On the river Rhine in Switzerland, there are reaction ferries: boats with no engine, no paddles, no onboard motive power at all. Here’s how they work — and a question about what other simple ideas are out there.A reaction ferry is a cable ferry that uses the reaction of the current of a river against a fixed tether to propel the vessel across the water.
image credit: Tom Scott
Such ferries operate faster and more effectively in rivers with strong currents.Some reaction ferries operate using an overhead cable suspended from towers anchored on either bank of the river. Others use a floating cable attached to a single anchorage that may be on one bank or mid-channel.via(wikipedia)
Where an overhead cable is used a “traveller” is usually installed on the cable and the ferry is attached to the traveller by a bridle cable. To operate the ferry either the bridle cable is adjusted or a rudder is used, causing the ferry to be angled into the current, and the force of the current moves the ferry across the river.
The ferry may consist of a single hull, or two pontoons with a deck bridging them. Some ferries carry only passengers, whilst others carry road vehicles, with some examples carrying up to 12 cars.