Building a model steam locomotive questions?

[PaxmanValenta]

Hi
I'm thinking of building a 7 1/4" gauge steam locomotive. I want to run it on coal and use copper fire tubes. Possibly super heater tubes too.

What diameter of steel tube for the boiler should I need and how thick should the steel be?

Also if I was doing my loco in 5" gauge what size boiler.

Normal steam locos have a fire brick arch inside the fire box. What is this for and is it needed on miniature locos?

 

[swj99]

Normal steam locos have a fire brick arch inside the fire box. What is this for and is it needed on miniature locos?

....... arches are used for the purpose of baffling temporarily the direct flow of the gases generated from the grate on their way to the boiler tubes, and cause the gases to flow "first back and then forward through the entire length of the firebox. This baffling is sufficient to accomplish the more perfect combustion of Y the fuel and to cause the gases to be entirely consumed before they have an opportunity to escape through the flues. This arch or baffle also tends to more evenly distribute the gases generated by the combustion to the entire inside surface of the fire box, resulting in a more free water circulation and increased evaporation, and consequently provides a better and more economical steam producing boiler.

http://www.google.co.uk/patents/US1231854

 

[John Webb]

Hi
I'm thinking of building a 7 1/4" gauge steam locomotive. I want to run it on coal and use copper fire tubes. Possibly super heater tubes too.

What diameter of steel tube for the boiler should I need and how thick should the steel be?

Also if I was doing my loco in 5" gauge what size boiler.

Normal steam locos have a fire brick arch inside the fire box. What is this for and is it needed on miniature locos?

There are a huge range of model locomotives about, and the boiler size will depend on what sort you are modelling. For example, a model of a standard gauge loco will have a smaller boiler than that of a narrow-gauge model running on the same 5.5" or 7.25" track.

The construction of boilers is particularly carefully controlled, and has to be checked after construction and every year or two by an independent assessor before you are given an insurance certificate; and without such a certificate you cannot run your loco outside your own back garden! I strongly advise finding your local model engineering society who have suitable running tracks available. You will find them helpful in both the construction and the running of your loco, plus giving you somewhere to run it.

 

[silverfoxcc]

Paxman

Have you got anywhere yet?