Bending turnout points for closure

[FJ and G]

I've observed older points that are separate from closure rails but on some of the high speed turnouts, it appears to be one solid piece and to make the turnout operate, the steel rails of the points seem to bend instead of pivot.

Am I seeing things or is this true?

I always thought that if you bend a piece of metal so many times, it will snap.

Also, I'm impressed at how thin the points are, yet they partially hold the weight of the train along with the stock rails.

Dave Vergun

[Hugh Jampton]

No, you are not seeing things,, this is what happens.

You're describing failure by metal fatige. Steel has what is called a fatigue limit. If the stress in the metal due to the bending is less than the fatigue limit then it will not fail. The distance the switch blade has to move, coupled with its thin profile ensures that the stress in the switch blade is less than the fatigue limit.

The key worh here is partially. The weight transfer from the stock rail to the switch blade is designed so that the switch blade does not carry more load than it is capable of holding.

[mudchicken]

The bent stockrail on the turnout side is the only thing here that gets permanently "bent" by a hydraulic jack. A 22 or 39 foot switch point is resting on switch plates and is not fastened to the ground ahead of the heel of switch. You can easilly generate enough moment arm to move 15-16 feet of machined rail over 5-6 inches laterally and structural metal fatigue will not be an issue for the life of the points. Those undermaintained wheels on a locomotive or railcar will do most of the wear and tear.

An old roadmaster correctly taught me to be worried more about the stockrail than the worn points.

[FJ and G]

I'm not on this forum too much but when I am, my questions always get answered in great detail. That's what I love about this place. Thanks!