Finally, things on 4709 are starting to move forward. Months of delivery delays, bankrupt suppliers and limited facilities now look to be history and the schedule of new work is looking like a major move forwards.
The first big work package will be the pony truck. With the exception of a few purpose-made bolts and a set of lubrication pads, 4709’s pony truck will be assembled from the now complete set of parts now in stock.
For the casual observer, the pony truck sits somewhere under the buffer beam and carries a significant portion of the locomotive’s weight, while guiding it on the straight, curves and associated pointwork.
In reality, this is a critically important component, comprising the two wheels, axles, frames and a set of reins to keep the structure rigid. Out of sight under the front of the loco, but fundamental to the operation of the truck is a massive racking plate which keeps everything together and lined-up. It’s also an essential component in the truck’s balance, which is assured by a massive solid steel casting, weighing in excess of a ton, which acts as a counterweight.
We’re hoping to have this jigsaw of vital components complete, with axle and wheels in February/March.
4709’s chassis has been waiting a while to find a home inside the workshop at Tyseley and with the imminent departure of two other locos, returning to their respective home railways, that day is drawing closer.
Joining the chassis will be the four driving wheel wheelsets. The three donor wheelsets from 4115 are already balanced, so an initial job will be weighing, balancing, preparing and assembling counterweights for the new axle and it’s wheels. The counterweights are easy to spot on any steam loco, as the solid semi-circular items attached to a segment of the wheel’s spokes. Clearly, these offset the mass of the rods and their circulating loads as the driving wheels rotate.
No less important is the counterweight’s role in reducing hammer blow - the impact passed through the wheel assemblies by the mass and rotation of the rods. Reducing hammer blow restricts wear and tear to the permanent way and loco itself. It also makes for a significantly more comfortable ride for the crew in the cab.
Another upcoming project, the eccentric sheaves, convert the radial motion of the driving axle into a linear motion to link the wheels to the expansion link for forward/reverse control of steam into the cylinders. As a two cylinder loco, 4709 will have four sheaves, one pair each side of the axle. Ours are ready to fit. They are ready to be refurbished and refitted to the main driving wheel axle and adjusted when the cylinders and rods are mounted/aligned.
That’s a pretty comprehensive list of work to be done in the coming weeks. Hard on the heels of the pony truck assembly and extention frame assembly, we are planning to specify and order a new smokebox, in itself a major project.
Drawing work for the smokebox is about to commence and quotes called for. More on that next time.
