Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines
Builds, Repairs, Show Your Machines! => Technical Tips, Builds, and Help => Topic started by: komet163b on February 18, 2020, 03:18:38 pm
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I do have a 1/4-28 tap, if you decide that's the direction to go. Likely have more than one, but found the first right away. Hoarding does pay off sometimes
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Unmachined fittings from PM? I could give it
a try. I run hot-n-cold on what nit to work on,
but I think I'll concentrate on the heating system
as the engine will work with the current fittings.
I'm aleady checking the Forest website and have
a few questions for them.
Thanks,
Wayne
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Wayne, I will have a look in my tap box...I might have a spare. If the tap can be found, you can buy unmachined fittings from PM. Would that solve your issue as to fittings?
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Hi Wayne,
I have attached some drawings of the burner for my 3.5" OD centre flue boiler and also a couple for the boiler.
You will see that the layout is similar to yours, albeit the flu on mine is a bit larger than yours, but they serve to show you how the burner attaches to the flu.
You will need to adjust the burner dimensions a little ( keep the adjustments in proportion ) to fit the slightly smaller flu on your boiler.
The Number 8 gas jet has an orifice of 0.25mm and is threaded 1BA.
They can be obtained from 'Forest Classics' and also from 'Pollymodelengineering' here in the UK
The latter can also supply the correct ceramic plaque required for the burner... both will export.
I hope this helps.
Best regards.
Sandy.
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Thanks for the interest.
The horizontal center flue is 1.5" x 9" and
has a total of 12 cross-tubes in an 'X' pattern,
which start about 1.5" in from each flue end.
The boiler body, which is inside a sheet-metal
shroud, is a bit less than 3.25" x 7" with the
flue centered inside and extending roughly
1" beyond the boiler on each end. In the
original setup the blowtorch shot into the same
end as the cylinder and steambox and exited
at the crank end. The original blowtorch looked
cobbled-up and not safe at all (takes a lot for me
to say something like that is unsafe).
So, any good ideas on heater sources? I was going
to place 4 200W buffered cartridge heaters in the
cross-tube 'X's' but am open to a good gas heater
setup as option number one. If it was a vertical
boiler I'd be tying to think of a way to fuel it with
wood. I don't think that would be an option here.
Thanks,
Wayne
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Hi Wayne,
An adjustable die allows you to adjust the depth of thread being cut so that you can get the preferred fit for the matching nut/bush. It needs to be used with the appropriate die holder which has the adjusting screws on it... usually 3 of them. The centre one is used to open the die and to lock it in that position... the other two are used to close the die up a little to obtain the required thread fit.
The centre one is first slackened off then the outer two are adjusted and then the centre one locked up again.
As for boiler gas burners... what size is your boiler and centre flu diameter?
I have some designs for ceramic burners which I use for my own centre flu boilers... perhaps one of these would be suitable, or can be adapted to fit.
They all run using bottled mixed gas 70/30 Butane/Propane readily available from outdoor pursuit stores and most general hardware stores.
If you let me know the sizes and I will see what I have that may suit your need.
Best regards.
Sandy.
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Well, thanks for the 'UNF' I've seen a few taps and dies but I'm trying
to digest the price. If you please, what is an 'adjustable' die? It is just
too bad that there isn't a ready-made selection of 1/4-28 fittings. I need
the taps for 'elective' work.
The following is on the critical path to steaming up.
I'm trying to figure out how to heat the boiler. It is a horizontal center-flue
with cross-tubes, and was heated by a time-bomb home-made blowtorch.
I'd like to keep it fired by bottled-gas but I'm having trouble imagining it.
I'm leaning to 4X200watt cartridge heaters and I'm working up some good
ideas on how to 'ballast' them. If not ballasted w/some soft steel in contact
they will heat-up, light-up, and burn-out. Hard lesson learned.
Thanks,
Wayne
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Hi Wayne,
1/4" x 28 is a standard UNF size so not an odd ball.
Hope that helps.
Sandy.
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Well, sounds like I may have to pull a rabbit
out of my hat. Never a pretty sight. I'll leave
the boiler fittings as is and look around for a
bit, but I'll be thinking of how to make a
conversion fitting on my own.
Thanks,
Wayne
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Wayne,
even worse than 1/4-28 threads are 12-28 threads which i have run across on several engines. I suppose this comes from builders who did not have access to the model engineering thread taps and dies being either 1/4-40 or 1/4-32. A 12-28 bolt is .216 o.d., only slightly smaller than a 1/4" bolt. If your threads really are 1/4-28, a standard 1/4" fine thread bolt could be used as a plug or adapted to other threads. I'm not sure what kind of fittings you need or what kind of tools you have available, but 1/4 -28 taps and dies should be available locally and combo tap and die sets for model engineering threads are available on ebay. Once you have some adapters made to go from 1/4-28 to 1/4 40, you can find most anything you need readily available.
If this does not help, more specific details as to exactly what kind of adapters you need would be needed.
crazydoug
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Good afternoon from Brooklyn!
I'm working on an old boiler/engine setup from
the 1920's and two of the boiler bushings are for
1/4-28 fittings. I do have a cap and no-working
pressure guage that serves to at least 'stop up'
those bushings and I checked them at Lowes on
their thread selection board. That is why I think
theiy are 1/4"(for sure)-28. I have other plans for
those access points and need some help with
any fittings at all that will fit properly. It seems
that 1/4-28 isn't that easy to find.
I've added a photo from the original sale.
Thank You,
Wayne