I have now reached the point where I can detail the exhaust manifold/blast pipe construction and remarkably the design turned out to be much easier than I had thought. As indicated earlier, I have been helped by the availability of a works drawing to give me the basic proportions and it has been an interesting exercise in fabrication. The full-size engine had an inverted 'V' manifold as the two exhaust exits from the slide valves were from the frame sides of the cylinders but, for our inside cylinder locomotives, we usually have a central drilling from the cylinder block up through the steam chest which makes the components simpler. As the top of the steam chest cover is angled down towards the rear, the blast pipe has to be set forwards and then upwards in a shallow reverse bend to be under the chimney centreline. I have included a sketch to show the idea and explain the construction. This includes the details of the exhaust steam connections both inside and outside the steam chest, where I have adopted '0' rings set in carefully turned and recessed seats (fig 7).
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