A Hand Crank Siren: How does it Work?
A hand crank siren is quite similar to an air raid siren, tsunami siren, outdoor warning siren, flood siren, or a civil defense siren. It is usually a mechanical or electronic device that is used to produce a high degree or loud sound that warns residents of that certain area of impending dangers, such as incoming tsunamis, earthquakes or floods. But in some cases, a hand crank siren is typically used to indicate the time of the day.
A Brief History of Sirens
Sirens were originally created to warn people of incoming air raids during the Second World War. As years passed, sirens were used to warn residents of incoming natural calamities and also nuclear attacks. In the most recent years, the traditional siren system was replaced with more advanced and specialised warning signals such as Electronic Sounders.
The modern sirens available today have the capability to generate a sound with up to 135 decibels even 30 meters away.
What is a Hand Crank Siren and how does it Work?
While the modern world produced more advanced, electronic sirens, some areas still use hand crank sirens. A Hand Crank Siren is a type of siren that has a distinct handle or crank at the back of the main head. What makes hand crank sirens different than other types of sirens is that it can be used in cases where there is no electricity available. There is no need for electric input since you will be using your energy to operate a hand crank siren.
As its name implies, a hand crank siren works by manually turning or cranking the handle a few times to produce a sound slowly getting louder for every turn. It has a motor that drives the shaft with an attached rotor, also known as chopper or fan, to both ends. In every rotor surround a stator, a sort of casing, which has a number of holes that are rectangular.
Each of the blades draws and forces air out through the slots inside the stator while the plates at the end of each of the blades stop or interrupt the flow. As a result, it creates rarefied and alternating compressed air pressure that produces a deafening sound.
Examples of Hand Crank Sirens
Whilst hand cranked sirens are much more modern today, here are some examples of sirens of the past:
The British Hand-cranked Portable Air-raid Siren
The British Hand Cranked Siren has numerous types of mountings, although the design of the siren itself remained constant. When the top handle is used, it opens and close the shutters in front of the siren and can create a dual tone. When the crank handle is turned faster, the siren produces a louder sound. Moreover, even though this hand crank siren is described as portable, it can be very bulky and difficult to operate.
The German Hand-cranked Portable Air-raid Siren
The German Hand Crank Siren is quite similar to the British Hand-cranked Portable Air-raid Siren, but this siren features a greater degree in terms of portability. It also has the dual tone which can be produced by operating the lever at the top of the siren.
The Vikings Horns Hand Crank Siren
Like the sirens that are used to warn people of incoming danger during the World War II, this hand crank siren produced a loud and eerie sound when cranked, and created a distinctive alert. It is made of metal housing and can produce a sound output of 115 decibels. It also comes with an adjustable single tone air raid.
Handheld Crank Sirens
These types of sirens are usually lightweight and small. Some handheld crank sirens can produce a loud and adjustable sound of 110 decibels. Such hand crank sirens are ideal for getting the attention of people from schools, camps or to just cheer on your favourite sports team.
Mounted Hand Crank Sirens
Like the antique hand crank sirens used in the 1930’s, these Hand Crank Sirens are mounted to the floor or sometimes a wall. It is usually placed on high grounds since some types can produce a loud sound of up to 130 decibels to get the attention of people especially in places where electricity is not available.
Conclusion:
Hand Crank Sirens originated back in the 1930’s and became very useful during the World War II for the safety of the people. Nowadays, there are many hand crank sirens that are available, not to warn people of incoming danger but to call for their attention. The bottom line is, Hand Crank Sirens can be used in any situation that requires an alert.