Steam engine was developed with the help of many scientists. First practical steam engine was a water motor made by Thomas Savery. First commercial steam was made by Thomas Newcommon & James Watt invented the Watt Engine by implementing it.
In 1801 Richard Trevithick made the world’s first steam locomotive at Penydarren Ironworks workshop. After some modifications it ran from Penydarren to Abecynon on 13th February 1804.
Types of Steam Locomotives
Steam engines can be mainly divided into two parts as Super-Heated Steam locomotives & Saturated Steam locomotives. Super-heated steam locos use dry steam (Steam generated by the boiler is re-heated to produce dry steam) to run. Saturated steam use normal steam generated from the boiler to run. But this system is less efficient.
Apart from this classification steam locomotives can be classified by its axle arrangement, locomotive design etc.
1. Tank Locomotives
These locomotives don’t have a separate tender to carry water & the water tank is fixed to the chassis. There are sub groups of this kind as Saddle Tanks & Side Tanks.
2. Tender-Tank Locomotives
These locomotives had another water tank on the locomotive chassis apart from the tender.
3. Garret Locomotives
These locomotives were designed according to an idea by a British engineer named Garret. He made a locomotive with 2 bogies & 4 cylinders which had the water tank, combustion chamber, driver’s cab & tender in one unit. These locomotives were designed to suit the hill country tracks. They were known as Garrets at the beginning & later they got popular as Beyer Garrets because these were manufactured by Beyer Peacock Company.
4. Mallet Locomotives
This was another articulated locomotive type as garrets which were popular in USA. The front water tank which can be seen in garret locomotives was removed it had a driven wheel set at the front & a driving wheel set at the back with high pressure cylinders. Worlds’ largest locomotive class is the Union Pacific – Big Boy class & they are Mallet Locomotives.
Parts of Steam Locomotive
1. Tender – Container keeping both water, wood, coal or oil.
2. Driving Cab – Area which the engineer and fireman controls the locomotive and tend the firebox.
3. Whistle – Steam powered whistle, positioned on top of the boiler and used as a signalling and warning device.
4. Reach rod – Rod connecting the reversing actuator in the cabin to the valve gear.
5. Safety valve – Pressure relief valve to stop the boiler exceeding the operating limit.
6. Generator – tiny steam turbine direct coupled with electrical generator to headlights.
7. Sand dome – Contains sand that can be deposited on the rails to increase traction, specially in wet conditions.
8. Throttle Lever– Handles the opening of the regulator/throttle valve (31) or maintaining the supply of steam to the cylinders.
9. Steam dome – Collects the steam at the top of the boiler so that it can be given to the engine through the regulator/throttle valve
10. Air pump – Supplies air pressure for operating the brakes. Usually a steam powered pump with steam cylinder coupled with air cylinder.
11. Smokebox – Gathers the hot gases that have passed from the firebox and via the boiler tubes. It may include a cinder guard to prevent hot cinders being exhausted up the chimney. Usually has a blower to help draw the fire when the regulator is closed. Steam exhausting from the cylinder is also directed up to the chimney through the smokebox to draw the fire while the regulator is open.
12. Main steam pipe – brings steam to cylinders.
13. Smoke box door – Hinged rounded door to enable service access to the smoke box.
14. Hand rail – Assistance rail for crew when moving along the foot board.
15. Rear bogie – Wheels at the back of the locomotive to assist the weight of the cab and fire box.
16. Foot board– Pathway along the locomotive to help inspection and maintenance.
17. Frame – Steel beams around which the locomotive is built. The wheels run in slots within the frames, and the cab, fire box, boiler and smoke box are installed on top.
18. Brake shoe, brake block – Utilized directly to all the driving wheels for braking.
19. Sand pipe – Deposits sand in front side of the driving wheels to aid traction.
20. Coupling rods – Links the driving wheels together.
21. Valve gear – System of rods and linkages synchronising the valves with the pistons and manages the direction and power output of the locomotive.
22. Connecting rod – Steel arm that changes the side to side motion of the piston into a rotation motion of the driver wheels. The link between piston and main rod is supported by a side to side slide-bar behind the cylinder.
23. Piston rod – Links the piston to the cross-head axle, which drives the main/connecting rods.
24. Piston – Driven in reverse and ahead within the cylinder by steam pressure, generating mechanical motion from steam expansion.
25. Valve – Regulates the supply of steam to the cylinders, timing is synchronised by the valve gear connected to the cab.
26. Steam chest – Small chamber on top or to the side of the main cylinder that contains passages used by the valves to distribute live steam to the cylinders.
27. Firebox – Furnace chamber that is constructed into the boiler and generally surrounded by water. Anything combustible can be used as fuel but usually coal, coke, wood or oil are burnt.
28. Boiler tubes – Transport hot gasses from the fire box through the boiler, heating the adjoining water.
29. Boiler – Water container that is heated up by hot gases passed via boiler tubes to generate steam.
30. Superheater tubes – Pass steam back through the boiler to dry out and ‘super heat’ the steam for higher efficiency.
31. Regulator– Regulates the amount of steam provided to the cylinders (8).
32. Superheater – Provides steam back through boiler tubes to superheat the steam to increase the efficiency.
33. Chimney– Short chimney on top of the smokebox to transport the smoke away from the engine so that it does not block the driver’s vision. Generally expanded down inside the smokebox – the expansion is called a petticoat.
34. Headlight – Lamp on front of the smoke box to offer forward visibility.
35. Brake hose – Air or vacuum hose for transferring braking control to connected rolling stock.
36. Water compartment – Container for water used by the boiler to provide steam that is usually exhausted from the cylinders.
37. Coal bunker – Fuel supply for the furnace.
38. Grate – Contains the burning fuel and enables unburnable ash to drop.
39. Ashpan hopper – Gathers the unburnable ash from spent fuel.
40. Journal box – Consists of the plain bearing for a driver wheel’s axle.
41. Equalising bars – Part of the locomotive suspension system, attached to leaf springs, free to pivot about their centre which is firmly fixed to the frame. Purpose is to even out the load distribution across axles on unequal or badly laid tracks.
42. Leaf Springs – Main suspension component for the locomotive. For each driving wheel there is a leaf spring suspending its axle’s journal box.
43. Driving wheel – Wheel powered by the pistons to push the locomotive. Driving wheels are balanced by weights so that the centre of gravity, of the driving wheels and rods, coincides with the center of rotation. There are Three sets of driving wheels in this example.
44. Pedestal or saddle – Joins a leaf spring to a driver wheel’s journal box.
45. Blast pipe – Guides exhaust steam up the chimney, making a draught that draws air via the fire and alongside the boiler tubes.
46. Leading bogie – Wheels at the front side to guide the locomotive along the track.
47. Coupler – Gadget at the front and rear of the locomotive for linking locomotives and wagons together.