[VirginianRailwayEnthusiasts] TAN Jackshaft Electric Locmotives

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The large three-phase, 25 cycle, wound rotor induction motors used on the N&W LC-1 and LC-2 and VGN EL-3A electric locomotives were rugged devices (no commutators).  Because of the difficulty synchronizing the starting of the lead and pusher locomotives in the twisting hills and hollows of the Pocahontas Division in the days before train radios, the LC-1 motors were designed to permit full load current to be applied for five minutes without movement (Elkhorn Grade Electrification, N&W Ry., Roanoke, Va., September 1915, p. 11)!  Because of the similarity, the VGN EL-3A's may have had this characteristic also.

An N&W memo "Electric Operation of Long Freight Trains" describes how heavy trains with an electric loco on each end were started, "In starting it is customary for the lead locomotive to drop back against the train bunching the slack against the pusher locomotive.  As soon as this bunching up of slack is felt at the pusher locomotive, the Engineman in the pusher begins to apply power, steadily increasing it until he has maximum accelerating current on the motors.  Concurrently, the Engineman on the lead locomotive, to whom this starting impulse is readily discernible, reverses his locomotive and commences to pull.  The lead locomotive thus takes up the slack and picks up the train, car by car, until the load has been sufficiently balanced between the lead and the pusher locomotive to accomplish an easy moving off of the train."

The above description makes it sound easy, and it might apply to starting a train on an easy grade, but on a heavy grade it might not work this well.  In that situation the capacity of the motors to stand under full current for five minutes until the train started moving might be vital.

Gordon Hamilton


  ----- Original Message ----- 
  From: Peter Groom 
  To: VirginianRailwayEnthusiasts at yahoogroups.com 
  Sent: Friday, June 06, 2008 5:08 PM
  Subject: [VirginianRailwayEnthusiasts] TAN Jackshaft Electric Locmotives


  I certainly had the DD1s in mind as an exception, but I think that DC jackshaft locos were otherwise pretty rare except perhaps in the earliest days of "steam road" electrification.  IIRC, the DD1s resulted from PRR's unhappiness with the low center of gravity  of "trucked" locos with axle-hung motors - it was hard on the track.  (Staufer, Pennsy Power)  The DD1s were, of course, very successful. 



  Pete Groom

  On Jun 6, 2008, at 4:46 AM, davep at quik.com wrote:

  . . . 
  Jackshafts were used because RR Lok designers were
  'comfortable' with them, and uncomfortable with gears:
  fearing mechanical losses
  and
  damage from mechanical shocks in RR environment.

  Jackshafts/siderods allowed motors mounted high,
  for easy maintenance, and to keep motors away
  from dirt. As an instance of DC/LV siderod
  design, one may ponder PRR's entire fleet of DD1
  electrics.

  best
  dwp






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