Wednesday, 29 April 2015

WOB Iron Ore Wagon Construction Tips

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 ladder and step.  Note that the ladder and step both have guards below them to protect them during production and shipping.  It is suggested to leave these guards in place until the majority of the finishing work on the wagon has been completed, to minimise the risk of damage during handling.

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, for example, around the brake cylinders and other detail items.  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, expecially in the visible areas.  A sanding stick or small file can be useful for this.

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.  Clear out the holes with a 1.8 mm drill in a pin vice.

Due to the difficulty of tapping the blind holes for the bogies, 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.  Note that the depth of the blind holes is 4.4 mm.  If using Kadee bogies, the supplied screws may need trimming to avoid damaging the floor of the wagon.

The holes for mounting the couplers are also blind, but should be drilled right through the floor with a 1.8 mm drill to obtain a strong fixing.  These holes should be tapped 2-56.  Note that one end of the wagon has two blind holes for couplers.  The one closest to the end of the wagon is for a Kadee coupler and the hole closest to the bogie fixing holes is for the rotary coupler option.  

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


The suggested bogies are Kadee #569 or #1569, the only difference being the width of the wheels.  Both Atlas and Athearn make similar bogies, but the advantage of the Kadee ones is that they add some weight to the wagon due to the use of a relatively heavy plastic material.


Option 1 - Kadees

The WOB is designed for Kadee "whisker" couplers.  Either the #158 (scale size) or #148 (normal size) couplers can be used, with #262 draft gear boxes.

The draft gear boxes supplied with the couplers do not fit as they have a different mounting hole position.  The #262 draft gear boxes are narrower and have been used because they allow details such as the brake hoses to be positioned the scale distance from the wagon centre line.  Also, the #262 draft gear boxes are easier to use as the lid snaps into position.

Note that the height from rail level to the coupler mounting surface should be 11.5 mm, the standard for Kadee couplers.

Option 2 - Glatzl (Sergent) Rotary Couplers

If desired, the wagons can be fitted with a rotary coupler at one end, as per the prototype, to facilitate unloading in a rotary car dumper (tippler).  Glatzl sell working rotary couplers and matching dummy couplers which are available from Sergent Engineering in the US.  The Glatzl couplers will couple with "scale" size Kadees but not with "standard" size Kadees.

Note that it is preferable to use Glatzl dummy couplers rather than a "scale" size Kadee for the "fixed" coupler as the relatively tight fight between the Glatzl rotary and dummy couplers results in better operation with a rotary car dumper.

Typical steps to fit a Glatzl rotary coupler are:

  1. Cut the rear portion off the Glatzl draft gear box leaving 16 mm of the draft gear box remaining.
  2. Drill a 2.3 mm diameter hole exactly in the centre of the circular mould mark in the coupler box.
  3. Fix the coupler to the end of the wagon opposite the ladder and handbrake wheel using a 2-56 screw.
To fit a Glatzl dummy coupler:
  1. Use a round needle file to slightly enlarge the hole in the shank of the dummy coupler so that it pivots easily in a Kadee #262 draft gear box.
  2. Cut away a small amount of plastic from the rear of the coupler knuckle to allow the coupler to fully swing from side to side in the Kadee #262 draft gear box.
  3. Assemble the couple in the #262 draft gear box and snap on the lid.  Fix the assembled coupler to the end of the wagon with the ladder and handbrake wheel using a 2-56 screw.


Small starter holes have been provided to locate the vertical handrail next to the handbrake wheel.  The handrail can be formed from 0.4 mm brass wire.  The length of the handrail, between hole centres, is 6.5 mm.  The holes should be drilled out, e.g. with a 0.45 mm drill bit.

Handbrake Wheel

Suitable handbrake wheels are available from a number of suppliers, including etched brass wheels from Model Etch.  Note that at least two styles of wheels have been used on the wagons.

If using etched brass brake wheels, one fixing option is to solder a length of brass wire (e.g. 0.4 mm diameter) to the centre of the brake wheel.  After filing or grinding any excess solder from the front of the wheel, the wire can be trimmed so it protrudes approx. 1.5 mm from the rear of the wheel.  Drill out the starter hole in the handbrake housing, e.g. 0.45 mm diameter, and glue the wire, and wheel, in place.

Air Brake Hoses

Small brackets are provided next to the couplers on each end of the wagon for air brake hoses.  Cast plastic hoses are available from Detail Associates, part number 6206.  Carefully drill out the starter hole provided in the supporting bracket to suit the diameter of the "pipe" on the air hose.


If required, additional weight can be added by gluing lead shot or small pieces of sheet lead between the various frame members of the underframe where it would not be seen in normal operation.


Either enamel or acrylic hobby paints can be used to paint the finished model.  The model pictured has been painted with Testors Model Master Enamel colourL "Signal Yellow".

Note that photos of virtually every WOB in various states of weathering are available at the Pilbara Railways web site.

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