Small gauge/scale boiler question

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Curtis_F
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Small gauge/scale boiler question

Post by Curtis_F » Tue Jul 15, 2008 12:32 pm

Gentlemen,

I've worked on large scale steel boilers and ASME boilers, but I don't know much about copper boilers in the smaller gauges.

In looking through the Raritan and the Kozo A3 plan books last night I noticed that neither boilers had any inspection ports aside from the steam dome, and only 1 blowdown near the back of the boiler. Is that common for the smaller gauges?

Do copper boilers build up sediment at the same rate as steel boilers? Slower? Faster? Same types of sediment (i.e. just whats in the water rather than those made from interaction with the boiler material)

Are most small gauge/scale boilers copper because of ease of construction? Historical reasons? Does steel not do as well in the smaller applications?


Thank you for your time,

Curtis F.
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sncf141r
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Re: Small gauge/scale boiler question

Post by sncf141r » Tue Jul 15, 2008 12:59 pm

Curtis;

Copper works easily, silver solders well, and does not rust.

Scale is dependent on the water and amount of it you boil away; hopefully, people wash out boilers.

You do not need a stamp (and, up here anyway, you need a company to hold that stamp for you) to "weld" copper, unlike steel.

Basically, you get an almost maintenance free boiler, that can be made to close dimensions.

IMHO, copper boilers for anything from small 7-1/2" down makes sense, if you can handle the upfront cost.

I've almost finished my 4th copper boiler, and have done quite a bit of full sized work, both maintenance and running. I'm licensed in the Province of Ontario as a "Steam Traction Operator" - whatever that means!

JohnS.

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gwrdriver
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Post by gwrdriver » Tue Jul 15, 2008 2:04 pm

Curtis,
In addition to what John has said, using steel for a small boiler is problematic due to the need to make a corrosion allowance in order to have a reasonable working life. The extra material thickness required for the corrosion allowance reduces the amount of available steam and water space in a small boiler and in a small scale narrow firebox boilers is unworkable. Typically in the USA we have always used 6"od as the tipping point. Over 6" the cost and difficulty of soldering copper often (but not always) made steel a better choice and the effect of the corrosion allowance on the steam space is proportionately reduced. Under 6" the opposite was generally true although with the price of copper at an all-time high, and places to find short lengths of large OD tube drying up, 6" may no longer be the tipping point. As someone will no doubt point out, weight is another consideration and steel adds more weight than copper but if the boiler won't generate and store steam, especially a small one, the additional weight doesn't do you much good.

Historically the lack of inspection ports has been common practice in small copper boilers because decades of experience has shown that with a little care to use good water and regular flushing will take care of most whatever sediment problems might arise. I sectioned an old (and apprently abused) copper boiler last year and found lots of mud ring grunge which was mostly (all?) rust stained lime or mineral scale. The rust came from using steel in contact with the water, steel studs in the fittings it appeared.

I think it's important to mention that steel and copper are quite different in their behavior and needs and what perhaps might be good practice for one might not necessarily be good for the other.
GWRdriver
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alanstepney
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Post by alanstepney » Tue Jul 15, 2008 3:00 pm

Over this side of the pond, 6" diam is also the usual point when one changes from copper to steel.

(Although take a look at Bill Shields photos (Steaming weekend) to see a FULL SIZE copper firebox!)

In many ways, copper is an ideal material for boilers, and given reasonable care they will last, and last.
I am having to build a new boiler for an engine I built 40 years ago. Not because the original has failed, but because I dont like the quality of workmanship that was the best I could do, back then.
However, over that time the loco has done a lot of hard work.

The big problem is cost, but given the long life, it doesnt seem so bad when looked at over the years.
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Post by pkastagehand » Tue Jul 15, 2008 3:27 pm

I was sort of thinking about steel for an A3 in 3/4" for cost reasons and the fact I have a TIG and thought I could manage the welding. But what GWR said got me thinking I'd better stick to copper. By the time I figured in the corrosion allowance I'd have no water legs to speak of around the fire box. The rest of it might have been doable. Still haven't gotten to the boiler yet so I'm not ruling steel out entirely yet.

Paul

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Post by gwrdriver » Tue Jul 15, 2008 3:46 pm

Paul,
The A3 is a mighty small boiler for steel, but still I think you are taking the right approach, that of weighting all the factors, material availability and cost, your skills and equipment, and design requirements, and then making your decision.

There are waterleg-less boilers such as the Briggs which is the favorite of the Aussies these days.
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Bill Shields
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Copper and Tig

Post by Bill Shields » Tue Jul 15, 2008 7:34 pm

Don't overlook the fact that if you are good at it, you can TIG a copper boiler - at least the main structural parts....then silver solder in the tubes and bushings.

Small boilers are best in copper. Most of the copper failures that I have fixed are a result of scale building up and causing loss of heat transfer.

No, one blowdown / cleanout isn't enough for any boiler - and smaller boilers don't need fewer - they need just as many - as a larger boiler.

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Post by Mike Walsh » Tue Jul 15, 2008 8:51 pm

Let's not also forget that it's quite a small boiler, so if you were to go with steel, you'd need to run quite a hot fire to be able to keep up with the steam consumption the locomotive would require..

Just my 2 cents.

Mike

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Post by Curtis_F » Wed Jul 16, 2008 3:48 pm

Mike Walsh wrote:Let's not also forget that it's quite a small boiler, so if you were to go with steel, you'd need to run quite a hot fire to be able to keep up with the steam consumption the locomotive would require..
Mike,

Thanks for the thought, but I'm not interested in a Raritan or A3. At one point I was looking at a Raritan, and bought a casting kit, but it spiraled out of control after that...

--------

And thanks to everyone who has responded. It sould like the real choices are a waterleg copper boiler or a briggs steel boiler. I'm leaning towards the steel one just for the added weight.

It won't be till the end of the year before I go to Marty for boiler work, so I have time to think about it.


Cheers,

Curtis F.
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Post by LVRR2095 » Wed Jul 16, 2008 5:01 pm

Curtis,
You proposed design looks quite a bit like the very first "Consolidation" designed by Alexander Mitchell. It was designed during the "consolidation" of the Lehigh and Mahanoy RR and the Lehigh Valley RR.
Super looking locomotive that worked on a premier railroad!
Keith (and a former LVRR engineer)

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Post by Loco112 » Wed Jul 16, 2008 6:55 pm

Thats a good lookin "paper Locomotive" Curtis.

Worhty of your efforts I'd say!

Are you going to offer castings and parts?
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Post by SZuiderveen » Wed Jul 16, 2008 7:18 pm

He doesn't need to offer castings and parts. It's the stock wheels and cylinders from the Raritan.

Actually, I think it looks more like an Argent Lumber Company narrow gauge locomotive. I think if you took the Raritan parts, tuned them into a 2-6-0, you could make an Argent #2, which is the later version of New Berlin & Winfield #2, the former sillhouette trademark of Live Steam magazine in the 70's.

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