Tinkering with tank wagons

Prior to the transfer of many liquid commodities to container tanks, there were a number of dedicated two-axle wagons for the transport of chemicals and compressed gasses, none of which are available off-the shelf in ‘N’ gauge. We take a look at some simple techniques for modelling tank wagons.

AMONG some of the most interesting Railfreight-era wagons to model are two-axle air braked wagons designed to carry chemical liquids, mineral slurries and gasses such as sulphuric acid, caustic soda liquor, carbon dioxide, propane and chlorine. China clay and calcium carbonate slurry traffic added interest to the scene when caustic soda liquor wagons were transferred to china clay traffic.

Tank wagons remain the least modelled type in ‘N’ gauge by manufacturers, despite the fact they would be popular additions to Railfreight-era themed layouts. It was not unusual for them to be worked in short block trains, mixed in trains of other wagons in singles, pairs or small blocks, or worked in short feeder trains of the Speedlink period.

With so little support from manufacturers beyond petroleum tank wagons, how can some variety be introduced to an ‘N’ gauge air-braked tank wagon collection?

There are a few options, from limited kit-building to extensively using two-axle underframes from ready to run wagons. Sometimes, the end result will be a representation whilst other projects will be more to scale. Mix and match is the order of the day to achieve a workable result. So, on to some tank wagon tinkering, in an effort to add more variety to the layout!

Off-the-shelf

Fortunately, many specialised tank wagons shared common construction features with the common two-axle ‘monobloc’ 46t TTA wagon, models of which are commercially available. A TTA/B wagon is produced by Peco, with its 15-foot wheelbase underframe being available as a modelling aid.

The underframe costs between £4.20 to £4.50 and is supplied with plastic wheels and a ballast weight.

An undecorated TTA/TTB kit with one-piece barrel is also available for £5.75. Both make an inexpensive starting point for experimenting with conversions, even though the model is basic. The underframe features the original springs and will need some upgrading with new buffers and discharge pipes. Nonetheless, it is an excellent choice for modellers starting out in wagon conversions. If something goes wrong, the cost is not crisis inducing.

Alternatively, the Graham Farish monobloc TTA tank wagon offers a more refined starting point but with the associated increase in cost. The barrel is open to a number of modifications including rounded ends, together with valve covers for compressed gas tank wagons and the conical ends of lagged tank wagons to model those used to

transport heavy oil and bitumen. The underframe may be fitted with smaller diameter barrels with both dished and conical ends to model a variety of chemical tank wagons. In fact, the underframes from various wagons offer the best option for modelling tank wagons in ‘N’ gauge. For example, the underframe from the old Grafar cement/ powder tank wagon with its Gloucester suspension is close enough, after being extended by about 5mm to 60mm over buffers to be used in a representation of two-axle TUA caustic soda liquor tank wagons, some of which were used on china clay traffic for English China Clays.

More options

Before hacking ready-to-run models to pieces, surely we could build some kits? Well apart from the undecorated Peco TTA, there is little readily available in kit form except Kit 37/37A produced by the ‘N’ Gauge Society. It consists of a useful plastic body kit which fits either the Graham Farish or Peco underframe to model Charles Roberts-built TTA chemical tank wagons. It includes different options for walkway and ladder detail to suit the diagram of the wagon being modelled. Optional conical or dished ends are also supplied along with a useful sheet of transfers which includes hazard markings and TOPS panels. At a push, the markings can be used to finish any number of tank wagons.

Another source of kits and components is Shapeways (www.

shapeways.com) where modellers place items made for themselves on general release. Maridunian Models is one supplier of ‘N’ gauge items suitable for modelling tank wagons including the popular carbon dioxide tank wagons in various forms, together with 3mm scale parts (www.shapeways.com/shops/

maridunian-models). Whether you are successful in finding the item you need will depend on availability because ranges can come and go quite quickly. The cost of 3D printed products, together with their limitations, should be taken into account too.

When the source of kits and readyto-run model parts are exhausted, it falls to the specialist manufacturers for the supply of wheels, buffers and other wagon fittings to support scratch building efforts. Perhaps one of the most comprehensive ranges for ‘N’ gauge detailing parts is N Brass Locomotives (www.nbrasslocos.co.uk) which includes many of the parts needed to upgrade wagons.

From there, the options include scratch building on the available underframes, starting with either sourcing tank barrel material from materials such as pipe or tube material, or making your own. Evergreen Scale Models styrene tube No. 236 is 12.7mm in diameter which works for smaller diameter tank barrels. It is easily cut to length and squared off for the fitting of tank ends.

Bespoke tank barrels

It is possible to tightly roll strips of 10thou styrene sheet around a metal rod, such as a drill bit, to create bespoke tank wagon barrels with some strength, as long as there is at least six turns of material. A small amount of solvent cement is applied after each turn and carefully so not to mark the side and top of the barrel when securing the tail of the strip.

More than one strip can be used to make each barrel as long as the second is carefully glued in place where the first ends, without any ridging. If there is a chance of a ridge distorting the appearance of the finished barrel, use a little grade 600 wet and dry paper to pare the tail down.

The real challenge with making your own barrels is how to finish the ends; model the top hatch and any valves along with a walkway (unless it is a compressed gas tank wagon with loading and discharge valves). Etched ladders suitable for walkway ends can be obtained in ‘N’ gauge, whilst etched grille material can be cut to size and used to build up walkway fittings.

The work is fiddly and will take time for each wagon. One has to accept that the resulting model may be a compromise. However, when finished well and with the correct markings, the resulting model might make a suitable stand-in until a kit or ready to run model becomes available.

Conical ends

An old trick used by ‘OO’ gauge modellers years ago was to make conical ends for the modelling of lagged tank wagons using thin styrene card, usually 20-thou in thickness for durability. They were used to convert old Hornby TTA tank wagons into lagged tanks, a conversion which worked well along with detailing and enhancements such as etched walkways and ladders.

A square or disc of styrene card larger than the barrel end is prepared and a small triangle or slot of material with the apex at the middle of the work piece cut out. Naturally, you will find when experimenting with this technique that 20-thou styrene is too thick for ‘N’ gauge models and 10-thou is too thin. The answer for lagged tank wagons is to use 5-thou brass sheet. It is easily worked and curved to make the ends without too much difficulty. The same technique is used as with plastic ends. Drilling a small hole in the middle of the brass helps with the formation of conical ends which is soldered for strength and finished with a file, followed by fine wet and dry paper. They are fitted with two-part epoxy glue.

Closing thoughts

The described methods were used to build a brace of former caustic soda liquor wagons. Conversions are often full of compromises due to the lack of suitable detailing parts and not being able to incorporate subtle variations as a result. Bear in mind that ‘N’ gauge modelling is often about creating the desired impression as much as a fine scale appearance and the N Gauge Society’s kits and the TTA conversion, when well finished, do look the part. No doubt, we will return to this large subject with more projects, such as bitumen tank wagons, in a future issue.

Two former caustic soda liquor tank wagons are pressed into china clay slurry traffic. Both are different wagons not commercially available, thus adding variety to the collection.

Prototype inspiration for one of the TTA wagons came from TTA No. TRL 51642 photographed at St Blazey on June 20, 1992 when in china clay slurry service. The original TRL livery is under the grime and dust somewhere! The N Gauge Society kit No. 37 was used to model this vehicle.

The Graham Farish TTA model is a useful starting point both for its underframe and the barrel, each of which can be adapted for different models. Its barrel might not be perfectly sized for some projects, but conversions usually involve some compromise.

TUA No. PR 70089 is a former Standard Wagon fuel oil tank pressed into mineral slurry traffic when photographed at St Blazey. It was one of a batch of wagons built in 1974 numbered PR 70068-92.

TTA No. TRL51963 is another former caustic soda liquor tank used in china clay traffic. It was photographed at Bescot in a mixed train with other slurry tank wagons on June 21, 1996. The Bachmann TTA can be used to model this wagon even though the model’s barrel is a tad oversize.

Former caustic soda liquor tank No. TRL 70723 built in 1977 by Standard Wagon, in unbranded condition. It was being used on china clay slurry traffic when observed at Exeter Riverside Yard on June 21, 1992. It could be modelled by extending the underframes from the old Grafar cement/powder tank wagon, the barrel rolling technique described below and brass conical ends.

Larger diameter tank wagon barrels may require more than one strip of styrene sheet which is butt joined to the first before continuing the rolling. The barrels are secured with solvent cement every turn or so.

Making up your own tank wagon barrels is easy to do, by rolling up 10-thou styrene strips to the desired diameter.