A friction wheel (also called a drive tire or kicker wheel) is a motorized wheel that alters or sustains the speed of a train by contacting it and creating friction.
Friction wheels can be orientated horizontally or vertically. When orientated horizontally, friction wheels are used in pairs and typically grip a fin on the underside of the train. However, some roller coasters use horizontal friction wheels that contact either side of the train. When orientated vertically, friction wheels contact the underside of the train.
Friction wheels are often used to move a train at low speeds. They are often used in stations and brake runs to push the train. Bolliger & Mabillard roller coasters feature horizontal friction wheels before the lift hill to synchronise the speed of the train with that of the chain, allowing it to enter the lift hill smoothly.
Friction wheels are used in lift hills. Unlike chains, friction wheels can be used on curved lift hills, which in turn allows for more compact layouts. However, in wet conditions the wheels create less friction and the train may slip.
Japanese roller coaster manufacturer Meisho Amusement Machines has used horizontal friction wheels to grip the sides of the train and slow it down.
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