The BR Class 8 Steam Locomotive Trust, who are currently overhauling BR Class 8 No. 71000 ‘Duke of Gloucester’, has sent RailAdvent an update on the progress being made at Tyseley Locomotive Works.
Firstly, the crankpin and stub axles for the crank axle, which is unique to 71000, have arrived in the UK from manufacture in South Africa.
The Duke is the only locomotive from the 999 BR Standard locomotives to have 3 cylinders. The power is sent from the third cylinder to the driving wheels via a crank axle on the front drive wheels.
The outside cylinders provide power to the centre driving wheels via the connecting rods, but all of the power from the middle cylinder goes through the crank pin.
During the latest overhaul, the wheelsets have been removed from the locomotive, and a routine inspection was completed on the crank axle and the axle bearings, as these are the most accessible. Upon inspection, the bearings were found to be unfit for use due to their wear and erosion.
The trust also completed an inspection of the driving and trailing axle bearings, and this also returned the decision that these should be replaced.
Overhaul progress showed white paint had been applied around the crankpin which means that it has been monitored for flexing.
Whilst working on the crank axle, the trust said that it looked ‘tired’ so they have decided to renew the stub axles and the crank pin.
After researching different axle steel specifications, an equivalent to the original steel has been sourced and has now arrived at South Devon Railway Engineering from South Africa.
When South Devon Railway Engineering pressed out the crankpin, signs of fretting were found, which showed that the crank axle had been flexing, and confirmed that the trust had made the right decision in building a unique crank axle.
With the new stub axles and crankpin now in the UK, work can begin on assembling a new crank axle.
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