WMC/WMD 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 brake hoses and end steps.

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.  For some parts around the brake cylinders where even a fine knife blade won't reach, a piece of wire (e.g. 0.8 mm spring steel wire) can be used to push against the support attachments and break them off.

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, but it is preferable to NOT drill through the floor to avoid the screws being visible on the finished model.

Due to the difficulty of tapping the 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.

Bogies

The bogie mounting points are designed to be 10 mm above rail level.  Depending on the bogies used and the height of their bolsters, it may be necessary to add washers or similar so that the coupler mounting surface is 11.5 mm above rail level.

Marbelup Models WMC/WMD Bogie

Marbelup Models has 3D-printed bogies of the correct design for the WMC/WMD available for sale.  Similar bogies, although of slightly different shape, are available from Black Diamond Models in Queensland.  The Black Diamond bogies are cast in white metal and are supplied fully assembled with wheels.

Assembly of 3D-Printed Bogies

The Marbelup Models WMC/WMD bogies are printed in two identical halves.  A set contains four pieces to make one pair of bogies.  As with other 3D printed parts, the first step is to removed the supports structure and clean up the small supports in the holes in the bogie sideframes, around the springs, etc.  Take care around the brake shoes to avoid breaking them.

The bolster section of each bogie half contains two holes intended for M1.4 screws (which are supplied with the bogies).  The larger hole nearest the narrow end of the bolster is a "clearance" hole and should be cleaned out with a 1.4 mm drill.  The smaller hole, nearest the bogie sideframe, should cleaned out with a 1.1 mm drill and tapped with an M1.4 tap.  (Drills and taps are available from North Yard in New Zealand.  The M1.4 tap is part No. 3014.  Refer to Page 5 of the North Yard Catalogue.)

An alternative to M1.4 screws is to use 1.5 mm x 6 mm self tapping screws, which are available from DCC Concepts - Part No. DCS-PH156.  If using self tapping screws, the smaller holes should be drilled out to 1.1 or 1.2 mm.  If the screws seem tight with 1.1 mm holes, try 1.2 mm, especially with bogies printed in Standard Resin (clear yellow rather than grey), which is somewhat less flexible.  The clearance holes should be drilled to 1.5 mm.

The bogie sideframes contain holes for fitting brass pinpoint bearings (available from Railwest Models).  These holes should be cleaned out with a 2 mm drill bit, after which the bearings should press fit into place.  The bogie is designed for 12 mm wheels with 26 mm axles.

When assembling the two halves, it may be necessary to trim the narrow end of the bolster by approx. 0.25 mm to get good alignment of the fixing holes and centre pivot hole.  (Later production will be made slightly shorter.)  After assembly, clean out the centre pivot hole with a 2.2 mm drill bit to suit 2-56 mounting screws.  (2.2 mm provides adequate clearance without excessive slop.)

Couplers

The WMC/WMD 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 WMC/WMD is also available with correct scale coupler height for WAGR/Westrail narrow gauge, in which case #252 draft gear boxes are used.

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.  The 2-56 6.35 mm (1/4") long screws commonly used for couplers are slightly too long for the blind holes.  Options are to shorten the screws by 0.5 to 1 mm, or to add a flat washer between the head of the screw and the coupler.  Railwest Models sells suitable washers with a 2.2 mm hole diameter.  If using scale coupler height, the height to the coupler mounting surface should be 13.8 mm.

Stiffening Rods

The WMC/WMD model includes provision for two metal rods to be inserted within the underframe structure to provide stiffness and guard against possible future warping of the plastic material over time.  Each of the transverse frame members includes two holes approx. 2.2 mm diameter, as part of the 3D print.

Location of stiffening rods

On the end sill, the hole for the stiffening rod is covered over by a 0.5 mm layer of plastic, opposite the handbrake assembly, as pictured below.  This can easily be drilled through for installation of the rod.  There is a corresponding hole on the diagonally opposite corner of the wagon.

Drill location for stiffening rod

The rods should be a maximum of 2 mm diameter and 140 mm long.  They can be of any strong metal, e.g. steel or brass.  One source of steel rod is threaded push-rods sold for radio controlled models by manufacturers such as Du-Bro, and available from many hobby shops.  These have a threaded section at one end, but the remainder of the rod is plain, about 1.85 mm diameter. Once the rod has been glued into position, the hole in the end sill can be filled with modelling putty and lightly sanded to restore the flat surface prior to painting.

Handrails

Small starter holes have been provided to locate the various handrails.

The WMC has just two handrails on opposite corners.  These can be formed from 0.6 mm brass wire.  Viewed from above, the handrail is an L-shape, with the horizontal portions about 6.25 mm long.  The height from the floor to the top of the handrail should be about 9.5 mm.  The vertical post nearest the coupler can be cut about 2 mm over-length to provide a secure (glued) fixing into the floor.  The vertical post near the side of the wagon should only be over-length by just 0.5 mm so the end of the wire is not visible from the side.

In addition, the WMD has 3 handrails on each end of the hungry boards.  Thinner brass wire, e.g. 0.4 mm should be used for these.  The hole centres for each handrail are 4.75 mm.  The WMD also has wire handrails/steps across the tops of the "chutes" at each end of the hopper.  The 3D print includes small notches for locating these, and the length of the wire should be 9.5 mm (8 required).

Note that the position of handrails and other details varies between different members of the WMD class.  The model depicts the most common arrangement, based on photos of various prototype wagons.

Door Lock Shafts

As part of the locking mechanism for the bottom discharge doors, there are two shafts which have to added using brass wire, either 0.5 or 0.6 mm.  The length of each piece of wire is 40 mm, although it is probably easier to feed a longer length of wire through the holes provided, then trim it to length with fine wire cutters after it has been glued into place.

Location of Door Lock Shafts

Brake Levers and Chains

The handbrake ratchet assembly on the end of the wagon includes a vertical groove to house a 10 mm length of 0.4 mm brass wire, to represent the handbrake lever.  Superglue is recommended for attachment of the wire.

A distinctive detail of the WMC/WMD are the chains running across the floor which connect the handbrake mechanisms with the brake linkage underneath the vacuum cylinders.  North Yard (NZ) make a suitable fine chain which is available from Railwest Models.

Threading the fine chain through the three guides at each end is a bit tricky.  It helps to use a piece of fine but soft wire as a "needle".  The 0.25 mm diameter inner conductor from "wire-wrap" wire used for electronics is suitable.  (If you ask nicely, you might be given a piece with your WMC/WMD!)  Once threaded through the guides, one end should be glued into the small notch provided for the purpose in the horizontal "angle iron" underneath the vacuum cylinder.  Once that end is fixed, the other end should be threaded through the support bracket for the handbrake which has a tapered keyhole-shaped hole.  When gently tensioned, the free end of the chain can be glued into the tapered hole to secure it, and the excess chain trimmed from underneath with fine wire cutters.

Weighting

With the Black Diamond (metal) bogies, the completed wagon weighs around 72 grams.  The "desirable" weight for a wagon of that length (140 mm) is around 95 grams to ensure optimum operation including operation of Kadee couplers.  (See the Sn3½ blog for more information.)

If requred, additional weight can be added by gluing lead shot or small pieces of sheet lead between the various frame members of the underframe, e.g. either side of the hopper doors, where it would not be seen in normal operation.

Painting

Either enamel or acrylic hobby paints can be used to paint the finished model.  The model pictured has been painted with Revell Hobby Enamel.

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WSH/XM Ballast Wagon Instructions

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 steps and the handwheels underneath the side of the wagon.  Note that the steps 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 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, 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.  

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

Bogies

HO Scale - 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.  Note that the depth of the blind holes is 3.4 mm for the HO model.  If using Kadee bogies, the supplied screws may need trimming to avoid damaging the floor of the wagon.

Sn3½ Scale - Marbelup Models makes specific bogies for the XM wagon, representing the prototype's standard gauge bogies with narrow gauge wheelsets.  The wheels should be larger than is normal for narrow gauge wagons.  Suitable wheels (14 mm diameter, 26 mm axles) are available from North Yard (NZ) and DCC Concepts.  Please note the gauge of the DCC Concepts wheels is slightly greater compared to  the NMRA RP25 standard, which can cause problems with the wheels "picking" point frogs.  It is suggested the DCC Concepts wheels be tested with your trackwork before purchasing in quantity.

The method of assembly for the bogies is the same as for the WMC hopper wagons except that the holes for the fixing screws are inclined at 10° above the horizontal so that the axles do not get in the way of the screwdriver.

Couplers

The WMC/WMD is designed for Kadee "whisker" couplers.  Either the #158 (scale size) or #148 (normal size) couplers can be used, with #262 draft gear boxes, although the normal size couplers are more appropriate.  Couplers are also available from Kadee in bulk packs without draft gear boxes.

The draft gear boxes supplied with the #148 or #158 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 the scale distance from the wagon centre line.  Also, the #262 draft gear boxes are easier to use as the lid snaps into position.

For the HO model, the coupler fixing screws should be trimmed to about 3.8 mm so the top of screw is flush with the deck of the wagon.  One option is to use a metal 2-56 screw to form the thread in the plastic material, then use a Kadee Nylon 2-56 screw for the final installation, which is easier to cut to length.

Since mid 2017, the design for the XM has been modified so that the couplers are at the correct height for WAGR standard gauge, i.e. 13.75 mm (measured to the centre of the coupler).  Note that the corresponding height from rail level to the top of coupler mounting surface should be 15.4 mm.

If desired to fit couplers at the Kadee standard height for HO (9.9 mm), the couplers should be shimmed down by approx. 3.75 mm.  An alternative, is to use a Kadee "overset" coupler which reduces the height by approx. 1.25 mm, although a shim will still be required to match the HO coupler height.

Note that the prototype XM wagons retained their standard gauge coupler height.  When used with narrow gauge "chopper couplings", the wagons at the end of a rake were fitted with "gooseneck" couplers to reduce the coupler height.

Wire Details

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

Discharge Doors Mechanism

Note that the eight 4-spoke handwheels have been printed as part of the model.  In addition, some spares have been printed at the end of each of the discharge hoppers.  Carefully cut away the spare handwheels using a sharp knife, and retain in case of any breakages.  Smooth off any remnants of the attachment points on the ends of the hoppers.

The longitudinal shafts are shown in blue on the diagram above.  Suggested sizes are as follows:

• HO, Outer Shafts: 0.6 mm wire, 25.75 mm long (4 required)
• HO, Inner Shafts: 0.6 mm wire, 27.5 mm long (4 required)
• Sn3½, Outer Shafts: 0.8 mm wire, 35 mm long (4 required)
• Sn3½, Inner Shafts: 0.8 mm wire, 37.5 mm long (4 required)

The transverse shafts are shown in red on the diagram above.  Suggested sizes are as follows:

• HO: 0.4 mm wire, 12.75 mm long (4 required)
• Sn3½: 0.5 mm wire, 16.5 mm long (4 required)

Before installing the various shafts, clean out the holes in 3D-printed material with a pin vice and drill bit fractionally larger than the wire size, e.g. 0.05 - 0.1 mm larger.  Drill carefully to avoid breaking any of the parts from the model.  For the longitudinal shafts, another option for cleaning out the holes is to cut a spare piece of wire, say about 100 mm long, at an angle with sidecutters, so as to leave a slightly ragged edge.  By holding this wire in a pin vice, it can be used as a crude drill to ream the three holes for each shaft.

Secure all the wire pieces in position with superglue.

Brake Rods

The are five brake rods to be formed from brass wire.  Suggested sizes are as follows:

HO Scale:

• Rod A - 0.4 mm wire, 24 mm long, bent 90° one end
• Rod B - 0.4 mm wire, 19.5 mm long, bent 90° one end
• Rod C - 0.4 mm wire, 11.75 mm long, bent 90° both ends *
• Rod D - 0.4 mm wire, 6.4 mm long, bent 90° one end
• Rod E - 0.4 mm wire, 36.5 mm long, bent 90° one end

S Scale:

• Rod A - 0.4 mm wire, 32.5 mm long, bent 90° one end
• Rod B - 0.4 mm wire, 26.5 mm long, bent 90° one end
• Rod C - 0.4 mm wire, 20 mm long, bent 90° both ends *
• Rod D - 0.4 mm wire, 9 mm long, bent 90° one end
• Rod E - 0.4 mm wire, 50 mm long, bent 90° one end

* Fixing hole for "chain" end of Rod C is marked by a dimple on the underside - drill through from underneath.

Secure all the wire pieces in position with superglue.

Brake Rods - Top View (Hopper hidden for clarity)

Vertical Handrails

Each of the vertical posts at the corners of the hopper has a vertical handrail, which can be formed from 0.4 mm brass wire.  The distance between the hole centres is 10.5 mm for HO, and 14.25 mm for S scale.

Corner Handrails

Small starter holes have been provided to locate the handrails near the handbrake at each end of the wagon..  The handrails can be formed from 0.4 mm brass wire.  The holes should be drilled out, e.g. with a 0.45 mm drill bit.

Viewed from above, the corner handrails are L-shaped, the longer leg of the "L" being parallel to the side of the wagon.

For HO, the horizontal legs of the "L" are 3 mm and 2.5 mm long.  The vertical legs of the handrail should be 5.5 mm long, including an allowance of  0.5 mm to be glued into the fixing holes.

For S scale, the horizontal legs of the "L" are 4.5 mm and 3.5 mm long.  The vertical legs of the handrail should be 7.5 mm long, including an allowance of  0.5 mm to be glued into the fixing holes.

Ratchet Handbrake Lever

A short length of 0.4 mm brass wire can be used to simulate the lever of the ratchet handbrake on each end of the wagon.  The length of the wire should be approx. 5.5 mm in HO and 7.5 mm in S scale.Glue the wire into the vertical groove in the handbrake assembly.  The bottom of the wire should be level with the bottom of the groove, with the remainder of the wire projecting upwards.

Uncoupling Levers

A spiggot with a vertical fixing hole has been provided underneath the wagon, next to the coupler, as well as a notched bracket towards the left side of the wagon, when view from the end.  The uncoupling lever can be shaped from 0.4 mm brass wire, with a 90 degree bend for attachment into the central fixing hole.   The diagrams below show the approximate shape to aim for, but feel free to adjust the measurements to suit your model.

After positioning the uncoupling levers, check that the coupler can swing freely and is not obstructed.  After fixing the uncoupling levers in place, it should still be possible to remove the coupler and draught gear box, e.g. for painting the wagon, by sliding it out towards the end of the wagon.

S Scale - Approximate Measurements

HO Scale - Approximate Measurements

Air Brake Hoses

Small brackets are provided next to the couplers on each end of the wagon for air brake hoses.  Cast plastic hoses in HO scale are available from Detail Associates, part number 6206.  In lieu of equivalent hose in S scale, the HO ones could be used also.  Carefully drill out the starter hole provided in the supporting bracket to suit the diameter of the "pipe" on the air hose.  A suggested drill size is 0.65 mm.

Cross Braces

The top of the hopper had small notches on the inside to accommodate 7 cross braces cut from 0.75 x 1 mm styrene strip.  The HO, the length should be 31 mm and, for S scale, 42 mm.  The braces should be pushed to the bottom of the notches so that the top of the braces is slightly below the top of the sides, as indicated by prototype photos.

Photo from Weston Langford collection showing cross braces.

Weighting

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

Painting

Either enamel or acrylic hobby paints can be used to paint the finished model.  

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