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Design

Principles

To build a new locomotive in the 21st century based on a mid 20th century design poses a conundrum. Do you slavishly reproduce the original design where components or processes may not be available or do you radically improve the design? In order to run the locomotive of British Railways lines, we have to keep to the original design - but not entirely.

We are fortunate in that an improved design was worked out by British Railways and was to form the basis of the Crewe Works Order Lot 242. This will form the basis of the build plan for Hengist. However, we want to try to go further. The designer of the engines, E.S. Cox, says 'The Class 6 4-6-2 locomotives turned out to be the least effective of all the standard types'. On a footplate trip from Carlisle to Shap summit where he handled the controls he says 'and have to confess to experiencing a wooliness quite absent in the other types'. So the challenge is to complete the real life tuning that the Clans were not to receive in service.

As a starting point, we have commissioned a feasibility study from the Advanced Steam Traction Trust to apply the learning from the 5AT Project to the locomotive. They have written a report for us and you can read about it by following the link below. Other areas that we will adopt include the Duke of Gloucester's trailing truck design with its coil springing. This gives a better ride than the laminated springs of the original Clan design. An area that is currently generating some debate is the tender design. The original Clans were coupled to the BR1 tender which had inset raves and a rear view window. The lot 242 Clans were to be fitted with the BR1B/C tender which has flush sides and greater water capacity. This would appear to be an obvious choice for Hengist as the more water, the better. Given that Hengist is likely to spend a fair amount of time on preserved lines with rear facing running, the rear view window and inset raves of the BR1 tender could provide much better visibility than the flush sided BR1B tender. The jury is still out on this one!

At the moment, nothing is fixed until the material is cast or machining commences. We're sure that there's going to be a lot of interesting discussion!

Click on the Links below for more details

Clan Improvement Report (CLIP)

Plain vs. Roller Bearings

Riveting vs. Fitted Bolts