[s-cars] Crank pulley failure pics

[Joshua van Tol]

The gear is supposed to be retained by friction between the back face  
of the gear and the front of the crankshaft, hence the very high  
torque figure for the crank pulley. The key is merely there to locate  
the pulley correctly during assembly. Even a nice strong separate key  
(as used in older engine designs) will quickly be beaten into a pulp  
if the pulley bolt loosens, or is not tightened correctly.



On Jul 3, 2006, at 1:06 PM, Igor Kessel wrote:

> Robert Myers wrote:
>> Hi Y'all,
>>
>> After the crank pulley problem has once again reared its ugly head I
>> have put some pics of my failed crank timing belt pulley with its
>> missing "key".  Kinda hard to see but the key, which is an integral
>> part of the casting and is not what we normally think of as a key,
>> simply broke off.
>>
>> http://chips-ur-s.com/crankpulley.html
>>
>>
>> Bob
>> urS6 for sale: http://chips-ur-s.com/S6.html
>
> I have just received a new pulley. This thing is made out of some kind
> of light metal alloy, and the "key" is in fact a tiny unconvincing
> dimple, maybe 8x6 mm, cast from the same flimsy unconvincing alloy.  
> And
> that wimpy thingy is supposed to sustain years and years of shearing
> torque applied to it by a turbocharged interference engine? Gimme a
> break! Why that rocket scientist from Ingolstadt would not put a grove
> in it and specify a Woodruff key machined of some real hardened  
> steel is
> beyond my comprehension.
>
> -- 
> Igor Kessel
> two turbo quattros
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