Linear Induction Motor (LIM) and Linear Synchronous Motor (LSM) roller coasters use electromagnetic waves to propel the roller coaster train. The train on this type of coaster has metal fins mounted to it in order to facilitate launching. LIM/LSM launch tracks have many (often more than 200) linear motors along the section of the launch track. A magnetic field is created by the LIMs along the track, which attracts the roller coaster train and sends it forward. The next LIM on the launch section of track is magnetized, and the previous one loses its magnetic field. This continually attracts the car forward until it reaches the end of the launch track at full speed.
LIM/LSM Launch Roller Coasters
LIM/LSM launch roller coasters utilise large amounts of electricity to propel the train along the launch track into the ride elements. A wide selection of roller coaster manufacturers now offer models using this form of propulsion. A big advantage of LIM/LSM is that it’s more or less maintenance-free, as you don’t have any wear contact in between the mechanical parts of the drive system.
Manufactured by Mack Rides of Germany, ICON at Blackpool Pleasure Beach is a double launch roller coaster using Linear Synchronous Motors (LSM) to propel the train along the track. The ride opened on 25 May 2018 at a total cost of £16.25 million.
These high-speed LSM launch mechanisms require a lot of power, the key to this is the energy storage system. Manufacturers are utilising supercapacitors (referred to as super caps), which bring together many of the benefits of batteries and capacitors but alleviate the shortcomings. While super caps typically store 10 to 100 times more energy per unit volume than a standard capacitor, they’re able to charge and discharge much faster than batteries and can tolerate many more charge and discharge cycles. Supercapacitors have been available for well over a decade but only in recent years, has development provided the load cycle and lifetime stability data to enable their wider deployment and LSM application.
Linear Synchronous Motors LSM are essentially unrolled electric motors. Basically, the stators become part of the roller coaster track and the ‘rotor arm’ is part of the roller coaster train. Linear synchronous motor (LSM) design uses active stators with copper windings attached to the track with an array of alternate-pole high-density permanent magnets attached to the train. These are arranged in a U-shaped ‘magnet bar’, leaving a ‘bottom open’ air gap to allow the linear stator modules to engage and propel the train.
When the stators run within this air gap, two very small contactless air gaps of about 6-7mm are maintained in between the magnet bar and the stator’s surface. These small air gaps bring the opposite magnets of the magnet bar really close together to guarantee a very powerful magnetic field, enabling a more powerful motor. The LSM system offers a more efficient source of power when compared to a linear induction motor (LIM).
LSM launched rides don’t have to induce the magnetic field [on the rotor element], like rides utilising linear induction motors (LIM) do. The downside, however, is that the train has to carry additional weight because it’s a high-density magnet. Even with this weight disadvantage, the LSM system can provide nearly double the efficiency of LIM technology. On occasion, a catch car is used to avoid the requirement for the train itself to carry the additional weight of the high-density magnet.
Video Explaining the Science behind LSM Motors
This excellent video from Disney Mechanical Engineers Angel and Josh explains how LSM launched roller coasters work. The ride featured in this example video is one of Disney’s fastest coasters, Rock ‘n’ Roller Coaster at Disney’s Hollywood Studios.