By mounting two wheels on inclined axles on the sides of a trolley, it is possible to change from free-wheeling to braking – simply by raising or lowering the handle.
This discovery has been made by Shaun Hume, inventor of the Fillaball – a family of plastic containers that don’t need lids, because when users pick them up, the inner part stays vertical with its opening on top, while the outer part with the handle swings up to form a closure.
The latest of these, the Fillaball Roller, can be pulled along the beach, and this has led to Hume’s latest idea, with two hemispherical side wheels with tyres, and axles, which are angled upwards so that their axes meet near the centre of the trolley.
If the handle is held in its normal pulling position, the wheels rotate freely and the footprints of the tyres on the ground are in line with each other. But if the handle is held much higher or lower than the normal pulling position, the footprints of the tyres on the ground are angled towards each other so the trolley brakes -- in much the same way that skiers can apply braking by inclining the fronts of their skis towards each other.
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