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Model Steam Engine Plans

Boilers

Model steam boilers are generally made up of three materials; steel, copper and brass for the main tube.

The brass versions tend to be for spirit fired models where a low pressure or volume of steam is needed. They are relatively easy to make but the drawback to brass is that the zinc included with the copper in the manufacture of brass is gradually absorbed into the water with the application of heat, so they do not last for any great period of time if used regularly. In this way the erosion causes weakness in the main boiler body material with age, meaning burst or leaking boilers are common.

Because of this age related problem, be wary of buying a used boiler made of brass unless it is pressure tested, however there are different compositions in the brass make-up meaning different wear or corrosion properties to provide brass for specific usages.

Copper on the other hand is a much better boiler material, but even that has its limitations. Fine, it barely corrodes, but it's linear strength is very limited so it is used generally for smaller sized boilers, usually up to no more than 6" (150mm) in diameter and no more than 24" (600mm) long, unless the boiler itself is supported properly along a chassis of some sorts.

Moving on to the larger diameter or length of boiler, steel is the best option, but even that has problems. It's a harder metal to shape; the welding has to be certified (done by a coded welder) to guarantee no weak or faulty welds; the wall thickness of the steel needs extra depth to allow for corrosion (rust)  and a replacement boiler may be needed within twenty years of regular use.

Generally for the scale of engine and boiler most model engineers work with the plans below relate to copper boilers that are silver soldered together, apart from the flash tube boiler which is a different arrangement altogether, but using material available to you is no problem provided you pressure test the boiler to at least double the proposed working pressure when completed and get it tested by a boiler inspector before insuring it and taking it out in a public place.


Available plans
Simple flash tube boiler                     -    very easy build   -   small                                  Free
Building an easy boiler                      -     largish easy build   -   easy to follow                  Free
Model boilers                                  -      general boiler guide                                            Free
Steam Engine Boiler from 2007        -      very large loco model boiler     general layout    Free

Pop Science boiler from 1949                      small boiler   -   easy build                                            
Pop mechanics boiler from 1963                  small boiler   -   very easy build  
Steam Whistle                                   
Dual concentric boiler                                  small model boiler   -   a bit vague but workable            
Simple steam engine and boiler
Virginia Steam Engine Plans                         3.5" locomotive
Only  2.67
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