The Fog Bell and Striker Mechanism
The fog bell, with its newly-fabricated striker mechanism, is now on display at the Maine Maritime Museum.
Some photos of the development of this project are available here.
This exhibit was constructed by the Range Light Keepers lighthouse preservation group to restore and test a mechanical fog signal. Commonly in use at many Maine lighthouses 100 years ago, we know of no complete examples of this design remaining today. This working assembly is a useful step in preservation of the Fiddler’s Reach Fog Signal originally commissioned in 1914 nearby on the Kennebec River. The tower was built 16 years after the completion of a lighthouse and range light along Fiddler’s Reach following the grounding of a large sidewheel steam ferry, the Ransom B. Fuller, on its scheduled run from Boston to Gardner.
This was the last major navigational aid to be added to the river system during the period when the Kennebec was a major highway for transportation and commerce in the region.
The Range Light Keepers, Arrowsic, ME are pleased to present this exhibit. It is the result of work by a team of committed and highly skilled volunteers:
The Tower: The Fiddler’s Reach fog signal is housed in a wood structure of a design typically erected along the Kennebec River beginning in 1898. The pyramidal form is designed to function as a stable base to house the striker components, provide a high point to hoist the weights and to support the large fog bell outside the tower wall at the edge of the river.
Fog Bell: 1900 McShane Bell Foundry, Balitmore, MD Cast for the USLHE, this bell is similar in size to the original 1,259 lb. MeNeely Bell used on the tower. The bell is mounted outside the wall for greater sound transmission. It is struck from the rim with a hammer. A clapper (not included) was used on occasion to ring the bell by hand. Fog bells were produced in standard sizes according to their application.
Beam: In 1972 a portion of the 16 ft. long beam was cut off to remove the bell after the fog signal ceased operation. The exhibit uses the actual remaining portion of the bell beam used at Fiddler’s Reach Fog Signal.
Hammer: The hammer delivers a pattern of blows determined by the striker to ring the bell. It’s weight is customarily 1/60 that of the bell in order to effectively activate the “voice” of the bell. This hammer was found to have the original connecting arm sawn off from the hub. A replacement arm, brace and linkage has been newly fabricated.
Fog Bell Striker Machine: George M. Stevens Co., Boston, MA. This “improved” model striker was produced by the clock maker that found a new market for it’s less than competitive tower clock machinery. Advertised as capable of 1000 blows on a single winding, it was purchased by the U.S.L.H.E for widespread use in Maine. Key to the operation is the Crane patented walking pawl escapement, seen below the drum, that slowly lowers the weights and transfers energy to wind the timing clock and swing the hammer. The striker has a small timing clock that sets the period between each cycle and a slotted brass count wheel to determine the pattern of blows, together known as it’s characteristic. These were available with different patterns. This striker is set up for 2 blows every 20 seconds. The mariner would consult the charts and light lists to learn the map location and characteristic of the various fog signals and listen in the fog to determine his position relative to the signal and the hazard nearby. Often multiple fog bells could be heard and provided additional useful information.
Lighthouse Keeper: The fog signal was a man-powered machine. The lighthouse keeper provided bio-mechanical energy to run the fog signal by cranking a gear to wind the cable around the drum that in turn raised the cast iron plates. Then he would set the machine in motion until the weights slowly ran out to the ground. How many hours between windings are determined by a number of factors, but 4 to 8 hours seems to be about normal. The keeper would also have to keep the machine in working order with lubrication and repairs so as to perform the duties necessary in keeping mariners safe on the water.
Weights: The weights were manufactured as part of the striker and are used to store the power to run it. The lighthouse keeper would use his muscles to raise the cast iron plates by cranking a gear on the cable drum. The force of gravity pulling down on the weights turns the drum to run the machine. Each plate is approximately 118 pounds. The bell tower had 13 plates loaded on the cable, equal to over 1500 pounds.
Pulley(s): The pulley redirects the force of energy and moves it in line with the steel wire cable. In the fog bell tower the cable is strung to a pulley inside the top of the tower and the cable was long enough to let the weights drop through an opening in the floor to the ground below. This gave the striker a longer period to run between windings. Additionally, the cable was strung through more pulleys to make it even longer, a technique called compounding. This required more weights be added to provide enough force to run the striker.