Making rear wheel safe....

[Rusnak_322]

I trust safety wire. Not only is it a good visual proof that I did tighten the bolt, in 12 years of racing and track days I never had a wired bolt come loose.

I did hate life at times as drilling a hardened nut with a hand drill and thin drill bit is the exact opposite of fun.

 

[scm]

When you are properly safe tying the bolt can not loosen because it would tighten the wire.

Sorry Hoosier, this assertion is a common but dangerous misconception!

As you might have learned in your apprenticeship lockwire (and loctite)
can only prevent loose bolts from falling off, not tight bolts from loosening.

Nuts or bolts don't come loose because they mysteriously begin to turn
themselfs ccw (which was of course prevented by wire or glue), but because
of loss of pretension, either by fatigue, head embedding, compression set...

So what wire or loctite do is fight the symptom, not the cause of lost bolts.
This is of course better than nothing, especially in case of drain plugs (this
is why they are still being safety-wired in modern racing), but is not enough
to operate highly stressed joints safely, where proper pretension means every-
thing (ever seen a highly stressed rod bolt lockwired?)

Apart from all that I'd like you to be a bit more careful with your assumptions
concerning my training, I had my apprentice at an aircraft turbine manufacturer
and was well trained in applying lockwire. I've also worked as mechanic in FIA
worldchampionship endurance racing and can assure you that safetywire is less
used in modern motorsport than ... well perhaps not you but many people think.

Kind regards
Sven

btw., imho your picture shows false wire application in the "boltheads" sketch
(bottom left), we were taught to apply wire to hexagon bolts over head, not around.

 

[Hoosier Daddy]

True enough Sven, I can apprieciate your input and believe it to be very accurate.

 

[AlphaDogChoppers]

Nuts or bolts don't come loose because they mysteriously begin to turn
themselfs ccw (which was of course prevented by wire or glue), but because
of loss of pretension, either by fatigue, head embedding, compression set...

This part of what you said tells me that you know WTF you are talking about.

A fastener is like a spring. Properly tightened, it holds an assembly together by being under tension. Once overtightened, it's like an overstretched spring. A properly torqued fastener is in the mid-range of its available elasticity so that it can maintain tension over the anticipated temperature range. "Properly torqued" is actually kind of misleading. "Properly tensioned" would be better. Trouble is, we can't measure that in most cases. We CAN measure how much torque we apply. How much tension is achieved for a given torque depends on many variables.

Thread pitch
Fastener size and length
Quality of thread finish
Fastener and assembly materials elasticity
Cleanliness of threads and lubrication

Engineers try to determine the correct torque to achieve the ideal tension range by calculating this factors. The coefficient of friction of the treads is the factor that is under the least control by the engineer writing the torque spec. Most torque specs are for clean, oiled threads. If anti-sieze is used, (including a dab under the head of the fastener,) the torque required to achieve proper tension can be as much as 20% less. Quite a difference.

 

[Rusnak_322]

As you might have learned in your apprenticeship lockwire (and loctite)
can only prevent loose bolts from falling off, not tight bolts from loosening.

Nuts or bolts don't come loose because they mysteriously begin to turn
themselfs ccw (which was of course prevented by wire or glue),

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!

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.

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.

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.

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.

 

[canyoncarver]

BULL SHIT!
When you are properly safe tying the bolt can not loosen because it would tighten the wire.

The only way it would is if you went the wrong direction or have a broken wire, usually caused by over twisting. If it is good enough security for jet aircraft and the pilot entrusting me with his life, it's good enough for me. But like I said at the beginning of the thread, and your comment proves it, it's not recommended if you aren't properly trained.

Great graphic, thanks for posting. I've got that same set of wire pliers from Dad, ex USAF. And you're right, it takes alot of practice to do it right.

 

[teazer]

Neither locktite nor safety wire can prevent these bolts from loosening (only from falling off).
But once applied the wire keeps people from checking proper torque, this is why loctite is safer.

Best regards
Sven

Absolutely 100% accurate. What that safety wire does is to stop the bolt from spinning out once it is loose. So it saves the bolt but doesn't keep it tight.

ADC is also correct that engineers try to work out the torque that will give the correct amount of tension. We used to measure con rod bolt stretch on Triumph twins to get the correct tension or pretension. Vibration is a whole other issue and it will tend to flex cases and over time may loosen bolts/nuts.

On a TZ350 the sprocket bolts come loose and the sprocket chatters against the hub and both wear out and bolts shear. Wire locking stops them from coming out but they still come slightly loose and allow that wear to take place. Just seeing lockwire in place is not sufficient.

I also learned to take lock wire over the head of the bolt (where it was used) and that was aircraft engines. We used a lot of tab washers and special lock nuts though. Thin wall deformed thread that just grab and don't come loose.

Back to the case in hand. Tab washers work fine.

 

[scm]

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