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Roller coaster up-stop wheels that hold cars to the track
A roller coaster wheel assembly. The underfriction wheels are on the bottom. The three sets of wheels clamp onto the track.
On a roller coastertrain, the underfriction, up-lift, or up-stop wheels are a device to keep the train from jumping off the track under intense movement. The design was patented in 1919 by John A. Miller.
