Re: Helper Locomotives

Msg # 994 of 1000 on RelayNet Trains/models/railways etc
To: ALL, From: JAMES ROBINSON Time: Sunday, 8-12-7, 5:49
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bladeslinger@earthlink.net wrote:

> mojaveg@mojaveg.lsan.mdsg-pacwest.com (Everett M. Greene) wrote:
>
>> Seems like a good description in an idealized situation.  Since
>> the rail lines are almost never completely consistent grades,
>> the neutral point will fluctuate as the grade varies.  I've seen
>> descriptions of operations where the front units will be braking
>> while the more rearward units will still be pushing/pulling at
>> full bore as a long train goes over a hill.  So there is some
>> art to getting the power balance correct at any moment.
>
> You do not want the helpers pushing while the headend is braking, as
> this could lead to jack-knifing.

It is sometimes done for short periods as trains crest grades.  It is a
slack control measure, where the head end locomotives begin to gently
collect the slack in the train in preparation for descending, while the
trailing locomotives keep moving the rear of the train up the hill.

The result, if done correctly, is less severe slack action in the train.
Of course, many engineers aren't very good at it, and can make the slack
action worse.  Some crews don't try to be fancy, and just run both sets of
locomotives in the same power or brake positions to simplify things.

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