Summative 6 - Fuzes Flashcards
Req, abrev, class of fuzes define
Define a fuze
A fuze is a device designed to function an item of ammunition under pre determined circumstances.
Req, abrev, class of fuzes: Abrev by position List
Expand the following abbreviations
PD
BD
PIBD
PD:
Point Detonating.
BD:
Base Detonating.
PIBD:
Point Initiating Base Detonating.
Req, abrev, class of fuzes: abvrev by function List
Expand the following abbreviations T CT MT VT CVT SQ DEL MTSQ TSQ PDSQ MO ET
T Time.
CT Combustion Time (May also be PTTF).
MT Mechanical Time.
VT Variable Time.
CVT Controlled Variable Time.
SQ Super Quick.
DEL Delay.
MTSQ Mechanical Time Super Quick.
TSQ Time Super Quick.
PDSQ Point Detonating Super Quick.
MO Multi Option.
ET Electronic Time.
Req, abrev, class of fuzes List
List the Genreal requirements (2)
and the other requirements (4)
SAFETY:
For storage and transport.
Against premature functioning.
RELIABILITY:
To High Order When Required.
OTHER: Optional delay setting. Easy time adjustment / setting. Minimum preparation for use. Multi role to minimise refusing. Standard weight. Must fit standard cavity size:
Req, abrev, class of fuzes: Classification List
What 3 categories dictate the classification of a fuze
Filing
Position
Function
Req, abrev, class of fuzes: Classification List
Fuzes classified by function have what three types?
Time
Impact
Proximity
Req, abrev, class of fuzes: Classification List
Fuzes classified by the impact function have what four types?
Super quick (SQ) graze delay Non-delay
Req, abrev, class of fuzes: Classification List
Fuzes classified by the Proximity function have what two types?
Variable time
Controlled variable time
Req, abrev, class of fuzes: Classification List
Fuzes classified by the time function have what three types?
Mechanical time
Combustion time
Electronic time
Req, abrev, class of fuzes: classification - functions List
A fuze that can use more that one function categorization is called what?
Multi-option
Mech devices and fuze components Safety principles
List
Explain what alignment is in regards to a fuze.
Which of the 3 broad fuze types should be either in or out of alignment?
having the striker offset, or ‘out of line or alignment” from the detonator by a shutter or other device that will move to be ‘in line’ when, for example, enough centrifugal force is applied to it (by firing).
Electronic - in line
mechanical - out of line
electro/mechanical - out of line
Mech devices and fuze components: Safety requirements
List
List 12 other requirements that can improve safety and reliability
Arming: Simple as possible, distinct from other process
Material compatibility
Design safety - cannot be assembled in unsafe manner, can be checked.
User inspection - be able to check state of safety features
Explosive train - barriers from main fill and detonator if using something more sensitive than Tetryl
Mechanical Lock - shutters and interrupter remain locked
Delay arming - System will remain safe until certain conditions are reached. no single circumstance should arm the fuze
In line train - no current in circuit allowed until safe separation is reached
software safety - modular, unique start and end.
Defensive programming
user drills safety- not possible to arm electro-explosives; saftey will not rely on drills
Reliability: less stringent requirement, safety reqs can reduce reliability by increasing complexity
Mech devices and fuze components: Holding devices
define
Define a holding device
A holding device locks other components in a safe position until arming is required; to unlock them when arming is required; and possibly to relock them in the armed position.
Mech devices and fuze components: Holding devices
define
Define a shear wire
A length of wire pinning a moving part to a fixed on
The wire is strong enough to hold the parts together until sufficient force is applied to the moving one.
Mech devices and fuze components: Holding devices
define
Define a striker spring and spring disc
The striker spring consists of a spiral spring surrounding the striker.
Striker separated from the detonator until overcome by a superior force.
The same function is performed by a corrugated spring disc.
Mech devices and fuze components: Holding devices
define
Define a detent / set back pin
A small metal cylinder or block working in a hole or recess.
Resting on a spiral spring under part compression.
Spring is used to keep the detent in a safe position.
Mech devices and fuze components: holding devices
define
define a Stirrup Spring and Ferrule
This consists of a thin metal cylinder with lugs turned over at each end and in opposite directions.
The lugs can be used to lock 2 concentric sleeves together and rest at opposite ends of each sleeve.
One of the sleeves is fixed and the other kept against a lug by a spring.
The lugs are designed to be straightened out by one of the forces acting on the fuze and allow the moving sleeve to be freed under action of the spring.
Mech devices and fuze components: holding devices
define
Define where and when saftey pins, cotters, and pull pins should be used.
Normally found in unspun ordnance such as mortars/rockets when centrifugal force cannot be used.
Mech devices and fuze components: holding devices
define
Define a horse head segment.
Two pivoted segments which, when closed together, prevent movement of a component
Only a rotational force (centrifugal) will cause the 2 segments to rotate out of the way
Mech devices and fuze components: Masking devices
define
Define masking device
It “masks” or obstructs the explosive train until arming is required, ensuring that accidental premature functioning of one part of the train does not affect the whole train.
Mech devices and fuze components: masking devices
define
Understand some simple shutters
understand delay arming shutters
There’s pictures in the notes
Mech devices and fuze components: masking devices
define
Define a delay or non-delay masking shutter.
Interrupter - A plunger inserted across the firing train channel, which may be locked or unlocked by the user prior to firing.
When set to the unlocked position it is free to move out of the channel, against a spring or centrifugal force. When set to the locked position this action cannot take place and the masked portion of the firing train remains ineffective.
This can be achieved either by a separate delay action firing pin, alternatively you may divert your detonating wave through a delay composition.
Mech devices and fuze components: Masking devices
define
What device has the same function as a setting bolt?
An interrupter
Mech devices and fuze components: Firing devices
define
What is a firing device?
A firing device is the component which provides the
stimuli to initiate the explosive train.
-It may be achieved by either electrical or mechanical.
-Electrical Firing: Conducting Cap (CC). Bridge Wire (BW). Exploding Bridge Wire type (EBW).
Mech devices and fuze components: Mechanical firing
List
List the three methods that may be used in a mechanical firing device.
Driving a firing pin into detonator using surface impact
Use stored energy (like a spring) actuated at a pre-determined time
Encapsulate the detonator in a heavy weight, which when decelerating, the force carries it into the firing pin.
Mech devices and fuze components: Electronics
List
What are the 3 advantages of electronic fuzes?
Lowers costs due to multi role function.
Versatility in arming.
Mechanical preparation or initiation.
Forces acting on fuzes: Forces
List
List the forces that are available to act on a fuze.
Set back.
Creep Forward.
Centrifugal Force.
Spin Decay.
Set Forward.
Air or Gas Pressure.
Stored Energy.
forces acting on fuzes
define
Define set back forces
This arises from the reaction of the mechanism to the acceleration forces applied in the gun onfiring.
During the acceleration phase this force is greater than the spin forces
The physical backward movement or anchoring of components compresses any springs which are placed axially in the fuze
forces acting on fuzes
define
Define creep forward force
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.
forces acting on fuzes
define
Define 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.
Many shutter mechanisms are operated by centrifugal force.
forces acting on fuzes
define
Define 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.
forces acting on fuzes
define
Define Air or gas pressure forces
Air or Gas pressure is sometimes used to drive a turbine to generate power for electrically operated fuzes
Used as an alternative arming method for non spun projectiles such as mortars.
Used occasionally in GW Safety and Arming Units (SAU).
forces acting on fuzes
define
Define set forward forces
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.
forces acting on fuzes
define
Define 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.
Forces acting on fuzes: common methods of operation
List
List the steps in this specific common mode of operation
Unlocking a component by set back forces.
Easing it on its seating during creep forward.
Swinging it to an armed position by the application of centrifugal force.
Initiation of the explosive train by set forward on impact.
intro to impact fuzes:
List
List the impact fuze actions (types)
Superquick (SQ).
Non Delay.
Graze
Delay.
intro to impact fuzes: SQ
List/define
List the three points that the mechanism consists of in a SQ fuze.
What does the sensitivity of a SQ fuze depend on?
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.
Sensitivity depends on the strength of the disc, shear wire or coiled spring.
intro to impact fuzes: Non Delay
Define
What is a non-delay fuze and how is it different from SQ?
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.
intro to impact fuzes: Graze
Define
What is a graze fuze?
explain their mechanism
A graze fuze uses set forward force experienced in sudden deceleration to allow a plunger or ‘graze inertia pellet’ with the detonator to overcome a ‘creep spring’ and impact the needle or striker. As this creates an air gap, the detonator is a flash type.
Have a small inherent delay.
intro to impact fuzes: Delay fuzes
Define
Define a Delay fuze
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.
intro to impact fuzes: Other impact fuze functions
List
What is required in an anit-aircraft projectile with an impact fuze?
A self-destruct device
intro to Prox fuzes:
Define
Define a prox fuze
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
intro to Prox fuzes: Groups of of prox fuzes
List
List the two groups of prox fuze
Variable Time (VT) Timer section arms the fuze electronically after firing. No setting for optimum height.
Controlled Variable Time (CVT) Can be set to activate the Prox function after a set time.
intro to Prox fuzes: Design considerations
List
List the 10 design considerations for a Proximity fuze
Rugged.
Able to function in all conditions.
Light weight.
Economical.
Able to fit existing projectiles.
Sensitive and rapid in operation.
Not easily jammed.
Not subject to false operation.
Safe to handle.
Have good storage characteristics.
intro to Prox fuzes: Design considerations
List
List the 10 design considerations for a Proximity fuze
Rugged.
Able to function in all conditions.
Light weight.
Economical.
Able to fit existing projectiles.
Sensitive and rapid in operation.
Not easily jammed.
Not subject to false operation.
Safe to handle.
Have good storage characteristics.
intro to Prox fuzes: Function
List
Describe the basic function of a prox fuze - 6 steps
On firing, setback breaks the ampoule or electrolyte which floods the energiser.
Clock starts (CVT only) and the shutter starts to rotate.
An electric igniter is short circuited until 3 5 seconds after firing.
Transmitter radiates radio waves.
Nearing the target… Doppler effect activates
FUZE DETONATES.
intro to Prox fuzes: Safety features
List
List some safety features of prox fuze
Battery is inert until ampoule is broken.
Clockwork mechanism prevents signal transmission or functioning until pre set time.
Shutter or S & A mechanism keeps explosive train out of line.
Electric components can be short circuited until safe to arm has operated as intended.
intro to Prox fuzes: storage and handling
List
What are the storage and handling requirements of prox fuzes
Protected from: Dampness Sunlight Heat Drop / Strike
Proximity fuzes are commonly stored
nose down.
intro to Time fuzes:
List
List the three time fuze types
ET - electronic
MT - mech time
T (or PTTF) combustion time
Intro to time fuzes: T fuze
define
Define a combustion time (T) fuze
uses a pyrotechnic delay to set time of function
obselete
usually ignited by set back forces
intro to Time fuzes: MT
List
List the types of mech time fuzes
THIEL - British MT Fuzes.
A series of wheels and pinions controls the escape of from a main spring which is wound up during manufacture.
JUNGHANS - American MT Fuzes.
This mechanism is actuated by spring assisted by centrifugal weights.
DIXI - Swiss Fuze.
This mechanism is driven by centrifugal force acting on driving balls.
intro to Time fuzes: ET
List
Explain electronic time fuze
Uses a microchip
highly accurate and is settable in 0.1 second increments from 1 second to 199.9 seconds. - set electronically
