[TheForge] Quesiton about a weird event

[xlch58 at swbell.net]

Demon Buddha wrote:

>
>
>     But the shaft didn't fail at a coupling.  I forgot to mention that 
> there was evidence of intense heat.  Thermal discoloration of the 
> shaft and buring of the area close to it.  Nobody noticed the event, 
> perhaps because the alley isn't a common hangout     

Sounds like it failed due to torsional vibration.  Torsional vibration 
has been a big problem for ships since the introduction of the 
reciprocating engine.   Whip is another problem, but your case sound 
like torsionals.    The break would typically occur at a node point, 
which would not have to appear at a coupling.  There probably would be a 
lot of local heat and the break could be pretty clean, depending on the 
steel and the construction.   Ships can have several restricted RPM 
ranges to prevent problems, though a misfiring cylinder, bad injector or 
a host of other mechanical problems can create a new resonance range.   

Charles