Good points raised here guys. I don't know any more background to this thread, was the debate just about running at 125psi? Not sure, our boiler inspectors / testers usually say there is no reason to go above about 80psi with a model boiler, but maybe that's just their own take on things, their own safety factor if you like.
What I do know is, our club is goverened by the southern federation of model engineering societies as far as boiler making and testing is concerned, and they have a strict Code of Practice for Boiler Testing. It's prepared in association with the representatives of various Model Engineering Bodies, the Trade, the HSE and the Insurance Companies, and accepted by them. So it's all down on paper somewhere what should and shouldn't be done.
Stew,
On a bit of a side note, I would recommend before you even start your boiler to join a society with a 3.5" gauge track, boiler inspectors and testers if you haven't already done so, and discuss it at length with them first. I say this because I believe some of LBSCs' designs are a bit 'out of date' compared to some of the current practices these days and some of the stuff he did is frowned upon. When I took my boiler in for our guys to have a look at, they were surprised that some of the joints are brazed with sif bronze .. this is what it calls for on the drawings, nothing too bad about that, but it's a difficult art due to the melting point of the bronze / copper being closer. Also, there are 2 longitudinal stays, one is hollow for the blower tube and it doesn't call for it to be soldered in place, our guys insisted it was, I think the drawing showed it just screwed straight into the back / front plate. Also, apparently curly thought nothing of plugging joints with soft solder, however, I think this is frowned upon these days. So it will definitely be worth just going through the drawings with some boiler inspectors / testers first.
Nick