In a Vacuum Brake System, the Brakes are held off by a Vacuum in the Brake System created by an Exhauster/Ejector. When the Brakes are applied, the Vacuum is destroyed by letting air into the System. When the Brakes are released, the Vacuum is recreated by the Exhauster/Ejector.

On disc brake vehicles, Brake Force in kN is usually roughly equivalent to the vehicle weight in Tons. So, for example, a 100 ton loco would be expected to have 100kN Maximum Brake Force. Altering this figure is the easiest way of adjusting the maximum brake force of the locomotive. For example, if your locomotive weighs 100 tons and you want a maximum Brake Force of 80kN, set this parameter to 80%.

For tread brake vehicles, the braking force is slightly less than the weight and thus a figure of 60-70% is more accurate.

This is where the Train Brake Cab Control characteristics are defined.

This is where the Handbrake is defined.

The maximum rate that the train brake can be released in Inches Hg/sec.

The maximum rate (non-emergency) that the train brake can be applied in Inches Hg/sec.

The maximum pressure possible in the Brake Cylinder in Inches Hg/sec.

The pressure in the Brake Cylinder at which the most Brake Force is available in Inches Hg/sec.

The maximum pressure in the Vacuum Brake System in Inches Hg/sec when brakes are released.

The minimum pressure in the Vacuum Brake System in Inches Hg/sec when brakes are released.

In a Vacuum System, these figures are actually entered in what may seem to be the wrong way around because a Vacuum is measured in relation to Atmospheric Pressure. A perfect Vacuum is a 30 inches Hg (0psi). The vacuum used in most UK Vacuum systems is 21 inches Hg (10.3psi) and Atmospheric Pressure is 0 inches Hg (14.7psi). Max System Pressure would be set to 21 and Min System Pressure to 0 although in reality 21 represents a lower pressure in the brake pipe than 0.

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