21/02/20 – Stop that wagon!

This week we’re taking a look at the work our Test Car 2 was built for, namely the slip/brake testing of freight wagons. 

For 50 years from the late 1960s the acceptance of new or modified wagons onto British Rail included dynamic brake testing predominantly carried out using the slip/brake method. This test measures the brake stopping distance performance of the wagon independently, i.e. not coupled with other vehicles in a train. 

In order to conduct slip/brake testing a special coupling arrangement was used on Test Car 2, the design of which originated from use on North Eastern Railway J21 and J25 type steam locomotives providing banking assistance on the Darlington to Kirkby Stephen line over Stainmore Summit in the 1940s and 50s. 

FIG 14 - Test Car 2 - RTC 12 July 1987 - 383

In addition to the slip coupling, the brake system on Test Car 2 was modified such that a test engineer could independently operate the brakes of the wagon under test without affecting the brakes of the test coach or locomotive which remained under the control of the driver. 

A typical slip/brake test train would consist of a locomotive, Test Car 2 and the wagon under test. Class47 locomotives were preferred for the slip/brake testing, not just because they had adequate power to accelerate quickly; also, the responsiveness of the engine control system of the Sulzer locos (compared to the English Electric locos) made it easier for the driver to control the speed more accurately with the short and often light trailing load of a test train. 

The slip/brake tests were normally carried out on the Down Slow line of the West Coast Main Line between Crewe and Winsford. To ensure safe operation a ‘T3’ possession of the Down Slow line was applied by the Crewe Coal Yard signalman, making sure it was blocked to all traffic and protected by stop boards and detonators at each end of the possession section.  

This section of line was particularly suited to the slip/brake testing because the test section was level, and the four-track formation allowed normal traffic to continue on the other three lines whilst testing was in progress. 

It was not permitted to carry out slip/brake testing during hours of darkness, thick fog or falling snow and at least 1mile clear visibility was needed before testing could commence; this was because the test engineer had to be able to clearly keep the test vehicle in sight at all times when the vehicle was detached from the test car. 

A slip/brake acceptance tests of a wagon would normally be carried out over two days, one for each load condition, so one day for empty and one day for loaded wagon. 

Each day would start with test engineers joining the test train at the Derby RTC, a loco would arrive from Derby 4-shed and would transit to Crewe. The train would pause in the station to pick up a Traction Inspector, (and some sandwiches) then continue onto the Down Slow line at Crewe Coal Yard. The T3 possession was then set-up to protect the line, the train brake systems were configured for test and static test checks for correct operation were carried out. These static checks included measurement of brake cylinder application timings and pressures on the wagon under test, and a continuity brake test on the locomotive and test car brakes. 

Heavy duty instrument cables were attached from the test car, along the outside of the locomotive and into the leading cab (normally through the drivers’ cab-side window) and connected to twin intercom speaker/microphone outstations. The locomotive was always manned by a driver and a traction inspector for slip/brake testing; this allowed the test engineer to communicate using the intercom directly with the traction inspector in the cab so as not to distract the driver from his duties. 

Once the intercom was tested and the static brake tests completed to the satisfaction of the test engineer, the slip coupling was fitted between the test car and the wagon, and testing could commence. 

A slip/brake test is described in stages as shown in the diagrams below. 

The test engineer calculated the wagon brake stopping distance for each slip/brake test run, taking the total distance from the point at which the brakes were applied on the wagon until the locomotive and test coach had stopped, then subtracting the distance the locomotive and test coach had to reverse back to collect the wagon. The results were plotted on a speed/distance graph. 

The stopping distance limit in 1987 for a wagon running at 75 mile/h was 951metres, the graph below shows test results just failing to meet this, therefore this wagon would have been subject to modification to the brake system before a retest. 

A deceleration meter fitted on the headstock of the wagon containing a calibrated accelerometer and a low pass filtered output onto a strip paper chart provided an accurate measure and characteristic of deceleration rate of the wagon throughout each slip/brake test. 

Tests were always carried out at varying speeds from 30 mile/h up to the maximum operating speed of the vehicle under test. On average 15 slip/brake test runs could be completed during a day’s testing, however the achievable number of tests varied depending on how slick the team on board was working, the type of locomotive, the performance of the wagon under test, and more often than not, the weather. 

J:\1 - Dave\Book Prep\TestTrains Book\Figures Test Trains Book\Figures Vol 2 Test Trains\Vol2-43 - FIG 131 - ECML Slip Tests TC2 -  30 Jun 1985 -Z.jpg

After testing was completed the slip coupling was removed and a standard screw coupling re-attached, the brake system was configured back in the normal manner and the statutory brake continuity test completed before the train was hauled out of the test site. The train would then proceed up to Winsford for a loco run-round before returning via Crewe to the RTC at Derby. 

In addition to wagons, on-track plant and coaching stock were occasionally slip/brake tested, for example this Cowans Sheldon 75t breakdown crane needed testing after it was modified by fitting air brakes in 1987.  

Due to the fall in wagons requiring testing and UK network access constraints, slip/brake testing on the UK network finished by 2010. Computer modelling and dynamometers offer alternatives to testing now days although this type of testing does continue in mainland Europe and has also been done on private lines. An example were the tests done some years ago at the GCR, albeit without the need for a test coach since the computer took over. The link shows a Youtube video of a GCR slip/brake test run using D123 in July 2009. https://www.youtube.com/watch?v=s3UfKOhYSMk 

Once the GCR is up and running again, keep a look out for events at Quorn when we hope to have Test Car 2 open to visitors again with displays and more information about its history and slip/brake testing.  

For those with an appetite for more detail, the full story of Test Car 2’s work during the 1980s and 90s, along with accounts of why and how wagons were tested for acceptance onto British Rail, can be found in Dave Bower’s Rail Vehicle Testing book. ISBN 9781999935603 https://www.bowerbooks.co.uk/ 

Lastly, we await news from the GCR following the government announcement tomorrow whether we can re-commence working on the fleet again, continuing we’d left off on the Yellow Coach and 2 tank wagons. Either way We’ll be back with another feature, or hopefully an update. See you then.

Vehicle Profile #7 – Brakevans

I though it best to give both Matt and Ross a break this weekend, so for the first time its me, Dave Bower, completing a weekly update, this week we focus on the van at the back of the train.

As early as the 1840s wagons or coaches were specifically adapted for a Guard, this was someone employed by the railway to protect the valuable stock carried by the train from theft or vandalism. As these ‘unfitted’ trains (vehicles not fitted with an automatic brake controlled by the locomotive) increased speed and weight the Guards took on more duties relating to the actual safe running of the train. By the 1870s what we now know as ‘brake vans’ were in use and in the case of goods trains meant the Guard was on hand to take action in the event of a breakdown, accident or the more common event of train separation. As the speed of goods trains still continued to increased the purpose of the brake van and the guard’s duties developed further with the Guard using the brake van’s handbrake to assist with keeping the train under control on downwards gradients or whenever he could see that the locomotive’s crew was attempting to slow the train. The Guard could also use the handbrake to keep the loose couplings taut between unfitted wagons  minimising the risk of broken couplings and if no locomotive was attached hold the train with the brake vans brake.

Different types of brake vans evolved, some with single verandas and others with a veranda at each end, normally with a safety bar or half height door to each side. In most cases a significant amount of ballast is installed in the form of steel, cast iron, water tanks or more commonly during and after the wars concrete, this was built into the underframe to increase the available braking effort applied by the van. Step boards are fitted, sometimes along the full length of the van along with multiple grab handrails for the use of the Guard or Shunter when required. Inside the van’s interior most are fitted with a coal stove for the guard’s heating and cooking needs, with a hanging rail above with hooks on for drying wet clothing. As well as a desk to complete the all important paperwork required by the company.

Most brake vans were not built with train brakes, only a wheel operated handbrake; because they were designed to be used at the rear of un-fitted trains. Some are however vacuum through-pipe fitted, in which case a brake application valve is installed inside the brake van but towards the end of brake van use between the late 60s and 80s vacuum and even air brakes were fitted.

Duckets on each side of the brake van provide the guard with safe viewing of the train , signals ahead and the lineside without the need for leaning out of the brake van. The seats by each ducket also have side and back pads which provide the guard with some useful support in the event of jerks or coupling snatches. The handbrake wheel is installed within easy reach of the guards ducket seats.

Lamp irons are fitted to carry a tail-lamp and also side lamps. It was the guard’s duty to check that the tail and side lamps were on-board, filled with paraffin, the wick trimmed.

Trains that are not fitted with the automatic brake throughout, i.e. unfitted, must in addition to the tail lamp carry side lamps. With one exception, it is not a requirement to display side lamps on freights when the automatic brake is connected and in use on all vehicles on the train. This was a LNER / BR Eastern rule and later adopted by all of BR in the 1980s

Side lamps are required to be lit at all times. They are designed to show a white aspect towards the locomotive to inform the crew that the train is still complete and following. if however the lamps were unlit, a red aspect could be shown via light shining through the rear red filter.  This could be misread by the crew as a stop signal. In a genuine emergency the Guard would rapidly apply and release the hand brake, jerking the train to grab the crews attention and display a separate red flag or light. If the train was fitted with a brake pipe the full length of the train, then all the Guard needed to do was release the vacuum or apply the air brake.

To the rear two red side lamps are displayed for trains operating on main or single lines.

or, one red light on the side furthest from the main line and one white light nearest for trains in loops adjoining main lines and running in the same direction. This also applies on double lines signalled for trains in both directions whilst travelling in the reverse direction.

Side lamps should be removed when in sidings.

There is a story of an express trains crew leaping from the foot plate of a loco when the Guard of a goods forgot to swap his mainline side lamp for a white.  Reputedly a down express came through Loughborough Central and saw in the distance beyond Empress Road bridge the 3 red tail lamps of a goods,  the driver applied the brakes and both he and the fireman leapt from the cab. The driver received cuts and bruises the fireman however hit the bridge and was killed. The Goods was in the Down Goods loop clear of the express waiting to pass.  How true the story is regards to location I cannot verify but I’m sure it is likely to have happened even if the outcome did not involve a fatality.

The Guards preparation duties include checking that all the necessary equipment was in the brake van.

  • A shunting pole which is a wooden pole about 6 feet long with a twisted hook on the end, this is used to couple couplings without the guard having to climb between the wagons,
  • A brake stick, used to lever down the handbrakes of wagons,
  • Two pairs of track circuit clips, for use in emergency situations to indicate to the signalman that a train is occupying that section. They are clipped over both rails of a track-circuited line so as to short circuit the track in the event of an incident or accident,
  • A spare vacuum hose,
  • Wheel scotches (minimum 2),
  • Fire extinguisher and fire bucket,
  • Side Lamps (x 2),
  • Tail Lamp,
  • Red and Green flags,
  • Paraffin for the lamps,
  • Coal and kindling to light the stove fire.

Other uses of brake vans includes those fitted with ballast ploughs under each end, that are used to assist with distribution of ballast and clearing the rails during ballast drop runs when at the rear of a train of bottom discharge ballast wagons such as Dogfish or Catfish type wagons.

As the running of unfitted trains dropped during the 1970s and finished in the early 1980s, many brake vans were withdrawn, shunted to the end of sidings and left to rot because they were filled with concrete so had to be dealt with differently when it came to scrapping. This probably helped provide more of a choice for the preservationists.  Nick has regaled us with stories of brake vans being worked from scrap yard to scrap yard as none were too keen to break up the vehicles as they were mostly concrete and wood.

In the Quorn Wagon & Wagon fleet we are lucky to have four brake vans, all of which have been restored for use at the GCR. In each case, in addition to the replacement of various sections of the bodywork, the restoration by the team has involved corrosion removal, applying rust prevention and wood preservatives, brake equipment overhaul, axle bearing maintenance, full internal refurbishment, stoves, new upholstery and painting, underframe scraping, full external repaint and sign writing.

Our oldest is S56010 a Southern 25T, 16ft wheelbase ‘Pilbox’ Brake built at the former London Brighton & South Coast Railway works at Lancing in 1930 to Lot No.3033, restored in 2018 including the complete replacement of one veranda and external timberwork, door planks and windows, stove re-built and stovepipe.

Next in order of age is M730562 an LMS 20T, 16ft wheelbase Brake built in Derby 1938, Lot No.1104, also restored in 2018, including the complete replacement of external timberwork.

Then we have B954268 a BR 20T, 16ft wheelbase Brake built in Darlington 1958, Lot No.3129, restored 2018 including replacement of a significant amount of external and veranda timberwork, however currently out of traffic due to wheelset damage.

Finally our youngest B954546 a BR 20T, 16ft wheelbase Brake built in Darlington 1959, Lot No. 3227, restored last year after 8 years out of use, work included timberwork replacement to the verandas although brake rigging work remains

Operationally at the GCR a brake van is marshalled at each end of goods trains, this is to assist with more timely changes of direction at each end of the line, which ensures that our brake vans are used regularly, but does mean that we have to keep on-top of the operational wear and tear.

Matt of course, and as some of our images show, did use to operate these vehicles during his tenure with the operations department, his biggest sense of helplessness was the dreaded sound of couplings rapidly tightening as the crew were a little exuberant with the regulator. With up to twenty vehicles and a foot of slack between each, whatever speed the loco has achieved in that 20ft is instantly applied to the brake van as the last coupling tightens, on a number of occasions he recalls bracing himself between duckets or grasping the brake standard as the inevitable approached, but as he confirms it is all part of the fun.

Next week we shall take a broad look at our departmental vehicles and the work they undertake on the modern day Great Central Railway, not all of our vehicles are used to demonstrate what they once did some still actually do the work they were built for and more.

How effective is the Handbrake?

Early wagon brakes were operated by a simple lever and acted on only a single wheel, however from the 1880s the handbrake design by Morton that we see on many of our wagons was developed.

The brake lever extended upwards from a centrally mounted ‘V hanger’ and brake blocks were pressed against the wheels by push-rods which passed through metal supporting loops called ‘brake hangers’. The long brake lever allowed the shunter to exert a considerable force on the brakes. Levers generally extended up towards the right hand end of the body and the handle on the end of the brake lever was usually painted white to make it more visible.

Whilst early wagons had single push blocks on one side of the wagon only, as the weight of wagons and their loads increased so did the amount of braking effort required. Greater braking effort came from using brake blocks on both sides of the wagon and later by using clasp brakes which have two blocks per wheel.

Various designs evolved to transmit and multiply the applied lever effort to the brake blocks to ensure that sufficient brake force could be easily applied to hold a loaded wagon on a gradient. A cam or slotted link arrangement is used so that the handbrake on either side of the wagon operates the brakes on both sides via the transverse shaft.

Example of cam operated brake transverse shaft lever handbrake.
Example of slotted link operated brake transverse shaft lever handbrake.
A ratchet or ‘Pin-Down’ loop is used so lever can be pushed down and hooked into the ratchet or pinned to secure the brakes.

Handbrakes can also be used during the operation of partially fitted or unfitted freight trains which have no means for the driver to brake the unfitted wagons when he needed to slow down or stop the train. The guard ‘Pins Down’ the handbrakes at ‘Stop and pin down wagon brakes’ locations (usually prior to a severe downhill section of track and known by train crew as part of their route knowledge) so that the handbrakes help ensure that the driver retains control of the train on the downhill section. The train then stops again at the bottom of the incline to allow the guard to ‘take up’ the handbrakes (release them).

The effectiveness of the handbrake on a new design of railway vehicle is established by conducting a static test, whereby the force needed to move a vehicle along the rails, with its handbrake applied, is measured. This resulting force is used to determine the gradient on which the handbrake will hold the vehicle.

In order to move the test vehicle along the rails, a hydraulic ram fitted with a calibrated ‘Load Cell’ is installed between the drawgear of the vehicle under test and an anchor vehicle on the same line. The anchor vehicle was parked with its brakes fully applied and chocks placed tightly under each wheel.

A test is not valid if the wheels slide along the rails, therefore it is important to carry out a test within a workshop, where the rails are clean, dry and preferably level. To ensure a consistent and representative application of the handbrake lever, weights are attached the lever that are equivalent to the standard level of effort that could normally be applied at the lever end by the average person weighing about 60kg applying the handbrake. The test is always repeated to assess the performance of the handbrake when applied from both sides of the vehicle.

The acceptability of the performance of a parking brake was assessed by establishing the gradient on which the vehicle under test could be held without rolling away. The British Railways standard requirement for the design of freight wagon handbrakes is such that each wagon must be able to hold its fully laden weight stationary on a gradient of 1 in 40.

The hydraulic ram is operated either by a hand pump or by an electrically powered hydraulic pump in order to haul the vehicle under test for a distance of between 8and10inches along the rails. The measurements taken from the load cell of the peak value of resisting force are used to calculate the equivalent holding gradient result as follows:-

Where:-       

After each test is completed it is necessary to return the vehicle back to its original position ready to start the next test.

Many locomotives, coaching stock vehicles and newer designs of wagons are fitted with a handwheel & screw type method of applying the handbrake.

The principle and method of testing is very similar however instead of using weights applied to the handbrake lever, a specified level of torque is used when applying the handwheel. This is calculated and applied with a calibrated torque wrench based on the diameter of the handwheel and the standard level of effort of 500Newtons applied at the handwheel rim.

An example of the table of results produced during a handbrake test on a wagon fitted with a handwheel type handbrake.

In general the handbrakes fitted to freight wagons are more than sufficient to hold a loaded wagon on a steep gradient when applied fully; therefore when they are applied to an empty wagon their effectiveness is significantly increased. As such, if an empty wagon is moved with its handbrake ‘ON’ then the effectiveness of the brake will cause the wheels to lock and slide; this can very quickly cause significant damage to the wheelsets in the form of wheel-flats and cavities that are costly to rectify.

This is an example of wheel tread damage caused by operating a vehicle with a handbrake on.