Off our trolleys?
Sir, – M Ross-MacDonald (July 2nd) counters Ned Monaghan’s position (June 30th) on supermarket trolleys – the old “pivoting casters or fixed casters” chestnut – by describing the manoeuvrability problem with the fixed pair plus pivoting pair arrangement, and outlining his preference for the four-pivot system.
I suggest that this argument is outweighed by two others. First, the problem of manoeuvring outside the supermarket (to one’s car, for example) when the desired direction of motion is at right angles to the camber of the footpath; and second, the problem of attempting to change direction of a heavily laden trolley either from either a standing start or at constant linear velocity.
These circumstances require the operator to supply either an actuating or restoring torque (twisting effort) about an axis of rotation, ie the operator’s lumbar spine.
For operators in sub-optimal physical condition, this may lead problems from muscle strain to disk lesions – mild discomfort to serious injury.
So for me it has to be the “fixed pair plus pivoting pair” system, although I would go for the fixed wheels on the front, where the emphasis is on linear actuation or correction. It may take a while to get used to, but safety first. It may also improve driving skills! – Yours, etc,