Modelling: Rebodied 21t hopper wagons

How to build, paint and weather a BR classic wagon: the rebodied 21t hoppers based on the plastic kit by Parkside Dundas.

Despite the thousands of 21t hopper wagons built by BR in the 1950s, one of the few options for modelling them in ‘OO’ gauge model is to build a Parkside Dundas kit. Rebodying in the 1970s added variety to the 21t hopper wagon fleet, and saw their survival into the BR Sectorisation era and eventually departmental use. This project shows how to build a rebodied HTV wagon using Parkside kit PC78 with vacuum brake detail.

THOUSANDS of steel-bodied 21t hopper wagons were built by BR between 1949 and 1959, mostly as unfitted wagons to several different diagrams based on the LNER design.

The were the mainstay of coal traffic, although they could be found working in coke and sand traffic too.

With more than 36,000 in traffic during the 1960s, which included LNER-built wagons, the 21t hopper wagon – or HOP21 – dominated coal traffic particularly in the north east of England, South Wales and the Yorkshire coalfields.

Until the introduction of air-braked coal hopper wagons, which included the HAA family and HBA domestic coal hopper wagons, the 21t hopper wagon was common throughout the country and despite the introduction of more modern wagons, the design survived to see a programme of rebodying in the 1970s to replace worn out hoppers.

In fact, hopper wagons of various origins were rebodied fairly regularly. Not all received vacuum brakes during rebuilding, and other improvements were made including the fitting of roller bearings and different types of side buffers.

The 1970s rebodied wagons are the subject of this article, where many of them received vacuum brakes on the standard 12ft wheelbase underframe.

The last batch of rebodied wagons fitted with vacuum brakes (HTV) in the B340xxx number range received upgraded suspension springs compared to earlier rebodied wagons. Also, they were renumbered in a new sequence along with late rebodied HTOs, instead of retaining their original running numbers.

Vacuum-braked HTVs were largely painted in BR bauxite livery (photographic evidence shows this was not always the case) and fitting of vacuum brakes did not always take place when the wagon was rebodied. It is an interesting fleet of wagons which exhibited numerous detail differences.

They dwindled throughout the 1970s and 1980s as coal traffic declined, particularly as a result of mine closures after the miners’ strike of 1984 and 1985. The unfitted HTO wagons were particularly hard hit.

Fitted HTVs were transferred to aggregate, sand and departmental traffic during the 1980s with the type becoming more or less redundant by the early 1990s. Large numbers were stored pending further use as they were withdrawn.

Transfer to departmental use saw them overhauled in number with reduced height bodies for use as ZDV spoil wagons (‘Tope’), or rebodied with open box bodies to form ZCV ‘Clam’ wagons with a fixed body or ‘Rudd’ with drop-side doors as replacements for worn out ‘Grampus’ wagons.

Rebuilding began in the late 1980s was concluded in the early 1990s – an interesting story in its own right which is outside the scope of this project.

Kit PC78

Parkside kit No. PC78 is a very good staring point and includes the standard underframe with push brakes and a sprue with vacuum brake parts. It can be used to model both vacuum-braked (HTV) and unfitted wagons (HTO) with new hopper bodies. Alternative axlebox cover detail is supplied too.

The hopper is moulded with the pair of vertical ribs characteristic of the rebodied wagons, and is composed of eight parts for the upper structure and a separate set of parts for the lower discharge door chute, which are assembled separately and brought together towards the end of the project.

Hand rail wire is supplied as 0.45 brass wire, although experience with building the unfitted/original design of HOP21 wagons shows that 0.3mm diameter wire is much more authentic in appearance.

The kit includes ‘OO’ gauge threehole disc wheels produced by Alan

Gibson and pre-TOPS markings for HOP21 produced by Modelmaster. Modellers wishing to apply more recent markings, such as stone traffic pool numbers and TOPS panels, will have to make them up from Fox Transfer sheets for vacuum brake wagons. The kit may be adapted to model the cut-down Tope engineers wagons by shaving 6mm off the top of the hopper and restoring the top rib.

Detailing parts

It is possible to refine the kit with detailing parts from Lanarkshire Models & Supplies, including: swan-neck vacuum brake hoses; cast coupling hooks (if ‘Instanter’ couplings are not being fitted); replacement cast spindle buffers or even buffers of a different pattern if a specific wagon is being modelled.

Different axle boxes are available from MJT Components (Dart Castings) as well as suspension spring castings.

The use of these parts will depend on the choice of operating coupling, the modelling of specific wagons and how far you really wish to go with what is already a time-consuming model.

Pre-assembly preparation

All plastic kits have some kind of moulding flash, tool ejection points and other minor flaws that must be cleaned up before assembly.

Each part is given a check for distortion, which may require replacement parts, and those areas where parts are shaped to fit together to see that nothing will interfere with assembly. In most cases, a gentle rub with fine abrasive paper will remove moulding marks from the inside faces of the hopper parts and mould lines from the top of the solebar mouldings.

Do not remove the short ribs on the inside faces of the hopper sides or end panels. They are small grab rails present on the full-size wagons.

Care is needed to ensure all assemblies are square and true to ensure the underframe runs correctly. The wheels must clear the discharge door part of the hopper for smooth running, and the top of the hopper itself must be square and level with solebars and headstocks to match similar wagons in a train.

One part of the model requiring particular attention is the underframe moulding. There are several moulding pips to shave off, or they will interfere with the wheels and may cause the solebars and headstocks from fitting together square.

Ensure the inside faces of the frame are smooth: they have to be to allow the lower section of the hopper and the discharge door chute to fit the underframe neatly without distorting it.

Once parts are checked, cleaned and test assembled without cement, the job of building the hopper can start.

Hopper assembly

An upper side and end panel are matched and glued together in turn before being brought together to make the hopper top subassembly, using the bevelling in the edges of the parts for a neat fit. Use an engineer’s square to ensure the top remains true as the solvent cement bonds harden.

The bottom sections of the hopper are trickier, the long side panels being slightly awkward to insert between the lower end panels without everything being knocked out of alignment.

The ribs have to line up correctly and without a gap between the lower and upper part of the ribs. Eventually, it will come together after some adjustment of the bonding edges.

Allowing the various subassemblies to ‘rest’ before proceeding is beneficial. The solvent cement needs time to evaporate, and bonds to become hardened. Heavy-handed application may cause the joins to have a ragged edge when brought together due to excessive melting of the plastic. Once the ‘welds’ are dry and hard, they may be cleaned up with wet and dry paper.

Underframe

Having removed the moulding pips from the inner frame of the underframe, assembly can begin, first by inserting the pinpoint bearings in the axleguards and choosing a suitable axlebox for the model. The roller bearing type was selected for this project and opened out with a 2.2mm drill to fit over the pin point bearings.

The smaller vee-hanger is removed from one solebar, which is fitted to the side of the underframe with the vacuum cylinder (cylinder to the right).

The headstocks are next, together with the vacuum cylinder, which is

mounted on top of the spigot on one of the end platforms.

The underframe is left to rest at this stage while buffers are cut from their sprues, cleaned of moulding flash and assembled to the shanks.

The linkages located under the end of the wagon are part of the vacuum cylinder sprue and may be fitted with a short length of 0.3mm wire as the linking rod. It is a fiddly area to complete and not visible from normal viewing angles, so adding them is entirely up to you. The push brake mouldings are next, and can be fitted to suit the desired gauge.

Discharge door chute

Once the underframe has rested from the application of adhesive and the wheels are fitted to check it rides square and level, the discharge door chute is assembled to it.

Note the staggered rebates on the bonding edges of the sides and sloping door panels that ensure it goes together square and with door panels the correct way round. Note the slots in the long sides designed to clear the middle member of the inner frame.

They benefit from being opened out slightly so the discharge door chute assembly fits it with the top edge just clear of the top of the frame, to allow the hopper top to sit neatly on to it.

Before fitting the discharge chute assembly to the underframe (from the underside), do a dry run to check it will fit the bottom of the hopper subassembly. Note that the bonding edges between the two subassemblies are bevelled for (hopefully) a neat fit.

This is perhaps the most important part of the whole assembly process, so be sure it all goes together correctly before fitting to the underframe.

The time taken to prepare the inner frame members now becomes obvious. The discharge door chute should and does fit neatly between the members without distortion – sometimes after a little fettling with a file.

Final assembly

It seems that much kit building time consists of test-fitting parts and subassemblies together. In the case of the HTV, these checks will ensure that final assembly with solvent cement is correct. Do a final check on the chassis to see that it rolls freely before fitting the hopper door discharge chute to it, remembering that it must protrude sufficiently above the inner frame for the main hopper subassembly to bond to it.

The underframe must remain square and the hopper has to fit it so the tops are straight and level from all angles, too. Be prepared to make adjustments as necessary; fettling is always time consuming, but worth it when it comes to achieving a smooth running model.

When building more than one wagon of this type, place them together on a piece of track and look down the train. Do they all match for height? This is really the last chance for adjustment.

Hopper detailing

Small triangular pieces located on the vacuum cylinder sprue are the hopper support brackets of which there are three types. They are located on the interior and between the lower hopper side panel and the top of the solebars.

Two things must be done before fitting them. Firstly, be sure that the underframe rolls freely and sits square on a flat surface. Once the brackets are fitted, adjustment will be much harder.

Secondly, fit the brake pipe that runs along the bottom of the hopper from one end of the wagon to the other. This is located on the same side as the vacuum cylinder. It is easier to measure, bend and fit the length of 0.7mm brass rod used for the pipe before the hopper brackets are fitted!

Hand rails

One of the trickiest jobs is making up the end hand rails. Indeed, this can take almost as much time as the main assembly process!

Start with a length of 0.3mm diameter brass wire and make a right angle bend in it with flat nose pliers. Thread on the hand rail brackets, ensuring they are the right way up.

Complete the wire bending by making a second bend about 31mm along the wire to create a ‘staple’ shaped piece, as the instructions put it. The legs of the staple are cut to length and the ends shaped to match those on the full size wagons. Each bracket is carefully fitted to its slot in the hopper end panel and the wire ends glued to the hopper sides.

The righthand end of the horizontal hand rail has no bracket, this being supported by the vertical rail which extends from the hopper end to the base of the nearest hopper end supports. Add the supports next: there are three at each end which may be replaced with L-section and T-section styrene strip from Evergreen styrene. The vertical hand rail may be secured after this has been fitted.

The upper horizontal rail is the easiest and also fitted to 0.4mm holes for strength. The underframe is finished with the brake levers (fit them the right way round!) and then the hopper discharge levers too.

Some changes were made to the models following assembly. The moulded underframe tie bars are inadequate and prone to breaking and warping. They can be replaced with thin brass or nickel-silver strip for strength.

Cast metal coupling hooks were added instead of Instanter couplings because the models would be fitted with Spratt & Winkle couplings to suit a particular layout project.

Painting and finishing

This was followed with a coat of (brown) plastic primer to fill any minute imperfections in the model, and as a foundation for BR bauxite. Top coats of bauxite were applied using paint from Phoenix Precision Paints.

The underframe, including headstocks, was painted black, while the interior of the hoppers was treated to a base coat of Tamiya flat red brown.

This was topped off with a mix of Tamiya ‘Dark Iron’ and flat aluminium to create the effect of exposed steel from the scraping action of a load as it slides out during unloading, followed by thin washes of coal black. Some traces of the load are left in the corners, represented by the appropriate colour: dusty matt black for coal, with a touch of talcum power, or weathering powder mixed in or a lighter buff colour for an aggregate load.

Washes of Life Colour rust shades or Tamiya matt brown or red brown, together with ‘Dark Iron’, can be used to apply grime to the hopper body after it has been coated with varnish to give an egg-shell finish.

The surface texture of matt and egg-shell varnishes is ideal for washes of weathering colours to adhere to, so apply washes that are heavily thinned in several coats to build up the effect, rather than one heavy application.

Patches of rust, almost black brown in colour, could also be applied to represent paint damage where steel has become exposed.

A little rusting was applied to the underframe, which was later treated with a dusting of Railmatch underframe dirt. Thin washes of rust colour will bring out the spring detail on the axleguards and moulded detail on the solebars.

A little oil staining around the axle boxes is a nice detail. Weathering can be a lot of fun, but take time to allow washes to dry.

When and where to add ballast weight is a good question, too. Some modellers wait until the model is finished, while others prefer to add it after assembly but before detailing is complete, when the underframe is being tested.

Filling the inside of the discharge door chute with fine lead-free shot and securing it with Araldite epoxy adhesive is the usual method.

Finally...finished!

Parkside Dundas Kit No. PC78 builds up into a very convincing model of BR rebodied 21t hopper wagons and is easily enhanced with detailing parts from various manufacturers.

However, the time to finish one will make the building of a fleet such as that seen in the accompanying images of HTVs in the B340xxx number series quite time-consuming, especially when long rakes are required.

But, as knowledge of the kit is gained, building time for each one (building them in pairs saves time) will be reduced.

As always, keep notes on weathering methods and paint colours for consistency.

Vacuum-braked rebodied HTV 21t hopper wagons are an important part of a 1970s and 1980s BR-themed layout where they were used in coal, sand and aggregate traffic. They join a fleet of various traditional BR wagons and predecessors to cover a wide time span of operations on the author's micro-layout.

Hopper assembly starts by adding upper sides and ends first to make halves before bringing them together.

The middle dividing panels are assembled and test fitted. Note that the short ribs on the inside of the hopper are retained – they are grab rails located around the inside surfaces.

Lower section of the hopper is next, with the angled end pieces fitted first.

The lower side pieces are awkward to fit neatly and require some fettling of the bonding edge for a neat appearance on the inside.

Parkside Dundas kit No. PC78 builds up into a convincing model of rebodied 21t hopper wagons. The hopper parts are thin mouldings which generally go together neatly. The underframe discharge door chute parts (A) are built separately from the rest of the hopper, which consists of lower ends (B) and sides (C), together with the upper structure (D, E).

Although the discharge door chute assembly and hopper should not be glued together like this, they do have to fit together in this manner, so a fitting test is desirable. The former from the underside of the underframe and the latter on top! This picture was taken with subassemblies out of the building sequence recommended by the instructions, but shows the relationship between inner frame and the hopper parts.

Assembly of the discharge door chute is assisted with rebates in the sides to ensure it goes together the correct way round. Testing the fit of various assemblies is recommended to check the fit. Some fettling may be required to achieve a good fit between the discharge door chute, underframe and dividing panels.

The slot in the discharge door chute assembly fits over the middle frame member.

While the hopper assembly sets and solvent cement allowed to evaporate away, the inner frame of the underframe is cleaned of moulding pips (A). Note the slots in the end platform to locate the hopper support brackets (B) and the vacuum cylinder spigot (C).

Wagons primed ready for BR bauxite paint. One end vertical hand rail had fallen off at this stage and was reinstated later in the project. Only scant amounts of adhesive were used during assembly for as neat a finish as possible, but sometimes it’s not enough to hold metal parts!

Weathering commences with a series of very thinly diluted washes of dark grey paint (Tamiya ‘rubber black’), which is allowed to collect in the corners between the sides and ribs.

Once the desired level of grime has accumulated on the model, rust blooms on the paint surface may be added with washes of Tamiya flat brown, that has been treated with a little matt yellow paint to lighten it. The same colours are used to rust in the underframes.

Despite the complexity of the kit, it builds up well if time and care is taken with assembly of the hopper sections. Neat joins are absolutely important if the hopper interior is to look neat and tidy.

A 0.3mm diameter wire was used for the end hand rails. Tricky to fit, but an important feature of the wagon.

Solebars and brakes are added to the inner frame. Note how fragile the axleguard tie bars are – they break very easily and are better replaced with metal strip.

Angle bracing or brackets is added to the exterior of the hopper (A). There are two sizes; one which is glued to the hopper ribs and one to the lower sides. The vacuum brake pipe is fitted first (B) and runs through the gap behind each bracket.

Coal hoppers of various types and eras are present in this view of an industrial customer’s exchange siding. The unfitted HOP21 and early rebodied wagons could work together in the early 1970s, but the former would likely be in much worse external condition than shown!

Another view taken at Peak Dale on September 18, 1986, with HTV No. 340094. The intended subject of this picture was the Class 31. As it happens, as a reference picture, the wagon is interesting, including its replacement heavy duty buffers and odd axle box covers.

Vacuum-braked heaven at Peak Dale, with HTVs and MSV wagons being used in aggregate traffic. HTVs Nos. B340329 and B340406 from the last batch of rebodied 21t hopper wagons are visible. Note the heavier suspension springs and spindle buffers. This view was recorded on September 18, 1986, and the 21t hopper wagons were soon to be replaced with modern air-braked wagons.

The Parkside Dundas kits for the rebodied and standard HOP21 wagons together with the Hornby model of the LNER version with its unusual brake arrangement provides wide scope for different models; both braked, unfitted, rebodied and with variations in the livery. As these images were examined, it became apparent that the underframes and lower hopper areas would need further subtle weathering.

Portrait of HTV No. B422681 showing the side of the wagon with the small vee-hanger on the solebar, opposite to that with the vacuum cylinder. It is fitted with roller bearings and spindle buffers.

The end view of No. B422681 which provides useful reference for the end hand rails and hopper brackets.