how does a train know its out of a siding?
Assuming you mean a mainline freight in the middle of nowhere with no one around for miles,that is one of the joys of modern technology. The locomotive and the "Fred" on the back communicate with each other. When the locomotive hits the mainline, the engineer hits a button. The train's computer knows how long the train is, so when the train moves the same distance (i.e. 5,000 foot train moves 5,000 feet) it tells the engineer. That is also how a long train knows if it can stop without blocking any grade crossings or other area that must be kept open.
Thank You.
The locomotive computer only concerns itself with the locomotive. The train crew has their Train Documentation that provides all the pertinent information concerning the train - loads - emptys - tons - length - HAZMATS and a number of other things that may affect the operation of the train. The Conductor is responsible for updating this document when pickups and setoffs occur. When the Engineer passes the point he wants to clear, he zeros the distance counter on his EOT console and watches the feet click by until the number exceeds the length of his train. Knowing the length of the train is vital in today's operating world.
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The latest distance counters can countdown distances and then they have an audible "beep" when they get to zero. The best counters were those on the GE Dash 9 that could count up or down. Even when setting off and picking up, I could keep up with how long my train was. Then GE went and screwed that up with a different type of counter on the EVO series.
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BigJim Then GE went and screwed that up with a different type of counter on the EVO series.
Then GE went and screwed that up with a different type of counter on the EVO series.
Everything else on those engines beeps, rings, screams, and chirps (esp. in cs/lsl territory), but yet the counter is silent. Don't ya love it?
The opinions expressed here represent my own and not those of my employer, any other railroad, company, or person.
zugmannEverything else on those engines beeps, rings, screams, and chirps (esp. in cs/lsl territory), but yet the counter is silent. Don't ya love it?
The "end of countdown" beep on the counter on our RS18U's is exactly the same pitch as the alerter penalty alarm. More than once I've set the counter for our "Polar Express" trains (so I'd know when the train had cleared restricted speed territory and could wind it up) then about panicked when the danged thing went off, thinking I'd gotten a penalty for something...
Larry Resident Microferroequinologist (at least at my house) Everyone goes home; Safety begins with you My Opinion. Standard Disclaimers Apply. No Expiration Date Come ride the rails with me! There's one thing about humility - the moment you think you've got it, you've lost it...
Is the train crew given the train length for the train bunched up and for the train stretched out?
Thanks to Chris / CopCarSS for my avatar.
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There was one railroad, either IMRL or IC&E, which gave lengths for bunched or stretched conditions. I remember seeing it on paperwork left on the engine on a run-thru train. It's interesting when I see foriegn line paperwork for a run-thru, often length and weight are different from our totals. Not a big difference, but noticable.
Who needs a counter? Most railroads have mile, quarter, half mile, and three/quarter posts. If you know your footage just convert to the next higher tenth of a mile. If the switch is at MP 123.4 and your train is 5700 ft, just figure it to be 1.1 miles (1.1 = 5808 ft.) and add (or subtract depending on how the mile posts run) and when the head end is at MP 124.5 you're clear of the switch. I started doing this when I was a conductor because often the conductor didn't have a counter or the counter was off. The counters on the stand alone EOT head end boxes (at least ours) are often wrong. It's fun to check the counter between mile and quarter posts and watch it count off 15000 feet in a quarter mile.
Jeff
When leaving a siding, the amount of distance due to slack is inconsequencial. Let's face it, with the kind of tonnage a train of any length out of sight distance, the locos will not be able to accelerate the train fast enough to get over the speed limit.
One thing that many do not know is that the distance counter is more often than not tied into the speedometer. So, if the speedometer is fast or slow the indicated distance is either longer or shorter. This is where the importance of getting a good reading through the "Test Mile" comes into play, along with a good understanding of math. The difference in the "True" speed and "Indicated" speed can be expressed in a ratio. That ratio can be used to find the "corrected" length of the train as it applies to the particular unit being operated. The more the speedometer if off, the more the indicated distance is off and this can be quite a bit of distance depending on the length of the train.
This ratio, found during the test mile, is also relavent to the speedometer readings across the dial. For example, the speed limit through the test mile is 30 mph. Timing the test mile shows a true speed of 31 mph. So, the speedometer "indication" is slow by 1 mph. So, how fast does one need to run in order to not be over the speed limit at say, 50 mph? 30 /31 = .967. Multiplying that ratio by 50 gives an indicated 48.3 mph.
Using this same ratio to find the indicated distace for a 5000 ft. train finds that according to that distance counter, at 4835 ft you will be out of the siding.
Which all goes back to the diameter of the wheels on the front truck of the locomotive (how worn and how slippery they be as counted by the tachometer in the wheelset)....
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