Variations in tape speed cause flutter, which can be reduced by using dual capstans. A torque amplifier is essentially two capstans connected together. It was raised by some firemen who turned some capstans and so raised it. Each gate leaf had two capstans, one to open it and another to close it. At low tide, the ropes were pulled taut with capstans. Machinery on the dock, including capstans and the lock gates, were worked by hydraulic power. This will still find out, what message has left Sarah on the capstans. Winches and capstans are machines designed to pull ropes. Warp winches with capstans are installed on the deck to haul the catch. However multiple pinch rollers may also be employed in association with one or more capstans. Local hydraulic capstans were included to rope-haul wagons to and from the cradle as necessary. During the open-boat whaling era in Japan (1570s-1900s), whales were winched ashore by large capstans. Modern capstans are powered electrically, hydraulically, pneumatically, or via an internal combustion engine. Capstans, traditionally, had unequal diameters and different flywheel masses. Capstans evolved to consist of a wooden drum or barrel mounted on an iron axle.