Thursday, 11 July 2019

XW/XWA Wheat Wagon Assembly Tips

Parts List

  • Couplers - Kadee #148 or #158 (see below)
  • Kadee #262 coupler boxes (supplied)
  • Fixing screws - 2-56 x 6.35 mm (¼") long, 4 required
  • Brass wire - 0.4 mm, 0.6 mm. 1.0 mm
  • Wheels - 12 mm disc with 26 mm axles, 4 wheelsets required
  • WMC/WMD Bogies including brass bearings, available from Marbelup Models
  • Paint and decals

Removing Support Structures

Carefully remove the support structure from the wagon.  It is suggested to use a sharp knife to cut the supports away from visible areas.  Take particular care around the brake wheels, and the door operating mechanism.  Note that the brake wheels have guards around them to protect them during production and shipping.

Once the majority of the support structure has been removed, carefully go over the wagon and cut away the small supports which typically extend from one part to another including, for example, inside the coupler housing.  An Exacto type hobby knife with a sharp pointed blade (Exacto #11 or similar) is quite useful for getting into the nooks and crannies.  

Go over the model and smooth off any remnants of the fine supports, especially in the visible areas.  A sanding stick or small file can be useful for this.

There are two temporary supports for the door operating mechanism which are intended to be removed.  If desired, these can be left in place until the majority of the assembly has been done.

Supports for Door Mechanism - to be Removed.

Bogie and Coupler Mounting Holes

The mounting holes for the couplers and bogies have been printed at 1.8 mm diameter to suit 2-56 screws.  

Due to the difficulty of tapping blind holes, the 3D print includes vertical grooves in the sides of the holes to help the screws cut their own threads, so tapping the holes is not required nor recommended.  If the screw does not cut its own thread easily, the hole may require cleaning out with a 1.8 mm drill bit, but take care not to drill right through.

The maximum depth for the coupler mounting holes is 7.25 mm.  Using a screw which is too long will damage the top surface of the model, so check the screw length and trim if necessary.

Note: An economical source of 2-56 screws in various lengths is Little Bird Electronics.


The XW is designed for Kadee "whisker" couplers using Kadee #262 draft gear boxes. Two options are available, depending on user preference for correct S scale coupler height or the commonly-used HO standard coupler height.

Both options use Kadee #148 or #158 couplers.

For HO standard coupler height, the coupler mounts low down on the end sill.  This is the default option. When assembled, the centre of the coupler should be 9.9 mm above rail height, which can be verified with a Kadee #206 HO coupler height gauge.

For correct S scale coupler height, remove the sections of the model as per the picture below, to provide a higher mounting platform.  If desired, the surplus "frame" below the couple box can also be trimmed.  When assembled, the centre of the coupler should be 12.2 mm above rail height.  The coupler height can be checked using a Kadee #206 HO coupler height gauge with a piece of 1 mm thick styrene sheet placed between the rails and the coupler height gauge.

Modifications for correct S Scale Coupler Height
The draft gear boxes supplied with the #148 or #142 couplers do not fit as they have a different mounting hole position.  The #262 draft gear boxes, which are available separately, are narrower and have been used because they allow details such as the brake hoses to be positioned close to the scale distance from the wagon centre line.  Also, the #262 draft gear boxes are easier to use as the lid snaps into position.

Wire Details

There are a few details to be added from brass wire.  The following sequence is suggested:

Door Mechanism

Door Mechanism Wire Details (viewed from underneath)

Secure all the wire pieces in position with superglue.

Corner Handrails

The corner handrails are simply straight wire, glued into the vertical groove in the 3D-printed support bracket.

Corner Handrails - 2 required

Roof Details

Roof details including roof hatches (4), roofwalk supports (5) and hatch bumper (8) are supplied on a separate sprue.  If desired, the curved portions of the upper body can be smoothed (by scraping or filling and sanding) to remove the stepping due to the 3D-printing process.  This should be done before gluing the roof details in place.

An alternate version of the model is available in which only the roof hatches are printed separately.  For this version, the roofwalk supports and hatch bumpers are printed as part of the body.  This simplifies assembly but some stepping will be apparent on the top of the body, as it is impractical to smooth the curved portions with the small details present.

Roof Details.  Note correct orientation for parts.

Etched Roofwalk and Steps

Folding Corner Steps
Folding Roofwalk and Ladders.  Check orientation before folding!

Detail of Roofwalk Folding
Ladder Attachment Point

Work Stand

A 3D-printed work stand is available which supports the completed wagon upside-down, without damage to the roofwalk components, for use when fitting bogies and couplers.


If required, additional weight can be added by gluing lead shot or small pieces of sheet lead in the cavities at the ends of the hopper.

Cavities provided for adding weight (both ends).


Either enamel or acrylic hobby paints can be used to paint the finished model.  The sample model was airbrushed with Model Master enamel "Gelb RLM 04" (yellow) over Model Master white primer.