# How does it work?

The Falkirk Wheel lies at the end of a reinforced concrete aqueduct that connects, via the Roughcastle tunnel and a double staircase lock, to the Union Canal. Boats entering the Wheel's upper gondola are lowered, along with the water that they float in, to the basin below. At the same time, an equal weight rises up, lifted in the other gondola.

This works on the Archimedes principle of displacement. That is, the mass of the boat sailing into the gondola will displace an exactly proportional volume of water so that the final combination of 'boat plus water' balances the original total mass.

Each gondola runs on small wheels that fit into a single curved rail fixed on the inner edge of the opening on each arm. In theory, this should be sufficient to ensure that they always remain horizontal, but any friction or sudden movement could cause the gondola to stick or tilt. To ensure that this could never happen and that the water and boats always remain perfectly level throughout the whole cycle, a series of linked cogs acts as a back up.

Hidden at each end, behind the arm nearest the aqueduct, are two 8m diameter cogs to which one end of each gondola is attached. A third, exactly equivalent sized cog is in the centre, attached to the main fixed upright. Two smaller cogs are fitted in the spaces between, with each cog having teeth that fit into the adjacent cog and push against each other, turning around the one fixed central one. The two gondolas, being attached to the outer cogs, will therefore turn at precisely the same speed, but in the opposite direction to the Wheel.

Given the precise balancing of the gondolas and this simple but clever system of cogs, a very small amount of energy is actually then required to turn the Wheel. In fact, it is a group of ten hydraulic motors located within the central spine that provide the small amount, just 1.5kWh, of electricity to turn it.

Watch the video below for a more detailed explanation about how The Falkirk Wheel actually works.