Thanks for for all the help and comment guys and Mayner the drawing explains all thank you. Its easy to make assumptions about fittings etc; which I often do and am proved wrong! I asked because for a number of years I worked under 1'11 3/4" gauge carriages, all only had one cylnder and some very ingenious pullrods to make it all work! I know, 20 mph narrow gauge but its worth knowing.