29/10/2026
Update on the 3 1/2 inch gauge BR Class 4MT.
Our members build has suffered a set back, with the engines twin boiler feed water pumps recently suffering a catastrophic failure.The pump was built some 20 years ago and left unfinished with one small but critical job to the pumps function awaiting completion.
At that period in time the member didn't possess a long series 1/8 twist drill which could punch through the two delivery connections within the pump body shown exiting on top of the pump. This missing feature was unfortunately completely forgotten about in the mists of time but came to light when a fire was lit and steam raised for its second run on the home track.
The three images show the re-built pump and its four connections. The pump is operated via two eccentrics set at 180 degrees from one another on the forward driving axle.
One pump continually supplies water (unless the bypass valve is open) to the boiler, the second pump also supplies water only when the bypass valve is shut.
In the original 20 year old version the second pump could not pump water into the boiler with the bypass shut. What it did was to push the cylinder out of the pump body and lock the whole engines reciprocating mechanism.
A plate fitted to prevent the cylinder glands from unscrewing during pumping potentially prevented more damage to the engine.
It just demonstrates the pressure and ultimate force that is created when a liquid is compressed in a cylinder
