The 4709 Group has sent RailAdvent an update on the progress to build GWR steam locomotive 4709.
After 50 years at Barry, exposed to the elements, parts that were meant to become the pony truck for 4709 have become corroded and now need to be replaced.
The pony truck was originally fabricated from components or heavy items that had been forged, bent and curved. These sections are no longer available, and restoration for the mainline involves a detailed assessment of each component.
Then there is the challenge of whether to replace or repair. There are no modern-day fabricators that can bend 5”x 5” x 5” x ½” T sections that the radius bars were fabricated with, so the originals have been sent away to a specialist for repair.
It was intended that the front end of donor locomotive, No. 4115, would be used on 4709 so that the work was a self-contained unit. However, a general drawing showed that the plan was unworkable as the leading frame stay was too light for a 47XX, so it was back to the drawing board.
A new frame stay casting is now needed as the function of the block of cast iron is to stabilise and dampen the front end of the locomotive.
On 4709, the casting will be hidden under the running boards, and a bell-shaped cowling will cover the 10″ hole that will be used for the counterweight.
A 3D model has been produced, and Caddick and Moss of Bristol have completed the pattern, with the casting due to take place soon.
Patterns have also been commissioned for the compensating beams, which will also be cast in steel in the coming weeks.
Fourteen new spring hanger brackets are currently being machined, and the reusable components from the locomotive's pony truck assembly are being refurbished.
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