2 rails in center on bridges

Transman posted:

Whats the purpose of the 2 rails in the center that start at a point you usually see on train bridges?

Those are called "guard rails", and in the event of a derailed car, they tend to prevent the car from "going over the side of the bridge". The guard rails would keep a derailed wheel set, or truck in alignment until after the bridge, thus potentially saving the bridge from serious damage.

Thanks 

I've heard a different discussion of the additional rails.  Lateral bridge movement, even if the bridge is not curved, can be a problem.  Additional rails inhibit the side to side motion of the bridge. IMO   Mike CT.   I've been wrong, and often, on this forum.   

FWIW, GarGraves offers 5 rail track for our model railroads. I use it on all of my bridges. HW's comments are spot-on.

Mike CT posted:

I've heard a different discussion of the additional rails.  Lateral bridge movement, even if the bridge is not curved, can be a problem.  Additional rails inhibit the side to side motion of the bridge. IMO   Mike CT.   I've been wrong, and often, on this forum.   

I think this is one of those times.

How are two additional rails, basically as flexible as spaghetti, going to impede a bridge's "side to side motion?"

What the hell is "side to side motion" anyway?

SMD,  Because they are spiked down to cross members bolted to the superstructure  they are not as flexible as you think

wb47 posted:

SMD,  Because they are spiked down to cross members bolted to the superstructure  they are not as flexible as you think

Spiking doesn't make them any less flexible.

smd4 posted:

wb47 posted:

SMD,  Because they are spiked down to cross members bolted to the superstructure  they are not as flexible as you think

Spiking doesn't make them any less flexible.

1) Those guard rails are not spiked down as often as the main running rails, i.e. the guard rails are NOT double spiked in every tie, as a rule.

2) If the bridge is going to move in ANY direction, none of the rails are NOT going to prevent it.

Mike CT posted:

I've heard a different discussion of the additional rails.  Lateral bridge movement, even if the bridge is not curved, can be a problem.  Additional rails inhibit the side to side motion of the bridge. IMO   Mike CT.   I've been wrong, and often, on this forum.   

Mike,
HW & smd4 are correct, it is all about trying to keep the derailed truck in line with the rails instead of skewing and taking out the bridge. 

Gilly@N&W posted:

FWIW, GarGraves offers 5 rail track for our model railroads. I use it on all of my bridges. HW's comments are spot-on.

Or you can purchase GG's straight sections of rail that are flat on the bottom and install your own guard rails.

Gilly@N&W posted:

FWIW, GarGraves offers 5 rail track for our model railroads. I use it on all of my bridges. HW's comments are spot-on.

I prefer to split the difference and go with one guard rail straight down the center of the track.  Makes laying bridge track go a lot easier and faster. 

"one guard rail straight down the center"   Yeah but what color is it?    Russ