Pauls Railway Web
Advanced Passenger Train - Experimental
Innovation of the braking systems.
One of the trains most important design features was the innovation behind the braking systems. The train was capable of running at high speed while maintaining passenger comfort, but the train also had to be stopped within standard signal distances and convention friction brakes were found to be incapable of doing this job so very early on in the APT programme it was decided to develop a new braking system, this became known as the Hydrokenetic brake. A hydrokenetic brake is a water turbine made as inefficient as possible so that energy can be dissipated without generation excessive amounts of heat. A pressurised fluid is pumped through a tubular axle and then passed back through a set of turbine blades, these blades are rotation at the same speed as the wheel set, the greater the pressure of fluid pumped into the wheel set the harder it becomes for them to rotate, energy is stored in the form of heat in the fluid, this is in turn returned to a central holding tank and cooled before being re-used.
Diagrams of the APT-E bogie design and the positioning of the Hydrokenetic brake system.
As the hydrokenetic brake system is only efficient at high speed the train was also fitted with conventional friction brakes, At speeds from 70 - 155 mph the hydrokenetic brakes were used and below 70 mph the friction brakes came into action to finally halt the train.
As APT-E was to be tested mainly on the Dalby test track the design team had time to experiment with systems allocated to the HK (Hydrokenetic Brake). APT-E would only be allowed onto the main line if the engineers could prove that the train could be stopped safely under high speed main line conditions so a one month commissioning period was set aside to test the HK brake and its reliability, this they achieved and APT-E was ready for mainline highspeed testing.
|During the commissioning period of the HK brake the POP train was
used extensively to test the various tweaks and re-designs of not only the HK brakes
themselves but also the HK
Its interesting to note that during the later development of the APT-E and the early stages of the APT-P, the ability of the train to stop within conventional distances was brought into question, the engineers had been given a guideline that if the braking system could stop with only a small percentage of the brakes out of action, (this acted as a safety margin Incas of problems) then the train would be given a service speed of 155mph, but as the engineers discovered the percentage of out of action brakes was significantly higher and the trains ability to stop was severely compromised, this in turn caused the train to be given a maximum speed of 125mph thus removing one of the trains main design features and was a major bug bear for the publicity team for years to come.
Email me on Paul@apt-e.org