INTRODUCTION TO FUZE & IT’S FUNCTION
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CONTENTS • • • • • • • • • • • • • • • •
PREFACE EXPLOSIVE TRAIN OF ARTILLERY AMMUNITION INTRODUCTION GENERAL REQUIREMENT OF FUZE VARIOUS SAFETY DEVICES IN FUZE FUZE CLASSIFICATION GENERAL CONSTRUCTION INITIATION PART MIDDLE MECHANISM MAGAZINE PART SAFETY IN FUZES FUNCTIONAL ASSURANCE OF THE FUZE FAILURE OF THE FUZES A LIST OF FUZES MANUFACTURED/USED BY ORDNANCE FACTORIES IS APPEN FUZES AT OF KHAMARIA UNDER PRODUCTION FUZES AT OF KHAMARIA UNDER R&D
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PREFACE While doing Newton’s thinking & Marathon efforts for production of fuze “Brain of the ammunition”, we normally forget that one big hole is sufficient in the cat’s house for mother cat & child cat. The same situation happens during fuze production sometimes. Every scientist / officers/staff starts their thinking with Einstein's solution and generally forgets the basic of the start. CONTENTS
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EXPLOSIVE TRAIN OF ARTILLERY AMMUNITION FUZE
BURSTING CHARGE
SHELL
CARTRIDGE CASE
PROPELLING CHARGE EXPLOSIVE TRAIN (UPON FIRING)
PROPELLING CHARGE
PERCUSSION ELEMENT FIRING PIN OF WEAPON
BURSTING CHARGE EXPLOSIVE TRAIN (UPON IMPACT)
PRIMER CONTENTS
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INTRODUCTION It is known that in any conventional ammunition, FUZE is one of the most important parts apart from shell, Cartg. Case, propellant, primer, Tracer, tail unit etc. Fuze is generally a mechanical device in a projectile designed to initiate its action at a predetermined time & place
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General requirement of fuze • • • • • •
1. It must have a body to contain. 2. A striker to function the detonator. 3. A detonator. 4. Good streamlined shape. 5. Proper shape for ballistics efficiency. 6. Must have enough strength to withstand the various forces acting on the the fuze. CONTENTS
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General requirement of fuze • 7. It must be air-tight. • 8. On long storage the explosive content should not get deteriorated.
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Metals used in the manufacture of fuzes •
1. The bulk of material is non-ferrous. The various forms of brass (Copper Zinc alloys) are most widely used. The advantage are :b) Do not corrode easily. c) Large numbers are produced quickly and easily machined . d) The mechanical strength is sufficient to withstand the stresses encountered during use. 8
Metals used in the manufacture of fuzes •
2. Ferrous materials are used for various components:b) Steel for set screws, washers and safety caps. c) Stainless steel for strikers needles. d) Tinned steel for spring. 3. Mazak is used for shutters and magazines. 4. Metals for manufacture of fuzes used with Lyddite are Shellite filled shell must not contain more than 0.1 % Lead to minimize the formation of sensitive Picrates. 9
Various safety devices in fuze Safety Device
Purpose for which used
How it gets removed.
1. Creep spring Provides safety during flight by preventing the inertia pellet from hitting the striker thus preventing pre-matures.
Thr creep spring over comes the striker due to rapid deceleration or set forward motion of the projectile on impact.
2. Detent with detent spring
Gets removed due to set-back force.
3. Safety cap pin
Provides safety while handling storage and safety on transport. ----DO----
It is removed before loading manually
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Various safety devices in fuze Safety Device
Purpose for which used
How it gets removed.
4. Safety lever and safety catch
To mask the detonator from striker.
Gets removed on centrifugal force.
5.Centrifugal bolt , Pea ball, shutter, masking bolt etc.
Making bolt shutter segment, striker and collars to provide safety in the bore.
By centrifugal force and shock of discharge.
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Various safety devices in fuze Safety Device
Purpose for which used
How it gets removed.
6. Segment, Tape and Collar
Prevents shutter to reach detonator.
On shock of discharge.
7. Spindle
Seals fire channel
By gas pressure.
8. Plunger and Pawl
Provides safety in the bore.
By air pressure.
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Fuze can be classified as under:1. Based on assembly with shells :-
1.1 Nose fuse – The fuze is assembled at the top/nose of the shell e.g. Fuze Fz-104, Fuze A 670M (OFK). 1.2 Base fuze – The fuze is assembled at the rear portion of the shell e.g. Fuze L29A3 (OFCh).
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Fuze classification 2. Based on magazine filling :2.1 Disruptive type – In which the magazines are filled with HE & produce a detonation wave. Used only with HE, HEAT shells. 2.2 Igniferous type – In which the magazines are filled with gunpowder & produce only a flash.Generally used with a powder filled shell but can also be in conjunction with a gaine. CONTENTS
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Fuze classification 3.
Based on fuze function :3.1 Direct action – The fuze requires head-on impact & it functions instantaneously e.g. Fuze Mine-1C (OFK). 3.2 Delay action – The fuze has in-built delay. It may be mechanical or chemical delay. Fuze A 670M has Mechanical Delay whereas Fuze Fz-104, Fuze 259 have Chemical Delay (OFK). 3.3 Graze action – The fuze is capable to function on glancing blow/grazing of ammunition on ground e.g. Fuze B-429, Fuze B-429E, Fuze DA 4A (OFCh).
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Fuze classification 3.4 Time action – Designed to function the projectile at the end of a predetermined time of flight, the time being adjusted by the gunner before the round is loaded. These fuzes are subdivided into the following types. 3.4.1 Combustion type – The required delay is given by train of powder which begin to burn as soon as shell is fired from the gun. The powder contained in two time rings, one of which can be adjusted to give various times of burning by altering the effective length of the powder train. CONTENTS
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Fuze classification 3.4.2 Mechanical Type – The delay is obtained by the unwinding of the spring of a clock work mechanism which is set to a definite tension by the gunner before loading. 3.4.3 Proximity action (Variable time (VT))– It functions on reaching within a critical distance from the target e.g. Fuze VT-8A (OFCh).
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Fuze classification 3.4.4 All fuzes used for surface to Air ammunitions have in-built self destruction which simultaneously works after firing from gun. It ensures actuation of un-used ammunition in trajectory after firing at specified time limits.
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Fuze classification In most of the nose fuzes, first two parts are exposed over the shell whereas the third part is within the shell in assembly. Due to this, all threads for first two parts are RHT and for third part is LHT, (exception –Fuze B429 & B429E) since gun rifling gives clockwise spinning normally. The above theory is viseversa for base fuzes. CONTENTS
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General Construction Fuze can be divided in mainly three parts 1. Initiation part (Striker part) 2. Middle mechanism (Delay &/or Safety part) 3. Magazine part
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Initiation part This part is generally activated on impact. The striker moves forward to penetrate/impinge the detonator or detonator moves backward to get penetrated which is considered as first action of the explosion train. In electrical/electronics fuzes, piezo generator gets crushed enabling to generate high value of current for a small time which enables the continuity of subsequent actions of the explosive train. CONTENTS
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Middle Mechanism In most fuzes middle mechanism is a delay device. The fuze is allowed to penetrate to the required depth into the target by imposing delay in its function to get maximum lethality/damage. Delay in fuze function is achieved 1. By chemical delay 2. By mechanical delay
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Middle Mechanism The chemical delay is achieved by introducing chemical powder of required sieve size limits, specified pressure & dwell time to achieve a specified density to attain a specified delay time limit. Mechanical delay is achieved generally by a clock mechanism.
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Magazine part Magazine part has chemical pallet(s) which have less VOD than detonator but more flashes to transmit the detonation wave to the chemicals of shell.
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Safety in fuzes Our essential requirement of any fuze being that the fuze MUST NOT function at my courtyard but MUST function at neighbour’s/enemy courtyard compels introduction of safety parameters in the fuzes. Safety is required during :1. Fuze production 2. Storage, handling & transportation
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Safety in fuzes 3. Shock of discharge from the weapon 4. Flight of the ammunition 5. Muzzle safety ( example-SDA) The devices incorporated in a fuze to attain the above objectives are called safety devices. In order to make the fuze function, the safety is removed. 1. By hand/manually 2. By overcoming/attaining required forces.
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Safety in fuzes The safety devices get removed or the fuze gets armed normally after overcoming the desired value of the following forces(especially for mechanical fuzes) 2.1 by set back force due to acceleration. 2.2 by centrifugal force due to rotation. 2.3 by set forward force due to retardation 2.4 by removal of chemical safety.
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Functional assurance of the fuze Functional assurance of the fuzes is ensured by proof at all related parameters 1. Instant mode 2. Delay mode 3. Safety of the gun
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FAILURE OF THE FUZES The fuzes may have following failures 1. Sealing failurefailure Fuze in safe mode should not function but it functions in static proof in unarmed condition. 2. BlindBlind Fuze fails to transmit its detonation wave to shell resulting non-function of the ammunition termed as blind. In this case, fuze may either partially function or may not function at all.
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FAILURE OF THE FUZES 3.
Low detonation-Fuze functions with weak detonation detonation resulting failure of the fuze function. 4. PrematurePremature Fuze functions either inside the bore of the gun or at the muzzle or in the trajectory within the specified safety distance. 5. Improper delaydelay Fuze functions before or after the specified time limits of delay. 6. There may be other defects specific to the type of fuzes.
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A list of fuzes manufactured/used by Ordnance Factories is appended below:FUZE 1. 104 M-12 2. FFV 447 3. FFV 651 4. FFV 64 C 5. 933 6. DASD 7. A670 M 8. PDM 572C1 9. BD 2B 10. 213 MK-5 11. VT 8A
AMMUNITION
ORIGINAL DESIGN
40 MM L/70 84 MM RCL/HE 84 MM HEAT 84 MM ILLG ROUND 30 MM ADEN GUN 30 MM NAVAL 30 MM BMP-II 155 MM AMMN 106 MM RCL 105 MM IFG 130 MM RVC/FVC
BOFORS, SWEDEN FFV, SWEDEN FFV, SWEDEN FFV, SWEDEN ROYAL ORD.,UK OFK/ARDE USSR BOFORS,SWEDEN ACTION, USA UK USSR
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FUZE
AMMUNITION ORIGINAL DESIGN
12. DA 4A 13. B-5K 14. L106 A3(NOSE) 15. L29-A3 UK 16. B-429 17. B-429E 18. 117 19. ALL WEATHER FZ 20. FAIR WEATHER FZ 21. MG-25 22. 259
81/120 MM MORTER 57 MM ROCKET 155/105/130MM 105 ANTI TANK
PEPA, FRANCE USSR BRITISH AEROSPACE ROYAL ORD.,
130 MM RVC/FVC 125 MM HE 105 IFG 23 MM GHASHA 23 MM GHASHA 23 MM SCHILKA 40 MM L/60
USSR USSR ROYAL ORD., UK USSR USSR USSR ROF, UK
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FUZE 23. 162 MK-9 M1 24. B-15 25. AT-4A ND 26. FZ MINE 27. FZ KONKURS 28. FZ PROXIMITY 76.2 29. FBN 2-I 30. FBN 3-I 31. FZ PROXIMITY 32. PD M9030 33. FZ B-25 34. FZ AVU-ETM
AMMUNITION
ORIGINAL DESIGN
120 MM MORTAR 125 MM HEAT BAR MINE BAR MINE KONKURS MISILE 76.2 MM NAVAL 250 KG/450 KG 250 KG/450 KG 76/62 MM SRGM 76/62 MM SRGM 140 MM ROCKET AREAL 100-120KG
ROF, UK USSR ARDE ARDE USSR ROF, UK
NESHCHEM,AFRICA NESHCHEM,AFRICA USSR
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Fuzes at OF Khamaria under production FUZE
AMMUNITION
ORIGINAL DESIGN
1. 104 M-12
40 MM L/70
BOFORS, SWEDEN
2. FFV 447
84 MM RCL/HE
FFV, SWEDEN
3. FFV 651
84 MM HEAT
FFV, SWEDEN
4. FFV 64 C
84 MM ILLG ROUND
FFV, SWEDEN
5. 933
30 MM ADEN GUN
ROYAL ORD.,UK
6. DASD
30 MM NAVAL
OFK/ARDE
7. A670 M
30 MM BMP-II
USSR
8. MG-25 9. 259
23 MM SCHILKA 40 MM L/60
USSR ROF, UK
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Fuzes at OF Khamaria under R&D FUZE
AMMUNITION
1. PD M9030 2. FZ B-25 3. FZ AVU-ETM 4. B-5K 5. Fuze multi mode hand grenade 6. ALL WEATHER FZ 7. FAIR WEATHER FZ
76/62 MM SRGM NESHCHEM,AFRICA 140 MM ROCKET AREAL 100-120KG USSR 57 MM ROCKET USSR Multi Mode Hand Grenade TBRL (DRDO) 23 MM GHASHA 23 MM GHASHA
ORIGINAL DESIGN
USSR USSR
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