PU451 Failure Report
- nigeljulian
- Mar 20
- 1 min read
At the Nene Valley Railway in May 2024 55009 Alycidon suffered an engine failure of Power Unit 451.
On return to the DPS depot the power unit was manually barred over confirming the triangle part of the engine along with the auxiliary generator were turning as expected however the main generator was static, pointing to a failure in the phasing case, likely the generator drive shaft.
Over the course of 2025 the overhaul of Power Unit 430, ex 55008, was completed and after a power unit swop in November this was successfully started in December, returning 55009 to twin engine operation.
Strip down of PU451 commenced and once the main generator was removed it revealed that the drive shaft had indeed failed completely.
The drive shafts are approximately 4 inches in diameter and 3 feet long. Further investigation appears to show the drive shaft has cracks that predated the final failure as there appears to be oxidation (rust) in the area of the break.
We are now in the position where we need to investigate the repair of the phasing case and potentially manufacture a new drive shaft.
These haven’t been made for well over 40 years and we don’t even have a technical drawing.
Therefore we are now looking at another serious challenge, copy an original or finding the Napier drawings to assist our quest and finally fund the whole process.
Please consider a donation to our ongoing power unit appeal via GoFundMe.
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Reading through the PU451 failure report, I found the part about the unexpected degradation under certain conditions really caught my attention. It made me think about how important it is to track patterns and small anomalies, almost like how detailed notes or structured support from a Healthcare Assignment Helper UK can make a difference when trying to piece together complex cases. I’m curious though—do you think these kinds of reports get enough attention outside of the specialist community, or do they mostly stay in a very narrow circle? It seems like sharing lessons learned more broadly could prevent repeated issues in other contexts.