Re: Flywheel cap screws


jabcamit@...
 




This is how I see it.

If the bolt  (assuming from any reputable maker) torques up to the specified tension without failing (irrespective of  manufacturer/grade), then it won't fail if the joint stays tight. The maximum forces the bolt sees are during the torquing process (90% of that force spent overcoming under head and  screw-thread friction, only 10% in tensioning the screw.  After tightening that 90% force no longer exists. 

The fly wheel joint fails if joint compression is lost (then allowing cyclic shear forces on the bolt). The less stretched the bolts are during assembly  the more likely this is to happen. Jabiru fitting bigger and bigger bolts reduced rather than increased flywheel attachment reliability because they were less stretchy. 

Locite is bad because the joint tightness cannot be subsequently tested by torquing. The bolt might be providing zero tension but the loctite prevents it from turning when torque tested. Nordloc washers overcome this (screws wont unwind due to vibration etc  but tightness torque can be checked.

Nordloc X series (effectively a Nordloc washer with additional Belleville characteristics) is perfect as  the Belleville spring effect will maintain bolt tension if/when the joint settles. 

BobP

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