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The Thunderbolt is a mechanical outdoor warning siren that was manufactured by Federal Signal Corporation from 1951 until its production ended in 1991.[1] It is a unidirectional, rotating siren with a large square-shaped horn, and can come in various colors, usually yellow, by request.
History
editThe Thunderbolt siren was developed between 1952 and 1990. It was the first "supercharged" siren, which uses a blower to force air into the rotor, greatly increasing the siren's volume. In the 1980s, when civil defense fell into disuse, thunderbolts across the United States were repurposed for nuclear and storm warning siren systems. During the Gulf War, Federal sent a number of modified Thunderbolt 1003s to Kuwait to warn its citizens of an air raid. These were the system 7000 series and were only found in Kuwait. Later, Kuwait's sirens were all replaced with Federal Signal Modulators. One system 7000 is on display next to a Federal Signal Modulator at the Kuwait General Administration of Civil Defense in Kuwait City, Kuwait. Eventually in 1990, the Thunderbolt was discontinued in favor of the new 2001 Siren Series. Since then many have sat abandoned or have been replaced by newer systems. In the 21st century, many communities lacking siren coverage have purchased Thunderbolts that once sat in various towns, and have been refurbished. Many Thunderbolts are also in private and legal possession.[2]
Design
editThe Thunderbolt came in several models. The Model 1000 was single tone, while the Model 1000T and Model 1003 were dual tone.[1] The Model 1003 also included two solenoid-operated control valves. They are used to create alternating steady, alternating wail, pulsed steady, and pulsed wail signals, which can be used as a fire warning. Otherwise, it is identical to the 1000T, but used the 5/6 rotor only. Although the 4/5 port rotor is compatible, it was never offered for the 1003. There were also 3 types of gas powered Thunderbolts known as the System series, System 7012 is a model Thunderbolt 1000, System 7022 is a model Thunderbolt 1000T. It is identical to 7012, but has a dual-tone chopper. System 7026 uses a model Thunderbolt 1003. There are other system series thunderbolts, and the only surviving ones have been converted to electric. Only two 4/5 port rotor 1003's exist currently, one in Saint Paul, Nebraska, and the other in University Park, Illinois. The 1003 entered production in 1961 or 1962, and ceased in 1990. The 1003 was the last production model built. The last sirens went to a township in Michigan; all of them have been removed and replaced since 2009. Originally the Thunderbolt used a motor and an Abart gear reducer driven by pulley to drive the large spur gear which makes the projector rotate. The pulleys utilized 3 different belt slots to change the RPM in which the siren rotates, from 2, 4, and 8 RPM. In 1980, Federal wanted to make the Thunderbolt more maintenance free, doing so by turning the motor and gear reducer to face each other and attached to make a direct drive system which rotated at 4 RPM. This rotator was used only on the B-series models. B-series units were only offered in 1980.
References
edit- ^ a b Federal Signal Corporation (June 1979). "Service Manual: Thunderbolt Siren" (PDF). Civil Defense Museum. Archived from the original (PDF) on 30 July 2022.
- ^ "Federal Sirens". Civil Defense Museum. Archived from the original on 15 November 2023.