Appendix 3
(The image is of a composite imaginary locomotive.)
1. Tender. Container holding both water for the boiler and fuel such as wood, coal, or oil for the firebox.
2. Cab. Compartment where the engineer and fireman control the engine and tend the firebox.
3. Whistle. Steam-powered whistle, located on top of the boiler and used for signaling and warning.
4. Reach rod. Rod linking the reversing lever in the cab to the valve gear.
5. Safety valve. Pressure relief valve to stop the boiler pressure exceeding the operating limit.
6. Generator. Electrical generator driven by small steam turbine for locomotive lighting and headlight.
7. Sand dome. Holds sand that is dropped on the rail in front of the driving wheels to improve traction, especially in wet or icy conditions.
8. Throttle Lever/Regulator. Sets the opening of the regulator/throttle valve (#31), which controls the pressure of steam entering the cylinders.
9. Steam dome. Collects the steam at the top of the boiler so that it can be fed to the engine via main steam pipe, or dry pipe, and the regulator/throttle valve.
10. Air pump or compressor. Compresses air for operating the brakes.
11. Smokebox. Collects the hot gases that have passed from the firebox and through the boiler tubes.
12. Steam pipe. Carries steam to the cylinders.
13. Smokebox door. Hinged circular door to allow service access to the smokebox to fix air leaks and remove char.
14. Handrail. Support rail for crew when walking along the foot board.
15. Trailing truck/Rear bogie. Wheels at the rear of the locomotive to help support the weight of the cab and firebox.
16. Foot board/Running board. Walkway along the locomotive to facilitate inspection and maintenance.
17. Frame. Carries boiler, cab, and engines and is supported on driving wheels and leading and trailing trucks. The axles run in slots in the frames.
18. Brake shoe and break block. Rub on all the driving wheel treads for braking.
19. Sand pipe. Deposits sand directly in front of the driving wheels to aid traction.
20. Side rods/Coupling rods. Connects the driving wheels together.
21. Valve gear/motion. System of rods and linkages synchronizing the valves with the pistons and controls the running and power of the locomotive.
22. Main rod/Connecting rod. Steel arm that converts the horizontal motion of the piston into a rotary motion of the driver wheels. The connection between piston and main rod is a crosshead that slides on a horizontal bar behind the cylinder.
23. Piston rod. Connects the piston to the crosshead.
24. Piston. Driven backward and forward within the cylinder by steam pressure, producing motion from steam expansion.
25. Valve. Controls the supply of steam to the cylinders, valve position relative to piston determined by valve gear connected to driving wheel. Steam locomotives may have slide valves, piston valves, or poppet valves.
26. Valve chest/steam chest. Valve chamber adjacent to cylinder, contains passageways to distribute steam to the cylinders.
27. Firebox. Furnace chamber that is built into the boiler and surrounded by water. Various combustible materials can be used as fuel but the most common were coal, coke, wood, or oil.
28. Boiler tubes. Carry hot gases from the firebox through the boiler, heating the surrounding water.
29. Boiler. Container almost full of water with air space above. The water is heated by hot gases passing through the tubes, producing steam in the space above the water.
30. Superheater tubes. Pass steam back through the boiler to dry and superheat the steam for greater efficiency.
31. Regulator/Throttle valve. Controls the amount of steam delivered to the cylinders, one of two ways to vary power of the engine (throttle governing).
32. Superheater. Feeds steam back through boiler tubes to superheat (i.e., heat beyond boiling temperature of water at boiler pressure) the steam to increase the engine efficiency and power.
33. Chimney/Smokestack. Short chimney on top of the smokebox to carry the exhaust (smoke) away from the engine so that it doesn’t obscure the footplate crew’s forward view.
34. Headlight. Light on front of smokebox to illuminate track ahead and warn approach of locomotive to other track occupants.
35. Brake hose. Air or vacuum hose for transmitting brake system pressure/vacuum to train brakes.
36. Water compartment. Container for water used by the boiler to produce steam.
37. Coal bunker. Fuel supply for the furnace, may be wood, coal/coke, or oil. Fed to the firebox either manually or, for bigger fire grates, by mechanical stoker.
38. Grate. Holds the burning fuel and allows ash to drop through.
39. Ashpan hopper. Collects the ash from the fire.
40. Journal box. Housing for the plain bearing on a driving wheel axle.
41. Equalizing beams/Equalizing levers/Equalizing bars. Part of the locomotive suspension system, connected to leaf springs, free to pivot about their center, which is fixed to the frame. Function is to even out weight carried on adjacent axles on uneven or poorly laid tracks.
42. Leaf springs. Main suspension springs for the locomotive. Each driver wheel supports its share of the locomotive weight using a leaf spring that connects the axle journal box to the frame.
43. Driving wheel/Driver. Wheel driven by the pistons to move the locomotive. Drivers are balanced with weights to reduce unwanted motion of the locomotive. There are three sets of driving wheels in this example.
44. Pedestal or saddle. Connects a leaf spring to a driver wheel journal box.
45. Blast pipe. Directs exhaust steam up the chimney, creating a draught that draws air through the fire and along the boiler tubes.
46. Pilot truck/Leading bogie. Wheels at the front to support weight of boiler front end/smokebox and reduce flanging forces between front driving wheels and rail when rounding curves.
47. Coupling/Coupler. Device at the front and rear of the locomotive for connecting locomotives and rail cars together.