What resists the lateral forces upon a railroad tie? Basically what holds a tie in place?

Question

What resists the lateral forces upon a railroad tie? Basically what holds a tie in place?

Answer 1

The weight of the tie itself, along with the dirt, rocks or other materials placed between the ties.  In addition, the weight of the rail and the spikes that are placed in the tie to keep the position of the rail from shifting.  When a train passes over, there is a downward force on the tie, not a pushing force.

Answer 2

The main thing that holds the rail upright is its shape, and the weight of the train above it.  The base of the rail is nearly as wide as the rail is tall, and it sits on a metal plate that is wider still, and spiked (or screwed) into the tie.  The train car (30 tons minimum) or the engine (200 tons) is enough to hold the tie down on the rail, and not tip over.  The spikes (or rail clips) are more to hold the rail the correct distance apart, not to keep the rail upright.

It's true that as the train goes into a curve that there are huge side forces involved, and dragging a lot of cars through a curvy trainyard too quickly can pull the cars right off the track, but for the most part just the sheer weight of the equipment will keep them on the track.  I've been on some stretches of old track that had all the spikes loose with age - as you go over it, the rail goes up and down, right off the ties, but wherever the wheels are touching, the rail is steady on the ties as if it were welded.

Answer 3

The above answers are correct, but the tracks do take a beating. They sink, they fall out of alignment, and everything gets worn out. When a maintenance crew approaches bad track, they start by replacing broken ties and worn rails, and then adding ballast. The new ballast is tamped underneath the ties to relevel the track, which is then relined, usually by the same machine. So it is a bit of a process.

A bit of a story: There's a h**l of a switch on my little railroad -- a shop track that we store equipment on. It's a normal switch from the points to the frog, but after that there's a hairpin kink that straightens the track out toward the shop site. When you shove a passenger car with eleven-foot trucks through that kink, the noise is truly blood-curdling. The truck is basically trying to spread the rails, which taxes the spikes and ties and moves the track around just a little each time. Areas like that (curves, kinks, low spots) take more stress and require routine attention.

Answer 4

The nail thats hammered in.

Answer 5

Ever try to shovel ballast!?  I have, and the jagged stones interlock together.  That's what keeps the tie from going sideways, the ballast on either side of the tie and the shoulder.

That's why you don't use pea gravel for ballast. And you DO groom your track shoulders.

Answer 6

I would say a combination of the weight of the tie, nailed to the track, and the gravel that surrounds it.

Also the added weight of the train on the tracks.

Answer 7

Ballast (Gravel) does. Lateral forces are still at work, since the rail needs to be able to move. (expand, contract, etc..etc.)

Answer 8

It is the "ballast", gravel or crushed stone tamped into and around the ties to keep them from moving. The more the forces, the more ballast required, for instance on high density lines there may be as much as 18" or more ballast beyond the ends of the ties to keep them in place. Even with all the ballast,  on curves the track is re-aligned quite frequently.

Concrete ties being heavier and having a wavy or textured bottom to grip the ballast better are more resistant to moving.