The V8 Powered Air Raid Siren

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During World War 2, many countries were at a constant state of fear from enemy attacks. The Blitz in Britain is one of the most famous examples of this. The United States however, was lucky to be one of the only major participants to receive almost no attacks on their soil during these times.

A German Luftwaffe Heinkel 111 flying over London during the Blitz, 1940.

The Americas were far away from the European conflicts of World War 2, and were at very little risk of coming under attack. Very few aircraft were capable of a Europe-America round trip.

The Germans were working on the Amerikabomber, an aircraft capable of flying to New York. The Junkers Ju 390 was the closest they got before cancelling the programme.

The prototype Junkers Ju390 ‘Amerikabomber’

After Germany’s defeat, the US and Soviet Union were in competition to be the dominant superpower.

This was the beginning of the Cold War.

The Cold War

In 1949, 4 years after the US Trinity nuclear bomb test, the Soviets detonated their first nuclear device.

The Trinity nuclear test, 10 seconds after detonation.

Then in 1957, they launched the R-7 Semyorka missile, the first intercontinental ballistic missile.

The US then followed with the SM-65 Atlas rocket in 1958. These rockets essentially sparked the space race that would culminate in the Apollo Moon landings.

The advent of intercontinental missiles capable of delivering nuclear weapons, aswell as increasing tensions between the Soviets and the US, meant the US was no longer safe from aerial attack.

SM-65 Atlas ICBM launch

The US wanted a better way to warn citizens of an incoming attack. At that point, many cities and towns had sirens still from WW2, but were often small electronic systems.

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The government required a siren that had the power to alert an area that would have previously needed many smaller electric sirens.

The Chrysler Air-raid Siren

1952 saw the introduction of the Chrysler Air-raid Sirens which were purpose built for this task.

It was a unit containing a power source, fuel tank, compressor and projectors.

A Chrysler Air-raid Siren.
Image by User PBMI CC BY 3.0

The power source was a Chrysler FirePower Hemi V8. This 5.4 L engine produced 180 hp, and 312 ft lbs of torque, and was mated to a three stage centrifugal compressor.

A 1951 Chrysler Hemi V8.
Image by Greg Gjerdingen CC BY 2.0

This compressor pressurises the air before flowing out the 6 large projectors. At 4,600 rpm the compressor discharged 2,610 cubic feet of air per minute, at a speed of 400 mph.

This system produced a siren 138 decibels (dB) in volume 100 ft away, the loudest siren device ever constructed. This sound was audible up to 25 miles away.

To show how loud this was, a rock concert is 114 dB, while an afterburning jet taking off from an aircraft carrier is around 130 dB. Due to how the dBs scale, the 138 dB siren is almost twice as loud as 130 dB.

Each city now needed fewer sirens , making warning the public easier. The ‘Warning’ siren was 8 seconds at full power, and 4 seconds off power repeatedly for three minutes. The ‘All Clear’ siren was full power for 1 minute, with 2 minutes off power, three times.

The sirens, while loud, were rarely seen as they were mounted high up on buildings, hills and dedicated towers. The high up location maximised their range.

A Chrysler Air-raid Siren on a tower in Seattle.
Image by Lunarbunny CC BY-SA 3.0

Survivors

By the 1980s the threat of nuclear war had relaxed, and many Chrysler Air-raid Sirens fell into disrepair. Their remote locations allowed them to be completely forgotten.

Also in Seattle, this siren has fallen into disrepair.
Image by Lunarbunny CC BY-SA 3.0 Seattle Tower 2

Some of the FirePower V8 engines found their way into the hands of hotrodders. They found with modifications these engines could produce well over 300 horsepower.

Some units have been saved and restored in private hands, and put back into running order.

A Chrysler Air-raid Siren in private hands.
Image by BrokenSphere CC BY-SA 3.0

The sirens were tested regularly to ensure their functionality, becoming a well known, but dreaded noise for the inhabitants of US cities during the Cold War.

These machines may now be collectors pieces, but in the event of a real nuclear attack, they were literally the announcers that the unthinkable had happened.

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The haunting wail of these sirens would have echoed out as nuclear tipped missiles rained down on the USA, changing civilisation forever.