HAA - The Wagon That Powered The Nation...

The Merry-Go-Round Concept

Merry-Go-Round trains began operation in the mid 1960s and were an innovative way of supplying coal from collieries to power stations using permanently coupled sets of high capacity, air braked wagons automatically loaded and unloaded in a non-stop operation. It is from this continuous coming and going that the term Merry-Go-Round (MGR) was derived. Rather than each wagon being shunted under the colliery storage hopper or emptied into the power station’s receiving hopper by a shunting locomotive the MGR train is drawn through at slow speed (typically ½ mph) by the train loco. At many power stations unloading took place on a continuous loop, thus avoiding the need to uncouple the locomotive. These included Longannet, Drax, Cottam, Didcot, Willington and Ferrybridge power stations. These loops are fully signalled to allow trains to be unloaded in succession.

Due to the requirement in the early 1960s to transport increased tonnages of coal (e.g. 34,000 tons was required by West Burton power station each week) to the new generation of power stations BR, Central Electricity Generating Board (CEGB) and the National Coal Board (NCB) needed to find a more efficient means of moving the coal. In response to this the MGR principle was unveiled by Gerard Fiennes in January 1963 and the High Capacity Wagon Design Committee was formed developing a new wagon coded HOP 32 AB (32 tonne payload, air braked) mineral hopper to be used in the MGR trains. The first prototype was ready in April 1964 and tests began at High Marnam power station although it has to be said that the NCB needed some convincing. One must bear in mind that investment was needed not only in new wagons but in permanent way, signalling, maintenance depots and high capacity bunkers able to load trains in quick succession. In the meantime Brush Traction also modified a Class 47 with Slow Speed Control (SSC) allowing it to run at a constant ½ mph.

The first use of MGR trains was in September 1965 at West Burton power station in Nottinghamshire where there was also a circular loop for unloading. The next power station to use the MGR system was Eggborough with the principle being extended to other power stations, cement and steel works and ultimately to the shipment of other raw materials such as iron ore and limestone

For unloading each wagon was fitted with automatic bottom discharge doors in the hopper controlled by fixed lineside equipment – cams automatically opened and closed the doors by means of safety catches and levers. However, not all MGR trains were loaded by rapid loading bunkers or unloaded as trains hauled by SSC fitted locomotives, particularly where collieries might be due for early closure and so outmoded handling methods remained in force. In some cases wagon moving devices were used such as where wagons were propelled by rubber tyred wheels leaving distinctive tyre tracks on the sides of the wagon hoppers.

As far as I am aware the first loco to be constructed with SSC was D1758 (later Stratford Union Jack celebrity 47164 and now 57305) allocated new to Tinsley on 23 May 1964. Apart from Class 33/2s, 50s and some Scottish based Class 20s and 26/0s the 200 SSC fitted Class 47/0s and 47/3s provided the backbone of the MGR fleet until the introduction of Class 56s from 1976. Thereafter all locomotives of classes 58, 60, 66 and 67 were fitted with SSC as well as some refurbished Class 37s. Interestingly the seven Class 26/0 D5300-D5306 converted in 1967 to work Cockenzie power station trains were the only Pilot Scheme locomotives to have been fitted with SSC – those Class 20s fitted with SSC were predominantly built in 1967/68. The SSC equipment fitted to Class 50s was removed when the locomotives were refurbished at Doncaster Works. As would be expected train set sizes vary depending not only on the locomotive but also on line and terminal restrictions and are typically between 28 and 45 wagons.

There are many advantages to the high capacity air-braked wagons of the MGR system compared with unfitted or vacuum braked 16T mineral and 21T hopper wagons, the design of which did not lend itself to automatic unloading. These include the fast loading and discharge of coal, automatic weighing, the requirement for fewer locomotives, wagons and sidings, better utilisation of rolling stock and train crew, less need for shunters and shunting, and greater speed and safety. Even over short distances coal carried this way was competitive. In short, MGR trains were a far more efficient, economical and speedy way of transporting coal from pit to power station not least because the new generation of power stations built from the 1960s were much larger. Indeed by 1975 60% of coal carried on the Eastern region of BR was in HAA MGR wagons.

The HAA Wagon and Derivatives

The two wagon prototypes, numbers B350000 (HOP AB, later TOPS code HAA) and B350001 (HOP 32 AB with canopy later TOPS code HBA) were built at Darlington Works in 1964. Whereas Darlington works was closed in 1966 nearby Shildon Works was modernised and continued building and repairing wagons until closure in 1985 and with the exception of 160 wagons built at Ashford built all 10702 HAA and 460 HDA (see below) wagons. Somewhat appropriately 350000 remains in County Durham and is preserved at the National Railway Museum’s Locomotion at Shildon. With the exception of continental stock these wagons represented the first series production of air-braked wagons for BR and were ultimately to become the most common single type of wagon in the modern fleet.

Apart from the exceptions mentioned later (and see table 2) the HAA design remained pretty much standard throughout its production run. Dimensions are given in table 1 below. Construction consisted of a steel underframe and framework supporting the galvanised hopper body. The body was made up of three steep sided chambers to assist the rapid release of coal through the double doors at the bottom of each chamber. The train brake operated on discs on two wheels on opposite corners of the wagon with the clasp handbrake operating on the other two wheels. Each wagon was fitted with Timken roller bearings, Oleo hydraulic buffers and single link suspension. The initial livery was black for the underframe and running gear, bauxite for the hopper framework and unpainted galvanised steel for the hopper itself.

As per the initial design, HOP 32 AB, some wagons were built or fitted with a canopy and this top extension allowed a greater payload of 32 tonnes thus utilising the maximum axle weight of 22.5 tonnes per wagon. However these canopies were only of use where the height of the colliery screens permitted their operation and were largely confined to Scotland.

In use it was found that the four cross struts on top of the body and intended to stiffen the sides were being damaged by the weight of coal dropping on to them and thus potentially causing distortion to the bodysides. The solution to this problem was to rivet a stiffening plate along the length of the body and dispense with the cross struts. From 1977 all new build or rebodied wagons were treated this way and the extra row of rivets distinguishes these wagons.

Table 1: dimensions

 

HAA HAA with canopy HEA Length (mm) 8001 8001 7420 Wheelbase (mm) 5563 5563 4572 Width (mm) 2692 2692 2700 Height (mm) 3200 3645 3250 Wheel diameter (mm) 1092 1092 1092 Tare weight (tonnes)* 12.5 13.25 13.2

*These are approximate weights and if anyone can confirm exact tare weights I would be grateful. Rebodied wagons are about 1 tonne heavier due to the thicker steel used.

The final batch of 460 MGR wagons was introduced in 1982 and being allowed to travel at a higher loaded top speed of 60mph were given the TOPS code HDA rather than HAA which were restricted to 45 mph loaded or 55 or 60 mph empty. This higher top speed was achieved by uprated braking and suspension which meant that the HDA wagons were better suited to long haul or Speedlink services.

With the elimination of unfitted and vacuum braked coal wagons HAA wagons dominated coal traffic prior to the introduction of high capacity bogie wagons, e.g. EWS HTA and Freightliner HHA. Such was the domination of coal transport to power stations that in the severe winter of 1978/79 widespread freezing of wet coal in wagons seriously threatened generating capacity. This was quite literally due to coal, which is washed, freezing in the bottom of wagons or sticking to the doors preventing closure and effective trials were carried out using an anti- freeze type chemical to treat wagon bottoms.

Today all surviving wagons are part of the EWS fleet and although the majority of the fleet has been withdrawn over 2000 remain in service. This reduction of the HAA fleet is not just due to new bogie wagons but to the shift to gas fired power stations in recent years. However, the increasing demand for coal due to surging gas prices may be the saviour for some HAA wagons in the short term. There remains the requirement for HAAs because of line restriction, for example, to Longannet due to the axle loading of HTAs precluding their use over the Forth Bridge.

The last remaining working using canopy fitted wagons is on the Hardendale – Redcar limestone service making use of a mixture of wagons with TOPS codes HBA, HCA, HFA and HNA.

Although out of the scope of this article mention must be made of the CDA China Clay hopper based on the HAA design (built in 1987) or converted from HAA hoppers most of which are still in service as well as the PFA limestone hoppers (built in 1969) and those wagons using redundant HAA and HEA chassis (see table 2).

The HEA Domestic Hopper Wagon

Apart from coal to power stations much coal was also transported for domestic and other industrial use where it was uneconomic to install specialised MGR unloading equipment. In 1976 the HBA hopper wagon was introduced to work these services and 1998 wagons had been built at Shildon by 1979. They are of a somewhat different design from the HAA wagon in that the hopper is made of steel and consists of two rather than three chambers with a simplified door operating mechanism. They had a payload of 32.5 tonnes and a maximum speed of 60 mph. In order that the wagons could travel at 75 mph they were modified with Bruninghaus springs and those built with or later fitted with Bruninghaus suspension were re-classified as HEA.

Amongst other things, HEA wagons have been used to carry coke, scrap metal (coded HSA) and the covered CEA version was even used to carry calcified seaweed. In August 2006 the only freight flows utilizing HEAs are coke trains from Port Talbot and Redcar to Scunthorpe Steelworks.

Conclusion

It is fair to say that like the High Speed Train, the Merry-Go-Round is one of the defining icons of the modern British railway industry. However, unlike the HST, all our lives have been affected over the last 40 years by MGR trains continually and reliably shifting coal from colliery to power station to supply us with our electricity needs. Railways were invented to carry coal. This is what they do best and the HAA wagon has carried on this tradition albeit as a radical departure from the way coal was previously hauled. For these reasons alone it would be fitting that a complete set of HAA be preserved as a lasting tribute.

References:

• Middleton, R.G., Problems of Discharging Coal from MGR Wagons in Winter, BR Research Report Ref: TM-DON-8, September 1981
• Monk-Steel, D., Bartlett, P.W. & Mann, T., BR Air-braked Coal Hopper wagons, Model Railway Constructor Annual 1987,pp 20-36 edited by Leigh, C., 1987