Wheels

The big drive wheels of Number 700 are approximately 145 cm in diameter. The diameter of the smaller bogey wheel in the front is approximately 85 cm.

• How many times would each wheel rotate if the locomotive travels 100 metres?

Rotations of large wheel :

Rotations of small wheel :

  

• Do you think this calculation would tell you anything about the expected wear on the wheels?

            

In each case, the perimeter of the wheel
is given by P = d.

So for the large wheel, approximately,
P = 3.1416 145 = 455.53 cm = 4.555 metres.

Hence the number of rotations is
100 / 4.555 = 21.95 rotations.

For the small wheel we have
P = 3.1416 85 = 267 cm = 2.67 metres.

Hence the number of rotations is
100 / 2.67 = 37.45 rotations.

Given that there is weight distributed equally
on the large wheel and the small wheel,
we would expect the wear on each wheel
to be proportional to the
number of revolutions it makes.
Hence there should be more wear on
the small wheel than the large.