Roller coasters how it works

 They strike fear into many, but we still love them! Here, we detail the engineering achievement that is the roller coaster

Some of the world’s most forward-looking engineering is actually in operation right now, in the unexpected setting of the world’s theme parks. From the pioneering 18th Century ‘Russian Mountains’, people have been hooked on the frightful thrill of a roller coaster – and ever since, the challenge has been to make an even bigger, even better, even more terrifying one. Today, they incorporate solutions that are at the leading edge of scientific development. This means they are able to accelerate as fast as a drag racer and let passengers experience G-forces way in excess of a Formula 1 race car. They do all this in complete safety, having passed the very strictest engineering standards. People travel for miles to ride on the latest roller coaster – they’ll even cross continents just to experience the latest thrill. But why? Here, we explain all

How roller coasters roll

Roller coaster trains are unpowered. They rely on an initial application of acceleration force, then combine stored potential energy and gravitational forces to continue along the track. This is why they rise and fall as they twist and turn.

 There are various methods of launching a roller coaster. Traditionally, a lift hill is used – the train is pulled up a steep section of track. It is released at the top, where gravity transfers potential energy into kinetic energy, accelerating the train. Launches can be via a chain lift that locks onto the underneath of the train, or a motorised drive tyre system, or a simple cable lift. There is also the catapult launch lift: the train is accelerated very fast by an engine or a dropped weight.

 Newer roller coasters use motors for launching. These generate intense acceleration on a fl at section of track. Linear induction motors use electromagnetic force to pull the train along the track. They are very controllable with modern electronics. Some rides now have induction motors at points along the track, negating the need to store all the energy at the lift hill – giving designers more opportunities to create new sensations. Hydraulic launch systems are also starting to become more popular.

 Careful calculation means a roller coaster releases roughly enough energy to complete the course. At the end, a brake run halts the train – this compensates for different velocities caused by varying forces due to changing passenger loads. 

Anatomy of a roller coaster

Roller coasters comprise many elements, each with its own specifi c physical characteristics. Designers give a ride character by applying an understanding of physics to build up a sequence of thrills. These are all interrelated and mean the experience of every ride is exciting and unique.

 Computer models can analyse the forces that will be produced by each twist and turn, ensuring they are kept within specifi c boundaries. Roller coasters may look like a random snake of track, but the reality is years of scientifi c calculations to provide just the right effects. 

The physics of the ride

All roller coasters begin with an acceleration force. This is to overcome inertia – the resistance to change in velocity. It is quantifi ed by the mass of the train, which depends on the individual load. Full trains will have more inertia than unladen ones. However, by applying more force during acceleration, they also store more potential energy to offset this. Designers work to reduce other sources of inertia such as friction-reducing low rolling resistance wheels.

 The aim of acceleration is to store suffi cient potential energy at the top of the crest for transferral into driving kinetic energy to take the train to the next ascent. Because of frictional and other losses, each subsequent incline will be shorter than the one before – not all the kinetic energy can be recovered into potential energy.

 Gravity is fundamental to roller coasters. Designers manipulate the effect of attraction between two masses to subject strong forces on the body. Weightlessness, for example, is caused by centrifugal forces cancelling out gravity forces. Centrifugal force feels like an outward force away from the centre of rotation when turning a corner. It’s as if the body is being pressed down into the train, but is actually the reverse: an external force is being supplied by the train towards the centre of rotation.