WW&F No. 10 - Official Work Thread

[Gordon Cook]

I've been working on refurbishing the spare Metropolitan injector for # 10 and can report pretty good progress.
For those who have pondered the magic that occurs inside of one of these devices here is a picture of it in pieces:

As you can see there's a lot going on in there!

The shiny parts are the two new tubes that I made to replace the damaged old ones. The internal valves which control the steam flow have been refinished and I'll be renewing a couple of the outside linkage parts to reduce the play.

Hopefully in a couple of weeks our fireman's side injector will no longer be the PITA that it is now.

[Steve Zuppa]

Nice work, Gawdon. 'Course, having an injector that works all the time  will take all the mystery away. Never did like mysteries, anyway.
Steve

[Mike Fox]

Gordon, Thanks for posting. I never knew they were that extensive. Looks like a lot of work.

[Ira Schreiber]

Back many moons ago when I was at the controls in the cab, we carried a gallon jug of cold water and a ball pein hammer. These were standard tools for getting a balky injector to pick up water. Crude, but effective.

Ira Schreiber

[John McNamara]

I see that a Makita cordless drill and a test tube are required tools for this operation. 

-John

[Gordon Cook]

Thanks. Steve, I hope a properly working injector doesn't make firing #10 any less exciting!
Ira, this gun has been hammered and abused quite a bit. I'm puzzled as to why whacking it would help, the only thing I can think of is the case where the check valve is stuck (that's on the right side in the picture, at the output into the boiler) but otherwise it shouldn't have any effect. Everything else that moves is connected to the operating lever.
And, yes John, you have a sharp eye, but those aren't test tubes. They belong to my other career, designing speakers.
I was experimenting with the ideal shape for port tubes for small vented (bass reflex) speakers, and shaping plastic tubing so it has a gradually expanding cross section from the middle to the ends. Ironically, the injector work gave me some insights into this, and I used the same principle as the delivery tube in the injector uses to smooth out the air flow through the port tube. In small, high output speakers the air velocity is limited by the noise it makes as it tries to go through the tube, so any improvement there improves the speaker's bass output which comes out the port.
Now, back to smoothing up the steam valve stem.

[Ed Lecuyer]

If I may inject myself into this conversation....

What exactly is an injector? Me, being a newbe to steam railroading hears terms like these all the time, but has no idea what they are or the purpose they serve.

Thanks,

-Ed

[James Patten]

An injector injects water into the boiler.  Steam comes in from the top, water comes in from the bottom, a miracle occurs in the middle causing the energy from the steam to turn into velocity for the water, which causes the water to overcome the pressure behind the check valve at the boiler and open the valve to let the water in.  Pulling the handle back causes the miracle to happen.

[Ira Schreiber]

Gawdon, et al,.
The ball pein hammer was exactly for the check valve as the water we used
had a high grass and straw content.
The injectors, Penberthy I believe, were controlled by globe valves and not levers. At just the right moment, a judicious tap of the hammer would get the check ball to move and allow water to enter.

[Keith Taylor]

Hello Gordon,
Beautiful work! Were the original tubes wire drawn? Did you have to make special reamers for the steam nozzle, combining tube and delivery nozzle? Please post some pictures of the tooling! Just curious, are the tubes straight tapers or are they a curved cross section. The Sellers injectors I've worked on had a curved inner taper, and I'd bet making a reamer for those would be very involved.
Again....superb work of which you should be justly proud!
Keith

[Gordon Cook]

Well, to be honest I am not familiar with 'wire drawn' . The originals are castings to be sure, with machined surfaces and threads. I believe the internal passages were formed by a core in the casting, but it is hard to tell because of the pitting and wear. I do understand the lost wax process and they might have been made that way, but that's a guess.
The tubes all have conical cross-sections, no curves.  I took plaster castings of the internal passages to measure their dimensions as accurately as I could. Linn Moedinger of Strasburg replied to an inquiry in RYPN's message board that they found that a curved section wasn't a noticeable improvement over the conical section, so I assume that the injector manufacturers discovered the same thing and went with the straight conical sections for ease of manufacturing. But your comment about the Sellars is useful and interesting. I am hoping that it will work far better than the worn 'gun' we have now, even if the dimensions and angles aren't exactly what the manufacturer originally specified.
I thought about making reamers, but after some research and thought I realized it would be far easier to just set up the compound rest and bore the tapers, so there isn't any tooling. The smallest tube is the combining/forcing tube and it is about .2 " at the smallest diameter, with a taper of around 2.5 degrees to the ends. I have assumed ( I know, I know!) that the tolerance required isn't that tight.
We'll be able to test all this next weekend, I hope, as all I have to do is assemble the injector and am waiting for the right packing material for the valve stems, which should come this week.
Thank you for your kind complements. I especially appreciate that from you, Keith!

[Keith Taylor]

Gordon,
"Wire drawn" cones have been cut by the steam, sometimes you will actually see a groove cut in the cone, if there were solid particles in the steam, from particulates in the water supply. I "think" the term wire drawing comes from the fact that the resultant worn hole resembles a wire drawing die. I am pretty sure the original cones would have been sand cast....but using "French Sand" which is very fine and allows excellent detail. I don't think the "Lost Wax" (Investment casting) was very wide spread outside of art foundries, back when injectors were made. I suspect that the makers mostly used "form tools" to cut the cones. Daniel Bernoulli would be proud of you!
Keith

[Gordon Cook]

On Friday night, the 26th, I installed the refurbished 6 1/2 Metropolitan injector on #10 after a little wrestling with the old one to remove a part from it that was needed.
On Saturday we fired up and I fully expected that the rebuilt injector would work, but, while it lifted readily, it would not inject. 
I would have liked to examine the combining/forcing tube from of the 'old' one, but I couldn't remove it with the tool that I had, and so we had to revert to the original 5 1/2 size injector that has been on #10 for the last 4 years.
By the sounds of the rebuilt unit when attempting to get it to work, I would guess that the new tube that I made was not generating enough pressure to open the check valve. So I'll bore it out and remake it with a replaceable insert so that I can do some experiments. The other possibility is that the steam nozzle was worn, as Keith had explained it was 'cut' from the steam, and maybe it isn't working well enough anymore.
Jason may be able to secure another Metropolitan of similar size and vintage for examination, so I'm hoping to get some additional information regarding the tube dimensions.
So the experiment continues....

[Keith Taylor]

Gordon,
Before you go back inside the injector...you want to check for any vacuum leaks on the delivery side of the injector. If you are getting a lifting action, but it is all coming out of the overflow...it sounds more like a tiny vacuum leak in the piping after the injector. You will also get that kind of reaction if you have a tiny steam leak in the steam valve and it is overheating the injector. Closing the overflow and  opening the starting valve should blow the water in the injector back into the tender tank, and theoretically cool water should replace the heated and allow the injector to work. From what you describe, however, it sounds more like a vacuum leak, probably at the point where the injector is attached to the delivery piping. The tiniest of leaks, almost undetectable will keep an injector for being able to lift the check against boiler pressure.
Keith

[John Kokas]

Good call Keith - I was going to suggest the same thing but you beat me to it..