Pinning the Brakes Down

[fender]

this may be a dumb question but I've read a lot about how and why brakes were pinned down on unfitted stock before various descents.

 

my question is what the wagon wheels actually did during the descent. I assume they ran against the brake blocks (as I've seen reference to 'hot brake blocks' caused by the friction), but surely in some combination of wet track/lightly loaded wagons there would be a tendency for the wheels to stop turning and skid along the track.

 

did this happen? or would all wheels always be turning as the train descended?

 

thanks.

[Torr Giffard LSWR 1951-71]

Aft'noon Fender,

 

It is equally possible to lock the train wheels using the train auto-brake as it was to have the wagon wheels lock under the handbrake. Rail head conditions have a lot to do with it. Train brakes are only effective when the wheel is turning.

Remember that partially fitted and unfitted freight trains had no means for the driver to brake the unfitted wagons when he needed to slow down or stop the train, therefore, the guard would pin 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 helped ensure that the driver retained control of the train on the downhill section. The train would stop again at the bottom of the incline to allow the guard to 'take up' the handbrakes (release them). Once wagon wheels locked and skidded the tendency was for the train to increase speed rather than decrease and having handled heavy freight trains on downhill sections, under poor rail conditions I can vouch for the bad feeling that you get as a driver when you have to release the train brakes again to get the wheels turning once more before reapplying the brakes. The key was to avoid braking where possible in known areas of poor railhead conditions.

On other sections of line the loco brakes combined with those of the brakevan (plus those of any fitted portion in the train) would be sufficient for the driver to retain control of the train.

 

Cheers

 

Dave

[The Stationmaster]

Interesting question and an answer as long as a piece of string I think. The way in which it was (supposed to be) done gives some clues about where we start from as sufficient brakes had to be pinned down to hold the train (stationary) to ensure that the train could only be moved by the engine applying power. Or to put it another way, the engine pulled the train against the force exerted by the wagons.

Now all of this presupposes that when the engine is applying the force to move the train the wheels of the wagons will still rotate sufficiently to avoid skidding (which will cause flats on the tyres of the wagon wheels) but there is still sufficient braking force exerted by the wagon brakes to keep the train under control. And because speed is kept very low simply ceasing to apply power and applying the brake on the engine will stop the train.

 

That's the theory. The practice will be slightly different because inevitably the pressure on individual brake blocks on wagons will vary a bit which means some wagons will do more than others to hold the train, the condition of brakeblocks will vary due to the amount of wear, and the rollability of wagons will vary due to various factors. So in practice some - usually very few if any - wagons might skid but most will provide some retardation until either you get to the bottom of the incline or the brake blocks catch fire and lose their braking effect. Experienced staff who were involved in this sort of working every day would soon develop a sense of which wagons could not be relied on to behave as expected when pinned down and judge carefully which ones would have the brakes pinned down. And some wagons were prohibited from being worked in this way.

 

Going back a good deal further in time wagons would be purposely skidded (using sprags) to add braking effect but I think in the later years of AWB (Apply Wagon Brakes) working the aim was to retard by the brake blocks rubbing a rotating wheel (which was how it was done in the USA on earlier freight trains, but with air brakes - called, I think, 'running against the air' or words to that effect).

 

So sorry but a precise answer is difficult. The last time I was on a train where it was done no wagons skidded but we finished up at the bottom of the incline in a very large cloud of smoke from burning brake blocks. Oh, and I can tell you from experience that it didn't work when tried on loaded HAA mgr wagons

[fender]

......

So sorry but a precise answer is difficult.

 

...

 

not at all! very informative, and thanks to Dave^^^ as well.

[big jim]

It amazed me that as late as 2008 (the last time i drove it) there were retro reflective AWB boards at the top of hawarden and gresford banks, not something you would expect to see being replaced in this day and age!

[Mick Boyd]

I seem to recall (but I may be mistaken) from my footplate days that the train should be moving slowly forward towards the downgrade whilst the brakes are pinned down to ensure, initially, that the wheels were turning and the vehicles didn't "pick their wheels up" and slip/skid.

 

Regards, Mick.

[coachmann]

The only time I pinned down brakes was at the Stop Board atop Miles Platting Bank. This was a definite 'Stop'. I, as fireman, pinned down the brakes, usually half a dozen or so depending on the drivers instruction. As I could not see the contents of the unbraked wagons, I simply pinned them down hard. On reaching the bottom in Manchester Victoria the train did not stop completely, so it was a case of unpinning on the trot. A bit of slap-dash would would make itself heard if a brake handle fell off its perch and started chattering!.

 

I imagine a rolling train such as on the Lickey would give the brakesman a chance to vary the brake pressure until the wheels were just revolving without going ito a slide.

[Boris]

From memory the NE procedure I have was that you arrived at the top of the incline in question and came to a stand having previously agreed with the driver (I think it was his decision whether to pin or not) that brakes would be pinned. The guard would walk to the front of the train, holding his brake stick up to indicate to the driver that was what was going on. Starting with the first unbraked wagon (you don't pin fitted wagons with the vacuum brake in use), you would indicate to the driver to draw forward slowly onto the incline. You would then walk alongside applying the wagon brakes as well as you could without skating the wheels, when the driver felt that enough brakes were applied he would give a signal on the whistle, at which point the guard would rejoin the train, indicating to the driver with a green flag waved from side to side that he was back aboard safely and the train could proceed. The idea was, as has been previously voiced, that the driver actually had to apply power to pull the train down the hill. The guard would keep the handbrake in the van as a back-up, although some guards would gently rub the shoes on the van to warm the shoes/tyres so they got better performance if the van brakes were needed for a descent.

 

You are absolutely on the nail with hot brake blocks, as train brakes do work on exactly that principle of dissipating kinetic energy as heat via increased friction. If you arrived at the bottom of the incline with smoke coming from at least one set of blocks you know you've been doing it right. I took a heavy train down the grade from Goathland to Levisham last year, including a steam crane (which are great numb stupid things) and several wagons of concrete sleepers. The rail conditions were bloody awful and we pinned out at the top of the grade (5 miles downhill and much of it is steeper that you realise) and part way down the hill the train started to get away from the driver a bit, the van shoes were nicely warm, on went the handbrake and between that and the rest of the pinned brakes we were ok. We passed Levisham having unpinned at the Up outer and a stop and examine was sent to the next box in advance because of a "large amount of foul smelling smoke coming from under the train". I had a hell of a job persuading him that it was supposed to do that!

[APOLLO]

On one of the Railway Roundabout videos there is a scene at the top of the Lickey Incline of a guard / shunter pinning down brakes whilst the train is moving, a planked walkway being provided for the purpose.

 

Here it is, pinning wagons at around 3 mins.

 

 

Brit15

[SHMD]

I absolutely love that comment that the H&S were "noted" then - 60 years ago!!!!

 

Kev.

[Donw]

This may seem a bit strange to those used to air braked stock but on british railways this was done on a regular basis on steep hillls from the dawn of railways. As for the heat and smell, when you come down porlock hill in a car you can tell how much the cars in front had to brake by the smell. Do airbraked trains suffer from repeated braking like a lorry does?

Don

[Swindon 123]

Do airbraked trains suffer from repeated braking like a lorry does?

Don

 

Repeated release and application in a short period of time of the brake pipe on a single piped air brake train will result in the deterioration in braking power. This is because the brake reservoir, from which the air to apply the brake piston is obtained, does not have chance to recharge properly. This cannot happen with a train running on the two pipe system as the brake reservoir is replenished from the 2nd "brake reservoir" pipe. Originally all trains ran on this system but to save money by not fitting the second pipe to a lot of freight vehicles, only passenger, freightliner and some other "select" trains ran on the 2 pipe system in later years. The same effect can be obtained by cycling the air brake between initial and off. I once did this for a trial on a long straight section of track with some empty 4 wheel tank wagons, which had a sharp brake in the empty condition, and ended up with the brake in the full service position with absolutely no retardation to the train.

 

Paul J.

[Swindon 123]

The reverse side to the stopping coin was the longer time taken to charge the air train pipe for brake release

 

I remember only too well the time taken to charge up the brake pipe on the Crewe- Pengam part of 4v63 Glasgow- Cardiff Pengam freightliner, which at the time ran as a 30 set. All right if it was made up off the original 2pipe sets, but in later years they had KFA's running in the rake as well they only had single pipes. Could take up to 10 mins to charge the brake pipe and that with a 56 in "compressor speed up" mode. If no 56 was available and you had a pair of 37's instead it could take a lot longer, and you sometimrs had to take 2 bites of the cherry as the loco main res would drop alarmingly and threaten to apply the brake with the low main air protection cutting in.

 

Happy days!

 

Paul J.

[Titan]

I thought that with a single pipe, in initial or gentle applications, the brake pipe pressure was still above the pressure in the brake cylinders, and thus the air in the single brake pipe was still capable of keeping the reservoirs suffficiently topped up should a full brake application be made?

[roythebus]

ISTR we adopted the single pipe system as this is standard in most of the world and especially Europe. Remember too on older stock fitted with the Westinghouse brake, you only had 3 brake applications before you run out of air!! You youngsters with the single pipe have never lived!

 

As for stopping unbraked trains, it took a lot of skill and a long time to stop! I speak from experience.