when going over points how do trains successfully cross them?

Question

looking at train points i have always wondered how come if on on side of the points there is a gap how do they cross them without slipping off the track

Answer 1

Remember, the wheels have flanges on them that extend below the top of the rail. This is of course what guides the wheels along the rail.

The full name of that which you are referring to are "switch points". These are the movable portion of the switch. When the switch is lined for regular movement, it is considered to be in the "normal(ed)" position and when lined for the other direction is considered to be in the "reverse" position.

The switch points are tapered. When lined normal, there is a gap created for the flange way of the wheels on one side, while the narrow switch point on the opposite rail makes contact with the rail for the wheel to ride on top.

When lined reverse, the gap disappears on the one side, and when the "throw" is complete, the situation is reversed, with the other rail now making contact while the other point has now created the needed gap in the other rail.

The frog is a device that allows the wheel flanges to cross over one rail to ride on the other several feet further down the switch. As precaution, adjacent to the frog on the opposite sides, you will see a short piece of rail, appearing to be connected to nothing. It is called the "stock rail". Its purpose is to ensure the flanges of the wheels follow the "groves" in the frog. Mounted on the inside of the rails, these keep the wheels from moving in the incorrect direction.

Answer 2

If you ever get a chance, look at the railcar's or engine's wheel, you will see that the inside outer edge protrudes much more than the rest of the wheel, its called the wheel flange-- as long as the switch points don't have a gap over, I'd say, an eighth of an inch maximum the wheel flange can get over the switch point and keep going. We use to use what we call switch point keys to actually stick down in switch points if they looked a little too gapped. Along most tracks we have switches which can be lined for straight movement or redirected to go another direction. If you are not use to looking at switches and the direction their lined it can be confusing sometimes. The switch points slide from side to side. The easiest way to determine where the train is going is to look at the outside rail, if the outside rail doesn't have any other rail touching it then the train goes straight, if it does then the train follows that rail. Determine the outside rail by looking at where other rail is running, if there is a company on the left with tracks going to it then the outside rail is on the right and vice-versa if there is a company on the right.

Answer 3

The gap is what makes the points work to switch the train from one set of tracks to another! Assuming the train is travelling from left to right and there are a set of points to switch the train on to a branch. The 'frog', the moving part of the points will move leaving a gap between the right hand running rail of the main line (looking towards the branch) and the points. If, however the train is to continue straight ahead the gap will be on the left. If there were no gap the train would indeed derail as it would try to go int two directions at once. There is a moving diagram at http://en.wikipedia.org/wiki/Railroad_switch
which explains things far more clearly than I can here in words.

Answer 4

It's because the gap isn't large enough to make the wheels come off. The gap is only a couple of inches wide, while the train wheel's diameter is 42 inches.