California's Railroad to the U.S. 1861 - 1996

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Southern Pacific GP20

P2K HO model by Ken Perry

P2K by Ken Perry

see text below

P2K by Ken Whitehead

Southern Pacific GP20 Data: from the SP Mailing List courtesy and © Rob Sarberenyi, (and used here with permission).

I've been studying EMD GP20's in anticipation of P2k's HO scale model due in July. Looking through the information and photographs, I offer the following data for Espee and SSW modelers interested in these units regarding their as-built configuration. Interestingly enough Extra 2200 South doesn't specify phase designations for GP20's, despite noticeable spotting changes and a significant difference in the frame/skirt treatment on GP20's built from January to April 1962, the last of this model built prior to start of GP30 production. Phase designations listed below are my own applications.

P2k's GP20 represents Phase 1a units (judging from the photo on their Web site), and by changing the radiator fans, Phase 1b's can be modeled. The only Phase II units built by EMD comprise SP #7200-7233 (re #4050-4083 in the 1965 system renumbering).

GP20 Phase 1a

SSW #800-809 (re #4030-4039) blt. 12/60 and 1/61:

  • Flared-top 48" radiator fans
  • Pan-top 48" dynamic brake fan
  • Side sill perforations on frame

SP #7234-7237 (re# 4084-4087, ex-EMD demos #5625-5628) blt. 8/60:

  • Flared-top 48" radiator fans
  • Pan-top 48" dynamic brake fan
  • Winterization hatch over 36" radiator fan
  • Side sill perforations on frame

GP20 Phase 1b

SSW #810-819 (re #4040-4049) blt. 12/61 and 1/62:

  • Pan-top 48" radiator fans
  • Pan-top 48" dynamic brake fan
  • Side sill perforations on frame

GP20 Phase II

SP #7200-7234 (re #4050-4083) blt. 1-4/62:

  • Pan-top 48" radiator fans
  • Pan-top 48" on dynamic brake fan
  • No frame perforations, thin frame like GP30
  • Last GP20's blt.

General Notes:

  • All SP/SSW GP20's have 36" cap-top fan ahead of the rear 48" radiator fan
  • Louver placement along the long hood is the same regardless of phase
  • All SP and SSW units equipped with 2350 gal. tanks, as were all GP20's built except Great Northern.
  • GN's GP20's constructed with GP9 Phase III style fuel tank/air reservoir and frame/skirt treatment.

Phase II GP20 eliminated the distinctive frame perforations, introducing the thin frame that would follow with the later GP30's (starting in 1962) and GP35s (1964). SP received the only Phase II GP20's built. This will require some work for modelers wishing to replicate these Espee units using P2k's model.

  • Extra 2200 South, Issue 2, February 1968, 'Model Roster of EMD GP20s'
  • Extra 2200 South, Issue 31 Oct-Nov-Dec 1971, 'Early Geeps, GP7-GP9-GP18-GP20' pp 7-14
  • Mainline Modeler, January 1986, 'The EMD GP20' pp 55-62
  • Southern Pacific Motive Power Annuals and Reviews, all years issued from 1966-'67 thru 1995

Mainline Modeler article contains near broadside photos of EMD demos 5627 (engineer's side) and 5628 (fireman's side). These were two of the four demos Espee purchased, becoming #7235 & 7236 (#4085 & 4086 in 1965). I found photographic evidence the winterization hatch on ex-demo units was still in place into the 1980's. Also in the MM article is a b&w builders photo of SSW 802, showing the handrails and stanchions are completely yellow on Cotton Belt's GP20's. Below that is a photo of SP 7206, depicting the Phase II frame difference. The article also includes excellent HO scale plans.

The only plastic HO scale GP20 offered until P2k's has been Tyco/Mantua's 1960's tooling, which left a great deal to be desired. Despite only 260 units built, GP20's were landmark diesels insofar as they heralded the turbocharged age for EMD locomotives (the SD24 notwithstanding), and helped usher in the second generation.

© Rob Sarberenyi

Modeling choices at the moment are:

  • For N Scale:
    • LifeLike
  • For S Scale:
    • American Flyer GP - that may be converted to a GP20
    • American Models perhaps a GP9 - that may be converted to a GP20
  • For O Scale:
    • Red Caboose made a GP9 - that may be converted to a GP20.
    • Lionel in 1994 released a GP20 in Blood Nose paint.

Model References:

  • Railroad Model Craftsman Dec. '69 Page 53 - Has a set of Plans.
  • Mainline Modeler Jan, '86. Page 55 - SP/SSW History, Plans, Roster, and photo's
  • Diesel Locomotive Cyc #2 Page 128 - GP20 Plans, Proto photo SP7234 ex demo GP20.

Lionel information kindly supplied by Britt Johnson

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