At what point is a boiler big enough to be steel instead of copper?

[shild]

Just wondering when a steel boiler is used and when copper?. I would think most anything that runs on the high line would be copper right? A copper boiler would be easier to build wouldn't it?

[cbrew]

it seems to be the 6 inch mark,

[Pontiacguy1]

There are a few 5" diameter steel boilers out there, such as the 5" diameter 0-4-2 Chloe boiler for 7 1/2 and 7 1/4 inch gauge. Cbrew is right, though, that anything smaller than that usually ends up being copper. From what I have seen, large 3/4" scale locomotives like a Northern or a Hudson might have a steel boiler, or a copper boiler. Anything smaller sized than that and it is usually copper. It ends up being an issue of heat transfer and of water space, as well as an issue of cost effectiveness. A larger boiler being made from copper will be very expensive. There are some that are made in 1 1/2" scale, but that's not the norm. The smaller locomotives will have less water space and less heat generated from a decreasing grate area, so most are made from copper. The smaller sizes can utilize copper pipe that is available, and usually the materials won't break the bank.

[shild]

Thanks guys!. Does the fire ever melt the solder on these copper boilers and cause problems?

[Chris Hollands]

Run one low on water and you should find out your answer pretty quick especially without a proper fusible plug or other safe guards.

[Steamer Al]

It scares me a bit when people ask these sort of questions maybe this is the wrong hobby for some ?

Well, we all have to learn sometime

[mattmason]

I have a 5" boiler on my 1" scale Coles 0-4-0. Six flues and 1/4" barrel, 3/8" tube sheets. absolutely free steaming, and I run it hard.

[gwrdriver]

Does the fire ever melt the solder on these copper boilers and cause problems?

With a properly made copper boiler, to a good design, under normal operating conditions, it would be HIGHLY improbable to have a melt incident, as our national failure record would support. What would considerably increase the probability would be to have a deep and hot coal fire in a poorly designed or made copper boiler, and have a careless operator let it boil it dry. That could ruin everyone's day in several ways.

I agree with what has been said so far, that at 6" diameter the builder has a decision to make about which material direction to go in. But it's not a coin-toss, or shouldn't be. Both steel and copper have their advantages and disadvantages, depending upon circumstances, and those and the abilities of the builder usually determine the choice.

[FKreider]

Ease of construction based on material is simply an opinion or point of view based on an individuals particular skill set.

There is a Raritan out there with a 4" steel boiler and the old 3/4" Northern Drawings and Instruction book by Martin Lewis (Little Engines) details construction of a steel boiler in addition to copper.

If one can afford it I think the general consensus is copper is far superior to a steel boiler due to rust not being a concern, they still age and corrode over time but will definitely out-last almost any steel boiler.

[jcbrock]

I run it hard.

Yes sir, you do.

[Marty_Knox]

Another factor to consider is the pressure you plan to operate at. Copper loses strength rapidly as the temperature rises.
100 PSI is probably the highest you would want to run in a copper boiler.

[gwrdriver]

Maximum WP is one of the advantages/disadvantages to consider.