Building Dancer - The Boiler

Dancer needed a boiler that would be somewhat larger than the size permitted under the Model Engineering exemptions in the New Zealand regulations.

- John Olsen

This would apply equally in the United Kingdom where, I believe, the sizes and pressures allowed are similar. This meant either finding an existing commercially made boiler of a suitable size, or building one. In the early stages of the project, this aspect was put aside on the basis that ‘something will show up.’ In due course, when I moved to Auckland, I found that Ken and Andrew Pointon at Colonial Ironworks (NZ) had designed and built a number of boilers in the size range required. One of their designs in particular had been built by a fellow society member in Hamilton. I was able to negotiate a copy of the drawings in return for some non-monetary consideration and the Pointons were very helpful with advice on how to proceed.

A boiler of this sort has to be built with traceable materials and all welding must be done by a suitably certified welder with several inspections along the way. The cutting, drilling and, where applicable, bending of tubes was able to be done by myself, as was the expanding of the small water tubes into place. The design is of the Yarrow type, with an 8 inch top drum and two 5 inch mud drums. The top drum has a small dome, made from the same diameter tube as the mud drums and capped off with a standard pipe flange and cover plate. The steam drum and mud drums are capped off with covers made from certified boiler plate, held in place with stays through the drums. The steam drum has three stays, while the mud drums each have one.