The Home Machinist!

Not sure what to call this post, and maybe lengthy discussions with Marty or Vance would
accomplish the same.

But I thought the group would benefit from the knowledge.

What differences are made in constructing an oil burning and front end throttle equipped boiler and what details need to be done in hobby scale?

Specifically, I'm assuming the boiler is essentially the same, maybe a smaller firebox hole. But steam feed to the turret, and front tube sheet?
How does one mount the throttle lever, and seal the front and rear openings? Does it make sense to make the actuating lever running through the dry pipe brass to reduce wear on the dry pipe?

Drilling holes in the backhead for the door, throttle bracket, gauge glass....

If there is something in print or online and it's easier to send me there I'll happily do that.

I do have Nelson's book, the Railroad Supply engineering book, and Gene's ten wheeler drawings. Just thinking there is more info that can be had.

Thanks,
Brian

Look at Shop Shed & Road as well ?

If you have a front end throttle, then you may only have an opening into the smokebox- that's the UK way of doing it, the throttle linkage goes along the boiler to the smokebox, and the throttle is in the smokebox.

Only (big) issue with this setup is that you have to seal the throttle in a hotter than steam environment, and it needs to be leak free from the steam>smokebox direction.

Passing the throttle through a drilled stay is entirely possible. If you are going to do this, I would recommend having a tube run from the backhead to the forward tubeplate, and then sleeve at the ends to align the rod. (so the rod is running in "air" ). I liked the setup of our Hudson, with a backhead mounted throttle, feeding steam one way through the superheaters (from firebox to smokebox), with the superheater after the throttle. That probably would not have been my dad's choice, but that is how the boiler was originally designed (???). (Said same boiler lacked room for an ashpan, as it was the only 3 course of stay Hoffman Hudson boiler we have seen...but it did mean it had 22" of grate...).

As regards oil fired design, it depends. If you can, do as per some prototypes, and put the burner at the front, facing backwards, with a stainless arch. If you can, fit so that you can draw steam after the superheater- for both the blower and atomizing oil- which means that the superheater will have to be before the throttle, and located in the smokebox (see ^) I would put a realistic sized door on the boiler- the tube sizes should be the same as for coal, so if someone else wants a coal fired engine, and you have fitted it as oil fired, it should be possible to take out the burner & fit coal grates, change blast nozzle, add a cinder screen (perhaps), and go. That would be much easier than if you have fitted a convenient 1" hole for the light off torch on oil fire...and that's it...on a 7.x gauge loco . NB- the steam pipe back from the superheater can't run through the boiler without insulation, otherwise the boiler will act as an attemporator, and cool the steam back to saturation temperature...

Fitting attachments to a boiler: Ideally, don't. The fewer holes in anything, the less likely it is to leak. (or, in 'trekky: the more they overdo the plumbing, the easier it is to stop up the drain). If you can, design/fit the attachments to solid material, rather than into the water spaces of the boiler. If the boiler is a steel boiler, then you may not need bushings. (depends on thread pitch chosen & size of fittings...). Ideally, the boiler design should indicate where to put bushes & pads on the boiler before construction starts. They are not that hard to put in place on flat plate- it's once you move to curved surfaces that the issues start multiplying. If you do need to put mounting holes into the steam space, use something that is rust resistant (Monel ?) as the screw material if you can. It is embarassing when the 4-40 tapped holes have their steel bolts leave via rusting off... (ask me how I know...as Chuck Hackett's sig read: Good Judgement comes from Experience. Experience comes from bad Judgement)

The more thinking you do now, the easier it will be later . Some people around here (and I'm not just meaning me !) have thought about this stuff for a while.

James

Thank you James,
That's why I'm asking now!

Brian

The only change I recommend for an oil burner is to use steel tubes, seal welded at the firebox end. That being said, there are a fair number of oil burners that have copper tubes. But I would suggest that you use a dome throttle. Properly made the Allen throttle works very well. The smokebox of an oil burner can get too hot for a ball valve throttle.
As for setting up the burner and firing pan, find the 3 part article by Joe Monte that was in Live Steam magazine. I followed that on a Consolidation I built for Pam and Wilbur Dong. Someone at LALS said it was the best oil burning Allen locomotive they had seen.

Here's the setup for the front-end throttle on my propane-powered Mike.
In use, there will be a shield around the ball-valve so it stays out of the direct heat passing through the tubes.

Note the lateral slide mount which allows heat expansion while holding the assembly against the throttle rod fore/aft forces. The holding screw+washer is not installed in the last photo.
The throttle rod from the back-head is stainless steel to minimize heat expansion. It's not yet installed in the photos, but the stay tube it fits through is visible.
Lastly, all the commercial plumbing test-pieces have been replaced with black iron equivalents.

Hopefully this will work properly. I've seen similar setups that work fine. The ball valve is a high temperature assembly acquired from a place that specializes in boiler fittings, located in Renton, WA. 'Don't remember their name...
~RN

Thank you Gentlemen.

I have Monte's articles here somewhere as well as a Bagley burner already in hand.
What about drilling and tapping into the boiler? I know Marty supplies a turret
connection 1/4 npt? Should the gauge glass be tapped into its own hole in the
top of the boiler?

I'm also no welder. Tagging rings for lagging and welding brackets for air pumps
and walkways and domes fill me with a sense of dread.

There's a lot of work and money in a boiler and I sure don't want to screw one up.

Thanks!
Brian

The gauge glass should always be mounted to a place where there is no flow to reduce the pressure on one end or another.

Generally, this means that the glass is not mounted to the turret. there are exceptions to the rule, but don't go looking for trouble.

I personally don't like tapping directly into the boiler shell, but a lot of people do it without problems -> perhaps this is an emotional hold-over from fixing a bunch of copper boilers where people threaded directly into the copper shell....LBSC did a lot of this and I shudder every time I see it.

makinsmoke wrote:Thank you Gentlemen.

I have Monte's articles here somewhere as well as a Bagley burner already in hand.
What about drilling and tapping into the boiler? I know Marty supplies a turret
connection 1/4 npt? Should the gauge glass be tapped into its own hole in the
top of the boiler?

I'm also no welder. Tagging rings for lagging and welding brackets for air pumps
and walkways and domes fill me with a sense of dread.
Brian

Yes, the top connection for the water glass should be separate from the turret. In fact, it should be within an inch or so of the highest point on the shell.
I know that the ASME requires all welding on a boiler to be done to the code, but that's not really practical with our small boilers. I don't see any problem welding on brackets or rings with a MIG welder. I think that is preferable to drilling and tapping into the boiler.

Thanks guys. Marty, I've seen a couple photos
of boilers you've built. They have three threaded
bushings at the top rear. It is standard to have three or is that something to be determined?

I'm also assuming additional clean outs are a good idea.

I keep seeing references to not using brass in a boiler. There are lots of piping fittings that folks are using hardware store fittings, notably thecsteam inlet and exhaust fittings into the cylinders on the Allen locomotives. Is that a problem or not?

Thanks,
Brian

Don't use brass in the construction of the boiler- the problem is that it may loose its zinc, and then it turns into something like swiss cheese.
Using brass in fittings attached to a boiler is less of a problem- if it does fail, then it is replaceable without needing a new boiler.

I like to put in separate bushings for the turret, top connection for the water glass, and the pressure gauge.
As for brass, I do not use it in the boiler, but some of the fittings that screw into the boiler are brass. I like the ones from Parker and Swagelok, because they are forged brass.

Marty,
What do you recommend for the lower sight glass connections?