Cylinders

The main body of the steam locomotive is in the shape of a circular cylinder.

• Can you suggest why this shape is chosen? You might consider its function, economy of production, and ease of manufacture.

In the 700 Series, this cylindrical body is very close to 10 metres long and 2 metres in diameter. To make the train below move, give the (correct!) approximate volume:

• 10 m3    ; • 30 m3 ; • 120 m3  ?

The cylinders in which the pistons move are also circular in cross section.

• Are there good reasons, not considered above, for this choice?

• If the diameter of the circular cross-section of a cylinder is 56 cm, what is its cross-sectional area?

• Make a list of the places in which the circle occurs in the construction of the steam locomotive.
                                                                          
    


• A circular cylinder is easy to manufacture, with relatively little welding. Of all cylinders of given volume, the cylinder of circular cross-section uses the least material. The inbuilt symmetry also ensures even heating of the boiler.

• A piston moves up and down inside its cylinder.
If any small rotation of the piston happens to occur, perhaps because of wear, the movement of the piston is not impeded.

• The formula for the area of a circle is
A = d 2/4, where d denotes the diameter.
Hence the required area is approximately
3.1416 56 56 / 4 = 2463 cm2.

• Your list might include the cross-sections of the boiler, chimney, pipes, piston cylinders. Also, the steam dome (top centre of the locomotive), pistons, lights, buffers, control wheels (in the cab).