Derg:
thanks
i have posted the link to both books to propose an explanation on how the shaft's splines have gone away as this is the problem RR has to solve. And this may in fact also include some clever redesign work to reduce vibrations, possibly even using some ingenious damping techniques or just making the splines much more durable if reducing vibrations prove to be difficult.
The scavenge oil tube to me is a clear example of
extremely poor machining and louse quality control - completely out of the way it is presented in the BBC program on building RR's engines
YouTube - Rolls-Royce, How To Build A Jumbo Jet Engine -HQ- (Part 1/4)
it is a MUST see it to learn how much science+effort goes into the engine. Some really interesting things are shown there - i would have written 'suggested reading' but it seems more like 'suggested watching' ?