Precision Clock, c. 1898
Strasser & Rohde
Glashutte, Germany
Until 1948, this astronomical precision clock was the heart of the Philadelphia City Hall clock tower. The clock consists of a Type B II Strasser & Rohde movement mounted on a 500 pound cast iron base. A small cam on the escape wheel arbor would lift a lever, which caused a valve to open. This in turn, allowed compressed air to pass through copper tubes to the dial room about 200 feet above in the tower. In the dial room, diaphragm and ratcheting devices for each dial exerted more than 700 pounds of pressure to move the 175 pound hour hand and the 225 pound minute hand. The primary air compressor located in the dial room was powered by electricity. In case of electrical failures, copper tubing had been run down to the basement where a water powered compressor would be activated. The weight that powers the movement was originally located behind a channel along the right side of the case interior. This ensured that the air friction to the swinging mercurial pendulum would remain consistent regardless of the position of the weight.
Donated by Dr. Warner D. Bundens, Jr., FNAWCC #1177
80.86.1
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