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Locomotive Cabs, and Crew Safety in Collisions

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Paul,  <o:p></o:p> I certainly do agree that an assessment of whether or not the posts failed depends on what they are intended to accomplish.  They may not have been intended to protect from collisions with railroad equipment.  I did read some material suggesting that collision posts were intended to protect from railroad equipment collisions as well as grade crossing collisions, but that was buried in an ocean of information, so I cannot conclude how it might apply to this case.  It would be interesting if a description of performance intent were found to supplement this structural specification that you posted:  <o:p></o:p>      (4) The outside end of each locomotive shall be provided with two main vertical members, one at each side of the diaphragm opening; each main member shall have an ultimate shear value of not less than 300,000 pounds at a point even with the top of the underframe member to which it is attached. The attachment of these members at bottom shall be sufficient to develop their full shear value. If reinforcement is used to provide the shear value, the reinforcement shall have full value for a distance of 18 inches up from the underframe connection and then taper to a point approximately 30 inches above the underframe connection. <o:p></o:p>  <o:p></o:p>  <o:p></o:p> In reading the above specification, I am struck by its vagueness.   Basically, it requires 300,000 lbs. of shear strength where the posts connect to the main frame.  Yet, without stipulating the height of the post, it is meaningless for practical purposes.  The shear strength of that connection would be just the beginning of defining what the post is intended to accomplish.  According to that specification, the “post” could be a couple inches high as long as it, and its weld, met the shear strength requirement.     <o:p></o:p> The post’s failure to stand the pressure of the collision was not a failure of that shear specification.  Nothing sheared.  The post bent over from inadequate column strength.  Either the post bent, or it acted like a lever to bend the frame to which it was attached.   <o:p></o:p> The shear strength of the connection of the post to the frame almost seems beside the point.  The point is the amount of force the post can take at any point on it without yielding by bending for any reason.  The post can withstand the least amount of force at its very top, and withstand more as it is applied more toward the base.  So the logical specification would be the minimum horizontal force that the post can withstand within say 2” of the top without yielding in any way.  Anything that strikes the post has the potential to apply force to the very top tip, so that has to be the point at which the minimum performance strength is specified.  <o:p></o:p> It almost seems to me that the specification is a rather flawed product of a lot of push pull between the locomotive manufacturer, the railroad industry, and a collection of regulating authorities.  So you end up with something that gives the illusion of solving a problem, but is relatively meaningless.  Then the locomotive builders execute their best interpretation of what they think is called for by the sketchy specification.   <o:p></o:p> I can see how the railroads would be reluctant to cross over into the issues of protecting locomotives from crashes other than grade crossing collisions.  That would be a wide-open field with a mighty big vehicle for safety system visionaries to play with.  The potential to add cost through mandated protections would be enormous.  And the railroads probably feel that following the rules is the best crash protection from colliding with railroad equipment.  But since they have no control over the matter of colliding with vehicles at grade crossings, they may welcome crash protection for that purpose.       <o:p></o:p>  <o:p></o:p>  <o:p></o:p>
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