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Class 08 shifted cranks

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oldboy reg

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I have heard about this defect on 08 shunters and wondered what and how this happens? Is there an explanation or better still a picture somewhere of this failure?
 
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xotGD

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Some preserved railways use 08s on passenger services. When this happens they manage to shift quite a few cranks from one station to the next.

(Sorry!)
 

36270k

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Used to happen on Class 08 from overspeeding. Would start when tracton motor seized.
Most Southern region Class 09's had an overspeed trip set at 27mph ( 20mph for an 08 )
 

pdeaves

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To answer the question of 'what' happens:
The connecting rods are not connected directly to the wheels. Because the frames are outside the wheels, the axles extend to cranks outside the frames, onto which the connecting rods are connected. The cranks act like levers and, with the large forces involved, try to twist the axles. When all goes well, this twist translates into rotational movement and the loco moves. Sometimes the forces overcome the cranks and they slip on the axles out of alignment. If not caught quickly enough it leads to bent coupling rods and untold other damage.

A rolling stock expert will be along shortly to correct anything I may have got wrong in what is intended to be a simplified description!
 

oldboy reg

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Hi Everyone, thanks for all your help in giving me a better understanding of what happens. I didnt realise a locking key or pin was not part of the set up. Great response and thank you.
 

BestWestern

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Met a few 'shifted' cranks in my time, usually they're on MK1s or MK2s though, they aren't normally allowed on the locos :D
 
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