Locomotives usually perform certain functions such as:
- A locomotive that attaches to the front of a train and pulls it along is called a locomotive.
- Station pilot – A locomotive is employed at a railroad station to switch passenger trains.
- Pilot locomotive – A locomotive connected to the train’s locomotive from the front of the train to facilitate dual operation.
- Bank engine – A locomotive connected to the rear of a train engine; this is possible through a hard sharp or start.
Locomotives are used in various railroad operations such as: pulling passenger trains, shunting and freight trains.
The wheel formula of a locomotive displays the number of wheels it has; popular methods include UIC classification, Whyte designation systems, AAR wheel formula and so on.
Difference between freight and passenger locomotives
The most obvious difference is the shape and size of the locomotive’s body. Since passenger trains move faster than other trains, air resistance plays a bigger role than it does for freight trains. Most passenger locomotives usually have a cowl along the entire length of the body; this may be for aesthetic reasons.
On the other hand, freight trains tend to have more reason to stop when the conductor has to get on and off the engine, and are more likely to move backwards, so they have a thin shroud around the actual propulsion system. This provides better visibility when moving backwards, and also allows ladders rather than stepladders to be fitted, which is much more convenient for personnel who have to climb on and off the locomotive frequently.
Freight locomotives are built for more torque (twisting force) and passenger locomotives are built for more speed. A typical freight locomotive engine develops between 4,000 and 18,000 horsepower.
The gears on passenger locomotives differ from freight locomotives in that their gear ratio is smaller, so the traction motor rotates fewer times per revolution of the wheel.
Generally, passenger engines require an increase in top speed, while freight engines require an increase in starting thrust as they push heavier trains. This leads to different gear ratios in the transmission (which in electric and diesel-electric engines does not have many gears).