Knuckle M-211 & M-216 AAR Qualification Testing


CTLGroup was contracted to conduct qualification tests on cast E type knuckles for freight car applications in the North American market.  Knuckles were tested in accordance to the Association of American Railroads specifications (AAR) Manual of Standard and Recommended Standards (MSRP) M-211 “Foundry and Product Approval Requirements for the Manufacture of Couplers, Coupler Yokes, Knuckles, Follower Blocks, and Coupler Parts” and M-216 “Knuckles, Types E and F – Fatigue Test”.

Static testing occurred to assess the abilities of the knuckle and coupler assemblies to successfully resist the loading conditions defined in AAR M-211.  Appropriate dimensional measurements were made prior to loading and after the application of 400,000 lbs. to determine the permanent set in the knuckles.  Once measured, the knuckle and coupler assemblies were loaded to a static load of 650,000 lbs. to assess the capacity in accordance with AAR requirements.

Fatigue testing was performed to evaluate the knuckles and coupler assemblies under the loading conditions defined by AAR M-216 for fatigue life.  Knuckle and coupler assemblies were fatigue loaded following the requirements defined in M-216 until failure occurred, which, for the samples tested, was an average in excess of 660,000 cycles fulfilling the fatigue life requirements.

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