A Design by Nigel Gresley ….
Back in 2005, Eddie Gibbons commenced work on building a pair of these magnificent loco’s based on the original works drawings.
With meticulous attention to detail Eddie has made great progress in creating two equally manificent locos’ allbeit in 5-inch scale. Along the way he has taken time to record the build process giving us ample opportunity to watch a true master-craftsman at work.
Build Summary ….
[…. to expand/collapse Stage Views – simply click on Stage Title]
Stage 1 - K3 Chassis Build
Stage 2- Tender Construction
Note 1 –
After the first year’s work on loco frames, I decided to start on the tenders. There’s nothing worse than getting a loco complete and ready to run, and then having to start on the tender – bitter experience!
Stage 3- Back to the Frames
Stage 4 - Suspension
Stage 5 -Pony Truck
Note 1 -Pony Trucks:
Eddie mentions that Gresley was very fond of swing links for side control of bogies and pony trucks and the A1 Pacific’s and all the pony truck engines were so fitted. The riding of the Pacific’s was not particularly good with the single bolster design used and they tended to be over-sensitive to track irregularities and all the engines ultimately had the bogies modified to spring side control.
Stage 6 - Cylinders
Stage 7 - Cylinders outside
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 .
Stage 8 - Cylinders inside
Note 1 –
As work progressed on the inside cylinders I realised the risks of each operation were becoming greater and that any error could cost my considerable investment in time and materials if it was not recoverable, so each step was made only after a lot of thought, making sure that no part had been overlooked before it was impossible to go back and correct the omission.
Each machining operation was also carefully planned in my head before committing to cutting metal. Hopefully I’ve got it right and I’m not ending this project with a glass case model.
I spent many hours pondering how to draw the inside cylinder, let alone build it. Having a copy of the full-size cylinder drawing helped with the detail, but actually getting my head around putting together a cylinder that was inclined in relation to its valve chest was really challenging. I followed the concept used for the outside cylinders, but the construction needed to be different, not least because the internal support plates were inclined in relation to the ends
The process begins in the obvious way with the preparation and machining of the end plates
Stage 9 - Cylinders continued
Stage 10 - Finishing the cylinders, Valve crosshead guides, Frame brackets and other tasks.
Note 1 –
This years work [2016-17] encompasses finishing the cylinders, making the valve chest end covers and valve spindle guides, making the valve spindle crossheads, making and fitting the bearing supports for the conjugated valve gear, Making the weigh shaft bearing housings and bearings and the footplate support brackets.
Stage 11 - Smoke box fronts, motion brackets omitted from previous stage, slide bars and the first of the frame bolts.
Note 1 –
Stage 11 covers the period from 2016 to October 2017 and covers work to the smoke box fronts and motion brackets that was omitted from Stage 10 and manufacture of the slide bars and the first of the frame bolts.
Earlier I had machined the smoke boxes on Allan Bones’ Harrison Lathe. At the time I didn’t have the material for the smoke box front rings, but Allan came up with some suitable discs of mild steel from which they were machined.