Boilers : copper or brass ?

[Brian JohnParticipant @brianjohn93961]

In the past, I have built my ”tiddler” boilers from copper tubing rescued from the scrap yard or purchased new from plumbers supplies. I have noticed that quite a few pre-fabricated boilers from China or made of brass.

I know that aluminium is a bad idea but is it the better to use copper or brass ?

[Andrew TinsleyParticipant @andrewtinsley63637]

Brass is fine for low pressure Mamod style boilers. For anything needing higher pressures, then copper is the way to go.

Andrew.

[SillyOldDufferModerator @sillyoldduffer]

Brass is cheaper and harder and stronger than Copper, BUT

• risks weakening due to dezincification,
• heat transfer is inferior to Copper,
• doesn’t handle expansion and contraction so well.

So Brass is OK is for toy boilers and full-size fittings, but less satisfactory for larger boilers.

Copper is almost ideal for model boilermakers because it’s relatively easy to work with: bent, soldered, brazed etc.   Unlikely to upset a Boiler Inspector because the material and construction methods are well-established. Pretty safe too – they tend to fail by opening up gently with a phut rather than a catastrophic bang.

Commerical Boilers are almost invariably made of steel.  Cheap and very strong, but harder to make in a home workshop, and extra difficult to prove are safe.

Aluminium corrodes and is hard to work with.  Other metals and plastics are possible, but the cons outweigh the pros.

I vote for Copper.

Dave

[JasonBModerator @jasonb]

Brass will be fine for the type of boilers you have made in the past but copper pipe and fittings will likely be easier to come by and that may well be the deciding factor. Brass won’t upset a UK boiler inspector as yours boilers fall under the UK 3 bar litre rule which allows for brass boilers.

Not sure I agree with Dave that Commercial boilers are steel. Most locos run copper as do the small to medium traction engines and there are a lot about with commerially made boilers so really only the larger TE’s that have steel boilers.

[noel shelleyParticipant @noelshelley55608]

As others have said brass is OK for small boilers but for real boilers it’s copper and I would say more commercial boilers are made of copper than steel in the modelling world. Noel.

[duncan webster 1Participant @duncanwebster1]

The different thermal conductivity of copper brass and steel will make  very little difference. The problem is getting the heat to transfer from flue gas to the metal, compared to that the temperature drop through the metal or between metal and water is  very small.

Ad Jason says, most model boilers are copper unless very small mamod size. Never seen a steel loco boiler in 3.5 or 5 inch gauge at our track, but someone will find an example  Guess the problem is corrosion allowance, which doesn’t scale down. Copper doesn’t corrode in our usage

[JasonB]

On JasonB Said:

…

Not sure I agree with Dave that Commercial boilers are steel. Most locos run copper as do the small to medium traction engines and there are a lot about with commerially made boilers so really only the larger TE’s that have steel boilers.

I meant most boilers in the world, not just model boilers!  Industry make millions more boilers than we do.  Can’t say Industry never use Copper, but it’s unusual apart from in some Coffee Machines.

Copper rarely ever used in stationary boilers I think.  Lancashire boilers were Iron at first, steel later. Copper is costly, even though it can be recycled. And for industrial use, steel is stronger.

I wonder when the last mainline steam engine was built with a Copper boiler?   Before Queen Victoria was an old lady I guess.  Copper fireboxes and tubes were used for much longer, but loco boilers have been steel for yonks.

Likewise, has any forum member ever made a Brass Boiler, and why?  The only advantage I can identify is cheapness, especially if a tube of the right size happens to be available.

Dave

[JasonBModerator @jasonb]

Everybody else seems to be talking model boilers.

I made a brass one about 45 years ago when at school to run the beam engine I made. As to why, it was brass specified on the drawings that I used.

 

[Brian JohnParticipant @brianjohn93961]

Okay, I will stick with copper. It is easier to come by and it is what I am used to. Thak you for the confirmation.

[Author]

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