Conversion Information

USA TRAINS SD-40-2 DIESEL LOCOMOTIVE

Due to the length of this locomotive USA Trains recommends a minimum of 8 foot diameter (4 foot radius) curves. The distance between the pivot point of the truck and the end of the locomotive causes the coupler to swing out quite far on curves. The locomotive will negotiate 8 foot diameter curves pulling or pushing cars with the couplers in the "coupled" position, however, when the couplers are in the "delayed" position you may need a 5 foot radius curve for most cars.

#831 or #837 G Scale
#1831 or #1837 #1 scale.

   Using the #831 coupler is the simplest way but the coupler will protrude excessively. Invert the locomotive and place it in a padded cradle or on a padded surface. Remove the original coupler and trim  3/8" (.375") off the swivel arm (see illustration). Assemble the #831 coupler and mount it to the original screw hole with a 4-40 screw. The snow plow will need to be trimmed to allow for proper coupler swing.

   The #837 coupler will be a very close coupling and certainly look more prototypical. Remove the original coupler and trim off 5/8" (.625") of the swivel arm just in front of the screw hole (see illustration). Place the unassembled #837 draft gear box (without the lid) on the swivel mount where the two lips at the back of the box hook over the back of the mount. Check if the front hole in the box lines up with the screw hole in the arm, test fit a 4-40 x 1/2" screw. If the holes do not line up file the inside of the lips of the box until the holes line up.

 Assemble the #837 coupler without the lid, hold the assembly together and carefully place it onto the swivel mount. It may be easier if the locomotive is on its side. Secure it with a 4-40 x 1/2 " screw. Check the coupler for the correct height, function, and clearance.

   If you choose to use the snow plows you will have to trim a large amount allowing the coupler to swing fully in both directions. Also, a little may need to be trimmed for the opposing coupler to clear during switching and negotiating tight curves and turnouts.