Chain dogs and lift engagement
How the train mechanically locks to the lift chain — and what happens at the crest.
Under each car, a chain dog (lift dog) rises to engage chain links on the hill. At the crest, a mechanism often releases the dog so the train can roll free into the drop.
Mis-timed release or speed at crest affects how aggressively the drop grabs — designers tune lift speed accordingly.
If you hear a clunk at the top, that can be dog disengagement and transfer to gravity — normal on many installations.
Different lift types (cable, elevator) replace this mechanism but solve the same problem: safe hill ascent then release.