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Re: Milwaukee Road SD9’s
Author: SP5103
Date: 03-19-2020 - 22:24

The original intent of freight service 6 axle designs whether 4 or 6 motored was to allow them to have a lower axle load permitting them to operate on lighter rail. SP's SD-7s and most of their 6 axle Baldwins were light on their feet, around 150-160 tons as I recall though 5200-5202 were like 125 tons (typical of a four axle road unit).

Railroads soon realised by ballasting newer orders to 180+ tons, the six motors and extra weight allowed them to far outpull a similar 4 axle at low speeds without frying the traction motors.

I don't know about MILW, but SP kept the light SD9s and GE 70 tons working the light rail/bridge branches until the lines were upgraded, sold or abandoned. Other railroads used SW1 single or mued (MILW) and other smaller switchers around 100 tons.

Anyone know whether the MILW SD9s were light or heavy?

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Subject Written By Date/Time (PST)
  Milwaukee Road SD9’s HUTCH 7.62 03-19-2020 - 21:54
  Re: Milwaukee Road SD9’s OPRRMS 03-19-2020 - 22:13
  Re: Milwaukee Road SD9’s SP5103 03-19-2020 - 22:24
  Re: Milwaukee Road SD9’s Jack S. 03-20-2020 - 07:51
  Re: Milwaukee Road SD9’s SP5103 03-20-2020 - 08:46


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