Station Road Steam sells this exact type of injector (no. 5) as A high-pressure injector for 120 psi working pressure in their parts shop. What if it has to be understood as literally for 120 psi?! In this case, I was simply overfeeding it with water – so the water-steam-ratio was way off its capabilities (see previously mentioned video).

How I Managed to Start the Injector

The steps, now, are pretty much identical to those described before, and with a bit of practice you will be able to shorten the process like shown in this YouTube video/clip (that was uploaded by a General Gordon owner after I went through the hassle).

  1. Open the water valve fully (or halfway, like in the video)
  2. Wait for the water to run out constantly from the overflow pipe
  3. Slowly, but steadily, open the steam valve
  4. See the water run faster (water/steam mix)
  5. Open the steam valve fully
  6. Shut the water valve until the injector picks up

Interestingly, this procedure is exactly what is described in the Stafford’s operating manual as the low pressure procedure. Which led me to the conclusion that nowadays there might be different types of injectors fitted. But this also means the information was there all the time – but, at least for me – out of context.

Also, with this method, you can go very low in terms of boiler pressure. My lowest attempt so far was at about 50 psi – the injector picked up on the first try.

Afterthought

The Feldbahn is provided with two powerful and functional injectors. With my current knowledge and minimal experience, I would prefer two different types of injectors – one for higher and one for lower pressures – because fiddling around with them while being on the track might lead to stressful situations. A simple ’turn on water and steam’, like ‘fire and forget’, would be much more comfortable.

Apart from feeding water into the boiler dynamically, I was already planning to attach a steam-powered (mechanical) feed pump to the engine. More about this can be read here.