An example device may include a rounded outer incline ramp and a rounded inner incline ramp surrounding a central axis. The rounded inner incline ramp and the rounded outer incline ramp may be inversely aligned relative to the central axis. The device may also include a piston carrier oriented in a direction parallel to the central axis. The piston carrier may include a first piston including a first roller positioned on the two ramps at a first point, where the first piston is configured to act on the two ramps in a direction parallel to the central axis. The piston carrier may also include a second piston including a second roller positioned on the two ramps at a second point opposite the first point, where the second piston is configured to act on the two ramps in a direction parallel to the central axis.