Train Air Brake Data Blueprint

In an Air Brake System, the Brakes are held off by compressed air, at a higher pressure than Atmospheric Pressure, in the Brake system created by a Compressor. When the Brakes are applied, the System is opened to the atmosphere, releasing air and reducing pressure. When the Brakes are released, the high pressure in the system is recreated by the Compressor.

Equipment Type
  • Air
  • Steam
  • Air Single Pipe
  • Air Twin Pipe
  • Vacuum Single Pipe
  • Vacuum Twin Pipe
  • Electro-Pneumatic
  • Electrically Controlled Pneumatic
  • Air Piped
  • Vacuum Piped

Max Force Percent of Vehicle Weight

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.

Control

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

Handbrake

This is where the Handbrake is defined.

Max Release Rate

The maximum rate that the Train Brake can be released in psi.

Max Application Rate

The maximum rate (non-emergency) that the Train brake can be applied in psi.

Max Cylinder Pressure

The maximum pressure possible in the Brake Cylinder in psi.

Pressure for Max Force

The pressure in the Brake Cylinder at which the most Brake Force is available in psi.

Max System Pressure

The maximum pressure in the Air Brake System in psi.

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 30inchesHg (0psi). The vacuum used on most UK Vacuum systems is 21inchesHg (10.3psi) and Atmospheric Pressure is 0inchesHg (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.

Min System Pressure

The minimum pressure in the Air Brake System in psi

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.

Distributor

Air brake control valve (derived from and known as a Triple Valve on older systems) mounted on each vehicle which controls the passage of air between the auxiliary reservoir and the brake cylinder and between the brake cylinder and atmosphere. The operation of the valve is controlled by changes in pressure in the brake pipe.

Normal Full Release Pressure

The pressure in the Auxiliary Reservoir when the brakes are fully released in psi.

Full Service Pressure

The pressure in the Auxiliary Reservoir After a Full Service Brake application in psi.

Train Pipe Control Ratio

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Max Emergency Res Pressure

The maximum pressure in the Emergency Reservoir in psi.

Max Aux Res Pressure

The maximum pressure in the Auxiliary Reservoir in psi.

Emergency Application Pressure

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Emergency Braking

Use only if the vehicle has an Emergency Braking Reservoir.

Trigger Rate

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Reservoir Pressure

The Max Pressure in the Emergency Braking Reservoir in psi.

Reservoir Capacity

The Volume of the Emergency Reservoir in cubic feet.

Reservoir Volume Multiplier

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Application Rate

The maximum rate (Emergency) that the Train Brake can be applied in psi/sec.

Charge Rate

The maximum rate that the Emergency Reservoir can be recharged in psi/sec.

Auxiliary Braking

The Auxiliary Reservoir is an air tank provided on each vehicle of a train equipped with air brakes to supply air for brake applications. More recently known as the brake reservoir.

Max Charging Rate

The maximum rate that the Auxiliary Reservoir can be recharged in psi/sec.

Max Reservoir Pressure

The maximum pressure in the Auxiliary Reservoir in psi.

Pressure Used From Pipe Per Pound Gained

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Pressure Gained From One Pipe Pound

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Retainer Type

Options: No Retainer / 3 Position Retainer / 4 Position Retainer

A Retainer is a manually operated valve mounted on many US freight cars to provide a constant minimum application even though the brake has been released from the driver's
brake valve in the cab. Normally, when brakes are released, all of the air in the brake cylinders is discharged to the atmosphere. By setting retainer valves, when the brakes are released, some of the air pressure is "retained", hence the name. Typically, a certain number of cars on the rear of the train would have their retainers set by the conductor.

There are 2 types of retainer valves, a 3 position type and a 4 position type. The operating positions are:

EX-Exhaust, normal will not retain air.
HP-High Pressure, will retain 20psi.
SD-Slow Direct Exhaust, will not retain air but will exhaust the air more slowly than normal.
LP-Low Pressure, will retain 10psi, only available on the 4 position retainer valve.

Triple Valve

Options: True / False.

The principal control valve mounted on a vehicle fitted with air braking. So-called because it has three functions - to apply the brake, to hold the application at a constant level and to release and recharge the brake system. It also has three connections - to the brake pipe, to the brake cylinder and to the auxiliary reservoir.

Although newer vehicles have a ‘Distributor’ instead of a Triple Valve, this is not yet supported, and thus you must select Triple Value in the Asset Editor.

Triple Valve Ratio

This is the ratio between the change in Brake Pipe Pressure and Brake Cylinder Pressure. Normally 2.5, so that a 1psi change in Pipe Pressure produces a 2.5psi change in the Brake Cylinder.

Retainer Slow Release

The Release Rate of air from the Retainer in psi/sec.