Switch designs

[Joe]

I was looking at some switches today waiting for the train to come in, and it looks to me like the switch motor actually bends the running rails when it moves the switch. Is this actually what's done, or is there a pivot point on it that I just didn't see (cause it was dark). If it's bending the running rails, those switch motors must be one hell of a strong motor.

[SubwayGuy]

I was looking at some switches today waiting for the train to come in, and it looks to me like the switch motor actually bends the running rails when it moves the switch. Is this actually what's done, or is there a pivot point on it that I just didn't see (cause it was dark). If it's bending the running rails, those switch motors must be one hell of a strong motor.

 

There is a pivot point

[metsfan]

Actually rail steel is quite flexible. If you look in some of my tie replacement posts you may catch where the tie insertion machine lifts the rails, separates, and inserts the tie, and lays it back down. The switch simply bends the rail one way or the other. If left alone the rails would come to rest about half way between positions. That being said, some are on pivots, but not as many as you'd think as those are low speed switches often used in yards and low traffic sidings.

 

 

Edit: If the rails were not flexible they would wear out in a matter of months from stress fractures. The wheels on the other hand are a bit harder but not by much or else they would damage the rails. Rail steel is in fact sometimes too flexible, and expands in hot weather, a condition known as "sun kink" where the restricted movement causes the expanded metal to bend between the ties. This is mostly a condition found in warmer climates such as the southern half of the usa.

 

- A