what are the things to look out for building a steel boiler

[terry1956]

Hi chaps, I have an old 7 1/4 gauge invicta that needs a new boiler.i sm thinking of making one from steel.i understand that the steel needs be of the correct type and needs to have the correct paperwork.i also understand thst as a good but not a coded welder that I will need to have two test welds tested.but what I am not sure off is this.can I use the currect boiler dimensions used for the copper boiler, or would I be better off using a larger section tube to allow for scale etc, as some people do. Anyone out there made a steel boiler who can let me know before I start on the drawings.thanks, michael

[pault]

Hi Michael,
slightly off topic, could you post a picture of this loco please, i have been looking for one Built by Hugh Saunders in the late 70's and wonder if this is it

[ejparrott]

Copper boiler drawings cannot be used to manufacture a steel boiler. You can use the external dimensions of the copper boiler of course, as a lot of things will be relative to this. Steel boilers however must have wastage built in, and the strengths of the two materials are completly different, so calculations produce wildly different dimensions

[terry1956]

Thanks for the replies. Sorry the loco is in parts and theres not much to see.i have read about the need for wastage mainly on the tubes, but how far do you go with need to take acount of wastage overtime and the ability for the boiler to heat up and steam. I have read on some American csites about people building steel boilers with an expected tube life of 5 or 10 years. Also read that the main problem is trapped condensation during the winter lay ups.

[maunsell]

Terry, I remember a 71/4" gauge Invicta running in the gardens by the Westgate Towers in Canterbury, Kent and I wondered if this is the same locomotive.

[terry1956]

Maunsell, I am in the S/W of the country so it was not me. there are a few large invictas around the country, maybe not seen so much these days as most clubs are more for public running and the design of the Invicta is not up for much of that.