Very early wagons had no brakes at all, the usual method of parking them
was to put a block of wood in between the wagon spokes. It soon became apparent
that some form of hand operated brake for parking vehicles was a good idea and
people experimented with various designs. The principle of the most popular
early design is illustrated below. This involved a hinged metal plate attached
to the bottom of the solebar with a wooden brake block bolted to it that
pressed onto the tread of the wheel. Brakes which function in this way are
called 'tread brakes'. In the example shown on the left this was operated by a
simple lever and acted on only a single wheel. Privately owned wagons with this
kind of brake were still seen as late as the early 1930's on running lines, and
probably survived until the Second World War or shortly after on privately
owned lines in larger factories, collieries etc. Railway company owned examples
remained in service into the early BR era. With the short wheel base (typically
five foot or one point six metres) of the very early mineral wagons it was
possible to arrange for these simple hinged brakes to apply to two wheels as
shown on the right.
Fig ___ Early hand brake designs
To 'park' a wagon the lever had to be tied down which was not terribly efficient. By the late 1830's some wagons were fitted with a loop of metal passing round the brake lever, close to the handle, and fitted with a toothed ratchet on the inside. The lever could be pushed down and hooked into the ratchet to secure the brakes but a sudden shock would often cause the lever to disengage. To avoid this problem the loop was drilled with a series of holes and a metal pin was attached (secured with a short length of chain). When the pin was passed through the holes it would lock the brakes on securely. This simple device has remained the most popular method of locking the brakes on goods wagons ever since.
Fig ___ Brake ratchet and 'pinning down the brakes'
This simple type of brake, with the hinged plate and very long brake handle, remained in use for many years. Examples were seen into the early BR era. They are usually referred to as 'long lever brakes'. In the photo below the brake handle has been tinted red to let it show up more. The wagon is based on a standard Peco chassis with the V hanger, right hand brake shoe and brake handle trimmed away. A new brake handle was added using 10x20 thou strip between the pin-rack and a small block of plastic glued to the underside of the chassis.
Fig ___ Wagon with 'long lever' brake.
In the 1880's a new design appeared called the Morton brake. The long brake handle extended upwards from a centrally mounted V shaped bracket (called a 'V hanger'). The brake blocks were pressed against the wheels by push-rods which passed through metal supporting loops called 'brake hangers'. The long brake handle allowed the shunter to exert a considerable force on the brakes. The handle generally extended up towards the right hand end of the body an arrangement called a 'right handed' brake, but some handles extended up toward the left hand end (left handed brakes). The handle on the end of the brake lever was usually painted white to make it more visible.
Peco, Graham Farish or Minitrix ten foot wheelbase wagons all have the Morton pattern brake. The brake levers are the same on both sides of the wagon, extending to the right. The Morton brake was a popular design which became part of the Railway Clearing House (RCH) standard specification for private owner rolling stock of 1923.
Fig___ Morton pattern brake gear & variants
To save money the hand brake was often only fitted on one side of the wagon, the other side having wheels with no brakes at all. This was done with both the 'long lever' and 'Morton' pattern brakes. During shunting the goods shunter often had to run alongside the wagon to apply the brakes but having brake handles on only one side of the wagon meant he often had to run across the track to get to the other side. Accidents in these yards often involved the loss of a limb and larger railway companies had special departments making prosthetic limbs for victims. Regulations and bye-laws were enacted to get the various users of goods rolling stock to turn wagons so that the brakes were all on the same side but this was seldom totally effective on a railway system with many wagon turn tables.
Fig___ Wagons with brakes on one side only
In older wagons, even with brake handles on both sides, the brake might only operate on one wheel. By the turn of the century railway company policy was to have a brake handle on each side of the wagon which applied a brake to both wheels on that side. This policy only applied to new wagons however, older stock with a brake handle on only one side remained in service into the early twentieth century.
On most wagons the brake handle only operated the brakes on the same side of the wagon, resulting in two so called 'independent' brakes, one on each side. By adding a connecting rod between the V hangers underneath the wagon the handle on one side could operate the brakes on all four wheels. The brake handles were then fitted with a cam arrangement on the V hanger end so that when one handle was operated the other did not need to move. This arrangement could only be fitted on wagons without hopper or bottom doors. An alternative design, intended to avoid payments to the holders of the patent on the Morton brake, had a cross link between the V hangers but with both handles at the same end of the wagon, right handed on one side, left handed on the other.
One money saving dodge was to have brake handles on both sides with a connecting rod between the brake V hangers but with only one wheel being braked on one side. The GWR modified several of their Iron Mink goods vans in this way in the later 1920's and this can be easily modelled by simply removing the unwanted parts of the brake gear from a standard Peco chassis.
In some cases wagons were built asymmetric brake gear, with the V hanger off-set toward one end of the wagon. This was mainly associated with wagons using a non RCH standard chassis (usually longer than normal) but retaining a large proportion of RCH standard brake parts. One arrangement, used by the Lancashire & Yorkshire Railway on their 12 foot wheelbase chassis, had two V hangers on one side but only one (mounted toward the right hand end) on the other. The opposing V hangers were connected together under the chassis. The same basic chassis was used both with and without vacuum brakes for a range of L & Y vehicles.
Fig___ L&Y end-door only 20 ton mineral wagon with asymmetric brake gear
It is perhaps worth noting that the wagons shown were built to carry coal for ships at about the turn of the last century but were transferred to general freight duties in the 1920's.
In about 1911 the RCH ruled that any stock built after that date had to have 'either side, right handed' hand brakes fitted by 1938. This means having a brake handle on each side of the wagon, each extending up toward the right hand end of the vehicle. The rule allowed for independent brakes on each side of the wagon (necessary for hoppers or wagons with bottom doors). Any stock not fitted with either side right handed brakes by 1938 was to be withdrawn from service. The railway companies were already building to this standard but a lot of private owner stock was still being built with brakes only one side and some older railway company wagons were still in service with this arrangement. Also some wagons had the brake lever extending toward the left end of the body. In the event, due to the financial troubles of the 1930's and the following war, some non-standard wagons survived the Second World War and a few made it as far as the 1950's.
Longer wheel base stock equipped with Morton type brakes sometimes had a long brake handle extending up from a central brake hanger but some used a standard length brake handle. The handle did not therefore extend all the way to the left hand end of the vehicle, but following standard practice it did always extend to the right of the V hanger.
The Morton brake was the most popular system for 'either side brakes' but it was not universal. The GWR for example built wagons which had a very short lever which could be mounted either on the left or right hand end of the chassis. This was the Thomas Brake, which was developed into the Dean Churchward brake (usually abbreviated to DC). Wagons equipped with DC brakes were in use into the 1950's at least. The DC brake used a 'worm drive'; the handle was attached to a rod with a screw thread and as this was turned the thread engaged with a toothed rack which applied the brakes. One big advantage of this design was that the brakes did not need to be 'pinned down' as the worm drive provides such high gearing. The worm drive is used on most model railway locomotives, the 'worm' is attached to the motor shaft driving a toothed gear wheel which turns the axle, you can make the wheels go round easily by turning the worm with your finger, but you cannot turn the wheels to make the motor spin. There were sometimes two V hangers on each side of wagons fitted with DC brakes, especially if it was longer than 10 foot wheel base, and the short handle was again painted white.
Fig ___ Thomas and DC Brakes
The shorter model wagon shown above has had its brakes modified to represent the Thomas type. On some of these wagons both brake handles were at one end of the wagon, so on one side of the wagon the brake handle is at the 'wrong end'. To model this brake type the brake handle and pin rack was removed from the right hand end of the Peco chassis, a small scrap of plastic was added under the chassis to represent the triangular support and a scrap of 10x20 thou strip was glued to this to represent the handle. The longer wagons, a GWR Open C, has the DC brake, with the double V hangers associated with a longer chassis.
Modelling the GWR high sided open was described in Railway Modeller May 2001 (Traffic for Tickling Article 3), modelling the GW Open C was described in Railway Modeller Jan 2003 (Traffic for Tickling Article 13)
One final variant seen on four wheeled stock was the end mounted brake handle. Both the pre-grouping Furness Railway and later the LNER built some four wheeled iron ore hoppers with the brake handle mounted across the end of the vehicle, the handle was operated at the right hand end on each side.
Fig___ Model of LNER hopper (in BR livery) showing brake handle
The model is based on a Farish ore hopper, the end supports should be closer together but the model was based on a single photograph and I only realised this much later. BR scrapped older wagons as a matter of policy and after about 1954 most of the non standard brakes on smaller wagons had disappeared.
Brakes on Bogie Stock
Bogie stock presents additional difficulties for brake designers. One option is to fit a separate brake system to each bogie with operating levers or wheels mounted on the bogie sides, the LMS diamond frame bogie had this kind of brake lever. Some designs put the operating lever or wheel on the front of the bogie, so the shunter had to get onto the tracks to apply the brake. Older bogie well wagons and the like in British Railways service often still had their awkward front mounted brake handles or wheels into the 1970's and possibly later.
The alternative is to mount the brake gear on the body of the vehicle and carry the action through to the bogies with linkages. Bogies wagons with this type of brake sometimes had a V hanger and lever mechanism (with the lever extending up toward the right hand end of the body). The Graham Farish 'sulphate wagon' has two brake levers on each side, on the prototype each lever acted on only one bogie. The handle of the lever operated brake or the hand wheel of the wheel operated brake is usually painted white. The GWR fitted their DC brake to some bogie stock, the handle being mounted on the under side of the chassis, usually somewhere about the middle.
Brake shoes and 'clasp' brakes
On early wagons the brake shoes themselves were shaped blocks of wood. Wooden brake shoes were used up into the 1930's on gunpowder vans, presumably to avoid the danger of sparks causing a fire. Cast iron brake blocks were in use by the 1880's and became the norm by the turn of the century. In most early brake designs the brake blocks only pressed on the inner side of each wheel. Later designs had two blocks per wheel, one pressing on the inside the other on the outer side of the wheel. These were called 'clasp brakes' and they are mainly associated with power operated vacuum and air-braked stock (discussed below). Do note however that not all vacuum braked wagons had clasp brakes. In the pre-grouping era I believe only the LNER used clasp type brakes in their standard design for vacuum braked goods stock although clasp brakes were the norm for passenger stock on all railways. Having said which I have seen one photo of a GWR registered milk tank wagon in the mid 1930's which had the Dean Churchward hand brake lever and clasp type brakes so perhaps there was a requirement for clasp brakes on passenger rated stock (if so I am not aware of it). One feature of clasp brakes is the lack of push rods between the central V hanger and the inner brake shoes on the standard four wheeled wagon chassis. This is because clasp brakes are operated by a mechanism fitted under the chassis between the wheels. Parkwood Models suggest simply removing the push rods from a Peco chassis to represent a clasp brakes chassis. This looks acceptable and to date I have had little success trying to add the outer brake shoes due to the depth of the flange on N gauge wheels. It should be noted that although BR adopted the LNER vacuum brake, which had clasp type shoes and no push rods, the standard four-shoe Morton pattern brake was also used for vacuum braked stock, usually this required a tie-bar fitted between the bottom of the axle boxes on each side. Do not go round removing the push rods on your stock unless you are sure the type you have modelled had the clasp type brakes.
Braking a train
An early goods train would have brakes on the loco tender which could be operated by the crew and passenger coaches carried a guard (the term 'guard' came from stage coaches) who could operate brakes on the carriage. Goods rolling stock however would only have a hand brake, which could not be operated whilst the train was moving. This made stopping the train rather tricky and after about 1850 goods trains had a separate 'Break Van' (this spelling was used up to about 1870). This was a wagon fitted with weights (typically ten tons) and a set of brakes acting on all four, sometimes six, wheels. There was usually a small 'hut' type structure provided for the guard (see also Brake Vans & Tenders below for further details on these vehicles). The rules required the guards van to be attached to the rear so there were railway personnel at each end of the train to warn other trains if there was a problem. With a heavy load an additional brake van might be marshalled toward the front of the rake as well although this would be another guard's wages to pay for. The train crew used the whistle to pass instructions to the brake van crews or guards.
Handling a train with no brakes on the wagons was a somewhat fraught exercise, when setting off the locomotive had to proceed slowly (about walking speed) until all the couplings had tightened, then apply full power to accelerate the train (although 20mph would be a typical speed for such a train). If the train went down a gradient the wagons would tend to 'catch up' with the locomotive, as the line leveled out there was a risk that the slack in the couplings would allow the wagons at the rear to slow down, then as the couplings were pulled tight the effect would ripple down the train until either a coupling broke under the sudden shock load, or the guard would get knocked off his feet in the brake van. This sudden tightening of the couplings is called 'snatching' and was a common cause of broken couplings. To avoid this it was standard practice to stop the train at the head of the gradient and for the guard to walk along the rake applying the hand brakes on the wagons, a practice called 'pinning down the brakes'. Once the brakes were set the guard would wave a green flag and the locomotive would drag the rake onto the incline. Naturally once the train reached the bottom of the incline it was necessary to stop so the guard could walk along the rake and release the brakes, a rather time consuming exercise. For more on the operational problems associated with and-brake only wagons see the section on Freight Operations - Categories of Goods Train and usage of rolling stock.
In America the clearances on the lines allowed a crew man to walk along the top of the goods vans and open stock so brakes were fitted with top mounted hand wheels. This meant the brakes could be applied whilst the train was moving but of course this took time. As the hand brakes on the British wagons could not be operated on the move when a train reached a downward incline the train would stop so the guard could walk along beside the wagons and 'pin down' the brakes to prevent the wagons pushing the loco down hill too fast. Pinning down the brakes took a fair bit of time and a train of wagons with only hand brakes had to travel slowly so the brakes on the loco and guard's van(s) could control it. Because of this various forms of wagon brakes were tried which could be operated either by the loco crew or by the guard at the rear of the train (who was in nominal charge of the train). These braking systems are called continuous brakes.
Continuous brake and automatic continuous brake
Any system that allows the brakes on all the vehicles in the train to be operated by one man is called a 'continuous brake'. An 'automatic continuous brake' has the additional benefit of automatically applying these brakes if the train splits in half. There were various experiments with mechanical continuous braking systems. George Stephenson patented a very simple mechanical brake in the 1830's which had a push rod connected to the buffers on the wagon. When the locomotive brakes were applied at the front of the train the buffers then operated the brakes on the individual wagons. At the time this was considered too expensive for general use and instead train speeds were limited to a maximum of about 25 mph. Stephenson also designed a steam powered brake for wagons but it was not taken up and steam powered brakes were only used on locomotives in the UK.
In 1856 the Lancashire & Yorkshire Railway's engineer Charles Fay developed the 'Fay' continuous brake for passenger coaches. This had iron rods under each coach with a universal joint at each end, the guard applied the brakes by turning a handle in the guard's van. This was not entirely satisfactory as the braking relied on the strength of the guard but it was taken up by several railways.
To provide power assisted braking everyone settled on devices operated by air pressure, the Caledonian Railway used a compressed air powered brake on passenger coaches in 1871. An alternative was to use a vacuum operated device in which the loco pumped the air out of the system to release the brakes, a vacuum brake system was used by the North Eastern Railway in the mid 1870's.
These air operated systems were initially not automatic but that feature was incorporated in the late nineteenth century and soon became standard. Stock fitted with continuous automatic brakes had a cylinder mounted under the chassis and flexible pipes on each headstock for connecting to the train. The use of automatic continuous brakes meant that, on passenger trains using corridor stock, only a single guards compartment was required and this could be set in from the end. On compartment stock it was slightly more problematic, the GWR 'B' set coaches were built in pairs and had a guards compartment at each end. By the time that multiple unit stock appeared a single guards compartment was usually located somewhere about the centre of the train. Under BR ownership the rule book stated that where there was more than one brake compartment (accessible) on a passenger train (coaches or DMU) the guards duty was to travel in the rearmost brake compartment unless his duties require him to be elsewhere. This was so that should the train be stopped for any reason on the open line the guard could make his way back up the line quickly to lay detonators on the track to warn any following train that there was an obstruction on the line.
Having witnessed a railway accident the American engineer Westinghouse worked on power assisted braking systems. His first offering was a non-automatic system using air pressure supplied from the locomotive to operate the brakes, called a 'straight' air brake which was widely adopted in America. The system was less than ideal, if the train parted the brakes did not apply on the detached section and would no longer work on the section attached to the locomotive, also if the train was long it took time to pump up the pressure in the rake of wagons making the system rather slow acting.
To make a brake operate automatically, whether it was an air or vacuum brake, required a cylinder or reservoir mounted on the wagon. In the vacuum brake this contained a piston fitted with a non-return valve. To start the system the locomotive pumped the air out, the non return valve allowed the air to be pumped from the far side of the piston. If the locomotive allowed air into the pipe, or if the connection broke, air would enter the cylinder and press on the piston. The non return valve in this case would not open. The vacuum brake was therefore operated by normal atmospheric pressure (28 lbs per square inch) and hence required quite a large piston to get sufficient force to apply the brakes. The piston was fitted with a spring so that when the pressure was equalised in the cylinder (either both sides had air in them or both were under a vacuum) the spring held the brakes in the 'off' position.
There were two common types of vacuum brake, one had a stubby cylinder mounted vertically to other had the cylinder mounted horizontally, the vertical type mated easily with the Morton pattern hand brake and became the norm. In the photograph below the cylinder and its actuating arm have been tinted red to make them more visible. The wagon has 'clasp' type brakes, so there are no push rods running from the V hanger to the inner brake shoes. Where the standard four-shoe Morton brake was fitted the push rods would be required.
Fig___ Vacuum cylinder
Rolling stock equipped with continuous automatic brakes is usually referred to as 'fitted' and stock with only a hand brake is commonly referred to as 'unfitted'. In Britain all stock 'fitted' with an automatic brake had either screw or instanter couplings as described above.
In 1873 Westinghouse patented an automatic continuous air brake, this uses high pressure air fed through a pipe, controlled either by the loco crew or the guard. The individual vehicles had a reservoir of air and the loco had to pressurise the system to release the brakes, if the train parted the brakes were automatically applied and the system operated quickly in normal use. This system, using air at high pressure, required a much smaller cylinder to apply the same force to the brakes.
In Britain there was a major trial of braking systems in 1875, promoted by the Royal Commission on Railway Accidents which had been set up the previous year. Five companies supplied locomotives and rolling stock and nine different systems were tried. This was where Westinghouse had his first major British showing.
Most British companies opted for the vacuum brake, and generally they adopted the Gresham brake (patented in 1878), but several British companies opted for the fast acting Westinghouse air-brake. An express passenger train weighing five hundred tons and travelling at 60 miles per hour on the level would be stopped within 360 yards by either system.
The Great Eastern, the North Eastern and the London Brighton & South Coast Railways were still air-braked at the time of the 1923 grouping. The North British Railway had used the Westinghouse brake but was in the process of changing to the more popular vacuum brake by the time of the grouping. As rolling stock travelled through the system the use of differing kinds of brake became a problem. Some vehicles were fitted with one kind of brake and through pipes to allow connection of differently equipped vehicles to either side (this was called 'piped' stock). A few were equipped with both air and vacuum brakes (called 'dual fitted'). Both these options cost money and added complication to an already complex network so by about 1930 all British companies had switched to the Automatic Vacuum Brake (AVB). On the continent and in the USA the Westinghouse air brake became the norm and all vehicles had to be 'fitted' hence wagons intended for cross-channel ferry working between Europe and Britain were 'dual-fitted' with both air and vacuum brakes.
In America a law had been passed in 1893 which stipulated that all railway vehicles, be they freight or passenger, had to be equipped with automatic air brakes. On the Continent air brake 'fitted' stock was the norm by the time of the First World War. In Britain however the fitting of automatic brakes was considered inappropriate to low value goods vehicles intended to travel in slow goods trains. Some unfitted wagons had the flexible connection hoses but were simply 'piped' as described above. These piped wagons could be marshalled into a fully braked train, allowing the automatic brakes on the remainder of the train to operate normally. The maximum permitted speed of the train was then determined by the number of piped vehicles in the rake (see also Freight Operations - Freight Train Speeds). Only wagons fitted with a continuous automatic braking system were allowed in trains travelling at any speed. In the context of goods traffic anything over 40 mph was classed as 'express' up to the mid 1980's.
The LNER/BR vacuum operated clasp brake was an asymmetric design, on one side there were two V hangers, on the other there was a rectangular arrangement to allow the use of a standard brake handle (this can be seen on the Peco fifteen foot chassis). Although this was the official standard there seem to have been a lot of vacuum braked wagons built using standard Morton pattern brake gear so I wouldn't worry about this unless you fancy messing about to add some variety to a rake of wagons. If you decide to modify a chassis do check with photographs to make sure that some wagons you are working on did use this kind of brake.
Fig___ LNER and BR standard vacuum brake gear
Failure of Continuous Automatic Brakes
In theory a train fitted with continuous automatic brakes cannot accidentally leave any wagons behind as if a coupling fails the brake pipes should separate and apply brakes on both parts of the train. However Messirs David Hansen, Clive Feather and 'Chippy' have discussed three incidents involving 'fully fitted' trains on the uk.railways news group. The oldest occurred in the later 1950's when a goods van (possibly two) was left behind on the East Coast Main Line around Montrose. This must have been tagged on to a passenger train as there was no mention of a brake van, brake vans were still mandatory for goods trains but, thanks to the safety of the continuous automatic brake, individual vans could be attached to passenger trains (four and six wheeled 'fitted' stock were only banned from passenger trains in 1959). The train came to a halt but the train crew, and staff on the line following the incident, failed to realise that the van(s) had been left behind. By the time this was spotted by a signalman another train was already in the section and it ran into the van. In the 1970's a loaded steel train found itself on the gradient at Beattock with only the brakes on the loco operating. The train accelerated and ran into the rear of the preceding train (also a steel carrying train) with enough force to kill one of the crew. More recently a Freightliner rake parted, the brakes were not activated and the rear portion of the train then rolled along under its own momentum into Carlisle. The signalman saw what was happening and diverted the errant wagons onto an avoiding line around the station but the wagons then derailed and demolished a bridge, some of the wagons ending up in the river. Apparently the full brake test had not been completed when the trailing section had been added to the train at Preston. I do not have details of exactly what occurred in each of these incidents however the assembling of a 'fitted' train requires that all the pipes (air or vacuum) are connected and that the stop cock valve on each pipe is opened. The valve being closed would prevent the brakes operating on any of the following wagons but any stock between the closed valve and the loco would function as intended. Crucially everything would appear normal to the train crew. If the train was on a gradient, as with the steel train, only the locomotive brake and any wagons connected to the loco with the cocks open would function. If the train parted at a point beyond the closed valve, as with the Freightliner incident, the train would continue as normal and as the brakes would never have been charged the loose wagons would be free to roll. This appears to be the basic cause of the second two incidents, however another contributor noted that he had seen a fault on an air braked vehicle where the hose became blocked and remained filled with air even when removed from the wagon. Regarding the steel train incident the contributor signing himself 'Chippy' added
I can't recall the Beattock incident, but a continuity test should have prevented such an occurrence. The only other possibility would be a incident such as that which happened at Darlington to a Deltic-hauled passenger train, when the brake-pipe cock was knocked closed by an object thrown up from the track. The train was signalled into the platform at Darlington, and was heading for the divergence without noticeable reduction in speed. A restaurant car steward realised that the train was not slowing, and used the communication cord.
The cocks mentioned can be seen in the photograph at the end of the
section on Goods Rolling Stock Design - Chassis - Couplings & Hoses. This
photo shows the hoses associated with an early BR twin-pipe air brake and the
standard vacuum brake.
Braking Developments under BR ownership
Following nationalisation British Railways initially stayed with the vacuum brake and this was included in the 1955 modernisation plan as a requirement for all new stock. By the early 1960's with heavier goods stock entering service the design of the standard British Railways vacuum brake incorporated a facility for automatic changeover for loaded and empty working. Longer wheelbase wagons with this feature have an arm extending toward the centre from the left hand brake shoe, this can be seen on the Peco fifteen foot wheelbase chassis. Following comparative trials of air and vacuum brakes in the 1960's the decision was made to change over to air brakes. All new stock built after 1971 was equipped with air brakes. Air brakes then had to be retrofitted to older vehicles when these were to travel in new high speed air-brake only services. This did not please the rolling stock leasing firms and the oil companies who owned their stock and had to foot the bill for the change over.
By the early 1970's vans and open wagons equipped with air brakes began to appear in sufficient numbers to allow the development of a network of air braked services. These vehicles were designed to run at 60 mph fully laden and could travel at 75 mph with a reduced load. The first all air-brake wagon load services began in 1972 and air-braked 'cartic' car transporters displaced from Motorail services were soon included to carry imported cars.
Some vehicles were built or modified with both vacuum and air brakes ('dual fitted') but this was not common. About three hundred ten foot wheelbase 'vanwide' vans and a smaller number of twelve foot wheelbase 'pipe' wagons were modified in this way, mainly to handle for Ministry of Defence traffic. An alternative was to add through pipes for air brakes to vacuum fitted stock, this was much cheaper and was much more widespread. A number of air-braked vehicles were also fitted with a through vacuum pipe (quite a few privately owned four-wheeled air-braked tanker wagons were so fitted and TOPS coded TTB). In late 1987 a number of twenty one ton end door wagons (TOPS coded MDV) had through pipes for air brakes added (re-coded MDW), these wagons were then used for coal and scrap metal in Scotland.
A lot of vacuum braked wagons continued in service into the late 1980's, the ubiquitous twenty one ton coal hopper (TOPS coded HTV) were still in use for coal, sand and crushed limestone (supplying tar macadam plants) up to about 1991. The twenty one ton steel mineral wagons coded MDV remained in use in South Wales moving coal and colliery spoil until about 1992. Some of the more specialised vacuum braked stock survived a lot longer than anyone expected. The ICI owned limestone bogie hoppers built in the 1930's were kept in service until mid 1998, although the vacuum fitted locomotives able to haul them were getting scarce and pairs of class 37's were the norm.
After 1996 unfitted trains were banned by Railtrack, and by this time many locomotives had only the facility for air braking fitted. This was a problem when dealing to the movement of old vacuum braked wagons, vehicles being sent to scrap yards or damaged stock being taken for repair. The solution was to break the rake up into three wagon 'cuts' with redundant HAA hoppers inserted between the cuts. The brake pipes on the HAA wagons are then connected using a long flexible hose, allowing them to be used to control the train.
The general trend has been to switch to disc brakes on more modern air braked stock (many of the modern wagon types use disc brakes), but Freightliners Ltd. when looking at replacement designs for the now ageing fleet of container flats in the late 1980's stated they were not interested in disc brakes, considering that the cheaper clasp type are perfectly adequate for their purposes. Clasp brakes remain the most common type on goods stock throughout Europe.
As discussed in the section on Track there has been a Europe wide study on the reduction of noise pollution caused by freight trains. One part of this study was the Eurosabot project, focusing on the design of the brake blocks used on modern tread brakes. The idea was to look at alternatives to cast iron for the brake shoes to reduce the damage done to the treads and hence the noise they make as they roll along and also to reduce the squeal when the brakes are applied. Thermo-elastic instabilities due to local heating of the contact surface and material transfer between block and wheel, dynamic instabilities and periodic wear were felt to be factors responsible for the generation and growth of roughness on the wheel treads. In the end no practical alternative to cast iron was found.
Adding vacuum brakes to a model chassis
The Minitrix ten foot wheelbase chassis has the large cylinder for the standard British vacuum brake system moulded onto the under side. Parkwood Models kits come with a brake cylinder that can be fitted if required but Peco, Farish and many kits using these chassis need a home made cylinder adding. The brake cylinder, when mounted under the wagon, was offset to one side and offset to the left of the V hanger. The Parkwood kits suggest mounting the cylinder on the letter P in Peco, moulded on the underside of the chassis kit. I have tried various methods for adding these brake cylinders. One method is to cut a length of empty ball-point pen refill, pass a lengths of Slaters 20 thou brass wire through this and pack it with Milliput, keeping the wire central as possible. One end of the wire is trimmed to about 2mm length and this is glued into a hole drilled in the bottom of the chassis (I use the tip of a pointed modelling knife to bore the hole). The trailing end of the wire is bent over into a square U shape and the free end is glued into another hole in line with the V hanger. A simpler method is to use a spare Peco wheelset, trim off the flange (I use toe nail clippers for this) glue the rear of the wheel onto a scrap of 30 thou card and trim this (you do not need to be very accurate here). The card backing is then glued onto the underside of the chassis. You can drill a hole in the centre and add a wire U shape as before, or you can just glue a strip of 20x20 thou to the wheel to represent the operating lever that connects to the cross linkage between the V hangers. The Peco wheel is actually rather large in diameter but in normal use it is almost hidden under the wagon. Both methods are more fully discussed in the section on Kit Bashing.
Fig___ Vacuum brake cylinders on model chassis
On hopper wagons it was not possible to have a cross linkage allowing a single vacuum brake to operate on both sides of the wagon so two reservoirs were commonly fitted. As these could not usually be accommodated under the wagon they were usually mounted on top of the chassis tucked under the end of the hopper at one end of the wagon. This can be seen on the Peco Grano and Farish hopper wagons. On bogie wagons it was usual to have a reservoir at each end, one for each of the bogies, and on hopper types these were again mounted on the top of the chassis. The sketch of the ICI limestone hopper shows the cylinders (shaded dark grey) mounted at each end of the chassis (c).
Fig___ Vacuum brake cylinders on a bogie chassis
The hand brake was still required for use when the vehicle was not connected to a locomotive and on four wheeled British stock the automatic brake was commonly connected to a standard four-shoe Morton pattern mechanism on 'fitted' goods stock. The vacuum brake piston operated a lever which turned the cross-linkage between the V hangers to apply the brakes. The connection to the cross link rod was fitted with a ratchet mechanism so the man applying the hand brake did not need to overcome the force of the return spring in the vacuum cylinder.
The principal disadvantage of continuous automatic brakes, air or vacuum, is that when a loco is not attached to the stock the brakes will be on. As a lot of shunting was done by men and horses or by gravity the automatic brakes had to be disabled so the wagon would roll freely. The pressure in the onboard reservoir cylinder was released by pulling on a short chain under the wagon. The location of this chain was usually indicated by a five pointed white star painted on the chassis.