Article - Issue 66, March 2016
What makes an exciting roller coaster?
Alton Towers has a new roller coaster ride, Galactica, due to open in April 2016, that will require virtual reality headsets and participants experiencing a level of G-force acceleration greater than that of a real rocket launch. Sarah Griffiths talked to engineers, designers and enthusiasts about the elements that all roller coasters share and what makes some rides scarier than others.
Yas Waterworld is Abu Dhabi’s largest waterpark and is home to the Bandit Bomber, an interactive roller coaster. Each four-seater coach on the 280 m track is fitted with water bombs and laser guns. Atkins worked with Vekoma on the ride’s design logic to integrate fast and slow elements so that interactive water elements across the park could be integrated © Vekoma Rides Manufacturing
It is thought that the origins of roller coasters date back to the 17th century, when ice slides were built in Russia. Wooden-framed structures up to 20 m tall would be sprayed with water and left to freeze so that thrill-seekers could toboggan down them. To this day, there are roller coasters across Europe known as montagnes russes, Russian mountains.
Opinion differs as to whether the French or Russians introduced wheeled carts to the slopes. Catherine the Great is reported to have demanded a design to be built in 1784 using wheeled carts instead of sledges on ice. Others claim that Belleville and Paris were the first – in 1817 – to introduce cars to rides.
What is accepted is that the first golden age of the roller coaster was in the 1920s, when there were more than 3,000 of them in operation. For a variety of reasons, including war and financial depression, the rides were so out of favour by the late 1970s that they faced extinction, with only 300 surviving.
Now, the number is up to nearly 4,000 and rides are being built at a rapid rate around the world. The use of magnetic and hydraulic propulsion systems has generated even faster rides with greater acceleration. The introduction of new technology such as virtual reality is set to increase the riders’ sensory experiences.
Original design for the Family Boomerang Rebound - being built by Vekoma at Paultons Park, Hampshire - the Park will be calling the ride 'Raptor'. The ride has a tyre-drive system that carries riders backwards up the right hand hill before the tyres disengage on the underside of the train allowing it to freewheel forwards, gathering momentum to travel round the track. The train has enough potential energy to climb the left hand spike before returning riders back to the station in the centre of the attraction © Vekoma Rides Manufacturing
Most roller coaster ‘trains’ are not powered and rely on a chain or launch mechanism to take them to the first, and usually tallest hill. Gravity then carries them around the twists and turns of a track, back to the start again. Potential energy is gained as a train is pulled to the top of a hill, and, when the train rushes down a slope, this is converted into kinetic energy. Kinetic energy is greatest at the lowest point of the roller coaster, where the train is at its fastest, and determines how high a train will be able to climb to gather potential energy on future inclines. It also ultimately dictates how long the ride will last.
Vekoma has created nearly 300 roller coasters worldwide. The Orkanen at Fårup Sommerland in Denmark, was installed in 2013 and has features including a speed bump, a carousel, steep drop, a 120° banked horseshoe followed by horizontal loops and s-curves © Vekoma Rides Manufacturing
It is this interplay between potential and kinetic energy that keeps a train moving over bumps and through loops, despite loss of energy through friction and wind resistance, so that brakes are needed to bring it to a complete stop at the station. These basic laws of physics are used not only to design a track, but to create a safe but thrilling experience for a rider.
Unpleasant bumpy and jerky tracks were a problem for older roller coasters, and users could end up with bruises on hips, knees, shoulders or ribs after a ride. The current design approach, however, means that a smooth ride is at the heart of a design. Using computer models, engineers have direct control over the flow of forces and can create a virtual ride that can be analysed before it is built.
Fraser Ross, Concept Engineer for Vekoma Rides Manufacturing, uses modelling when creating new roller coasters. A new ride developed by Vekoma called Orkanen, at Fårup Sommerland in Denmark, is an example of how the updated design method is used. It boasts organic, naturally flowing shapes, limited lateral swinging dampened by shock absorbers, padded ergonomic seats for comfort and a restraint system designed for children as small as 1.1 m tall. This ‘suspended family coaster’ has been well received since it opened in 2013, and five more have been ordered for theme parks worldwide.
Roller coaster rides are meant to be thrilling but not dangerous. International safety standards form part of the approach to help the roller coaster designers and manufacturers meet the safety requirements and engineering quality and design safety reviews of rides by the client, third party, national bodies and high level, experienced engineers. Analysis and computer simulations make use of finite element analysis (FEA) models, dynamic analysis and risk and hazard calculations. Each project uses a product lifecycle management (PLM) approach and design-for-maintenance to optimise the maintainability and the durability of the roller coaster over its expected lifetime. Component testing is carried out to validate equipment, ensure structural integrity and establish wear for endurance. Tests include factory-acceptance tests, ride assembly try outs, ergonomic and restraint tests.
Each year in the UK every roller coaster undertakes the equivalent of a car MOT in the form of an Amusement Device Inspection Procedures Scheme (ADIPS) to ensure rides are checked for safety every season. Many UK roller coasters have their ADIPS certificate displayed in the control booth window.
FEEL THE FORCE
Positive G-forces are experienced by passengers when moving upwards at speed, while accelerating, when pulling back up at the bottom of a drop or going through a tight corner. They become negative when decelerating, cresting over the top of a hill and when dropping back down. Concept engineers take into account the vertical, lateral and longitudinal accelerations on the passengers and the train. Human tolerances depend on the magnitude of the G-force, the length of time it is applied and the direction in which it acts. People would experience a higher G-force falling into bed than on a roller coaster; however, the duration of that G-force to the bed is so short it is almost imperceptible.
The limit for positive, or vertical, G-forces for a thrilling but comfortable experience where the blood is forced away from the head so the body feels heavy, is around 6Gs, the same experienced by fighter pilots. Entering into the bottom of a loop, riders would usually experience around 4Gs of vertical force, which effectively means five times their bodyweight is being pushed into their seat. This feeling only lasts for a split second, so is thrilling but not too intense.
For an ‘airtime moment’, when there is a fluttering, breathless feeling in the pit of the stomach, engineers can incorporate a ‘camelback’, or hump-shaped hill that travels in a straight line, with ZeroG (or less) of vertical acceleration, which will make riders lift out of their seats and add a sense of thrill to a ride.
When a train accelerates or decelerates, longitudinal forces act forwards and backwards, pushing passengers back into their seats or forwards into their restraints, making a launch seem even faster, or braking more urgent. Both positive and negative lateral G-force accelerations are experienced as a train races round curves, with the tightness of a curve determining the magnitude of the lateral force being experienced by a passenger.
THRILLS NOT SPILLS
A cobra roll involves two half loops with a twist in the middle. This shows the Vekoma Giant Inverted Boomerang at Shanghai Jin Jiang Park. The passengers are upside down at the crest of the cobra they are experiencing positive Gsand are held in their seats by centrifugal force © Vekoma Rides Manufacturing
G-force is only one of the ingredients needed to create a thrilling ride. Brendan Walker, Professor of Creative Industries at Middlesex University and Principal Research Fellow in Computer Science at the University of Nottingham, has been dubbed the ‘world’s only thrill engineer’ by The Times. He works with theme parks on rides and says that an exciting ride relies on a combination of physical and psychological elements.
Rides are designed to excite the senses, and this should begin with the appearance of a roller coaster. It should look impressive, exciting and even a little intimidating to someone waiting to ride it, to set their expectations for a thrilling ride.
Roller coasters should also make people feel as if they can do the impossible, such as fly unaided or survive a high drop. Features such as loops and plunges are incorporated, which act on the vestibular system in the inner ear. This system senses acceleration and a yanking feeling, known as ‘jerk’, to create thrilling sensations.
Professor Walker explains that roller coasters should make riders feel as if they have lost control, which triggers the body and mind’s state of alertness, or arousal. This can be caused by unusual forces such as jerk, or varied jerks known as ‘jounce’. The feeling of being out of control can be triggered by rapid acceleration as well as sudden drops and loops, but variety and the element of surprise are needed to sustain a state of arousal.
Combinations of features might include a negative G-force experience known as a ‘hop’ to produce a lurching feeling in the stomach, followed by a pull out of a drop to create positive G-force, with designers manipulating a rider’s expectations and building suspense. The 'clothoid loop' is a defining feature in many modern roller coaster designs – see Inverted teardrop.
In order for riders to feel the force of a clothoid loop or with corkscrews, the train they are sitting in has to have enough kinetic energy to reach a high enough speed to carry them, upside down, safely through the loop. While the great majority of roller coasters use traditional lift hill chains to pull a train up the initial highest hill, now rides are being built that are capable of launching trains at much higher speeds.
Electromagnetic launch systems, introduced at the end of the 1990s, require no moving parts and so require less maintenance than hydraulic launch systems or traditional lift hill chains. They use electrical impulses to attract or repel ‘fins’ on the underside of roller coaster trains. Vekoma uses two types: linear induction motors (LIM) and linear synchronous motors (LSM).
The main difference between the two is where the magnets are positioned. LIMs use sets of electromagnets mounted on a track, to which alternating current is applied to create a magnetic field. A train is propelled rapidly forward when its metal fin passes through the magnetic field generated.
In contrast, strong magnets are secured to a train on a track in an LSM system and rely on the basic principles of attraction and repulsion (using a DC motor). When a train approaches magnets on the track, it is attracted to them, and when it passes over them the magnetic field is reversed to propel the train away from the magnet, forward down a track. When sets of track magnets are fired rapidly, they can propel a train at great speeds.
Alternatively, hydraulic launch systems, that have similar function principles to a ‘catapult’ mechanism on an aircraft carrier, are used for the world’s three fastest roller coasters – see Hydraulic motors.
Hydraulic launches have the advantage of consistent power requirements and are used on some of the world’s fastest coasters, including the Formula Rossa at Ferrari World in Abu Dhabi. This ride uses 48 hydraulic motors to fire riders to 240 km/h in five seconds.
Early roller coasters included circular loops to invert riders, but a constant radius required a high velocity to complete the loop, subjecting riders to a high centripetal acceleration at the bottom of the loop as well as a more intense vertical G-force, resulting in discomfort.
To solve this potentially dangerous problem, engineers came up with the clothoid loop, which is an inverted teardrop shape that is effectively a section of a spiral in which the radius is constantly changing.
The radius of curvature is much larger at the entrance and exit of its loop element than in a circular loop, allowing for a much more comfortable transition as well as less intense vertical G-forces.
Smaller radii at the top of the loop also mean trains can travel with a lower velocity at the top, while still completing the loop, giving a larger centripetal acceleration with a lower speed and a more comfortable, but thrilling experience for passengers.
Professor Walker believes one of the biggest barriers to creating bigger, faster and more imaginative rides is the high level of capital needed. As roller coasters cost in the region of £10million to £20million to build, the parks need to ensure a wide enough demographic of customers to make the investment worthwhile, which can limit innovation.
However, new ride design software is allowing engineers to create more organic roller coaster elements that have not been seen before. Rides using organic shapes are designed to create more fluid, graceful, less artificial rides to give the effect of flying or diving into water. The next generation of roller coasters could look radically different from the geometrically shaped ones with specially shaped loops and vertical drops that we know today.
New track shapes will be created such as a cross between a clothoid loop and a corkscrew. This will allow the rider to experience the sensation created by a clothoid loop and corkscrew simultaneously. By mixing the two, a ride will not only look new and exciting, but will provide new stomach-churning sensations for riders too.
Situated in Europa-Park’s Iceland-themed area, the Blue Fire ride (created by Mack Rides) in South-West Germany has five trains with seats for 20 people in each. The lap bars that hold the passengers in place contain embedded pulse monitors. Riders can purchase a DVD that shows their faces and their pulse rates during the ride © Europa-Park
Marcus Gaines from the European Coaster Club has seen other innovative trends being implemented. More manufacturers are coming up with lap bar designs that give riders greater freedom of movement. Lap bars used to be popular, and were used on rides with only positive G-forces, such as Scorpion at Busch Gardens, Florida, but now they are being used utilised by some companies on coasters with negative G-forces and inversions other than a standard vertical loop.
The shape of the seat also plays a role in securing the rider in place. The design can make rides seem scarier, particularly if customers are flung upside down, enhancing the adrenalin buzz of a ride.
There is also a move away from steel tracks back to wooden ones, to capture a bygone age of roller coasters, and to save money as they are typically cheaper to build than big steel coasters. While they are not currently popular in the UK, firms elsewhere are pushing their limits, building faster, steeper wooden roller coasters with loops. In the US, Rocky Mountain Construction unveiled its first wooden roller coaster to go upside down in Silver Dollar City, Missouri, in 2013, and will unveil the world’s first launched wooden roller coaster at Dollywood, in Tennessee, this spring. Last year, Martin and Vleminckx Rides built two wooden coasters in China that featured corkscrew inversions.
A trend that is starting to make its way into theme parks is the incorporation of virtual reality into roller coasters to enhance the sensory experience. For the past couple of years, Mack Rides in Germany, in partnership with a local university, has been working on combining VR with roller coasters. In 2015, the public got the chance to try out the world’s first VR Coaster at Europa Park, in Rust, Germany.
Alton Towers has been working with the Guildford-based firm, Figment Productions Ltd, to revamp its Air roller coaster to create a VR roller coaster experience. From April 2016, the ride will have an out-of-this-world theme and is to be called Galactica with riders wearing headsets based on the Samsung Gear VR system.
Figment has developed Vector VR, a patent pending system that includes a custom sensor, fixed next to a rider’s seat, with an inertial measurement unit that constantly monitors the movement at that point on the train and compares it to a ‘master path’ captured by the same sensor.
The visuals that show up on a rider’s headset controlled by the Vector software algorithms sync with the sensor so that they match the motion of the roller coaster train and position the rider in the right space in the virtual world. The headset also adds tracking for rotational head movements, completing the picture to match what the rider sees with what their vestibular system tells their brain they should be seeing. This is key to minimising motion sickness and the system means that a 90° sweep can easily be manipulated to become a 360° turn. Galactica riders will also be in a prone position intended to increase the sensation of flying, allowing riders to stretch their hands out and feel the wind in their face.
With a hydraulic launch, a ‘catch car’ runs underneath the coaster’s train and track on the end of steel cable locks. At the other end, a large winch drum is attached to a series of hydraulic motors. Hydraulic fluid is forced into a number of accumulator chambers, compressing nitrogen gas. When the ride is ready to launch, valves are released allowing the nitrogen gas to push the fluid back through the motors, causing the winch to spin up and pull the cable along.
Nitrogen is used as it is highly compressible and returns to its original volume quickly. After the launch, the catch car travels back down to the launch area, ready to attach itself to the next train. While this happens, the fluid is pushed into the accumulators, in effect recycling the whole launch process.
SHORT HISTORY OF THE COASTER
What is considered to be the first true roller coaster opened at Coney Island in New York in 1884. LaMarcus A Thomson built the wooden Gravity Switchback Railway. Back then there were no brakes on the track; instead a brakeman would ride on the train, manually operating brakes on the wheels.
In 1912, engineer John Miller made a huge safety improvement that remains an integral part of today’s modern roller coasters, upstop wheels. These are an extra set of train wheels that run on the underside of the track, designed to prevent a train from flying off, crucial for moments of negative G-force or for looping upside down.
The first steel roller coaster appeared in Germany in 1906. Showman Karl Gabriel introduced the world to the 10 m tall Devil’s Wheels at the Munich Oktoberfest. Gabriel created the steel roller coaster so that it was portable and could be easily dismantled, relocated and rebuilt.
The Matterhorn Bobsleds at Disneyland in California, built by Arrow Developments, was the first steel coaster using tubular track that enabled sharper turns. It was this 1959 roller coaster that created the surge of interest in steel coasters, and the downturn in wooden coasters.
It wasn’t until 1975 with the Corkscrew at Knott’s Berry Farm, California, that thrill seekers would be flipped upside down. The popularity of steel roller coasters became apparent in 1986 when, for the first time, steel coasters outnumbered wooden ones.
During the 1990s and early 2000s there was more than a decade of competitive building, with theme parks battling to have the tallest or longest steel coasters. The UK played its part, with Lightwater Valley opening The Ultimate, which at 2,268 m became the longest coaster in the world, holding the record for nine years until the Steel Dragon 2000 opened in Nagashima Spa Land in Japan. Blackpool’s Pleasure Beach claimed the ‘world’s tallest’ record in 1994 with the Pepsi Max Big One measuring 65 m tall; today that record is held by the 139 m high Kingda Ka at Six Flags Great Adventure, New Jersey.
Compiled by Marcus Gaines, European Coaster Club,
ON THE UP
Just as roller coasters seem to push and pull their riders in different directions, the future of the rides themselves is diverging. Use of organic-shaped rides and virtual reality technology will lead to more immersive and smoother experiences for riders, while noisy, back-to-basics wooden tracks will play on more primal fears to arouse the senses.
What is certain is that there will be faster, more testing experiences on offer than ever before. There are now nearly more than 4,000 coasters to ride, in what is being hailed as the dawn of the second golden age of roller coasters.
Fraser Ross has been a Concept Engineer at Vekoma Rides Manufacturing BV since 2012. Fraser’s work, hobby and life is centred around roller coasters and theme parks. He specialises in designing roller coaster track layout and related analytical assessment of vehicle dynamics.
Professor Brendan Walker is a technology-inspired artist, engineer, and broadcaster who specialises in the creation of tailored emotional experience. He originally trained as a military aeronautical engineer at Imperial College, before studying design at the Royal College of Art.