In dynamic braking the traction motors are switched to work as generators, so the turning wheels meet resistance and the electricity they produce is dumped as heat through resistor grids cooled by roof-mounted blowers. It slows the train without wearing brake shoes or drawing down the brake pipe, which makes it the first tool for holding speed on a descending grade. Its force acts only at the locomotives, so slack bunches toward the head end, and it fades at very low speed.
Ease her into dynamic braking before the crest, she'll want to run away from you halfway down Sherman Hill.
Engineers say they are in dynamics or in the DB; a unit with its dynamic brake cut out gets noted on the paperwork because it changes how much the head end can hold.
Also heard as
- dynamics
- dynamic brake
- DB
Related terms
Slack
The free play in couplers and draft gear that lets cars move a little toward or away from each other.
Brake pipe
The air line running the full length of a train that charges and controls every car's brakes.
Power
The locomotives assigned to a train, or locomotives in general.
Bail off
To release the locomotive's own brakes during an automatic application so that only the cars do the braking.