Thanks for responding guys. I’ve managed to get the S50 timed and running on air after refitting the valve box nuts (7BA). I’ll make an exhaust pipe next, once I find the thread details and then possibly make some oilers for the flywheel shaft.  Of course a boiler is needed but copper is certainly not cheap these days – need to find a bargin, or an old boiler or a long bit of copper pipe gojng spare!   Regards Simon.

Jason, Many thanks for the info. I now have the full set of “Sally” pages (I think!) and noted the thread spec for the exhaust; being familiar with BA etc, I note that this is a ME thread, is this because it works well with brass and hence was adopted by the craftsmen of the day? I am Ex REME (Brit army) and dealt with many thread sizes over the years, fixing optical and mechanical sighting and survey etc systems on various older kit going back to the 60’s, and probably before in some cases, right up to the Challenger II tank period, but never came across the ME spec’d thread.  I probably have to make the transition now and buy a set of these if I want to take this forward. Anyone selling a set??  🙂 Many thanks – enjoying the challenges and getting my hands dirty again! Simon.