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[quote user="cordon"] I will try to answer the question about forces.   [/quote]I welcome your effort to diagram and explain this, but it does raise some questions in my mind.  I do not believe the features you label as "force bearing ridges" are actually load carrying features.  They are simply size reductions on the knuckle mass.  Those reductions are correspondingly filled in with mass size increases of the coupler body.  These mass changes are done is steps, and are curved to match the swing of the knuckle pivot.  Moreover, in your diagram, I think you have the features you label as force bearing ridges reversed. In actuality, the knuckle mass steps down as it approaches the lock-engaging portion, whereas your diagram suggests that the mass is stepping up to a wider mass.  So, in the true configuration, they would not be able to carry load.  They would simply pull apart as they do if you were to release the lock on a closed knuckle with the knuckle pin missing.  If I am not mistaken, your diagram shows the basic concept of the original Janney design where the lock only prevents the knuckle from pivoting.  It does not prevent it from pulling out in line with the lengthwise direction of the train.  With this design, the knuckle pin does indeed share the load as a shear force.  The load would be shared between the knuckle pin and the lock.  Look at it this way:  In your diagram, if the knuckle were closed with the lock engaged, and if you removed the knuckle pin; the knuckle could be pulled out even though the lock is still engaged (and considering that the "force bearing ridges" would not stop it as mentioned above).What the original Janney design has evolved into with the modern coupler is a lock that prevents direct pullout in line with the train, as opposed to preventing knuckle pivot.  With this modern design, it is the engaged lock that prevents the knuckle from pulling out if the knuckle pin is missing.  It is not the features you label as "force bearing ridges". The mating faces of the knuckles have a sort of reverse curve or ogee form that creates a hook effect.  This hood effect transfers the tensile, pulling force through the coupler centerline, directly to the lock.  So when the lock is engaged, there is no force that is trying to cause the knuckle to pivot.  When you release the lock, the knuckle is pulled forward, engages the knuckle pin, and pivots on it.When couplers are mated, the force is transferred from the mating knuckle faces directly to the locks, and the locks transfer the force directly to the coupler body.  These forces are transferred on the train centerline as tension, and they do not induce any pivot force on the knuckles.
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