Comments on: Joint Face Design http://www.ret-monitor.com/articles/384/joint-face-design/ Specific mission-critical info for professionals Thu, 09 Feb 2012 15:52:36 +0000 http://wordpress.org/?v=2.7.1 hourly 1 By: Terry http://www.ret-monitor.com/articles/384/joint-face-design/comment-page-1/#comment-6158 Terry Thu, 20 Jan 2011 05:57:44 +0000 http://www.ret-monitor.com/articles/384/joint-face-design/#comment-6158 If you look at the kinematic degrees of freedom present in the conrod big end bearing joint, it becomes apparent that the joint can only transmit axial forces along the line between the wrist pin and crankpin centers. And the bearing itself can only transmit forces in compression between the bearing and journal surfaces. This means that only one side of the conrod bearing is loaded at any given time. The conrod bolts and rod cap in a 4-stroke only see dynamic loads during the exhaust/intake stroke. The rod bolt preload should be sufficient to ensure that the beam/cap joint never separates under these dynamic loads. If the joint separates, surface fretting will occur. The rod bolt/nut may also loosen, since the only thing keeping them fastened is the prevailing thread friction due to preload. If the beam/cap joint separates, fretting damage will occur, regardless of whatever type of alignment feature is used- serrations, ring dowels, fractures, pins, shoulders, etc. If you look at the kinematic degrees of freedom present in the conrod big end bearing joint, it becomes apparent that the joint can only transmit axial forces along the line between the wrist pin and crankpin centers. And the bearing itself can only transmit forces in compression between the bearing and journal surfaces. This means that only one side of the conrod bearing is loaded at any given time.

The conrod bolts and rod cap in a 4-stroke only see dynamic loads during the exhaust/intake stroke. The rod bolt preload should be sufficient to ensure that the beam/cap joint never separates under these dynamic loads. If the joint separates, surface fretting will occur. The rod bolt/nut may also loosen, since the only thing keeping them fastened is the prevailing thread friction due to preload. If the beam/cap joint separates, fretting damage will occur, regardless of whatever type of alignment feature is used- serrations, ring dowels, fractures, pins, shoulders, etc.

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