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Thunderbolt siren

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Thunderbolt Model 1003

The Thunderbolt siren was an electro-mechanical warning siren once manufactured in the United States by Federal Signal Corporation. The Thunderbolt siren consists of three motors. The blower motor is housed inside a large rectangular motor box typically found at the base of the siren (or in some installations on a wooden platform mounted half way up the utility pole, other methods include mounting a long wooden platform halfway up between two poles.). This motor is connected to a standpipe which blows or pumps air up to the "chopper" motor. As the chopper spins, the air forced into it escapes out of rapidly opening and closing holes, creating the siren's sound or "roar." Finally, a rotator motor turns the siren's projector horn 360 degrees when in operation. The Thunderbolt could be shipped as using single- or three-phase power and could either be pole-mounted or roof-mounted.

File:T49.jpg
Thunderbolt Siren in Topeka, KS
Federal Thunderbolt siren installed on Chase Bank building Newark, OH
Federal Thunderbolt siren installed on Chase Bank building Newark, OH

Thunderbolt history

The Thunderbolt was first produced by Federal Enterprises (now Federal Signal Corporation) in 1952. There were three models manufactured:

  • Model 1000, a single-tone siren which generated 127 dB of sound (measured from 100 feet away from the siren);
  • Model 1000T, a dual-tone version which generated 126 dB at 100 feet;
  • Model 1003, a dual-tone version with the added capability of producing a Hi-Lo fire signal. This model also generated 126 dB at 100 feet.

The dual tone Thunderbolt 1000T/1003 models have often been described by siren enthusiasts and casual listeners alike as having the most eerie and ominous sound due to its very distinctive dual tone that is usually sounded in a minor third. On all Thunderbolt models, the pitch of the siren was adjustable; most often, no two Thunderbolt sirens in the same community sounded the same (unless adjusted for consistency). Some lower pitched 1000T's have been described as sounding like a very loud dial tone. On single tone 1000 models, the sound from the blower motor can be more noticeable giving this version somewhat of a bass-like background sound, setting it apart from the sound of other single toned siren models. The rotator motor/projector horn had three speed settings — 2, 4, or 8 RPM.

Typically, these sirens were/are often seen painted bright yellow. This has more recently come to be known as "Civil Defense Yellow", although on occasion, one might find a Thunderbolt painted in other various colors to meet the community's needs. Very early examples of the siren could be observed with the projector horn painted "zebra striped" black and yellow, or red and white (most often the former). The projector horns on early models were fitted with two sets of metal grilles welded to the front opening of the horn. This was to exclude debris and birds from building nests inside. By the late 1950s, the manufacturer removed the grille design in favor of a protective black mesh screen.

The Federal Thunderbolt was the siren of choice by many Civil Defense authorities and emergency management agencies from the early 1950s through the late 1970s. By the 1980s, sales of the Thunderbolt were beginning to decline. Despite its popularity, the Thunderbolt was a high maintenance siren. Because of this, many of the cities and towns who had Thunderbolt sirens installed initially in the 1950s and early 60s were reluctant to replace them with newer ones, opting instead for more advanced/low maintenance models as suitable replacements, even a later model 1000 (series C), producing 131 dB instead of 127 dB, could not compete[1]. In 1988 Federal Signal introduced a new single-tone siren called the 2001DC [2]. This siren utilizes a DC or "battery backup" power feature, enabling the siren to be operated during a power failure, operates on only 2 motors, and requires far less maintenance. As the Thunderbolt only operates on AC power, the introduction of the 2001DC spelled the end of the Thunderbolt siren, and Federal Signal phased out the Thunderbolt series in 1990.

Thunderbolt Siren Today

Disconnected & Replaced Thunderbolt 1000 (Pictured Left) in Siloam Springs, Arkansas

Federal Signal no longer makes replacement parts for the Thunderbolt siren, with the exception of the rotator, which is used on the 2001 series siren, and the chopper, which is used on the Model 2 siren. Some towns in the US and some siren enthusiasts have taken to purchasing once decommissioned Thunderbolts and other Cold War-era Civil Defense sirens, restoring the units, and giving them a second "life" by selling or donating them to towns or communities in need of a good refurbished unit.

The Thunderbolt logo/decal insignia changed little in its 38 years in production. At the beginning in 1952, the name Thunderbolt was not seen on the siren, instead just the name "FEDERAL" immediately followed by Federal's logo at the time, a stylized circled "F" with a lightning bolt inside the circle striking towards the front of the "F". In the mid 1950s the siren's logo was changed to read "THUNDERBOLT" preceded by the aforementioned circled F logo connected to a second lightning bolt running through the word THUNDERBOLT, and there were a series of wavy lines above and a series of spaced or "pulses" lines below the word "THUNDERBOLT." The lines may have represented wail and pulsed warning tones respectively. Although this logo was not used on the siren in the beginning, it did appear in Federal's trade literature for the siren in 1952. This would be the siren's insignia for the remainder of its production life, except for the updates to Federal's "F" logo. Sometime in the early 1970s the "circled-F lightning bolt" logo was updated to a basic block style "F." When Federal Sign and Signal became Federal Signal Corporation in 1976, the company again updated the Thunderbolt logo to include its current block stylized red "FS" logo. This is the most commonly seen example of the Thunderbolt logo as it is the most recent. Some older roof-mounted "T-bolts" (pre 1976) that house the blower/cabinet housing inside its respective building have been observed to have intact examples of the old "circle F" or early 70s "block F" Thunderbolt logos. This is one way of estimating a "T-bolt's" age from an exterior view. The Civil Defense logo accompanied the Thunderbolt logo on the blower motor and could be seen on either side of the rotator motor. The Thunderbolt logo was usually seen across both sides of the rotator motor, on the upper left and right hand corners of the blower motor, and sometimes on the control cabinets.

U.S. Cities and Other Towns Using Thunderbolt Sirens, Past and Present

FS/FSC=Federal Signal Corporation

AS/ASC=American Signal Corporation

Trivia

During the early years of its production, the Thunderbolt siren's main purpose was to be sounded in the event of a nuclear attack/drill or air raid. By the late 1960s and early 1970s, the majority of cities and towns that had Thunderbolts and other outdoor warning sirens would begin using them more for severe weather/tornado warnings. (Although a few American cities were using sirens for weather warnings as early as 1960). By the 1980s as the Cold War began to "thaw" the Thunderbolt (along with most outdoor warning sirens) became better known to the American public as "tornado sirens" rather than "air raid" or "civil defense" sirens.

In the movie Forrest Gump at the very beginning, a Thunderbolt siren can be seen on the roof of one of the buildings in the camera pass.

The siren was featured in many Civil Defense films including one from the early 1950s titled "Let's Face It" (a close up of a single tone model 1000 painted "zebra striped" black and yellow (sounding the alert tone.)

In 1959 Chicago Mayor Richard J. Daley ordered his fire chief to sound the city's air raid sirens (all Thunderbolts at the time) at the moment the White Sox won the pennant, prompting many unaware citizens to be alarmed of an air raid or nuclear attack.

The early versions of the 2001DC siren utilized the same exact rotator motor design as the Thunderbolt.

The chopper of the Thunderbolt siren is based on the Model 2 siren, which is still in production.

  • Civil Defense Museum has a number of mp3 audio files of sirens.
  • Buddy Harris has located and is currently restoring a model 1000 that was in Jacksonville, Florida.
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