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  • Proposed Electric Hydraulic Brake for Railroad Freight Service

    Discussion in 'The main mechanical design forum' started by HSSRAIL, Mar 29, 2012.

    1. HSSRAIL

      HSSRAIL New Member

      Jan 2012
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      The current freight train braking system in use was developed by George Westinghouse in the 19th century it is a completely pneumatic device that contains the following elements on each freight car or wagon in a train. Individual air hoses and a cut-in valve and train line. The joining of the airhoses is done by hand. A triple valve which is the brains of the system and storage tanks for compressed air. The triple valve either allows compressed air to flow to the storage tanks, or brake cylinders based on the preassure in the air brake line that runs the length of the entire train. A reduction in air preassure in the train line causes compressed air to flow from the storage tanks to the brake cylinders on each car in the train. How much the brake cylinders are preassurized to depends on the amount of reduction. If neutral state was 90 psi in the train line and the preassure went to 75 pounds this would cause less of an application of the brakes than if the train line went from 90 psi to 40 psi. When preassure rises in the train line the storage tanks are recharged until they can't hold any more air than the valve allows the train line to go back to equilibrim in our example 90 psi and the brakes are released. Very rapid reductions in train line brake preassure cause the third feature of the triple valve to operate putting the brakes on in an emergency braking situation. American Railroads currently run trains in the 7000 ft to 8500 ft range. There are numerous gaskets and piping in this system air leaks or malfunctions of the triple valve can place freight trains into an emergency braking situation without being desired. Train brakes will apply automatically insofar as if the connections between rail cars is disrupted as in the train has parted the system stops the train. In a derailment situation the train will be stopped even if the crew is not aware that part of the train has derailed when the air line is severed a derailment may be quite advanced at this point however;

      Limitations of the air brake: or Why replace this thing?
      1) Application of the brakes is not simultaneous throughout a train. There is a time delay between the brakes being fully applied on the first car in a train and the last car. In derailment scenerios this results in the back of the train plowing into the stopped portion in front of it causing the characteristic jack knifing.
      2) Cold weather impedes charging the system and getting the brakes to release. The system becomes rather unpredictable in extreme cold weather scenerios.
      3) It is a fully manual system since electricity is not used in the system there is no electric recorders that could help determine which freight car has a malfunction that is causing the brakes to apply or not release. Intitial brake testing at origin terminals where trains are made up involves the necessity of manually walking a set and release on both sides of a train.
      4) Railroads move shipments in trains. It is necessary for freight cars to make connections between different trains to move from point A to point B. This is known as the freight classification process. Breaking up an inbound train involves cutting out the brakes on each individual car since there is no electricity in the system this is a manual process. The air on each car must be completely trained from the brake cylinders and storage tanks on a 120 car freight train this is a time consuming process. Cars are than sent down an incline and under gravity are switched into various tracks which sort them by common destinations. After a new train is made up the air hoses that have been uncoupled must be reconnected and the system recharged, walking inspection performed problems corrected before the new train can depart.

      The air brake means that inbound freight trains can not be classified right away they must be prepped for classification. Outbound trains can not depart right away they must be prepped for departure. Cold weather compounds the problems. Given the number of components in a freight train the probability that one will fail so even though the system is somewhat reliable on an individual rail car basis it hardly passes that test on a train basis. American freight trains frequently experience problems with their brakes.

      Need for an Incremental approach:
      There is a large amount of rolling stock throuout the world converting it to an alternate braking system all at once has been deemed impractical because of the large costs involved. Thus any new braking system developed must be backwardly compatible with the existing strait air system.

      An Electric Hydraulic Brake
      To meet the needs of being backwardly compatible means that each railroad car must be an independent enity. Most electric hydraulic brakes rely on an electric hydraulic pump this application can not use this because there is no electric train line that can be used to operate it.

      1) Mechanical Hydraulic Pump connected thru a clutch to the wheels of the freight car that will charge the hydraulic fluid to the necessary pressure and not further than that thru the clutch.
      2) An alternator and storage battery on each car to power the electrical components
      3) Strait air train line and connecting hoses for use when the car is operating in a train made up of strait air cars
      4) Electric rotary valves that control the flow of hydraulic fluid to and from the Hydraulic pump to the brake cylinders
      5) A digital triple valve that reads the air preassure in the train line and applies the brakes on the car or releases them based on the train line brake preassure.
      6) A wireless card that can communicate with other rail cars equipped with this system and syncronize the trainline preassure and braking pressure and communicate with the locomotive how the system is working. This system would record brake piston travel for purposes of doing an initial brake test digitally on the car. The wireless card would also allow the brakes to be cut out for classification thru a couple of key strokes on the locomotive and could receive lineside requests to apply the brakes allowing very precise control of the railcar as it is rolling down the incline into a classification track. The wireless card could also measure the ride quality and send that information to a central computer as well as system diagnostics.
      7) A train made up of cars only equipped with this system thru the wireless card could operate completely electrically. If an automatic power connection existed on these rail cars the storage battery and alternator could be dispensed with as well as the wireless card. In this mode the system would be completely electrical-hydraulic and compressed air would be out of the equation and the wireless card would not be needed as their would be a contineous electrical connection thruout the whole train.

      I submitted my idea to the Association of American Railroads and never received a response. Perhaps this is not feasible although I can't figure out why. Can anyone on this forum give an opinion about the feasibility of this system?

      Best Wishes


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