Many thanks guys for your input, I think i will stick to a conventional steam raising boiler and utilise DCC control from the tracks for the servo's, as you state it is the largest 18" gauge locomotive Bagnal Built and the model is not far off the sizes of small 16mm live steam locomotives and these are mainly gas or meths fired with radio control systems for operating the servo mechanisms. You have given me some ideas that could be utilised to simulate steam when I come to build a smaller prototype. below is where I am at **broken link removed**