Lift Hill - Anti-rollback Device

Anti-rollback Device

The familiar "click-clack" sound that occurs as roller coaster train ascends the lift hill is not caused by the chain itself. The cause for this noise is actually a safety device used on lift hills -- the anti-rollback device. The anti-rollback device is a standard safety feature, typically consisting of a continuous, saw-toothed, section of metal, forming a linear ratchet.

Roller coaster trains are fitted with anti-rollback "dogs" which are essentially heavy-duty pieces of metal which fall and rest in each groove of the anti-rollback device on the track as the trains ascend the lift-hill. This makes the "clicking" sound and essentially allows the train to go upwards only, effectively preventing the train from rolling back down the hill should it ever encounter a power failure or broken chain.

This feature was derived from the similar feature originally used on the Mauch Chunk Switchback Railway in Pennsylvania, starting in 1846. The two uphill planes that cars were drawn up under the power of a stationary steam engine had two slightly different early forms of this anti-rollback device. The entire concept of the modern roller coaster was also initially inspired by this railroad.