The 26L Charging System. When Locomotives couple on to their cars, whether it be 100 cars or just 5 cars, the Automatic Brake system charges these cars. An 80 car train that has been depleted of air in the Cars Air Reservoirs may take 20 minutes or so to charge up to the usual 90 Lbs. that most Freight Carriers operate at. If these same cars has just been left by another locomotive consist it may take only several minutes.
The Valve also has a Maintaining feature that permits the valve to overcome leak- age to a certain point. Of course if a pipe or hose has pulled in two the Maintaining feature will not keep up with the leakage.
Most older locomotives have hand brakes either in the ratchet handle style or the brake wheel. They both do the same thing; They pull tension on a chain that is attached to the brake cylinder, which manually pulls the brake cylinder out, usually on the rear set of wheels or rear truck.
Some New GE Locomotives have a Parking Brake, and is supported by its own Brake cylinders, as another Braking system. This only applys to the Front Loco. in a consist.
Dynamic Braking is when current (electricity) is rerouted making the Engines Traction Motors into generators. All this current is routed up to a Dynamic Brake Grid, kind of like a giant resistor, and a Dynamic grid cooling fan to cool the Grids and keep them from burning up. Not all engines have Dynamic Brakes, but most carriers who have to descend Mountain Passes have them.
When Dynamic Braking is active it releases the Automatic brakes on the Engines, since both braking systems would result in too much resistance and cause the wheels to slide.causing flat and shells on the wheels. The exception is Blended braking, which see below.
Most Dynamic brake systems operate from 0-700 Amps. Some newer locomot- ives have Extended range Dynamics which is even better. This System saves dramatically on Brake shoes, requiring less braking on the freight or passenger cars on long descents.
Blended braking is used on some Passenger Equipment to make braking even more efficient. Created by Electronics blended braking will use some Automatic brakes while in the lower range of Dynamics, but the more Amperage the Dynamics use the less Automatic Brake cylinder pressure is used. In full Dynamics the Automatic Brake will still be completely released. Blended braking is tied into the wheel slip and other circuits on Locomotives.
On long descents such as Tehachapi you'll hear a whinning noise that changes tone from time to time. This is the Engineer moving the Dynamic handle back and forth. On EMD Engines the Dynamic Grid cooling fan operates at different speeds according to the Dynamic handle. The more Amperage, the faster the fan turns.
next time: Safety systems