6. Fuzes Flashcards
Define Fuze?
Fuze is a device designed to function an item of ammunition under pre determined circumstances.
Fuzes are classified according to
what three categories?
Filling (ignif or disrupt) Position Function
Fuzes classified by FUNCTION have what
three types?
TIP
Time, Impact and Proximity
Impact Fuzes are divided into which three
categories?
Super Quick(SQ)
Graze
Delay
What do the Following acronyms mean?
VT PIBD MTSQ MO ET PD
variable time point intiating base detonating Mechanical time super quick multi option electronic time point detonating
GENERAL REQUIREMENTS
SAFETY
RELIABILITuY
What are the OTHER REQUIREMENTS of a fuze?
Standard weight Optional delay setting Multi role to minimise refusing Must fit standard cavity sizes Easy time adjustments/setting Minimum preparation for use
What are the types of Masking Devices?
- Shutters (Sliding or Rotating)
- Delay Arming Shutters
- Delay or Non Delay Masking Shutter (Interrupter or
Setting Bolt)
What are the advantages of electronics in
fuzes
Lowers costs due to multi role function Versatility in arming Mechanical preparation or initiation
What are the two categories of shutters?
Delay or non-delay
What is Set forward
The relative forward movement of components
when a fuze decelerates on impact
List the Forces Acting on Fuzes (7)
Set back
-reaction due to acceleration forces applied on firing
Creep Forward
-When acceleration phase ends, springs compressed re-assert themselves; permits spinning forces
Centrifugal Force
- generated by the lateral velocity imparted by spinning, acting on components outside the CG
Spin Decay
-decay of angular velocity. Can use to trigger self-destruct devices
Set Forward
-Relative forward motion from deceleration on impact
Air or Gas Pressure
-used for turbines; alternate arming method for non spun projectiles
Stored Energy
-Usually a wound spring to operate clockwork devices or shutters
What are the Four Methods of function for
mines/mechanical fuzes
Pull Pressure Pressure release Tension release
What is?
- Set Back
- Creep Forward
Set Back:
This arises from the reaction of the mechanism to the acceleration forces applied in the gun on firing.
The physical backward movement or anchoring of components compresses springs
Creep Forward:
-When the acceleration phase ends, components which have been locked tend to ease forward on their seatings.
-Springs which have been compressed begin to
re assert themselves.
-This gradual unlocking process permits spin forces to act on components susceptible to them.
What is?
- Centrifugal Force
- Spin Decay
Centrifugal Force:
Any component whose centre of gravity is off the axis of the fuze tends to be thrown outwards as a result of centrifugal force generated by the angular velocity
imparted to the projectiles.
Spin Decay:
In the same way that a projectile loses linear velocity, it loses angular velocity.
This decrease in angular velocity can be
used to trigger a self destruction device.
What is?
- Set Forward
- Air or Gas Pressure
Set Forward:
-The relative forward movement of components when a fuze decelerates on impact.
-This can be used to move an inertia pellet
striker onto a detonator.
Air or Gas pressure
- Sometimes used to drive a turbine to generate power for electrically operated fuzes
- Used for non spun projectiles
What is?
Stored Energy
Stored energy is usually a spring
(mechanical) used to operate clockwork
devices or to move shutters.
Chemical energy in an energiser for example,
may be used to generate electrical power or
gas under pressure.
What are the 3 types of Time Fuzes?
Mechanical
Combustion (Powder Train Time Fuze - PTTF)
Electronic
How are time fuzes is designed to function?
Time Fuzes are designed to function after a predetermined time whilst in flight
There are three types of MT Fuze. What are they?
Thiel - British MT Fuzes
A series of wheels and pinions controls the escape of
from a main spring which is wound up during manufacture
Dixi - Swiss Fuze
This mechanism is driven by centrifugal force acting on driving balls
Junghans - American MT Fuzes
This mechanism is actuated by spring assisted by centrifugal weights
Position of fuzes vs Impact CATEGORIES. List Each (3) and (3)
Superquick Graze Delay -Point Detonationg -Base Detonating -PIBD
Impact Fuze - Types./ ACTIONS (4)
xx
SNGD
Superquick (SQ) Non Delay Graze Delay
Describe Superquick Fuzes (SQ)
a needle supported by a thin metal disc or a hammer/striker supported on a shear wire
or coiled spring exposed to a direct blow on impact with the target
Non Delay Fuzes
These fuzes differ from the SQ fuzes mainly
in being less sensitive
The mechanism usually consists of a steel
hammer / striker supported on a stout shear
pin.
Graze Action Fuzes
The interior mechanism of graze action fuzes is so arranged that when the projectile is checked in flight or receives an appreciable deceleration
A moveable part, usually called the graze, inertia pellet or plunger moves forward to carry the detonator on to the needle (or vice versa).
A creep spring keeps the two apart until this deceleration is experienced
Graze fuzes have a small inherent delay
Delay Fuzes
These fuzes usually have a masking shutter, interrupter or pyrotechnic composition in built into the detonating train between the initiator and the fuze magazine so there is a slight delay between the actuation of the initiator and the firing of the magazine.
This may be achieved by channelling the flash from the initiator around a longer route or slowing it by having to wait for the pyrotechnic composition to burn through before it reaches the next component.
Position CATEGORIES and description (3)
xx
Point Detonating Fuzes (PD)
-Fitted in the nose of projectile and normally shaped to conform to contours of projectile.
Point Initiating Base Detonating Fuzes (PIBD)
-Consist of initiating assembly in nose of projectile and fuze in base.
Base Detonating Fuzes (BD)
-Situated in base of projectile, cylindrical in shape.
Define Proximity Fuze
xx
Proximity fuzes are automatic time fuzes,
- with or without PD element,
- (that are) designed to function a projectile at the optimum lethal distance from the target,
- provided that in the case of aircraft targets, the trajectory passes sufficiently close.
Proximity Fuze Terminology
And what settings are available for MO? (4)
Proximity Fuze: A fuze that reacts to the proximity of the target and detonates the shell. Variable Time (VT) WW2 term for Proximity Electric Fuze old US term for Proximity Multi Option Fuze e.g. M734 –Proximity –Superquick –Delay –Near Surface Burst
Difference between VT and CVT?
xx
Variable Time (VT) Timer section arms the fuze electronically after firing.
Controlled Variable Time (CVT) Can be set to activate the Prox function after a set time.
Explain The Doppler effect
xx
Radio waves are emitted by the fuze, some of the waves are reflected and picked up by the receiver
The time taken to return affects the Reflected waves, which interfere with the radiated waves to give a beat
known as the Doppler effect
As the fuze gets closer to the set target distance the impulses increase to a defined peak value and the fuze functions
Storage & Handling of Prox Fuzes, need to be Protected from:
SHDD
Sunlight
Heat
Dampness
Drop / Strike
- Stored nose down
What are electronic fuzes?
What are the power sources
Electronic fuzes are functioned by a current passing through electric leads from some sort of battery Power Sources: –Battery –Turbine generated –Precharged –Electostatic
Design Considerations of Proximity Fuzes (8)
Rugged Economical Able to function in all conditions Light weight Safe to handle Not easily jammed Able to fit existing projectiles Sensitive and rapid in operation Have good storage characteristics Not subject to false operation
Have good storage characteristics
Types of holding, locking and safety devices (8)
SSDCSBSH
Shear wire
STRIKER SPRING and spring disc
Detent/setback pin
Centrifugal balls
Stirrup Spring & ferrule. (3-part sleeve)
BORE riding pins. (on outside of fuze)
Safety pins, Cotter and PULL pins
Horse head segments. (2 pivoted segments)
Define Firing Device?
- The component which provides the stimuli to initiate the explosive train
- It may be achieved either mechanically or electrically
*Electrical - Bridge wire, Exploding Bridge wire, Conducting cap
What is a common method/example of the 4 Stage for Arming?
Unlocking components by SET BACK
Easing it onto its seating on CREEP FORWARD
Swinging it into position via CENTRIFUGAL FORCE
Initiation of the train via SET FORWARD
What is a
- Combustion Fuze?
- Mechanical Time Fuze?
- Electronic Fuze?
-Combustion fuzes rely on their timing on the burning of a train of pyrotechnic comp.
-Embody a clockwork mechanism which is actuated by setback forces on firing
-Uses the latest microchip tech, can be set from
1-199secs
What are the Design Safety features for Fuzes? The system shall be so designed that:
- Cannot be assembled in an unsafe condition
- safety arrangements can be checked during and after assembly
What methods / tools can be used to set Time Fuzes?
Rotation
Fuze Key
Fuze Setter
Fuzing setting machine
