Don’t Smash the biscuits!

Wagons specifically developed to meet shippers needs can increase railway revenues, lower the shippers’ costs and improve efficiency, explains independent railway engineering consultant David Burns

A Chinese biscuit manufacturer, when asked why he was not using the railway, replied: `why should I? I can get 12 tonnes of biscuits on an 8 tonne truck, but I can only get 22 tonnes in a 65 tonne railway wagon. On top of that, by railway, the biscuits get broken!’ The answer is a `grocery wagon’.

An American power station manager, when asked why the station was changing from rail to barge for transporting coal, said, `on this movement I will save US$0.001/tonne-km!’. For this power station the savings could easily amount to US$10 m per year. The answer is higher capacity, and more efficient coal hopper wagons.

The truck and the barge are formidable competitors for today’s rail freight industry. The truck is a mass-produced vehicle. As it does not have to withstand in-train stresses, it is light weight as well as inexpensive, It is usually easy to load – and overload – and, most important, has high utilisation, typically up to 400 000 km per year. To make matters worse, average life in inter-city service, in developed countries, is about four years. As a result, there is a constant upgrading of technology.

The barge operates on the river, maintenance of which is usually heavily subsidised by government. A barge, with capacity of 15 to 25 wagons, has few wearing parts. It is, usually slower, which is no problem for low-value goods, such as coal. But, interestingly, there are many instances where coastal shipping can compete on time with the railway.

There are a number of technologies that can enable railways to compete more effectively. One of the most important is the choice and design of freight wagons. Unfortunately, there are misconceptions when it comes to changes in freight wagon designs. Here are some examples:

· Wagons must be of the same basic design. The argument is that standardised wagons are much more likely to get a back haul and, thus, good utilisation. Some railways, using this logic have had loaded km reach 80% of total km. However, as these railways lose their transport monopoly, they are losing market share. No shipper wants to load televisions in an empty coal wagon, and a biscuit manufacturer does not want to pay for a 65 tonne load when he can only get 22 tonnes in the wagon.

· Wagons must not exceed a specified axleload. Railway track and bridge engineers are very much against accepting an increase in axleloads. Why give yourself a headache? Yet, in most cases, the maximum axleload was set on the basis of yesterday’s technology. In practice, axleloads are exceeded every day by the occasional overloaded wagon, while specified forces on the rail are frequently exceeded by out-of-round or flat wheels.

· Technical standardisation. The wagon must meet technical design standards, some of which date from when the railways were first built. European railways have a standard buffer design, while Indian Railways uses very large wheels and a high coupler height. The wagon must not exceed a specific moving dimension, and the list continues. Many railways state this standardisation must continue as every wagon must be able to couple to every other wagon!

If this approach continues, there is little hope for the railway industry. Wagons must be designed to meet shippers’ specific needs, something that was probably first appreciated in North America, where 35 years ago they had five basic wagon designs, but today there are over 100.

Higher Axleloads

The single most important factor in wagon design is axleload. Raising the axleload from 22.5 to 30.5 tonnes can lower transport costs by 40% (RG 6.01 p407) and, in fact, if track maintenance is improved, it can be at a lower track cost. As savings are on future tonne-km, they can easily pay for any future track and structure upgrading.

It is not only the design and the carrying capacity of the wagon that is important, but from an overall railway economics prospective, the net-tare ratio must be as high as possible. The higher the ratio, the higher the load that can be carried for a given axleload, and the lower the tonnage the railway must move at its own expense. Part of the result of increasing allowable axleloads is that the net-tare ratios of wagons have increased from about 2.4 to a current high of about 5.8.

The demand for standardisation is based on the logic that any wagon must be capable of going anywhere. Yet for some time there have been exceptions to this. For example, most railways have loading gauge exemptions where larger wagons are only allowed on specific routes. Loads carried in European wagons depend on the class of track over which they travel, and Indian Railways now allows five-unit wagons with smaller wheels for specific intermodal services.

The cost of the wagon can be about 20% of the total cost of transport, yet European wagons, because of their specification, are about 50% to 150% more expensive than their North American equivalents per unit of capacity. As an illustration, replacing the side buffers with a centre coupler not only reduces weight, but cuts wagon cost by about US$4000.

There is no question that specialist wagons increase the proportion of route run empty. With a good wagon, designed to permit back hauls where possible, and modern methods of movement control, some wagons can have loaded km in the order of 65%, and in limited cases as high as 80%. In addition, as the net-tare ratio is improving, the cost of the empty back haul has also declined.

Today in North America the average rail tariff is about US$0.02 per tonne-km, about half that of 20 years ago. The railways have also managed to regain market share, thanks in part to the use of specialised wagons, with around 40% of tonne-km now moving by rail. The following are some examples of specialised freight wagons.

· Coal hopper. Many railways still carry coal in a universal type of gondola. It has doors on the side so that it can be loaded and unloaded by hand, and has a net-tare ratio of about 2.4. When the railway is forced to compete for that one-tenth of a cent, it has to improve the design of the wagon. The standard gondola was in due course replaced by bottom dump hoppers, which increased payload and reduced unloading costs. The next development was rotary dump hoppers, which permitted further increases in load and, at the same time, lower costs. More recently aluminium bodies have been widely introduced, and when coupled with 32.5 tonne axleloads, net-tare ratios have reached 5.8.

· Centre beam bulkhead flat. Products such as timber, plywood, and wallboard must today be loaded with a fork lift truck from the side, and the bulkhead flat wagon was developed for this traffic. To stop the bulkheads from bending, the floor and end structure have to be very strong resulting in a very heavy wagon. The development of the centre beam bulk-head flat wagon was developed for this traffic. To stop the bulkheads from bending, the floor and end structure have to be very strong, resulting in a very heavy wagon. The development of the centre beam bulkhead flat car has enabled a structurally simpler and much lighter wagon.

· Bulk cement hopper. Transport of cement by rail is difficult for many reasons. Given the extreme weight of the product, cement plants are usually located relatively close to use, making it hard for rail to be competitive. The car is often used as the warehouse at the bulk mix location, or the wagon-road transfer station, so utilisation is often poor. In addition the characteristics of cement are such that the wagon usually has a short life, say 10 to 15 years. These facts result in the need for a robust but inexpensive wagon.

· Pressure differential hopper or tank. There are many instances where the wagon becomes part of a production line with the product in liquid or powdered form moved directly from the wagon into a processing plant. For this purpose, the pressure differential car has been developed. The car is pressurised, usually to one atmosphere, and the product is blown directly from the wagon into production machines. Common uses of this type of wagon are in the food processing and plastic moulding industries. This saves the manufacturer storage, double handling, and product losses.

· Covered hopper. The covered hopper now comes in many shapes and sizes. Whereas yesterday one size suited all, today the wagon is designed for the product. Hoppers range in size from an 83 m3 cement wagon to a 180 m3 plastic pellet wagon.

· Multi-unit wagon. Permanent coupling of a number of wagons was first developed in the 1950s, and it was quickly found that if there was a problem with one wagon, then all were out of service. It was not long before each wagon became self-contained. With the development of better maintenance practices, the multi-unit concept was reintroduced in the 1980s. A multi-unit wagon can save a substantial amount of weight and cost by replacing couplers and buffers with slackless drawbars, and sharing brake valves and bogies, if articulation is used. It is now proving to be very successful, especially in three-unit and five-unit sets.

· Skeletal container wagon. Many railways use a standard flat wagon that was designed to carry at least 50 tonnes. It has a floor that makes it capable of carrying all types of cargo, yet when carrying a 40 ft container with a maximum of 37 tonnes, it has a very inefficient net-tare ratio. The standard shipping container has all the advantages of being able to be loaded like a truck, but it can be expensive to move by rail on a standard flat wagon.

All that is basically required is a centre sill and bogies. In fact, with reasonably permissible axleloads, only two axles are required. A modern single axle suspension that permits a degree of rotation has made possible an 11.3 tonne wagon able to carry a 40 ft container, or two 20 ft containers where higher axleloads permit.

· Double-Stack wagon. Stacking one container on top of another was the real revolution in container transport. It has dramatically changed the economics of freight transport, reducing wagon capital cost by 60% and operating cost by at least 40%. To maximise the benefits, five unit articulated wagons are required; however, this requires the railway to be able to accept 36 tonne axleloads; although this only occurs when the four container locations on adjacent units are loaded to the maximum. To avoid the problem, the heaviest loads can be distributed along the train. Unlike other types of unit train, not all axles are loaded to the maximum, so this type of wagon will usually not cause bridge or track problems. The savings have justified increases of vertical clearance on thousands of km of North American track.

· Hi-cube box. Originally a small wagon was designed for sacks of grain or similar products loaded by hand. The doors were the weakest part of the wagon and were small. Any impact from shunting wagons, or from the slack running in or out, seldom damaged the sacks of grain. Relatively lightweight goods, such as refrigerators, did not exist. Today’s products are loaded with fork lift trucks, and even with big doors, this is expensive and slow. About 20 years ago the box wagon was considered obsolete, and it was generally replaced with the inter-modal container or a special purpose wagon. In North America this situation has recently changed, largely because of the economics of the double-stack container wagon. This often justified the cost of increasing track clearances, and this means that the box wagon can take advantage of the larger loading gauge. The best example is a wagon for carrying car components with over 300 m3 of internal capacity, which is 4.5 times that of a standard 40 ft container.

· Tank wagon. Early tank wagons were, essentially, a tank on a flat wagon. Now the wagon is a tank with the bogies directly attached to it. There are around 10 types of interior coating to protect the products in the tank, and many safety devices are available to minimise secondary damage from an accident.

· Grocery wagon. The Milwaukee Railroad, in conjunction with the AAR, tried to discover why it was losing the movement of boxed goods such as grocery products and beer. The railway mounted a camera inside a box wagon and sent it on its way. The camera filmed dancing boxes and occasionally, when the slack between the couplers ran out or the wagon was shunted, flying boxes. Hardly ideal for biscuits. From this research came what in the USA is called the `grocery car’. This has specialised shock absorbing couplers and moveable internal walls. For most products, the weight limit is reached before the cubic limit. To further reduce damage, inflatable air bags can now be placed between the stacks of boxes.

· Refrigerated wagon. There was a time in North America when it was thought that no more refrigerated wagons would be built. They were very expensive, capacity was limited, and unlike the refrigerated truck, there was little control over the temperature in the wagon as the train crew could be many wagons away. Modern refrigerated wagons, with 225 m3 of capacity, take advantage of large clearances for double-stack and not only have state-of-the-art insulation and electronic temperature sensing but GPS locating devices and radio transmitters too. If an out-of-range temperature is sensed, the wagon’s location is transmitted to a central location and the railway is immediately notified. Burlington Northern & Santa Fe is buying 500 of these monsters.

· Steel coil wagon. Historically, the steel coil was loaded into a gondola or flat wagon and wedged in place. The outside sheets of the coil might get damaged, and the biggest problem was that usually the concentrated load could only be safely carried over the bogies. Today there are steel coil wagons where the coil is loaded into a longitudinal channel built into the wagon. Depending on the weight of the coils, they can now be carried over the whole length of the wagon.

· Multi-purpose wagon. An interesting approach to wagon design is the multi-purpose wagon. It may have a sliding roof and sides and loaded and end doors too. One variant has an adjustable upper floor to carry car parts in one direction and completed vehicles on the return. This Scandinavian wagon (right) is actually a pair of two-axle cars with a drawbar coupling, so it attempts to minimise tare weight. However, with a net-tare ratio of only 1.5, it is obvious that this particular car is severely restricted by the axle load and the maximum moving dimension.

So be warned! Trucks are getting heavier and more fuel efficient, and leaving aside road congestion, their service is getting better. Barges too are more efficient than they were. Governments are refusing to tax trucks or barges appropriately; so the railway industry must compete by pushing its technology as hard and fast as it can.

Axleloads and clearances, especially vertical clearances, are critical to the future of the industry, but choosing the right wagons that meet shipper’s exact requirements will be equally important.

Getting the biscuits and coal to their destinations at a competitive price, and with the biscuits unbroken, must be one of the railway industry’s goals.