The term couplers passing what does this means?

Question

The term couplers passing what does this means?

Answer 1

A different take.

Where I come from, what Rango describes is what we call a "bald headed joint."  This is when trying to couple cars and, owing to mis-alignment (especially on curved track with longer cars) the coupling is not made, with the couplers off set.  here, the draw bars must be aligned by hand to make the coupling.

I think you are talking about "coupler-bypass."  When under way, the cars can get to bouncing up and down on their springs, especially in areas where track level is not up to snuff.

What happens in extreme cases is, when one car is at the "top" of the bounce, while the one it is coupled to is compressed hard on the springs, the vertical distance of the knuckles is exceeded.  Where extreme, one coupler drops below the other enough to where the "hand-shake" comes apart.  Not due to equipment failure, such as a broken knuckle or broken draw-bar, but simply because the relatively small coupler faces just by-pass one another, resulting in a train separation.

These incidents are very rare, but they do happen.  For one thing, the slack must be neutral at that exact point, otherwise tension on the couplers will not allow them to by-pass.  But, this can lead to another, more common (and more serious) problem, called "cradle effect."

Consider the same bouncing effect, but the couplers are under draft, with no "neutral" slack at the coupling.  Here, draft has the couplers essentially welded together.  This allows the up and down "pumping" of the equipment, in some cases, to allow trucks to separate from the car (they're not attatched, you know.  The cars just sit atop them) or for L/V ratio to be exceeded, which will allow flanges to over-ride the outside rail in curvature, resulting in a derailment.

This happens when, at that exact moment, a car is at the top of a major pumping action, and tension comes on the draft gear.  The position of that car, riding too high, is frozen in time and place until a slack change allows the car to again sit with all weight upon the trucks.

Don't know if I answered the question or confused you further, but there ya go..

Answer 2

couplers have to line up, much like your fists clasping each other

imagine one coupler shifted to the right slightly

and the other one shifted the other way

now when they come together instead of your hands gripping one another, they bypass sliding together

same wiht coupler, instead of grabbing one another they miss.

the sideways pressure can easily derail a light car when this happens.

usually it happens on a curve where the cars are not aligned very well to begin with