Sunday, 11 September 2016

AQNY AZKY Assembly Tips

Parts List (for HO scale model)

  • Bogies: e.g. Kato 31-602 Barber S-2 Roller Bearing Bogies with 840 mm (33") wheels. 
  • Couplers: Kadee #148 or #158
  • Coupler boxes: Kadee #252 (supplied)
  • Air Brake Hoses, e.g. Detail Associates #6206 or Kadee #438.
  • Brake wheel e.g. Kadee #2025 or similar
  • Brass wire: 0.3 mm and 0.4 mm for handrails, and brake piping
  • Fixing screws: (see below)
  • Glue, paint, decals
  • The AQZY (ammonia tank wagon) requires a tank from a Frateschi chemical tank car.  These cars are available from some Perth hobby shops or online.  The Frateschi tank is slightly smaller than scale size but is a pretty good representation of the prototype tank.
Marbelup Models has limited stocks of the Kato bogies for sale.

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 and delicate parts.  Take particular care around the bottom of the steps, and the triangular bracing inside the centre portion of the wagon.

The following image highlights the more delicate parts, some of which are only visible once the outer layers of supports have been cut away.

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, on the end ribs and bogies bolsters.  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 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 3.3 mm.  The bogie fixing screws may need trimming to avoid damaging the floor of the wagon.

The wagon includes projections from the bolsters, to match the height of the Kato bogies, and provide "3-point suspension" to minimise side-to-side rocking of the wagon.  If fitting other types of bogies, these projections may need to be modified or removed.

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 steel 2-56 screws in various lengths is Little Bird Electronics.  


The suggested bogies are Kato 31-602.  These are pretty much "exact", differing only in having 2 springs visible at the bolster ends rather than 3. Note that the Kato bogies have the correct size wheels 840 mm (33") which are smaller than those fitted to most other Westrail standard gauge wagons.

Note that the depth of the blind holes for the bogies is 4.3 mm.  The fixing screws may need trimming to avoid damaging the floor of the wagon.  Do not drill the bogie mounting holes right through, as they will be visible on the finished model.

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


Because of the thin floor section, the model has been designed so the coupler and draft gear box slide into a recess in the end sill.  Make sure that any remnants of support structure from the 3D printing process have been cleaned up from inside the coupler mounting recess.

You will need to remove the cylindrical projection from the top of the Kadee #252 draft gear boxes - highlighted in red in the diagram below.

The draft gear box will probably be a snug fit inside the mounting recess.  A hole has been provided for a 2-56 fixing screw to prevent the coupler from being pulled out.  Note that the maximum length of the screw is 3.9 mm, so it is likely the screw will have to be cut to length.  Provided a metal screw is first used to create a thread in the provided hole, a nylon screw (e.g. Kadee #256) can be used for the permanent fixing.  A nylon screw is much easier to cut to the desired length.

Kadee nylon 2-56 screws are available from good hobby shops.

Brake Piping

The brake piping can be formed from 0.3 and 0.4 mm brass wire.  There are long, angled pipes at each end, and short 90 degree pipes connecting to the brake valve/cylinder assembly.  The main pipes running along the inside of the wagon frame are printed in place.

The diagram below shows the approximate dimensions for forming the brake piping.

The shorter pipe to the brake cylinder is 0.4 mm as is the long pipe at the same end.  The other 2 pipes should be 0.3 mm.

Small starter holes have been provided for attachment of the brake piping.  These should be opened out with a small drill bit or broach.  (Sets of tapered broaches are available from good hobby shops.)


The wagon has short handrails at each corner, and an L-shaped handrail attached to the brake wheel supports.  These can be formed from 0.4 mm brass wire.  Small starter holes have been provided to locate the handrails, which should be drilled out, e.g. with a 0.45 mm drill bit in a pin vice.

The holes for the horizontal four handrails are 4.3 mm apart (centre to centre).  These handrails should be bent with an inside radius of approx. 0.6 mm (e.g. using a 1.2 mm drill bit).  The total height of the handrails should be approx 2.5 mm and, when installed, the top of the handrail should be 1 mm above the wagon deck.

The L-shaped handrail should also be bent with a inside radius of approx. 0.6 mm.  The horizontal leg should be approx. 6.5 mm long, and the vertical leg approx. 7.5 mm long.

All handrails should be fixed into position with superglue.

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.  A suggested drill size is 0.65 mm.

An alternate (cheaper) brake hose is the Kadee #438.  These have a rectangular mounting pin which requires the holes to be drilled out to approx. 0.8 mm.  It is suggested to drill the holes out in a number of stages, using successively larger drill bits, to avoid over-stressing the brackets.

Uncoupling Levers

Notched brackets have been provided at both ends of the wagon for the uncoupling levers, together with a longitudinal hole just below the coupler.  The uncoupling lever can be shaped from 0.4 mm brass wire.   The diagram below shows the approximate shape to aim for, but feel free to adjust the measurements to suit your model.

After positioning the uncoupling lever, check that the coupler can swing freely and is not obstructed, prior to gluing it into position.

Handbrake Wheel

A 0.5 mm spigot has been provided on the handbrake assembly, to which the wheel can be glued.  If necessary, open out the central hole in the handbrake wheel with a 0.6 or 0.7 mm drill bit to fit over the spigot.


With the suggested Kato bogies, the completed AQNY weighs approx. 24 grams.  For this length wagon, the NMRA recommended weight is 125 grams, although some modellers feel that the NMRA weight recommendations are excessive.  A total weight of somewhere between 100 and 115 grams is probably about right.

Due to the "skeletal" design of the wagon, there is not much scope to add weight where it can't be easily seen.  Weight can potentially be added to the container "load".  If using the Marbelup Models BIS sulphur containers, provision has been made to fix weights inside the containers.  It is suggested that any added weight be concentrated over the bogie ends of the containers, to avoid causing the wagon to sag in the long term.


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 colour "Gelb RLM 04".  (Gelb is German for yellow!)  A white undercoat (e.g. Testors Model Master 2748 enamel) is recommended to enhance the yellow colour.