From John Brown
Airport and supermarket trolleys with four caster wheels may be difficult to control
(Letters, 19 December 1998, p 104), but there is a reason for having
them. When several trolleys are nested together, they can still be steered,
after a fashion, by the staff. Having fixed wheels, either at the front or the
rear, would make this impossible with more than one or two nested trolleys.
At Athens airport, they have found a solution to this problem. Each trolley
has a fixed front wheel which is raised off the ground when it is nested with
another trolley. A caravan of nested trolleys thus has a single fixed wheel at
the front and many caster wheels behind.
I had been thinking about this problem and was considering some sort of
wheel-locking mechanism that would be released when the trolleys were nested,
but whoever designed the trolleys for Athens airport has come up with a simpler
and more elegant solution.
Esher, Surrey
