Today's Message Index:
----------------------
1. 09:48 AM - Re: Checking bolt torque (Bob H)
Message 1
| INDEX | Back to Main INDEX |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Checking bolt torque |
I would use your second procedure of removing bolts, clean threads of any residue
and reinstall to correct torque, using suggested Locktite.
It is more common practice in US to install bolts dry as torquing dry provides
a more uniform/repeating loading and bolts used a cadmium plating to provide lubricity
and corrosion protection. However, many fastener suppliers have been
forced away from cad plating because of toxicity issues in the plating process.
When you add a Locktite to threads, friction is reduced and bolt receives higher
loading for a given applied torque. Jabiru must have accounted for this higher
loading when making that recommendation.
Taking a tensile bolt to 90% of Yield is a risky business in that the variations
in thread geometry/hole tolerance and friction and torque wrench errors can
easily cause overtorquing. We usually select a torque value around 60% of Yield
to provide sufficient margin for errors. If a situation requires higher clamping
forces, a larger dia fastener is chosen. With hardware already in service,
installing shear pins is a way to takeout that loading and reduce bolt torque
to a more reasonable level.
It would be interesting for Jabiru to indicate what the mode of failure has been
on those bolts; a shear overload or tensile fatigue. And the bolt pic showed
failure in threads which can indicate that threads are overloaded and geometric
stress concentrations from thead form contribute to failure. You don't want
threads in bearing and the bolt grip length is sized to carry shear loads on
smooth shank, never in threaded portion.
Bob H
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=78653#78653
Other Matronics Email List Services
These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.
-- Please support this service by making your Contribution today! --
|