How do subways work?

[TriboroughBridge]

I'm very curious as to how subways work.

 

First, how do subway trains accelerate? I know you push the throttle and the train goes, thanks, but when the throttle is pushed does it move only the first car & pulls the others? or when the throttle is pushed all cars are accelerated & each cars move by itself

 

Second, how do trains stay to the track? all I know is the wheels of the train rest on the track, if this is true how do they move? It's not like a car that has grooves in the tire to help it move. is it the weight of the train? Also does this also apply when a train is driving up or down a hill?

 

How do trains go up or downhill (outside) when there is snow/rain? wouldn't that make the tracks slippery?

 

Last, how are subway tunnels between rivers made? I know there's a tube that's put underwater, but does it get put all the way to the ground or does it get put deep below the water, but is made suspended, like a bridge. Also can subway tunnels cross over/under each other while underwater or is that impossible?

 

All your answers are greatly appreciated!

[ParkStUnder]

1. Each car has motors so they are all powered, which is why subway trains can accelerate relatively quickly.

 

2. Each wheel has a flange on the inside which keeps it on the rail. The weight of the train on a relatively small area of contact between wheel and rail creates enough friction so that the wheel can push against the rail and get traction, even going up a reasonable hill (up to 5% or 5 ft in 100 ft. or so)

 

Yes snow / rain can make tracks a little slippery but not enough to prevent them from working. Regular trains have sanders to help with traction in these situations, don't know if they are ever used on rapid transit cars.

 

Tunnels under rivers can be done 2 ways - by digging deep under the river bottom, or by lowering pre-built tubes onto the river bottom.

 

Not sure if there are any underwater tunnels that cross, would be possible but would require one of them to be very deep to do this.

[Roadcruiser1]

1) There is a propulsion system that pulls the train forward. Basic principle in all man made moving objects. In this case it's a motor (traction system).

 

2) See above.

 

3) They travel much slower in the rain and snow, because the tracks are slippery.

 

4) Tunnel boring machines drill a tunnel underneath the river bed into the bedrock, and yes there is something called a submerged floating tunnel too.

[Roadcruiser1]

Submerged floating tunnels.

 

[Kamen Rider]

Please, watch the Nazi Banksters Crimes Ripple Effect at http://jforjustice.co.uk/banksters

[Roadcruiser1]

It has been proposed multiple times though.

[Kamen Rider]

Please, watch the Nazi Banksters Crimes Ripple Effect at http://jforjustice.co.uk/banksters

[Eric B]

Both of those (a floating tunnel under the Atlantic, as well as an elevator tower to space with a connection to one to the moon) are ideas featured on "Extreme Engineering".

[Joe]

The contact patch of the wheel on the rail is about the size of a dime, IIRC.

 

On tangent track, the flanges don't actually rub on the sides of the rails...or at least they shouldn't be. Wheels these days are conically shaped and will ride in their natural centerpoint unless severely worn.

 

Now, when traversing switches, having good flange condition is essential. Sharp flanges will pick switches and cause all sorts of nastiness.

[GreeneggsnPelham]

So what, I can propose a tower to the moon.

 

Hmm, jerk much?

[TriboroughBridge]

1. Each car has motors so they are all powered, which is why subway trains can accelerate relatively quickly.

 

2. Each wheel has a flange on the inside which keeps it on the rail. The weight of the train on a relatively small area of contact between wheel and rail creates enough friction so that the wheel can push against the rail and get traction, even going up a reasonable hill (up to 5% or 5 ft in 100 ft. or so)

 

Yes snow / rain can make tracks a little slippery but not enough to prevent them from working. Regular trains have sanders to help with traction in these situations, don't know if they are ever used on rapid transit cars.

 

Tunnels under rivers can be done 2 ways - by digging deep under the river bottom, or by lowering pre-built tubes onto the river bottom.

 

Not sure if there are any underwater tunnels that cross, would be possible but would require one of them to be very deep to do this.

 

 

 

1) There is a propulsion system that pulls the train forward. Basic principle in all man made moving objects. In this case it's a motor (traction system).

 

2) See above.

 

3) They travel much slower in the rain and snow, because the tracks are slippery.

 

4) Tunnel boring machines drill a tunnel underneath the river bed into the bedrock, and yes there is something called a submerged floating tunnel too.

 

 

Thank you very much the both of you! Much appreciated! I've been very curious for a long time how the subways worked, so thanks!

 

And thank you roadcruiser1 for the tunnel diagram!