---------------------------------------------------------- Engines-List Digest Archive --- Total Messages Posted Sat 12/02/06: 1 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 09:48 AM - Re: Checking bolt torque (Bob H) ________________________________ Message 1 _____________________________________ Time: 09:48:25 AM PST US Subject: Engines-List: Re: Checking bolt torque From: "Bob H" 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 ------------------------------------------------------------------------------------- Post A New Message engines-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/Engines-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/engines-list Browse Digests http://www.matronics.com/digest/engines-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.