runaway box cars

[jettrainfan]

i was looking at a model railroad video when i found this...

http://www.youtube.com/watch?v=mqlc7cAoDxA&feature=rec-rn-3f-2-HM

It was sad to hear that the passenger died. I hope that guy is still doing OK today.

[Jim Banner]

I saw that video a few years back and it had quite an effect on me.  I can no longer drive through level crossings without looking for trains, even though the level crossing is protected by lights.  The only other person I know that has this strange affliction works for the railway - as a signal maintainer.

Jim

[jestor]

I too saw this video some time ago. I was wondering at the time why the boxcars did not activate the crossing signals. Does it take a locomotive to activate them?  What about a local running in reverse?  I guess what I'm really asking is how is a crossing signal activated? 

[Jim Banner]

Signals are activated by current flowing from one rail to the other rail through the wheels and axles.  The voltage used is low and the required current flow is high, so the resistance has to be extremely low.  I guess 8 axles is not low enough.  I remember seeing several jiggers, each with trailers, going out to fix some track.  It was surprising that the whole bunch together could not trip the signals.  Nor could a rail grinding train with two locomotives and several grinder buggies in between.  The latter was one of the worst examples of idiots in automobiles I have ever seen.  As the train approached the crossing on its way to work, the engineer repeatedly blew crossing sequences, and finally, just held the cord down.  Do you think traffic would stop? Not on your life.  There were no flashing lights so the drivers refused to stop.  It didn't matter that the train had the right of way and that any unit in the train could have squashed them flat.  The engineer finally had to creep into the crossing (rail grinder locomotives are specially fitted for extremely low speeds) and still the cars were trying to go around the train.

I will see if I can find some number on voltage and current.

Jim

 

[glennk28]

The other question I have is why did a crew leave cars without a skate or chain under a wheel

Glenn Joesten, shortline conductor--so I know about such safety devices. 

[NarrowMinded]

There is a crossing near my house that kids would lay any thing metal they could find, like broken fence  poles across it  to trigger the crossing signals, it had traffic backed up for blocks. A crew came out and made some adjustments and the kids fun was over, maybe that crossings electronics needed to be tuned a little.

NM

[glennk28]

There is a bond wire (jumper) around each rail joint in a crossing circuit.  I know of a place where kids would pry off the bond wire--but a train would still trigger the crossing signal.  But, it wouldn't clear..  gj

[jestor]

Thanks for the info. I had always wondered how a crossing signal was activated. The other evening a NS train was approaching the crossing near my house. The crossing signal/gates were activated.......the train stopped about a hundred feet from the crossing and turned off the headlights to sit there awhile before preceding on to the quarry a few miles down the line.  As soon as he turned off the headlight, the crossing signal stopped and the gates went up. I was looking at that and wondering.....how'd he do that? Then a while later when the train was ready to procede......As soon as he turned on the lights the crossing activated again and the gates went down. It got me thinking ......did the crew in the loco have some way of controlling the signal....because I didn't see anybody get out of the loco. 

[jward]

since the standard crossing circcuit is the same as the circuit that activates the signals, even one freight car should have activated it. think of it this way, if a carrolls away from an industry and fouls the main track, you'd want the signals to detect that.

many of the newer crossing signals are motion activated, rahter than the traditional setupo which only detected whether a train was present, but not its speed. that is why the signals turn off when the train stops, andturn back on when the train restarts.

the traditional  setup was actually two sets of circuits sumperimposed on each other so as to be directionally sensitive, i.e the they are activated when the train is a specific distance from the crossing but turn off as soon as the train clears the crossing.

when i worked for the railroad, we'd often tie the train down at a gate protected crossing. south bound, we stop within 100 feet of the road and tie the train down, northbound, we'd have to pull completely past the circuit, then reverse direction and head south until we cleared the crossing. luckily we had engines on both ends of this train all the time.

why did n't we just park it elsewhere? the branchline we were running on had alot of grades, and many road crossings as well. this waas the only level place we could stop without blocking somebody's road crossing. believe me, farmer's get irate when they can't get to their fields because you left the train on their private crossing.