An equalising valve attempts to make the brake pipe allow pressure follow the equalising reservoir pressure. The train brake pipe runs along the length of the train.The pressure in the equalising reservoir is reduced to apply the brakes or increased to release the brakes. The main reservoir and equalising reservoir gauges in the loco show the pressure in these reservoirs. The equalising reservoir is fairly small, so the pressure in it changes fairly quickly. The train brake controls the pressure in the equalising reservoir, by allowing pressure in from the main reservoir or venting it to the atmosphere. It has a smaller reservoir called the “equalising reservoir”. The loco has a master reservoir that is kept pressurised at 90psi.You must then wait for a/ the vacuum to be created again (21 inches Hg in the UK) then b/ for the vacuum to be destroyed along the length of the train again when re-applying! And believe me, when approaching buffers at a terminal station, that could feel like an eternity and make ones toes curl up and the bum muscles tighten!Very true, and there are similar issue with modern Westinghouse air brake systems.Ī single-pipe Westinghouse air brake system (like OP is asking about) works more-or-less like this: Do that and the brakes will release completely. If you try and release the brakes a little bit, well you can't. It can take a few seconds (depending on train length) before maximum effect at which point you realise it's too much. With those you need to judge brakes much more carefully. Originally posted by Glenn:But try doing that with the older vacuum brakes for instance, and you would be in trouble (I speak from personal experience on that!). That is of course a rather simplified description, and there are always variations to be found in all systems. You must then wait for a/ the vacuum to be created again (21 inches Hg in the UK) then b/ for the vacuum to be destroyed along the length of the train again when re-applying! And believe me, when approaching buffers at a terminal station, that could feel like an eternity and make ones toes curl up and the bum muscles tighten! But try doing that with the older vacuum brakes for instance, and you would be in trouble (I speak from personal experience on that!). With the more modern electrical systems, brake effect is infinitely variable between release and maximum - on a bit, off a bit, off a bit more, on a bit and so on. Generally speaking, the methods for operating these systems will differ. Again, because it is basically an electrically operated system, the effect is (as fast as electrical current travels) instantaneous along the whole length of the train. Yet a more modern type of braking - dynamic - is even better as it does not use air brakes (Except in emergency situations and at very low speeds). EP (Electro-Pneumatic) is an electrically triggered air valve fitted to each 'car' which operates the brakes after an electrical command is sent to all those valves simultaneously. The same is true of older vacuum brakes (and steam brakes for that matter!).īut for more modern EP brakes, the effect is pretty much instantaneous throughout the entire length of the train. Breaking techniques vary from train to train and from country to country.Īs Cuavas states above, it does take time for the air pressure to change throughout the length of the train - the longer the train / air pipe, the longer it will take for maximum braking effect to take place. But I am not completely sure what you mean in saying " braking difficulty easier or harder ". It really depends on the type of braking.
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