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Train exiting the Tehachapi Loop in Kern County, California.
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Previously:
https://www.homemadetools.net/forum/...561#post123084
https://www.homemadetools.net/forum/...031#post120283
https://www.homemadetools.net/forum/...607#post132631
https://www.homemadetools.net/forum/...765#post133147
Thats a lot of tractive effort!
Rising at a steady two percent grade, the track gains 77 feet (23 m) in elevation in the Loop
Is a consist that long Really safe though? It’s a long way for the air pressure to flow and make the safety brakes work.
This is not a direct answer to your question but a good example of what a PIA it must be to fully understand the system.Quote:
Originally Posted by Drew1966
Long video but well worth the time if interested in the subject.
https://www.youtube.com/watch?v=3lSOh-ES-o8
Here's one explaining the EOT (end of train device). Long 17 mins. 8:55 explains failures.
Interesting thing I learned, the rules seem to change at +/- 2% grade.
https://www.youtube.com/watch?v=BY99KerpoYE
They were interesting, thank you Jim. But I still think that a consist that long could be dangerous, mostly due to the time it would take for the pressure to release from the brake lines along the entire length of the consist.
I always say if you can't explain it you don't understand it. And I can't explain it.
I believe it has a lot to do with the lowering of the brake pipe pressure just a small amount controls the AB valve in each car which controls a cylinder full of air to apply the brakes on that car.
This is from John Bentley
At tarorigin.com
SERVICE BRAKES: This is the type of brake application normally used for braking. This level of braking is achieved with a 6psi to a 26psi reduction in the brake pipe pressure. When the AB valve senses the difference in pressure air is ported from the reservoir to the brake chamber. Air pressure acts against the diaphragm and brakes are applied. Braking with the Service Brakes offers up to 75% of a train's Emergency Brake capability
Actually the one shown probably isn't even considered a long train but since we can't see the rear it could still have more than double the amount of wagons we can see that haven't come onto the scene. From the looks of what I could see there may have been around 100 wagons almost all of them were container type many were double stacked. You will often find up to 160 wagons for each 2 locos across the plains, fewer for mountain passes. so more probably 100 to 2 with possibly or probably 1 or more locos in the rear. For the really long trains you see crossing Lower Arizona you might see 2 locos placed near the center as well, a lot depends on what the freight is. Containers are usually much lighter than coal, Iron ore, or crushed rock. So less tractive force is required for the double stack container unit train than one of other comedies or mixed wagons. On our last trip to Seattle we saw several trains over 3 miles long.Quote:
Originally Posted by Drew1966
A railway worker once told me they are more concerned with tractive force than braking force because it is not as if you are going to be stopping at the next intersection when the light goes red like in a car. They plan their slow downs miles in advance.
I’m pretty sure the freight trains here in Australia use safety brakes where the brakes are applied by reducing the pressure, just like maxi brakes on a semi-trailer.