Rusnak_322 said:
So all those parts that fall off of Harleys are not because of the thing shaking, but because of a of loss of pretension, either by fatigue, head embedding, compression set...? They shook the pretension out of the bolts!
Yep, you got it, that's what's happening. Pretension gets lost, hence the bolt comes loose,
and then vibes start to turn the bolt out. First loose, then spin. Not other way round.
Bolts loosen, especially on old bikes that shake, that are threaded into 30 year old holes that have had bolts removed repeatedly, and possibly over tightened.
Certainly, worn threads in rotten aluminum won't allow to tighten the bolt properly.
Consequences described above. No contradiction to what I'm telling you.
Rev a vintage race bike up in the pits, especially a 2 stroke, and then do the
same for a modern 600cc race bike and tell me that the old bike isn't trying to shake
its self to pieces.
The old bike
is trying to shake itself to pieces, o.k.? That doesn't make it
any better, but again, the vibes cannot turn a properly tightened bolt, first it
will have to come loose (which is massively enhanced by the vibes of course).
I don't know how can you say that stainless steel wire will not prevent a tight bolt from loosening?
It might not prevent the threads from pulling out, but unless the wire breaks, you are not going to
turn more then a few degrees.
I was perhaps not precise enough but think of the torque it takes to properly
tighten a let's say M6 (approx =1/4") fastener, some 10Nm. Let this be an allen
key bolt and now take a pair of pliers and try to release it. See what I mean?
Under no circumstances are vibes alone strong enough to turn this bolt (they
don't even apply a torque to it), it must come loose first to be then "shaken off".
Of course the wire is a good way to prevent the loose bolt from getting lost,
and in some cases (drain plugs) this makes all the difference... but in others,
as e.g. bolts that apply brakediscs or sprockets to the hub, things are different.
Bolts are not designed to withstand the shearing loads that occur when the
devices mentioned are no longer properly clamped to the wheel.
The reason that modern race bikes are not wired as much is because they have a lot better hardware then you will find on older bikes. When I first started racing, the header nuts were large and made of a metal that was as hard as warm fudge. The last modern bike I wired was a 2003 R6 and the header bolts were so thin that you could not drill a 1/16th in hole in them without breaking through to the threads. They also were very hard to drill.
Also, the FIM is expecting a different level of professionalism than club racers, the bikes should be prepared to a higher level.
I raced WERA and then AMA. The AMA guys didn't have to wire the same things as the club racers for the same reason. Then WERA gave into the people bitching that it was too hard to wire modern bikes and let a lot of that slide. I was active in the discussions on the WERA BBS back in the day.
This may be all true, but you'll have to admit that safety wire can't cure neither rotten threads
nor buttersoft bolts, we need Helicoil and stronger bolts to do so, the wire is mainly a hint to
the scrutineers that this bolt has been taken care of.
I'd suggest the following:
Properly applied lockwire is never a fault as it improves safety (and provides some nice old
school racing looks) but must not keep anybody from regularly checking proper torquing of bolt.
O.k.?
Best regards
Sven