Stage 7 – Cylinders outside

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Outside Cylinders

Completing the outside cylinders and primary smokebox machining - refer Note 3 below

Note 2 – The outside cylinders

After the 2013 Harrogate Exhibition, I made a start on the outside cylinders.

I eventually concluded that the cylinders would need to be fabricated because there were no suitable castings available. I had looked at the Enterprise and V2 castings for the Martin Evans designs and those for the V2 from Michael Breeze, but whilst these were well enough designed none had the ability to properly represent the prototype design used for the LNER pony truck locomotives.

In the early designs like the K3s and O2s the three cylinders were separate, the outside bolted to the frames, which had a large cut out each side into which the inside cylinder was located. This was bolted to the outside cylinders. This created a massive and very stiff assembly that I wanted to replicate on the models.  Later engines were fitted with a single casting (the monoblock) for the three cylinders

I spent a lot of time deciding on the materials and looked at cast iron, steel and bronze. I ultimately discarded cast iron due to the difficulties associated with joining it. I have silver soldered and brazed cast iron, but it is a process that can be unreliable, and I considered it would be liable to serious problems on such complex fabrications.

Steel was a much more attractive prospect but having discussed it with a number of experienced model engineers who were concerned about the cylinder friction and corrosion issues and who suggested cast iron liners in the cylinders which would have created issues with cylinder wall thickness or maintenance of scale bore dimensions, I concluded that bronze cylinders with brass supporting sections would be the way to go

I’d actually drawn the cylinders about 15 years before, mostly during lunch breaks at work, until the use of non-company software on our computers was banned. The details were put together from the H4 and K3 GAs, photographs of them under construction and a certain amount of knowledge I had from working on the full sized A4 and some drawings where a lot of the details were LNER standards. I didn’t actually get a drawing of the K3 cylinders until after I had started construction and I was surprised to discover I hadn’t done too badly and decided not to change what I had done and accept the minor deviations from prototype.

I have shown the outside cylinder GA and drawings of the individual components to give some idea of what you are seeing in the following photographs. These are the original drawings and some changes have been made to simplify the assemblies as the work progressed.

Following the 2014 exhibition work eventually got underway properly again in July. Perhaps retirement at the end of July speeded things up but it didn’t feel like it at the time. Looking through the photographs shows that a lot of progress was made, to the extent that I have only taken this instalment as far as the end of February 2015. So the following describes the majority of the work on the outside cylinders and the primary machining of the smokeboxes .