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

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Model Train Help EBook

Southern Pacific F7B-Unit SNAIL

Model Construction

© 2007 David Reed

The F7 B-unit is pretty straight forward. The side panels are just sheet steel welded together, so there are no seams. Using an X-acto chisel blade remove the seam joints on the shell. Cut off roof over hang on ends. The end door gets fitted with a new end door and buffer plate, #209 by Details West. Add this detail after all body work is done. Also add to the end Detail Associates MU hoses #1508. Fill in the middle windows, leaving the outer 2 in place. Please note that not all window placements are the same for each B-unit. #8211, for example had one window on one side, so photos are important. Leave the side doors as they are. Sand the body smooth and fill in any imperfections. There is a small hatch above the frame skirting that needs to stay also. Take note that the frame skirting may vary from unit to unit.

From the roof, remove the dynamic brake fan, steam generator and the molded on lift rings. Next we add new parts to the roof. Add new lift rings from Detail Associates #2206, add Detail Associates exhaust stacks #2401 to what is already there to extend the stacks. The last item to add to the roof is the steam generator set from Detail West #118. Place the steam generator in the same location as the molded on part. When that is completed, add the brass tubing and roof covers as on the snowplow.

Drill and mount Walthers dress-up kit #822 to the shell. It will take all ladder grabs, unless a photo shows other wise.

Paint and decaling is all that's left; the entire B-unit is painted Engine Black and the decals used are Micro-Scale #155 SP MofW set. That is straight forward and everybody has their own way of doing that. After the body is completed add the windows from the dress-up kit.

With body completed, all that is left is the truck side frames. With Athearns plastic side frames, you can change the journals, so they match your prototype. Photos will help, as each truck could be different. When you have completed the journal modifications add your brake cylinders and air lines and the truck side frames are complete. Your Snail is now ready to power your Rotary Snowplow.


  • Athearn
    • F7 B-unit Powered or Unpowered

  • Details West
    • #118 steam generator set
    • # 209 end door & buffer plate

  • Detail Associates
    • #1508 MU cables
    • #2206 lift rings
    • #2401 exhaust stacks
    • #2805 EMD blomberg square journals
    • #2806 EMD blomberg slope journals
    • #3102 fuel tank set

  • Walthers
    • #822 Dress-up Kit for F7s

  • Paint
    • Engine Black

  • Decals
    • Microscale #155 MOW set

Most Southern Pacific Motive Power Annuals/Reviews have at least one photo of a snail.


N Scale:

  • Bachmann
  • Kato
  • LifeLike

HO Scale:

  • Athearn
  • Bachmann
  • Highliner
  • Stewart

O Scale:

  • ?

F7B Snail Page

Model Rotary Snowplow Page

Rotary Snowplow Page

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This document © 2007. Richard.A.Percy