Nathan Monitor Injector in 2.5"

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AnthonyDuarte
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Nathan Monitor Injector in 2.5"

Post by AnthonyDuarte » Tue May 21, 2019 11:00 am

I started designing the 2.5" Monitors back in August 2014. I figured they would make a nice dummy body on a locomotive I hoped to build.
Well, going through Nathan drawings and looking over model injector designs, this project grew into a love for steam injectors that got a little out of control.

I've had a working prototype on my locomotive since before Eccentric Engineer ever sold an injector, but I've never been happy with its operation.
The injector part of it worked fine, but the getting the valves to seal properly and easily operating the handles was never to my satisfaction. This is the 4th, and I think, the final design of this injector. It's surreal seeing one built up that represents what the production run will look like. I've only ever seen all 56 parts together in CAD before now!

For the main steam valve (topmost valve), I've experimented with a 90 degree turn valve and a push-pull style valve, and neither worked great. So I went back to the drawing board and had a look at the real thing again. They use a double lead thread. So I decided to go one further and use a triple lead thread on the model. This means the handle goes from closed to fully open in just a hair over 1 full turn.

The trick with the primer valve (middle valve) is it doesn't have room to spin around more than half a turn, so it also features a triple lead thread. This opens it more than enough with just 1/4 turn. It also has a hexagonal key on the spindle, so that it can be easily rotated to a convenient location, depending on which side of the boiler the injector is on.

The water valve is just for looks (bottom), but it still has packing to give it some resistance so it stays wherever you put it. Control valves on the tender will be used to control water flow.

The delivery cone is threaded into the front casting, which unscrews from the overflow body. So removing the delivery cone is as simple as unscrewing the front piece. The steam and combining cone are threaded into the main body, and can be removed with a long 3/16" socket drive. They all come out through the front without disassembling the injector further. Which means different sized nozzles can then be threaded back in! I plan on offering two different delivery rates for these injectors. 5 pints (same as the Standard Injector) and 6.5 pints for larger 2.5" engines.

Stay tuned,
Anthony
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ccvstmr
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Re: Nathan Monitor Injector in 2.5"

Post by ccvstmr » Tue May 21, 2019 11:21 am

Anthony...KUDOS to you! Not only have you envisioned a fantastic piece of live steam "jewelry", you gave ample consideration to injector operation AND another important aspect...service!

Over the years, have showed many live steamers how to service a few different types of injectors...while the loco was steamed up. Have found it's best to turn the water supply on and let it run. Helps minimize fingers getting burned. The tools...well, they've all survived so far.

Good luck to you as you expand your injector product line. The couple injectors I've seen...not only look super...but work great! Can't ask for any more for a live steam appliance. Keep up the fantastic work and keep us posted! Carl B.
Life is like a sewer...what you get out of it depends on what you put into it!
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FLtenwheeler
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Re: Nathan Monitor Injector in 2.5"

Post by FLtenwheeler » Wed May 22, 2019 4:36 am

Hi Anthony

I want to see pictures of the miniature triple lead threads. You are a master of miniature engineering.

Tim
He who dies with the most unfinished projects: Should of put more time into their hobby.

AnthonyDuarte
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Re: Nathan Monitor Injector in 2.5"

Post by AnthonyDuarte » Wed May 22, 2019 3:05 pm

Tim,

The steam valve is 3/16” OD with 3 leads at a .075” pitch.
Doesn’t really show on the spindle but you can sort of making out 3 leads on the chamfer of the yoke.

Forgive the dirty fingers!

Anthony
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Fender
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Re: Nathan Monitor Injector in 2.5"

Post by Fender » Wed May 22, 2019 4:35 pm

Anthony, when you say you used a triple-lead thread, is this the same as a thread with three starts? In other words, one turn of the handle moves the valve a distance equal to three times the thread pitch?
Dan Watson

AnthonyDuarte
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Re: Nathan Monitor Injector in 2.5"

Post by AnthonyDuarte » Wed May 22, 2019 8:09 pm

Fender wrote:
Wed May 22, 2019 4:35 pm
Anthony, when you say you used a triple-lead thread, is this the same as a thread with three starts? In other words, one turn of the handle moves the valve a distance equal to three times the thread pitch?
That is correct.

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Fender
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Re: Nathan Monitor Injector in 2.5"

Post by Fender » Wed May 22, 2019 8:27 pm

That must be a bear to set up. But then, all my experience is with a manual lathe. I can see how the first start is made, but the the second and third starts must be evenly spaced between the first one.
Dan Watson

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Bill Shields
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Re: Nathan Monitor Injector in 2.5"

Post by Bill Shields » Wed May 22, 2019 8:38 pm

easy as pie on a CNC lathe...doing it by hand requires that you start the thread at different 'positions' on threading dial...or have a way to index the part 120 degrees.

'tis very nice work indeed.
Too many things going on to bother listing them.

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Dick_Morris
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Re: Nathan Monitor Injector in 2.5"

Post by Dick_Morris » Wed May 22, 2019 10:46 pm

On a manual lathe you can set the compound rest parallel to the ways. Cut one thread to depth, reset the tool one thread pitch, cut the second to depth, reset the thread by one thread pitch, and cut the third thread. Note that the angle of the thread in greater than for a single start thread, so the clearance on the tool bit has to be ground accordingly.

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Re: Nathan Monitor Injector in 2.5"

Post by Harold_V » Thu May 23, 2019 1:47 am

Parts run between centers can be easily indexed by simply using a three jaw or a four jaw chuck, depending on the number of entries desired. The jaws become your indexing and driving mechanism. Worthless for chucked parts, though.

By using this method, you can keep the compound angle of 29° for feeding the threading tool instead of plunge feeding. For tougher materials, that often is a better choice, as the flow of chips from plunge feeding is often troublesome and is known to create premature tip failure. Free machining brass/bronze? Doesn't really make much difference.

H
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Fender
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Re: Nathan Monitor Injector in 2.5"

Post by Fender » Mon Jun 03, 2019 6:02 am

Anthony,
One small detail about the installation of these injectors that I have observed on full-size locomotives, is that there is a small hole in the overflow pipe just below the injector. This apparently serves two purposes. When the injector is started, water can be seen coming out the hole, Indicating that water is going out of the overflow, and that the priming valve should be closed, or that the water valve needs adjusting. It also admits air into the overflow pipe, preventing water from being siphoned from the tender after the steam is shut off, assuming the injector is mounted above the water level in the tender.
In a full-size loco it may not be practical to hang out of the cab to look at the end of the overflow pipe, but this is also true for some live steam locos as well, where you must lean over to see it, so it’s desirable to have an in-cab indication of the overflow status.
Dan Watson

AnthonyDuarte
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Re: Nathan Monitor Injector in 2.5"

Post by AnthonyDuarte » Mon Jun 03, 2019 11:00 am

I have been away at LALS and Train Mountain the last two weekends giving the new monitors a good workout, and I took some videos that I will post a bit later. On our models the engineer sits a couple feet away from the overflow rather than a dozen+ feet, so it's very easy to hear the difference between dry steam vs. water coming out of the overflow. Due to the weight of the water and distance we're lifting, they prime nearly instantly. Might take 1-2 seconds if the tender is almost empty. Still, siphoning is a very real problem, and drilling a tiny hole close to the injector will fix that. A good recommendation for any high-mounted injector.

Video to come shortly.

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