Van_den_Berg_AH.pdf

THE DESIGN OF A SPIN STABILISED FUZE

by

Abraham Hermanns van den Berg

Thesis submitted in partial fulfilment of the requirements for the degree of Master in Engineering (M ecltanical)

at Potchefstroomse Universiteit

vir Christelike Hoer Onderwys

Study Leader: Mr A. Wolhuter

January 1996

VERTROULIK CONFIDENTIAL

ACKNOWLEDGEMENTS

I would like to thank Naschem (Pty.) Ltd. for the opportunity that was granted to me as employee to develop a low cost fuze and to utilise the project for the purposes of my studies.

My thanks also to mr A Wolhuter for his enthusiasm and participation in the project and his contribution to the establishment of this document.

Lastly, I would like to thank my parents for their unfailing support, interest and motivation.

DOCUMENT NO.: 5270-000000-715001 ISSUE NO.: 1 CONFIDENTIAL VERTROULIK

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ABSTRACT

The ammunition manufacturer in South Africa has developed an increasing need for a low

unit cost fuze for use on large caliber spin stabilised ammunition. This was brought about by

the current state of affairs that local ammunition manufacturers have to concentrate more on

exports due to the shrinking defence budget of the S.A.N.D.F. This, in turn, has prompted

the development of a low cost fuze demonstrator.

The objective ofthis project was to develop and demonstrate a prototype low cost fuze. The fuze has to comply with all the specifications of existing fuzes. After considering different

concepts, the final concept was decided on. A detail design phase followed after which a

small number of fuzes were manufactured. The basic safety and functioning modes of the

fuze were tested and good results were found. The indications are that the fuze will cost

less than a third of the price of the existing fuze and will comply with all the necessary

requirements.

DOCUJ.VIENT NO.: 5270-000000-715001 ISSUE NO.: 1 CONFIDENTIAL VERTROULIK

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VERTROULIK. CONFIDENTIAL

OPSOMMING

Lae eenheidskoste van buise vir spingestabiliseerde ammunisie het toenemend 'n vereiste

geword by ammunisie vervaardigers in Suid Afrika. Dit word te weeg gebring deur die feit

dat die ammunisie vervaardigers tans meer moet konsentreer op die uitvoermark as gevolg

van die drastiese besnyding van fondse vir die S.A.N.W. wat voorheen die hoof klient van

die ammunisie vervaardigers in Suid Afrika was. Dit het die ontwikkeling van 'n lae koste

buis demonstrator tot gevolg gehad.

Die doel van hierdie projek was om 'n lae-koste prototipe buis te ontwikkel en te demonstreer. Die buis moet aan aile vereistes voldoen waaraan die bestaande buise voldoen.

Na verskeie konsepte geevalueer is, is daar besluit op 'n konsep wat gebaseer is op 'n

pirotegniese middel wat wegbrand. 'n Detail ontwerpfase het gevolg, waarna 'n klein

hoeveelheid van die buise ver\raardig is. Die basiese veiligheids- en funksioneringsvereistes

is getoets en goeie resultate is verkry. Voorlopige beramings dui daarop dat die buis minder

as 'n derde van die bestaande buis gaan kos en aan aldie nodige vereistes sal voldoen.

DOCUMENT NO.: 5270-000000-715001 ISSUE NO.: 1 CONFIDENTIAL VERTROULIK.

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TABLE OF CONTENTS

Paragraph

ACKNOWLEDGEMENTS

ABSTRACT

OPSOMMING

1. INTRODUCTION

2. FUNDAMENTAL PRINCIPLES OF FUZES

2.1 Definition and Purpose of a Fuze

2.2 Fuze requirements 2.2.1 Basic requirements 2.2.2 Applied forces 2.2.3 Additional requirements

2.3 Fuze Mechanisms 2.3 .1 The Striker- or Inertia Pin Spring 2.3.2 The Detent 2.3.3 The Rotor or Shutter 2.3.4 The Clockwork Mechanism 2.3.5 Ball Rotors 2.3.6 Spiral Unwinder 2.3.7 The Piston and Cylinder System

3. THE EXISTING FUZE

3.1 Background

3.2 Major Components 3.2.1 Fuze Body 3.2.2 The Safe and Am1ing Device


Page

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2

3

4

8

9

9

11 11 13 15

16 16 17 17 17 18 19 19

20 20

20 21 22

3.2.3 The Super Quick Mechanism 3.2.4 The Delay Mechanism 3.2.5 The Setting Mechanism


4. DEVELOPMENT OF A LOW COST FUZE

4.1 Motivation

4.2 Market Analysis 4.2.1 Historical Allocation of United States Army Ammunition Spending 4.2.2 World-wide Fuze Contenders

4.3 Concept Design and Layout 4. 3 .1 Requirements 4.3.2 Concept Generation 4.3.3 Basic Concept and Functioning ofthe Demonstrator Fuze 4.3.4 Design Concept Iterations

4.4 Detail Design 4.4.1 Specific Requirements 4.4.2 Design Calculations 4.4.3 Drawings

4.5 Funds

4.6 Detonic Elements

4. 7 Manufacturing

4.8 Fuze Test Simulator

4.9 Tests and Results 4.9.1 Spin test 4.9.2 Drop test 4.9.3 Partly anned drop test 4. 9.4 Minimum set -back test 4.9.5 Maximum set-back test

4.10 Design Improvements

5. CONCLUSION


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23 23 24

25

25

26 26 27

28 28 29 32 36

37 38 40 40

40

40

41

41

42 42 42 44 45 46

47

49

6. RECOMMENDATIONS

BIBLIOGRAPHY

Literature


Military Standa1ds and Specifications

APPENDICES

APPENDIX A: B-SPECIFICATION FOR LOW COST FUZE APPENDIX B : CALCULATIONS FOR LOW COST FUZE APPENDIX C: MARKETING PAMPHLET

ILLUSTRATIONS

50

51

51

52

FIGURE 1 : CONFIGURATION OF FUZE WITH MAJOR COMPONENTS 21 FIGURE 2 : PYROTECHNIC TUBE CONCEPT 30 FIGURE 3 : FAN CONCEPT 30 FIGURE 4 : PISTON AND CYLINDER CONCEPT 31 FIGURE 5 : CONFIGURATION OF LOW COST FUZE WITH MAJOR COMPONENTS 32 FIGURE 6: BEFORE SET-BACK 33 FIGURE 7: DURING SET-BACK 33 FIGURE 8 :AFTER SET-BACK BUT BEFORE PYROTECHNIC BURNOUT 34 FIGURE 9 : AFTER SET -BACK AND PYROTECHNIC BURNOUT 34 FIGURE 10: FUNCTIONING ON DIRECT IMPACT 35 FIGURE 11 : FUNCTIONING ON GRAZE IMPACT 35 FIGURE 12: PHOTO SHOWING INTERNAL VIEW OF FUZE AFTER RECOVERY 46 FIGURE 13: PHOTO SHOWING IMPROVED ROTOR AFTER RECOVERY 48

TABLES

TABLE 1 : FORECAST OF FUZE PROCUREMENT FOR 1995 TABLE 2 : FEASIBILITY OF DEVELOPMENT TABLE 3: CONCEPT CONFIGURATIONS TABLE 4: DROP TEST ORIENTATIONS


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27 28 36 43

1. INTRODUCTION


Naschem, a Division of Denel ltd., has been concerned with the manufacturing of fuzes

since its inauguration in 1971 as an affiliate of Armscor for the manufacturing of large

calibre ammunition. Initially, Naschem was only responsible for the provision of ammunition

to the South African Defence Force, but this has been changing in the last few years as result

of the decreasing budget of the S.A.N.D.F. and the uplifting of the arms embargo. This

caused the emphasis within Naschem to shift to the international market. In order to

become competitive in the international market, however, it is of utmost importance for

Naschem to consider the cost of its products. In the past, cost was not the major concideration, but in the rapidly changing business environment that Naschem finds itself in,

it is becoming increasingly important to decrease the cost of its products without sacrificing

reliability and quality.

The mission of this project was to develop a low cost fuze for use on large calibre spin stabilised projectiles, which can replace the existing fuze at a lower cost and provide improved functioning reliability while still maintaining adequate safety.


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2. FUNDAMENTAL PRINCIPLES OF FUZES

2.1 Definition and Purpose of a Fuze

In lay terms a fuze is defined by the Shorter Oxford Dictionary (1959:765) as: "A tube casing filled or saturated with combustible material by means of which a military

shell or the blast of a mine is ignited and exploded".

In military terms, the following definitions are more appropriate:

"A fuze is defined as an endeavour of man to control the bursting of a shell by means of a

priming composition, without understanding the rules of combustion." (Ministry of supply 1978: 18).

"The word 'fuze' is used to describe a wide variety of devices used with munitions to

provide basically the functions of safety, arming and firing." (US Army Materiel Command 1969: 1).

There is a wide variety of munitions in existence and new ones are continuously being

developed. Because of the variety of types and the wide range of sizes, masses, yields and

intended usage, it is natural that the configuration, size and complexity of fuzes also vary

over a wide range. Fuzes extend all the way from relatively simple devices such as hand

grenade fuzes to the highly sophisticated radar fuzes for missile warheads. In many

instances the fuze is a single physical entity, while in other instances the fuzing system

consists of two or more interconnected components placed in different locations within or

even outside the munition.


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Because of the important and exacting role of fuzes, leading nations, such as the USA,

employ the most advanced technology available in the design and manufacturil}g of fuzes and are constantly advancing the state-of-the-art. [3, 4]

Fuzes are generally classified as follows:

Artillery fuzes, including mortar fuzes

Aircraft bomb fuzes

Fuzes for under water stores, e.g. for mines, depth charges.

Static fuzes, e.g. fuzes for anti-tank mines

Other fuzes

Probably the greatest variety and the greatest complexity of design is shown amongst the

fuzes for artillery and armour weapons. The greater ingenuity in design is necessary because

these fuzes have to withstand far greater forces being fired from a gun, than any other type

of fuze. Artillery and armour fuzes are also produced in larger quantities than any other type

offuze. [1]

Different types of artillery fuzes are available:

Time fuzes

Proximity fuzes

Percussion fuzes or Point detonating fuzes. This includes direct action impact fuzes and

graze action fuzes. (When the projectile hits a target at a small impact angle and ricochets away, it is called graze action.)

Mortar fuzes

Base fuzes


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Small arms fuzes

VERTROULlK CONFIDENTIAL

Compression ignition or adiabatic fuzes. [1,4]

The Direct Action Percussion Fuze (hereafter called the DA fuze) is of particular interest to this study. This type of fuze functions on direct impact with the target. It is usually very

sensitive and will even operate against frail targets such as the thin skin of an aircraft. [ 1]

The concept of the propagation of the explosive train is inherent to the understanding of

fuze design, starting with the initiation and progressing to the burst of the main charge in the

warhead. Initiation starts with the "signal" such as the target sensing or impact. This

"signal" must be amplified by such devices as detonators, leads and boosters that have

sufficient explosive output to detonate the main charge. Since the detonator contains

explosives that are very sensitive, it is the basic role of the fuze not only to signal the

presence of the target, but also, above all, to provide safety during handling. [ 4]

2.2 Fuze requirements

2.2.1 Basic requirements

2.2.1.1 Handling Safety

As an approach to providing adequate safety, present design philosophy calls

for a fuze to have at least two independent safety features, either of which

must be capable of preventing an unintended detonation. To comply with the

safety requirements, the primary explosive elements are mechanically masked

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2.2.1.2

2.2.1.3


from the secondary explosive elements or the main charge. An example of

this is the out-of-line element such as a rotor or slide. The fuze must be

assembled in the safe position to ensure handling safety during assembly. [ 4]

Arming

This is a mechanical event which is designed to take place as the shell is fired,

or after the shell leaves the barreL Before the fuze is armed, it should not be

capable of being armed by any conceivably rough usage or by any drop in any

position which is likely to occur in service. The moving parts of a fuze are

securely locked together and only a particular combination of forces must be

applied on the fuze to unlock them. This combination of forces is provided

by the firing of the projectile which includes the fuze. [1]

The fuze may never remain in the partially armed position. As soon as the

force is removed, the fuze must return to the unarmed position. [ 4]

Muzzle safety

The fuze should be designed in such a way that the detonator cannot be

initiated while the projectile is in the launching tube. This is particularly true of artillery, mortar and rocket fuzes. This is called muzzle- or bore safety and

is achieved by providing one of the safety features used to ensure handling

safety with a delayed arming. The muzzle safety distance is a specified

distance after muzzle exit, before which the fuze may not be armed. In most

of the present fuzes this is provided by a clockwork mechanism which delays

the arming. [ 1, 4]


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2.2.1.4 Functioning


The ultimate objective of the fuze is to ensure that the detonator causing initiation is detonated at the desired instant. After arming the fuze, all that is

needed for the initiation of the explosive filling is sensing the target, after

which functioning takes place. [1,3,4]

2.2.2 Applied forces

2.2.2.1

2.2.2.2

In addition to performing the basic functions of safety, arming and firing, however,

the fuze must withstand the following forces in such a way as not to hamper the

functioning ofthe fuze:

A cce lerati on forces

This force affects all fuzes fired from a projector of any type and may be of varying intensity. As a result, the inertia loading of the fuze components is

very high. This force is commonly called "set-back" from the fact that the

fixed portions of the fuze tend to leave the free or movable portions behind.

Centrifugal forces

Almost all guns used in the armed forces are rifled, except for mortars and

similar projectors. The rifling or spiral grooves in the gun barrel engrave a


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2.2.2.3

2.2.2.4


copper or nylon band fastened securely to the projectile and cause it to rotate. Consequently, the fuze is subjected to radial acceleration in addition to the axial acceleration forces during firing. This is commonly called "spin".

Acceleration continues until the projectile leaves the gun barrel and the projectile commences to lose its rotation due to friction with the air through

I

which it is passing. This is known as the "decay of spin". Centrifugal forces

are applied to the fuze components for the time span during which spin

prevails. The intensity of the force is proportional to quadratic of the spin

rate.

Deceleration forces

As with spin, once the projectile leaves the gun barrel, it ceases to accelerate and commences to lose its forward momentum due to air friction. Free

components that experienced set-back on acceleration, now tend to move

slowly forward again. This action is called "forward creep". When the

projectile hits the target it decelerates violently. This is called "set forward" and is commonly used to initiate the explosive components of the fuze.

Side-slap

It is impossible to achieve a perfect fit between a projectile and the barrel of the gun from which it is fired. Lateral movement of the projectile relative to the barrel is possible and this may become a rapid side to side movement as

the shell accelerates up the barrel. This movement is called "side slap" or

"balotting". This motion can be quite violent in worn guns.


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2.2.2.5

2.2.2.6

Longitudinal slap


The greater part of the side slap is at the nose, because the driving band of

the shell, usually situated at the rear, holds the rear of the shell fairly

stationary. This means that the shell momentarily turns sideways in the

barrel. While sideways across the barrel, the projectile momentarily jams and decelerates and then accelerates again so that its progression up the muzzle is

a series of jerks rather than a smooth acceleration. [1]

Yaw forces.

Yaw is a result of excessive longitudinal slap, dynamically unstable projectiles or some other disturbance of the projectile and is a behaviour during which the projectile starts oscillating round the axis of flight. The frequency of this oscillation is lower than the spin rate, but if superimposed on each other, this

causes higher centrifugal forces to be applied to the projectile. During fuze design, this is taken into account by using a safety factor.

2.2.3 Additional requirements

2.2.3.1 Manujacturh1g

As fuzes are manufacture in large quantities, they should be designed in such

a way as to be adaptable to automated mass production and inspection

methods. This is necessary in order to minimise human errors m

manufacturing and assembly, which in turn cuts production cost. [ 4]


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2.2.3.2

2.2.3.3

External dimensions


All fuzes have certain dimensional limits within which they must be designed.

This differs from fuze to fuze depending on the application. The space

assigned to the fuze and the important dimensions are shown on a calibre

drawing (e.g. MIL-STD-333A 1979 : 3-8)

Other requirements

Other requirements may anse, depending on the application of the fuze.

Aspects such as water tightness, withstanding extreme temperatures and

withstanding vibration, should be considered during the design of the fuze.

2.3 Fuze Mechanisms

All the relevant fuze mechanisms currently being used, or used in the past, were evaluated in .

order to ensure a wide perspective on the problem and the possible solutions.

2.3.1 The Striker- or Inertia Pin Spring

The striker- or inertia pin spring consists of a spiral spring supporting the striker to

keep the striker separated from the detonator until overcome by a superior force.


PAGE 16 OF 52


This mechanism is used either for arming purposes during firing or for initiation

during impact. [1]

2.3.2 The Detent

This is a form of plunger, consisting of a small metal cylinder or block working in a

hole or recess usually in the fuze body and supported on a spring. The spring is used

to keep the detent in a safe position in or behind a moving component, thus locking

it. During firing the detent is required to release the component which it is holding in

place. This is normally brought about by using centrifugal forces. [1]

2.3.3 The Rotor or Shutter

This consists of a component containing a detonator which is positioned off centre

relative to the centre line of the fuze. The rotor or shutter is normally kept in the

safe position by some safety mechanism like a detent or inertia pin. After arming, the

shutter rotates around a shaft to bring the detonator in line with the rest of the

detonic train. In fuzes for spin stabilised projectiles, this is normally made possible by ensuring that the centre of mass of the shutter or rotor is positioned in such a way

as to ensure that the shutter rotates around the shaft during spin. [1]

2.3.4 The Clockwork Mechanism

The clockwork mechanism is probably the oldest time delay mechanism which is still

in use in fuzes. Since the development of the watch in 1674, fuzes have been


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equipped with clockwork mechanisms, but progress m this field only became

apparent in the 18th century. [1]

The clockwork consists of a series of connected gears that are also connected to the

slide or rotor and a. pallet and pinion mechanism. The function of the pallet and

pinion mechanism is to regulate the turning rate of the gears (similar to watch mechanism) and ultimately the shutter or rotor. The series of gears is used to increase the oscillating frequency of the pallet.

2.3.5 Ball Rotors

A ball rotor is a type of shutter which consists of a steel sphere or ball. The ball

often has a groove cut around one end and has a hollow shaft co-axial with the

groove. The ball rotor is arranged to lie in the fuze so that in the unarmed position

its axis is at an angle with the axis of the fuze. In this position it cannot be initiated

or transfer detonation. It is held in this position by a smaller ball or balls which

engage the groove. These balls move outward under centrifugal force, mostly after

the release of a detent or inertia pin. The centrifugal force causes the ball to incline

its axis until it is lined up with the main axis of the fuze after which the fuze is armed.

As the ball rotor is made of highly polished steel it does not at once attain the same

degree of angular velocity as the fuze body, but builds up speed slowly. It therefore

provides a certain degree of delayed arming.


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2.3.6 Spiral Unwinder


The spiral unwinder system provides delayed arming in fuzes due to the effect of

projectile spin. The unwinder consists of a tightly wound spiral coil of soft metal ribbon, located concentrically with the spin axis around a fixed hub and surrounded

by a circular cavity. After set-back has ceased, projectile spin causes the free end of the ribbon to move outward across the gap to press against the cavity wall.

Continuing spin transfers successive portions of the coiled ribbon progressively

outward until all ofthe ribbon has unwound from the central hub. The time taken by

the unwinder to unwrap, provides the arming delay. As the last coil of the unwinder

opens, successive members in the arming process are released or unlocked. The

unwinder is used to block a striker in the safe position, to restrain an explosive train

barrier and to provide electrical switching. This method is dependant on high spin

rates.

2.3. 7 The Piston and Cylinder System

This method is sometimes used in mortar fuzes and is based on the principle of

damping. It consists of a piston which fits closely in a closed cylinder and is

supported by a spring. When the piston is released, it moves within the cylinder as

result of the spring force. The air in front of the piston is compressed, which inhibits

the movement of the piston. A vent is provided through which the air escapes to

determine the speed at which the piston moves in the cylinder. When the cylinder

reaches a certain point, the shutter is released and the fuze is armed.


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3. THE EXISTING FUZE

3. 1 Background

The fuze currently in use for armour rounds is used as an example as this is the latest fuze to

be developed by Naschem. It is regarded as the latest technology mechanical fuze available

in Naschem. This fuze, as with all the other fuzes manufactured by Naschem, is based on a

design that originated from the M48A3 fuze which was developed during the second world

war and has not changed since 1968. [1]

3.2 Major Components

A fuze consists of different mechanisms - each of which is designed to serve a certain

purpose. These mechanisms are called the Major Components and are shown in Figure 1 : Configuration of fuze with major components


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' -------- __ _j


Figure 1 :Configuration of fuze with major components

3.2.1 Fuze Body

The fuze body is the housing which contains all the other components. The fuze

body has to comply with certain dimensional requirements which are described in the

l\1IL-STD-333B document. This is for standardisation purposes.


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3.2.2 The Safe and Arming Device


The Safe and Arming Device (hereafter called the SAD) is situated in the base of the fuze and is responsible for keeping the fuze safe when required but also to ensure

arming after firing. It contains mechanisms to provide safety during set-back and

spin and to provide muzzle safety. The SAD is an entity on its own and may be sold

as a separate item.

The SAD consists of a body or housing in which all the components are contained, a

rotor (which includes the detonator), a gear chain (which regulates the rotation of the rotor to provide muzzle safety) and the booster (which contains an explosive pellet).

The SAD of a fuze has to comply with the following requirements:

No component must arm during a drop test of 1.5m.

With all the safety mechanisms intact, no component must arm during a 2000

r. p.m. spin test.

With the set-back safety mechanism removed, the spin safety mechanisms may

not arm during a spin ~f 1000 r.p.m. and must arm during a spin of2000 r.p.m. Complete arming may only take place after a certain time, depending on the use.

The set-back mechanisms must arm during the lowest set-back experienced.

All the components must withstand maximum set-back acceleration.

The SAD is the most complicated and most important component of a fuze and is

also the most expensive.


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-- - - - -- -- --- i


3.2.3 The Super Quick Mechanism

The Super Quick mechanism is situated in the nose of the fuze and is responsible for the initiation of the fuze when the fuze is set on Super Quick mode. This mechanism provides a fast reaction to ensure detonation outside the target and provides

sensitivity of the fuze when used on frail targets like soft skinned vehicles. On the

other hand, however, the mechanism must be insensitive enough to prevent initiation

by rain.

The mechanism consists of a cap, a cross bar assembly which dissipates rain drops, a

Super Quick detonator, a striker and a crushing element which prevents the striker from touching the detonator during set-back.

3.2.4 The Delay lVIechanism

The Delay mechanism is situated directly above the SAD. The Delay Mechanism has

the three primary functions.

It provides a delayed functioning when the fuze is set on Delay mode

It serves as a backup in case of a Super Quick failure It provides Graze Action functioning.


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The Delay setting on the fuze is typically used when it is required that the fuze

should detonate a certain time after impact (used for trenches) or when the fuze is required to be less sensitive (when used on targets behind foliage).

The Delay mechanism consists of a plunger (containing the delay detonator and a spin safety mechanism), a housing in which the striker is assembled and a closing screw to keep the housing and plunger in position. The delay detonator is positioned

to the side of the centre line and a flash tube is provided on the centre line to ensure

that the flash from the Super Quick detonator reaches the SAD.

3.2.5 The Setting Mechanism

The Setting Mechanism is situated under the Super Quick mechanism but above the Delay mechanism. The function of the setting mechanism is to facilitate the selection

between Super Quick and Delay mode.

The setting mechanism consists of a setting sleeve which facilitates the selection, an

interrupter which is supported by a spring and pulls away during spin, and a retaining

screw which keeps the components in place.

When set on Super Quick, the setting sleeve is positioned in such a way as to permit the flash from the Super Quick detonator to pass through should the fuze experience spin. In the Delay mode, the setting sleeve prevents the flash from the Super Quick detonator to pass through and only the delay detonator can initiate the fuze. The

delay mechanism is never disabled and serves as a permanent backup for the Super

Quick detonator.


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4. DEVELOPMENT OF A LOW COST FUZE

4. 1 Motivation

Although the armour fuze and other similar fuzes have proved themselves very reliable

during years of service, they have one major handicap and that is high cost. In order to become competitive in the international market, it is important for Naschem to consider the

cost of its products. To this avail, it was decided to design and development of a new fuze

for the following reasons:

The fuze is the only component of a round of which the cost can be significantly reduced

by improving the design. A few improvements can be made to the other components of

a round, but they will not provide significant cost reducing. The present fuze is based on

old technology which provides adequate functioning reliability and safety, but is not

necessarily the most cost effective way to obtain the required specifications. This is

especially true of the muzzle safety mechanism used in the fuze (the mechanism providing delayed arming) which is situated in the SAD. As far as could be determined, all the armour and artillery fuzes produced in the world use a clockwork mechanism to

provide muzzle safety. If a more cost effective delaying mechanism could be found, it

will reduce the price of a fuze drastically.

Secondly, an improved design will save more money than improving manufacturing

facilities would. Quality and productivity are both important parameters in the process of manufacturing competitive products. However, they are both dependant . on the


PAGE25 OF 52

I

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design ofthe product and attention to these parameters alone cannot make a competitive

product out of a bad design. [5]

4.2 Market Analysis

A full understanding of the fuze market is essential and must precede the design phase.

No information concerning any other development of a low cost fuze was found. The only

reference given to low cost is for fuze FU I FA 02 which was developed as a training fuze.

However, the fuze is still based on the same technology as the other fuzes and it is doubtful

that the fuze could be significantly cheaper than existing fuzes. In fact, the graze action

mechanism used in the fuze was found to be very difficult to manufacture, making the fuze

expensive. Some cost reducing exercises in the production of fuzes, which included plastic

moulding of the gear trains used in fuzes, were performed in USA. [2]

To evaluate the feasibility of the project, the following figures concerning the fuze market were collected:

4.2.1 Historical Allocation of United States Army Ammunition Spending

It is indicated that 11% of funds made available annually for ammunition is allocated

to the procurement of fuzes. This amounted to a budget of $2560 million during 1989. [2]


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4.2.2 World-wide Fuze Contenders

The following fuzes are identified as possible contenders of the Low Cost fuze (the figures are forecast figures for 1995 made available in 1987 by the DMS worldwide

study and forecast of military fuzes):

Table 1 : Forecast of fuze procurement for 1995

DM211 25 000

DM241 10 000

DM51 20 000

FU I FA 0 1 and 02 30 000

L112A1 10 000

L32A2 20 000

L85 15 000

M48A3 35 000

M577 200 000

M572 15 000

M739 400 000

All the fuzes mentioned in the table are of basically the same design as that of fuzes

presently in production at Naschem.

At an estimated unit cost of $50 (cost of fuze PD M739), this amounts to $39 million fuze procurement funds. If the Low Cost fuze could obtain a 5% market


PAGE270F52


share at half the unit production cost and 75% of the price, Naschem would have

made an additional profit of almost R2 million for 1995. [2]

A study was done to justify the development of the fuze. The objective was to determine what number of fuzes will have to be manufactured to cover the

development costs. Table 2 : Feasibility of developmentcontains the results from the

exercise.

Table 2 : Feasibility of development

This will probably be covered by the production of fuzes during one year.

4.3 Concept Design and Layout

4.3.1 Requirements

To ensure that the design conforms to all the requirements, it is important to

stipulate these requirements. This is done by means of a B-Specification. The B-

Specification of this fuze is based on that of existing fuzes and is included in

Appendix A All the requirements as stated in the B-Specification was considered

during the design, but for the purpose of the demonstration only some of the

requirements were evaluated.


PAGE280F52

i

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4.3.2 Concept Generation

4.3.2.1

Probably the most expensive and critical item in a fuze is the SAD and in particular

the mechanism providing the delayed arming for muzzle safety. The emphasis was

thus initially placed on developing an alternative device providing delayed arming

which is at least as reliable as the clockwork mechanism, but is less expensive.

The following possibilities were identified:

The Pyrotechnics Tube

A tube containing pyrotechnic composition can provide a time delay after

which a shutter is released. The ignition of the pyrotechnic composition will

be by means of a striker initiating a detonator during set-back. After a

predetermined time the pyrotechnic composition must burn through after

which one of two events can take place. The flame from the pyrotechnic

composition can initiate another composition which burns away completely,

leaving a passage for the movement of the shutter or a detent through the

space where the burning composition was. Otherwise, the combustion gasses

of the pyrotechnics can build up pressure to push a pin out of place which can

release the shutter.

DOCUMENT NO.: 5270-000000-715001 . ISSUE NO.: 1 CONFIDENTIAL VERTROULIK

PAGE290F52

I -------_I


PYROTECHNIC COMPOSITION

RELEASE PIN

Figure 2 : Pyrotechnic tube concept

4.3.2.2 The Fan

The movement of the shutter can be inhibited by a fan of which rotation is

regulated by making use of air friction. During set-back and spin, the shutter

will be released and start moving to the armed position. A fan is coupled to

the shutter by a gear mechanism and will start turning as soon as the shutter

starts moving. The rotating fan will cause air friction which will regulate the

movement of the shutter to provide the required delay of arming.

GEAR FAN

SPRING DETONATOR

Figure 3 : Fan concept


PAGE300F52

4.3.2.3


The Piston and Cylinder

Of the mechanisms mentioned in section 2.3, the only arming time delaying

mechanism which was considered, was the piston and cylinder concept.

DETONATOR

SPRING

PISTON WITH SMALL HOLE

Figure 4 : Piston and cylinder concept

After evaluating the three concepts, it was decided that the only way to cut the cost

of the fuze significantly would be to redesign the whole fuze and not only the SAD

as planned initially. Of the three concepts mentioned, the pyrotechnic time delay

mechanism was singled out as the most practicible concept.

The next phase was the development of a totally new fuze concept based on the

pyrotechnic arming mechanism.


PAGE310F52


4.3.3 Basic Concept and Functioning of the Demonstrator Fuze

NOSE

DELAY STRIKER

DELAY

GRAZE WING

PYROTECHNIC COMPOSITION

STRIKER CUP

INSERT M563 DETONATOR

ROTOR

FUZE BODY

V9 /V19 DETONATOR

BOOSTER PELLET

BOOSTER CUP

Figure 5 : Configuration of low cost fuze with major components

The concept of the delayed arming mechanism is based on the burning away of a

pyrotechnic composition in a cup.


PAGE32 OF 52

Figure 6 : Before set-back


I .

Figure 7 : During set-back The fuze must remain in this condition before being fired.

The delay composition is initiated during set-back and burns through in the allotted time span.


PAGE330F52


Figure 8 :After set-back but before pyrotechnic burnout The Delay Element ignites the pyrotechnic composition in the Striker Cup which is supported on a spring . The spring pushes the Striker Cup upwards onto the delay

Figure 9 : After set-back and pyrotechnic burnout When the pyrotechnic composition has burned away, the Striker Cup moves up and releases the Rotor. The Rotor then swings around due to spin and is locked in the armed position with the detonator directly below the striker


PAGE340F52


Figure 10 : Functioning on direct impact On direct action impact the Nose colapses and the striker is pushed into the detonator, causing initiation.

Figure 11 : Functioning on graze impact During graze action the Graze Wings cause the striker to be pushed into the detonator, causing initiation.


PAGE350F52


4.3.4 Design Concept Iterations

During the detail design stage of the demonstrator, many iterations of design were

necessary. The following table gives a summary of the configurations and the

reasons for changes incorporated:

Table 3 : Concept configurations

CEPT CONFIGURATION REASON FOR CHANGE 1. Two detonators in Rotor (Delay Initial requirement was for a dual action

and Super Quick) fuze Setting mechanism separating

Striker Cup from Delay 2. One detonator in Rotor Difficulty was experienced with the

No physical barrier separating implementation of the setting mechanism Striker Cup and Delay with this design. Dual action can be

Striker Cup assembled from implemented when a fom1al development bottom project is launched.

.., Anning Ring separating Striker Physical separation of the Striker Cup and ;). Cup and Delay the Delay Element is necessary to prevent

Setting mechanism and dual pyroteclmic composition from cnunbling action incorporated in Rotor during vibration. The setting mechanism

Solid nose could again be implemented in this design. The solid nose could be moulded.

4. Booster Cup changed to support Easier assembly of the components is SAD from the bottom facilitated and stresses in components are

lower. 5. More space created for Calculations of spring showed that more

movement of Striker Cup space is needed for the Striker Cup Spring. 6. Rotor made smaller Rotor had to change due to dimensions of

Only one detonator (Super detonators. Dual action requirement is not Quick) in Rotor necessary for demonstration

7. Graze Wings incorporated Graze action functioning is an important Striker Cup assembled from top requirement. Incorporation of Graze wings Am1ing Ring discarded brought about other changes. Springs supporting Graze

Win_gs


PAGE36 OF 52

8.

9.

10.

11.

12.

13.

14. 15.


Table 3 : Concept configurations (continued) .. ::

Rain dispensing mechanism To make the fuze insensitive to rain, incorporated a rain dispensing unit is required. Graze Wings overlap with Delay Graze Wing/Delay Element

overlapping is required to prevent the Delay Element from hitting the pyrotechnic composition during a

on nose.

Rain dispensing mechanism discarded Rain dispensing is not a requirement Springs removed from Graze Wings for the demonstration. Calculations Detent incorporated in Rotor will confirm the feasibility of Delay composition omitted, stronger mechanism. A detent is a cheaper detonator incorporated to ignite spin safety mechanism. Pyrotechnic pyrotechnic composition composition takes long to bum away

and can provide muzzle safety on its own.

Graze Wing Springs changed Manufacturer made these suggestions Other minor changes which were incorporated for easier

Graze Wings improved by moving centre of Striker Cup and Delay Striker changed Lighter components were needed to to enable of facilitate the of the Delay composition reinstated A faster pyrotechnic bum away Alternative detonator incorporated in composition could be found. Rotor Insert under Graze Alternative fixing method of Graze To avoid the insert . w

4.4 Detail Design

After and during the concept design phase, calculations were done to verify that the

fuze will be able to withstand the forces acting on it. To simplify the method of

detail design, variables were specified on the component drawings for the important


PAGE370F52

- -------- ------------ ---------'


dimensions which were used during the calculations. This facilitated the easy

alteration of dimensions during the design phase.

4.4.1 Specific Requirements

4.4.1.1

For this fuze configuration, specific requirements were identified which had to be

complied with. To determine whether th~ fuze complies with the requirements, either calculations, simulations or physical testing was used.

Before firing

The external dimensions must be according to Military Standard

The Striker Cup must penetrate the Rotor to prevent it from rotating

The Delay Element may not touch the pyrotechnic composition in the

Striker Cup

The Graze Wing must overlap with the Delay Element to prevent it from

pressing onto the pyrotechnics during a drop on the nose ofthe fuze

The M563 detonator in the Rotor may not initiate the V9/Vl9 booster

relay when detonated in the safe position

The Rotor must be free to rotate under all conditions

If the pyrotechnic composition should ignite spontaneously, the fuze must

remain safe.


PAGE380F52

! ________ I

4.4.1.2

4.4.1.3

4.4.1.4

During Set-back


All the components must withstand set-back

The Striker Cup Spring and Delay Striker Spring must allow arming to

take place

The Striker Cup must not touch the Rotor on set-back to prevent damage

of the striker tip

The movement of the Striker Cup must allow arming of the Graze Wings

During and After Arming

The Striker Cup must not pull out of the Rotor before pyrotechnic

burnout

The Striker Cup must pull out ofthe Rotor after pyrotechnic burnout but

must still penetrate the rotor cavity to act as a stop for the Rotor

The centre of gravity of the Rotor must be such that the Rotor arms

during spin

The Graze Wings must allow enough movement of the Striker Cup for

armmg

The Rotor must be locked positively after arming.

On Target Impact

During graze action, functioning of the projectile must take place. The components must withstand the forces during target impact.


PAGE39 OF 52

-- ---------- .. _j

4.4.2 Design Calculations


As far as possible all the functioning parameters and important component

dimensions were calculated. The design calculations are included in Appendix B.

4.4.3 Drawings

Drawings were created for manufacturing purposes. Due to the confidentiality of the

project, formal drawings are not included in this document but the important dimensions on the components are indicated on drawings included in the design

calculations (Appendix B)

4.5 Funds

For the initial development and to prove the feasibility of the fuze design, funds were

required for a small number of fuzes and a concept demonstration proof Further funds may

be made available for the full development by a client. To this avail a marketing pamphlet,

included in Appendix C, was prepared for the Naschem marketing personnel.

4. 6 Detonic Elements

During the fuze design, existing detonic elements were used as far as possible. The only

detonic components that had to be developed were the Delay Element and the Striker Cup.

The following requirements were stated for the above mentioned detonic elements:


PAGE40 OF 52


The Striker Cup must contain a pyrotechnic composition that burns away leaving as little

residue as possible in the Striker Cup.

The time delay needed from Delay Element initiation to Striker Cup burnout was 50

msec 20 msec.

The cap used in the Delay Element must be sensitive enough to ensure initiation at

minimum set-back acceleration conditions. The energy value at which initiation was

required, was fixed at 12 mjoule.

The Delay Element and Striker Cup were developed successfully and complied with all the

requirements.

4. 7 Manufacturing

Five fuzes were manufactured for testing purposes. During the manufacturing of the first

sample of fuzes, some changes were also incorporated to facilitate manufacturing of the

components.

4.8 Fuze Test Simulator

The fuze test simulator is an installation at Naschem which enables the recovery of fuzes

when fired from a 76 mm gun.


PAGE41 OF 52


4.9 Tests and Results

4.9.1 Spin test

4.9.1.1 Objective

4.9.1.2

4.9.1.3

The objective of this test was to confirm safety of the fuze at a spin rate of 1000 rpm and arming at a spin rate of 2000 rpm

Method

The Support Plate with the Rotor and the spin safety mechanism were spun

first at 1000 rpm and then at 2000 rpm. Arming of the Rotor was observed.

This was repeated three times.

Result

The fuze remained safe at 1000 rpm and was armed at 2000 rpm.

4.9.2 Drop test

4.9.2.1 Objective

The objective of this test was to confirm safety of the fuze set-back mechanisms and structural integrity when dropped from a height of 1.5 m.


PAGE420F52

4.9.2.2

4.9.2.3

Method


The complete fuze was dropped onto a concrete surface from a height of 2 m

in the following orientations:

Table 4 : Drop test orientations

Nose up 5

Nose down 3

Nose horizontal 1

Nose 45 up 1

Nose 45 down 1

Results

None of the set-back safety mechanisms were armed after the drop test. The

fuze remained safe to handle and fire.

During the nose up drop tests one of the three Graze Wings dislocated from

the Striker Cup on each of the drops. This can be attributed to the loose fit

of the Striker Cup in the cavity in the Insert. The safety mechanism is still

acceptable as the fuze remains safe to handle and fire. The drop test was

repeated a few times on one of the fuzes without repairing the dislocated

Graze Wings. After 4 drops all the Graze Wings were armed. The fuze is

not required to be dropped more than once during this test, so this did noi


PAGE430F52


amount to a test failure. With all the Graze Wings armed, the fuze still

remains safe as long as the pyrotechnic composition is not burnt out.

During the drop test with the nose orientated horizontally, the Detent Spring

was found to have dislocated from the Detent. This can be attributed to

excessive moving space of the Detent. A stop will have to be incorporated to

prevent the Detent from swinging too far and dislocating the Detent Spring.

4.9.3 Partly armed drop test .

4.9.3.1

4.9.3.2

4.9.3.3

Objective

The objective of this test was to confirm that the spin safety mechanism can not be armed by means of a drop.

Method

The Graze Wings were armed manually and the fuze was dropped (orientated horizontally). The radial orientation of the fuze was varied during the test.

Result

Again the Detent was allowed to swing too far which caused the Detent

Spring to be dislocated. During the drops where the Detent_ Spring stayed

intact, the Rotor was still safe.


PAGE440F52


4.9.4 Minimum set-back test

4.9.4.1

4.9.4.2

4.9.4.3

Objective

The objective of this test was to confirm armmg of the fuze set-back mechanisms during minimum set-back conditions and to ensure that the

residue of the pyrotechnic composition does not inhibit movement of the

components.

Method

The fuze was tested in the fuze test simulator at a set-back of 14 000 g's.

After recovery, the fuze was opened and the arming mechanisms were

inspected.

Result

The set-back mechanisms were all armed. The residue formed by the

pyrotechnic composition did not have any negative affect on the arming of

the fuze mechanisms. Figure 12 shows the inside of the fuze after being

recovered from the test.

DOCITh'IENT NO.: 5270-000000-715001 ISSUE NO.: 1 CONFIDENTIAL VERTROULIK

PAGE45 OF 52


Figure 12: Photo showing internal view of fuze after recovery

4.9.5 Maximum set-back test

4.9.5.1 Objective

The objective of this test was to test structural integrity of the components during maximum set-back and spin conditions and to ensure that the residue

of the pyrotechnic composition does not inhibit movement of the

components.


PAGE46 OF 52

4.9.5.2

4.9.5.3

Method


The fuze was tested in the fuze test simulator using a rifled bore at a set-back

of 25 000 g' s. After recovery, the fuze was opened and the components were

inspected for possible damage.

Result

The Rotor Shaft, which was press fitted into a hole in the Support Plate, fell

through the hole and onto the Booster Pellet which caused the Rotor to

dislocate. Again the residue formed by the pyrotechnic composition did not

have any negative effect on the arming of the fuze mechanisms.

4.10 Design Improvements

Due to the problems that were experienced during the tests, improvements were made to the

design of the fuze:

The hole in the Support Plate for the Rotor Shaft was changed to prevent the Rotor

Shaft from being able to fall through on set-back.

A better stop for the Rotor was incorporated.

The locking mechanism for the Rotor was improved.

The Striker Cup was changed to ensure improved safety.

Some of the materials specified for the components were changed to more available

materials.


PAGE470F52


A closer fit of the Striker Cup in the Insert was incorporated to prevent warm gases

from the pyrotechnics from leaking through to the detonator in the Rotor. The closer fit

will also help to prevent the problems that were experienced on the drop test.

The position of the Detent was changed to prevent the Detent from swinging too far and

causing dislocation ofthe Detent Spring.

These improvements were incorporated into the fuze and the maximum set-back test (par. 4.9.5) was repeated with the improved fuze. All the problems that were experienced with the initial design were resolved using the improved components.

Figure 13: Photo showing improved Rotor after recovery


PAGE..J8 OF 52

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5. CONCLUSION


A low cost fuze can cause a revolution in the fuze manufacturing industry. Indications are

that this fuze, if produced in large quantities, will cost less than a third of the existing fuzes.

The results indicate that the fuze does comply with all the specified requirements. It must be

kept in mind, however, that the objective of this project was to demonstrate a concept and it does not address all the functioning and safety parameters.


PAGE490F52

~ ~- --- -~---~-~---


6. RECOMMENDATIONS

It is recommended that funds be made available for the further development of the fuze.

More extensive testing will have to be done to prove the functioning reliability and safety of

the fuze. This will include a recovery proof and other dynamic proofs to test muzzle safety,

arming, direct action sensitivity, rain insensitivity, indirect firing functioning and graze action

functioning. Static and environmental tests will also be necessary to prove safety of the

fuze.


PAGE 50 0F 52

Literature


BIBLIOGRAPHY

[1] - Ministry of supply; The Textbook of Filling; Restricted; 1978

[2]- Webb, Michael, ; DMS Military Fuzes- World-wide Market Study and Forecast; DMS inc.; 1987

[3] - Headquarters, US Army Materiel Command; Engineering Design Handbook, Ammunition Series, Fuzes; AMC Pamphlet; November 1969

[4]- Wheeler, dr: J.P., van Zyl, dr. F.E.; Fundamentals of Fuzes- a Compiled :Manual; Naschem document no. LF 146/82; 1982

[5]- Dr. Hunt, Michael; Design- The Key Technology; The South African Engineer; Vol. 44; April 1994.

[6] - Mott, R.L.; Machine elements in Mechanical Design; Columbus; Charles E. Merril Publishing Company; 1985

[7]- Standards Research; SAE Standard AEll : Spdng Design Manual; Warrendale; Society of Automotive Engineers; 1990

[8] - Pisano, A., McCarthy, M., Derby, S.; Cams, Gears, Robot and Mechanism Design; New York; American Society ofMechanical Engineers; 1990

[9] - School of Ammunition; Fuzes- Basic Principles; Precis no. 204; August 1977


PAGE 51 OF 52


Military Standards and Specifications

{ 1} MIL-STD-1316C : Fuze, Design Safety Criteria for.

{2} MIL-STD-1472D : Human Engineering design criteria for military systems, equipment and facilities

{3} MIL-STD-333B : Fuze, projectiles and accessory contours for large caliber armaments

{ 4} MIL-STD-81 OE : Environmental test methods and engineering guidelines

{ 5} MIL-STD-331B : Fuzes and fuze components, environmental tests for

Note: Sources in the military field are not readily available. These documents were the only

applicable sources available at Naschem. Although the sources may seem outdated, it must be noted that little development in

this field failed to prompt the updating ofthe documentation.

DOCUMENT NO.: 5270-000000-715001 ISSUE NO.: 1 CONFIDENTIAL VERTROULIK.

PAGE 52 0F 52

-------- ----- ----------

APPENDIX A

B-specification for Low Cost Fuze

(40 pages)

DOCUMENT NO.: 5270-000000-715001


This document contains confidential information related to the defence of the Republic of South Africa. The provisions of Section 118 of the Defence Act, Act No. 44 of 1957, as well as the provisions of the Protection of Information Act, Act No. 84 of 1982, are applicable to this document. This document must be sent back to Naschem, a Division of Denel (Pty) Limited when no longer requirefl

TITLE

DOCUMENT NO.

ISSUE DATE

AUTHOR

SUMMARY

KEY WORDS

.TITLE PAGE

CRITICAL ITEM DEVELOPMENT SPECIFICATION (TYPE B2) OF THE LOW COST FUZE

5270-000000-115001

SEPTEMBER 1995

A.H. VAN DEN BERG

The document contains the design and testing requirements for the Low Cost Fuze

B2-Specification, Development, Mechanical fuze, Direct action, Graze action, Pyrotechnics

DATE OF ORIGINAL ISSUE SEPTEMBER 1995

DOCUMENT: 5270-000000-115001 ISSUE NO.: I CONFIDENTIAL VERTROULIK

PAGEl OF40

PARAGRAPH

TITLE PAGE

TABLE OF CONTENTS

1. SCOPE

2. DOCUMENTATION

2.1 Applicable Documents


2.1.1 Military Standards and Specifications 2.1.2 Military Documents

3. REQUIREMENTS

3.1 Fuze Definition 3 .1.1 Fuze Diagram 3 .1.2 Interface Definition 3.1.3 Major Component List 3 .1. 4 Coll1111on Items

3.2 Characteristics 3.2.1 Perfom1ance Characteristics ofthe Fuze 3.2.2 Physical Characteristics ofthe Fuze 3.2.3 Functioning Reliability of the Fuze 3.2.4 Maintainability ofthe Fuze 3 .2. 5 Envirol1ll1ental Requirements 3.2.6 Transportability 3.2.7 Cost

DOCUMENT: 5270-000000-115001 ISSUE NO.: 1 CONFIDENTIAL VERTROULIK

PAGE

PAGE20F40

1

2

5

5

5 5 5

6

6 6 6 8 8

9 9

10 10 11 11 13 13

-- ---------- -------------------------------- ------- ----------------

3.3 Design and Construction 3. 3 .1 Materials, Processes and Parts 3.3 .2 Electromagnetic Radiation 3.3.3 Product Marking 3.3.4 Workmanship 3.3 .5 Interchangeability 3.3.6 Safety


3.3.7 Human Performance/Human Engineering

3. 4 Documentation

3. 5 Logistics 3.5.1 Tools supply 3.5 .2 Personnel and Training

3. 6 Major Component Characteristics 3. 7 Precedence

3. 7. 1 Documentation 3. 7. 2 Design requirements value system 3. 7.3 Classification of failures

4. QUALITY ASSURANCE PROVISIONS

4.1 General 4 .1.1 Standards 4.1.2 Test Design 4.1.3 Test Equipment and Measuring Techniques 4.1.4 Responsibility for inspection and tests 4.1.5 Test Specifications 4.1.6 Test Method Development 4 .1. 7 Design qualification methodology

4. 2 Quality Conformance Inspection 4.2.1 Quality Conformance Examination and Tests 4.2.2 Examination and Inspection Methods (Test Category A) 4.2.3 Static Functioning Tests 4.2.4 Environmental Resistance Tests 4.2.5 Dynamic Tests

4. 3 Documentation Audit 4.3 .1 Design Review 4.3.2 Documentation Status

4. 4 Design Qualification Testing 4.5 Reliability Growth Plan

4. 6 Cross Reference Matrix

5. PREPARATION FOR DELIVERY


13 13 14 14 14 14 14 16

17

17 17 17

18

18 18 19 19

20

20 20 20 20 20 21 21 21

23 23 23 25 26 31

34 34 34

34

34

35

36

PAGE 3 OF40

I

----------- ------------------------------------------------------------ --------- ---------

6. NOTES

6.1 Reviewing Authority

6.2 Standardisation

6. 3 Abbreviations


APPENDIX Al : FUNCTIONAL DESCRIPTION OF FUZE

APPENDIX A2 : PRELlMINARY CLASSIFICATION OF FAILURES

TABLES

TABLE 1: REQUIREMENTS- VERIFICATION CROSS TABLE 2: CLASSIFICATION OF FAILURES

ILLUSTRATIONS

FIGURE 1 : FUZE LEVEL SCHEMATIC FUNCTION DIAGRAM


PAGE40F40

36

36

36

36

37

39

35 40

38

1. SCOPE

VERTROUUK CONFIDENTIAL

This specification establishes the design, performance, development and test requirements for the Low Cost Fuze. The item is hereinafter referred to as the fuze.

2. DOCUMENTATION

2.1 Applicable Documents

2.1.1 Military Standards and Specifications

2.1.1.1 MIL-STD-1316C : Fuze, Design Safety, Criteria for.

2.1.1.2 MIL-STD-1472D: Human Engineering design criteria for military systems, equipment and facilities

2.1.1.3 MIL-STD-333B : Fuze, projectiles and accessory contours for large caliber armaments

2.1.1.4 MIL-STD-810E:

2.1.1.5 MIL-STD-331B :

2.1.1.6 MIL-STD-490A:

2.1.1.7 MIL-STD-961B :

2.1.2 Military Documents

Environmental test methods and engineering guidelines

Fuzes and fuze components, environmental tests for

Specification practices

Military Specifications and associated documents, preparation of

Ammunition and Explosives Regulations (RSA) (SANDF), Volume 1, Pamphlet 20, Part 2. Ammunition and Ammunition Package Markings.


PAGE50F40

3. REQUIREMENTS

3.1 Fuze Definition


The fuze shall be a point detonating mechanical fuze with the following functioning options :

Super quick or instantaneous direct action mode. Super quick or instantaneous graze action mode.

The fuze shall be attached to the nose of a shell and shall :

Render the round safe during handling, storage and launching Arm the round during deployment Detonate the projectile on the target

3.1.1 Fuze Diagram

3 .1.1.1 Appendix A1 shows a typical fuze level schematic block diagram applicable to the fuze, showing all the major features in the form of a functional description.

3.1.1.2 The fuze has an external interface with the filled shell. All internal interfaces shall be the responsibility of the sub-contractor, and shall be determined by the design concept chosen to meet safety and performance requirements. They shall be controlled on design drawings as applicable.

3.1.2 Interface Definition

3 .1.2.1 External Physical Interfaces

MIL-STD-333B shall be applied as a guide in the design of fuze profile and outerfaces. (Figure 4 in the MIL-STD applies).


PAGE60F40

---------------------- __________________________ _j


(a) Fuze/Filled Shell Outerface

(i) Physical Fit

The fuze shall fit into the filled shell ofthe round. The following interfaces shall be specified on the design drawings :

Fuze thread and magazine configuration. Shell nose end thread and explodering

configuration.

(ii) Seating Faces

The seating faces of the two items shall ensure that a watertight seal is obtained.

(iii) Explosives Contact Face

The fuze configuration shall ensure contact between it and the explodering system. The contact between the fuze and the high explosive filling shall ensure that it does not crack, chip or crumble during vibration, shock or jolt testing of the assembled round.

(iv) Dimensions and Tolerancing

The geometry and symmetiy dimensions and tolerances shall ensure that the fuze does not disturb the balance or flight characteristics of the projectile.

3 .1.2.2 External Functional Interfaces

(a) Fuze/Filled Shell Outerface

DOCUMENT: 5270-000000-115001

(i) External Profile

The external contour of the fuze shall ensure that aerodynamic stability of the projectile 1s optimised. The contour shall be chosen m conformance with the guidelines contained m MIL-STD-333B.

ISSUE NO.: 1 CONFIDENTIAL VERTROULIK

PAGE70F40


(ii) Detonation Transfer

The detonation energy output transferred from the fuze booster shall be sufficient to ensure that a TNT filling of T .B.D. kg nominal in the projectile will produce a full detonation. The energy level to achieve this, shall be established by empirical tests on the round.

3 .1.2.3 Internal Interfaces

The internal functional interfaces involve the following forms of energy transfer : (a) mechanical movement due to rotation and acceleration

forces. (b) heat transfer due to temperature gradients caused by

friction or temperature fluctuations. (c) detonation power transfer during initiation ofthe detonic

elements in the detonation train.

The internal physical interfaces involve dimensional interfacing of the components of the fuze.

3.1.3 ::Major Component List

The major components shall be specified by the designer.

3.1.4 Common Items

Where possible, existing components and detonic elements shall be used in the design of the fuze.


PAGE80F40

3.2 Characteristics


The function diagram in Appendix Al is to be used as a guide to the following description :

3.2.1 Performance Characteristics of the Fuze

The fuze shall withstand the forces exerted on it during firing of round. The design of the fuze is done using a safety factor of 20% over the

normal maximum operating conditions.

The following are the key functions of the fuze, which apply at any temperature and muzzle velocity:

3 .2.1.1 Direct Action

The fuze shall function on impact at any range between 60 m and the range of the system on direct impact. Impact angles between target and projectile axis may lie between 90 and 20.

3.2.1.2 Graze Action

The fuze shall function on impact at any distance between 60 m 3000m on graze action. Targets may vary between natural soft sand or ground, armoured vehicles or concrete bunkers.

3.2.1.3 ShelfLife

The fuze shall have a minimum guaranteed shelf life of 10 years in existing normal magazine and depot facilities.

3 .2.1.4 Bore and Muzzle Safety

(a) The fuze shall not arm or detonate at any time while in the gun barrel.

(b) The fuze shall have a muzzle safety distance of 20 m minimum.

(c) The fuze safety and arming device shall be activated by a combination of axial and radial acceleration forces.


PAGE90F40


3. 2. 1. 5 Arming Distance

The fuze shall be fully armed at a maximum distance of 60 m.

3 .2.1.6 Initiation

All fuzes shall function instantaneously on impact. Function time shall be not more than 100 micro-seconds to the initiation of the main charge.

3 .2.1. 7 Sensitivity I Insensitivity

The fuze sensitivity/insensitivity shall be such that it : (a) will not function when fired through.

ram

grass growing more than 1 m high leaves of trees

(b) will function upon impact with a 25 mm thick plywood target or a 1,6 mm mild steel sheet target, at a distance between 60 m and 1 000 m from the barrel muzzle.

3.2.2 Physical Characteristics of the Fuze

3 .2.2.1 External Dimensions

The external fuze dimensions shall not exceed : - Flange to nose length - Intrusion depth

3.2.2.2 Mass ofFuze

96,5 mm max. 58,0 mm max.

The filled mass of the fuze must be between 600 g and 800g. The filled mass for the fuze shall be specified on the design drawings after the completion of the design.

3.2.3 Functioning Reliability of the Fuze

A failure is defined as the situation where the fuze does not function as required or as intended. The fuze shall have a minimum functional reliability of 90% at 90% confidence level


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3.2.4 Maintainability of the Fuze

The fuze shall not require specific maintenance during the first ten years of its shelf life.

3.2.5 Environmental Requirements

Unless otherwise specified herein, the fuzes shall not suffer damage, deterioration or degeneration of performance beyond the limits of this specification when subjected to any environmental condition or any combination of environmental conditions specified herein. Environmental tests and test conditions are based on an analysis of user requirements and the expected life cycle profile ofthe ammunition.

3.2.5.1 Natural (Storage) Environment

The fuze shall, in its unpacked and packaged states, be unaffected by continuous and prolonged exposure to any combination or sequence of the following conditions; whether fitted to the round or as a separate item.

Extreme temperature Relative humidity Temperature and Humidity

Salt fog

Immersion in water

Up to a maximum of 90% Cycling for 28 days under extreme temperatures of -50C to +70C, and

. with the maximum relative humidity level of95% Moist, salt laden atmosphere (to a 5% concentration) Up to a depth of 1 m maximum (in inner container)

The performance of the fuze shall conform to specification after having been subjected to these conditions.

DOCUMENT: 5270-000000-115001 ISSUENO.: 1 CONFIDENTIAL VERTROULIK

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3.2.5.2 Environment for transportation and handling

The fuze shall, in its unpacked state, be unaffected by continuous exposure to any combination or sequence of the following conditions :

(a) Vibration The fuze shall withstand and perform within specification after being subjected to transport induced vibration at high and low temperature extremes required by this specification. Vibration shall be applied in three orientations of the item. Transport simulation must apply to armoured vehicles (AFV) and air cargo.

(b) Rain The fuze performance shall not be adversely affected by exposure to simulated rainfall, for a period of at least forty minutes, in both packaged and unpacked conditions.

(c) Thermal Shock The fuze (unpacked) shall function within specification after being subjected .to at least three cycles of temperature shock at temperature extremes of +52C 2C and -20C 2C. The cycle time shall be at least 1 hour at each extreme temperature.

(d) Immersion in water/Water tightness The fuze shall withstand immersion in water at a depth of 1 m for at least 15 minutes. The item shall be at 20C above the ambient temperature. The round shall be packed in the inner container.

(e) Altitude The fuze shall perform within specification when fired dynamically at any altitude between zero and 2 000 m above sea-level.

3.2.5.3 Induced (Mission) Environment- (Round/Ballistic environment)

The fuze structure and mechanisms shall remain safe and operable under the ballistic environmental conditions created during dynamic firing (See par. 3.3.6.6).


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3.2.6 Transportability

The fuze shall be safe to transport and shall not require any special packaging/equipment or vehicle other than that normally required for the transportation of the round. The item, assembled to the round, shall withstand air transport and supply by parachute to operational areas. (See also par. 3.2.5.4).

3.2.7 Cost

The design of the fuze shall be such that the cost of manufacturing is kept as low as possible.

3.3 Design and Construction

Materials, processes and parts used shall be of high quality, suitable for the purpose and shall conform to applicable military and/or other reliable and traceable specifications. Criticality of materials used shall be traceable via a logical and acceptable process, (e.g. FMEA, FTA) to performance, safety and/or reliability criteria. The fuze shall be designed and constructed in accordance with MIL-STD-1316C (paragraphs 4.3.4, 5.2.3, 6.4 and 7 are excluded) and MIL-STD-333B.

3.3.1 l\'Iaterials, Processes and Parts

3.3.1.1 Where possible, locally manufactured materials and parts shall be used.

3.3.1.2 The materials from which the fuze is to be made must be either compatible with explosives of all classes or be in such a state that it will provide no safety hazard should it come in contact with explosives.

3.3.1.3 No material, used in the fuze, shall be deemed a hazard to human life under normal handling conditions and environments.


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3.3 .1.4 All critical items/components are to be traceable to specific starting material batches, dates of manufacture and lot/batch test and process results.

3.3.2 Electromagnetic Radiation

The fuze and/or its detonic elements shall not be susceptible to electromagnetic radiation. MIL-STD-1385B shall be used as a guide for design purposes.

3.3.3 Product Marking

The fuze is to be clearly marked indicating lot number, manufacturer and fuze type (in accordance with the Armscor marking drawing).

3.3.4 Workmanship

Workmanship shall be of such a nature as to ensure the safety, reliability and functionality of the product without hindrance to the assembler or operator.

3.3.5 Interchangeability

Where possible, components which are interchangeable between different fuze types, are to be used.

3.3.6 Safety

3.3.6.1 The fuze shall be designed and constructed with MIL-STD-1316C as guideline.

3.3.6.2 Safety procedures are to be drafted for assembly, handling, testing and for rendering the fuze harmless.

3.3.6.3 The fuze is to be constructed that, in the event of the detonator igniting, when the fuze is in the unarmed condition, it will not


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VERTROULJK CONFIDENTIAL

transfer, ignite or burn the remaining detonic train elements, nor seriously injure the person handling the fuze/round.

3.3.6.4 The fuze shall remain safe for handling and shall be safe for firing when subjected to:

(a) Unprotected 1,5 m Drop during handling The impact resulting from an unprotected 1,5 m drop on a hard surface in any orientation (item shall not be fired)

(b) Mechanical Shocks or Jolts A series of mechanical shocks or jolts as it would endure during transportation, for a crash hazard

(c) Thermal Shock Thermal Shock between -50C and +70C (at least 3 cycles)

(d) Aircraft (Parachute) Drop (Refer also to par 3.2.6) An aircraft (parachute) drop test when assembled into the round and fully protected in its packaging as prepared for air-supply

(e) Static Electricity Build Up/Discharge An instantaneous static electricity build up/discharge of at least 30 kV.

3.3.6.5 Spontaneous Initiation (Rapid Fire Conditions)

When assembled to the round, the fuze shall not be susceptible to spontaneous ignition or detonation (cook-oft) when it is kept in a hot barrel or gun chamber for a prolonged period, during rapid-fire conditions.


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3.3.6.6 Integrity under dynamic firing conditions

The fuze shall withstand the following combination of conditions without any adverse effects. During the internal and external ballistic phases ofthe projectile launch cycle, the fuze is subjected to rotational and axial acceleration forces. The maximum conditions are as follows :

Axial acceleration 25 000 g's Deceleration in flight (horizontal) 0,08 m/s/m Rotation at barrel exit (at 950 m/s) 23 000 rpm Thermal shock : for the extremes -20C, +52C Altitude variations : from sea level to 2 000 m above sea level

The interior mechanisms of the fuze shall not be affected by these conditions. It shall be protected from heat generated from air friction, rain and from low temperatures.

The fuze structure and mechanisms shall remain safe and operable under the ballistic environmental conditions created during dynamic firing. These conditions are as follows :

(a) Integrity under dynamic acceleration forces The fuze shall withstand a maximum axial acceleration of 25 000 g' s, but must arm within the limits given.

(b) Integrity under dynamic rotational forces The fuze shall not arm at 1 000 rpm. The fuze shall withstand an angular velocity of at least 23 000 rpm.

3.3. 7 Human Performance/Human Engineering

3.3.7.1 When necessary, the depot personnel must be able to remove the fuze from the projectile, using the appropriate spanner.

3.3.7.2 MIL-STD-1472D shall be used as a guideline in fuze design to ensure that human engineering aspects are adequately considered.


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I

--~-~---~---~-- --~------------ -----------------~~-~~----~--~~--- --- -----~---~- --- --------------------- -- ____ _j

3.4 Do-cumentation


The following documentation must be available for the design qualification of the fuze to be finalised. This documentation shall be according to MIL-STD-490A or MIL-STD-961B, and the Supplier's Configuration Documentation system.

3.4.1 Development Specifications for the round and fuze.

3.4.2 Product and Acceptance Specification for the fuze.

3.4.3 Product and Acceptance Specification for the round incorporating the fuze.

3.4.4 Test and Design Qualification Specifications for the fuze.

3.4.5 Design Qualification Report for the fuze.

3.4.6 MRI for the fuze.

3.4. 7 Drawings with classification or characteristics.

3.5 Logistics

3.5.1 Tools supply

Fuze spanners shall be provided to enable removal of the fuze in the event of rework or inspection having to be done. No other particular logistics requirements shall apply, other than those applicable on the 76 mm and 105 mm rounds.

3.5.2 Personnel and Training

3.5.2.1 Personnel

Not applicable.


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..,.-====rn~ NASCHEM='

3.5.5.2 Training


(a) No special training shall be required to use the fuze, other than that currently being used for the 76 mm and 105 mm rounds.

(b) Training aids shall be supplied, and shall include, but not be limited to : Sectioned fuzes Schematic diagrams Slides and transparencies Updates oftraining manuals

3.6 Major Component Characteristics

The major components of the fuze shall be designed to meet all the physical and performance requirements. Physical and functional requirements of each major component or sub-assembly, shall be described in the product specification.

3. 7 Precedence

3. 7.1 Documentation

The User Requirement Specification and Development Specification for the round shall take precedence over the requirements of this specification in case of conflict. In the event of conflict between this B2-specification and other sub-system B2-specifications the conflict shall be resolved by reference to the higher level specification and the Technical Committee.

When requirements of this or related specifications cannot be met, the matter shall be referred to the Technical Committee and the User for a decision about the acceptance of proposed performance, or a modification to stated requirements.

DOCUMENT: 5270-000000-115001 JSSUENO.: 1 CONFIDENTIAL VERTROULIK

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3.7.2 Design requirements value system

The following requirements categories are important in this product :

3.7.2.1 Safety mechanism reliability (bore, muzzle)

3. 7 .2.2 Arming mechanism reliability - functioning

3.7.2.3 Terminal functioning

3.7.2.4 Cost ofitem

3.7.2.5 Non-strategic materials and processes

3. 7 .2. 6 Physical characteristics (size, mass, outer profile)

3. 7 .2. 7 Standardisation

For further details, reference shall be made to the Round Specification.

3.7.3 Classification of failures

A preliminary classification of failures is included in the Appendix. It may be used as a guide to the importance of characteristics in the development of the fuze.


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4. QUALITY ASSURANCE PROVISIONS

4.1 General

4.1.1 Standards

The purpose of testing shall be to demonstrate design conformance to requirements. As such, all components to be subjected to formal demonstration testing, shall be free of material defects and shall conform to dimensional (interface) requirements. The Supplier shall be responsible for the demonstration of Quality ofDesign.

4.1.2 Test Design

All tests where functional or physical characteristics are being evaluated or demonstrated shall be based on rational experimental design supported by statistical techniques. Test designs shall further be supported by defect analysis, classification of defects and tolerance analysis where applicable.

4.1.3 Test Equipment and Measuring Techniques

Measuring techniques shall be developed and qualified within agreed accuracy and reproducibility requirements. Test equipment shall be qualified and calibrated and calibration certificates shall be available at all times.

4.1.4 Responsibility for inspection and tests

Unless otherwise specified the Contractor shall be responsible for the execution of all static tests. Unless otherwise agreed upon the Contractor shall use his own or any other acceptable test facility.


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4.1.5 Test Specifications

Test specifications shall be compiled to describe the test methodology in detail. For example purpose of tests, test dates, sample quantities, test lay-out, test equipment and conditions, sentencing conditions, responsibilities of persons attending the test and data recordings shall be described.

4.1.6 Test Method Development

For design qualification purposes, it is necessary to develop and specify suitable tests and test methods (when they do not exist) to : evaluate and verify safety (statically, dynamically) evaluate and verify functioning (statically, dynamically) evaluate and verify resistance to environmental conditions.

4.1.7 Design qualification methodology

4 .1. 7. 1 General

Detailed descriptions of the various applicable test methods and techniques, the data recording requirements and special conditions are presented in the sections following the test lay-out.

The qualification tests are divided into four categories, viz .. : Mathematical analysis and simulation Visual and dimensional inspection Static (and environmental) testing Dynamic testing

4.1. 7.2 Design Calculations- Modelling and Simulation

(a) Mathematical Analysis

DOCUMENT: 5270-000000-I I 500I

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