Can Helpers be independently Controlled to Stretch or Bunch a Train

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Eng8492

New Member
I saw a train pass with heavy braking and slipping wheels but the helper on the end was notched up pretty high.

If the engineer was trying to stretch the train, I would think that the helper would be cut out or idled while the lead power pulled with brakes bailed off and train brakes were applied.

If the engineer was trying to bunch the train, I would expect the lead engine to be idled down and braking.

1) Could the helper have been notched up to bunch the train?
2) If helpers are not used for bunching or stretching, why do u think the helper on the end was notched up high while the freight cars had heavy braking?
 

papio

Active Member
Could it have been notched up dynamic braking you were noticing vs notched up throttle?
 

RCH

Been Nothin' Since Frisco
Yes, this is called "independent mode" ("putting the fence up") where the trailing consist(s) are controlled separately from the head end. Some territories have mandatory independent zones, milepost limits where the head end and DP consists must be controlled independently to limit in-train forces. I prefer to operate with the DP consist in independent mode all the time so I can better control the train. The only time I'll marry up the head end with the DP ("take the fence down") is when I need to get the DP caught up to the head end throttle setting, such transitioning out of dynamic at the beginning of a long climb or after the rear has come over the crest on a long descent. Once the DP is where I want it, I put the fence back up. Some other engineers I know don't like to run the head end and the DP separate any time and only do it to comply with the mandatory independent zones.

As far as the scenario you describe, there's no telling what the engineer was dealing with in terms of the train and the territory. It's possible to stretch brake the train, where air is used but throttle is applied. This can be an effective way to control the train on undulating territory. If the head end is not equipped with dynamics, they are inadequate or they are cut out, it would be more likely the engineer would use stretch braking to control the train. Without being qualified on the territory you observed this train on, it would be difficult for me to judge what another engineer was doing.
 

Eng8492

New Member
Yes, this is called "independent mode" ("putting the fence up") where the trailing consist(s) are controlled separately from the head end. Some territories have mandatory independent zones, milepost limits where the head end and DP consists must be controlled independently to limit in-train forces. I prefer to operate with the DP consist in independent mode all the time so I can better control the train. The only time I'll marry up the head end with the DP ("take the fence down") is when I need to get the DP caught up to the head end throttle setting, such transitioning out of dynamic at the beginning of a long climb or after the rear has come over the crest on a long descent. Once the DP is where I want it, I put the fence back up. Some other engineers I know don't like to run the head end and the DP separate any time and only do it to comply with the mandatory independent zones.

As far as the scenario you describe, there's no telling what the engineer was dealing with in terms of the train and the territory. It's possible to stretch brake the train, where air is used but throttle is applied. This can be an effective way to control the train on undulating territory. If the head end is not equipped with dynamics, they are inadequate or they are cut out, it would be more likely the engineer would use stretch braking to control the train. Without being qualified on the territory you observed this train on, it would be difficult for me to judge what another engineer was doing.

Thanks for the authoritative info!

It was confusing because there was a curve.

I was pretty sure I heard some brakes here:

http://youtu.be/chKHmRV7RtA?t=4m52s

And more certain that the brakes were applied here:
http://youtu.be/chKHmRV7RtA?t=5m20s

The sound Im listening to is not the higher frequency wheel skidding around the curve, but the lower frequency hine.

And the helpers went by here-- when u see the video let alone hear them you see why they were not in dynamic.


http://youtu.be/chKHmRV7RtA?t=6m40s


This is the east end of the valley that has Seligman, AZ in it. After the train passes there is a 2 miles of flat and then 1.8pct down grade over 3-4 miles
 




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