spring (material n hardware)

7/24/2019 Spring (Material n Hardware)

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TOPIC :



INTRODUCTION

On completion of this topic you should be able to :

Identify various types of springs and list materials used in their I I

iiiconstruction.

Describe characteristics of springs and their applications.

Describe testing and inspection methods of springs.



HISTORY OF SPRING



HISTORY OF SPRINGS

Non-Coil springs have been used throughout history.

Even a resilient tree branch can be used as spring.

It is because the wood has a flexible structure

(Ex !rchery and "ows # $ilitary Catapult%

$ore sophisticated spring devices date to the "ron&e !ge



WHAT IS SPRING?



! spring is a device that changes its shape in response to an external

force' returning to its original shape when the force is removed.

he energy expended in deforming the spring is stored in it and can be

recovered when the spring returns to its original shape.

)enerally' the shape change is directly related to the amount of force

exerted.

If too large force is applied' the spring will permanently deform and

never return to its original shape.

SPRING??



SPRING STEEL

*pring *teel is a special classification

of steel that has

+ )reat hardness

+ *trength

+ Elasticity

!dditional alloying elements in spring

steel include

+ $anganese

+ Chromium

+ *ilicon

+,anadium

+ $olybdenum

!pplications include

+ *prings

+ *teel rules

+ $easuring tapes

+ eeler gauges

Material such asrubber andplastic may be

used too .



SPRING

amiliar uses of spring include

Supplying motive power - in toy mechanisms' watches and clocs. !lso

to close piston engine valves .

As a counter balance - a door closing devices and to a certain extent in a

car suspension .

As a shock absorber

For vibration control - in engine mounts and instrument vibration pads

Force measurements / calibrated springs in weighing machines andinstruments .

Retention / retaining rings' circlips or spring washers .



YPE OF SPRING



he variety of spring configuration can be classified under five main type 0

lat or leaf

1elical or coil

*piral

orsion

Disc

TYPE OF SPRING



FLAT / LEAF SPRING

! leaf spring is a flat beam designed to deflect under load 0

Centre is usually firmly anchored' while the ends are lined by movable

shacles to the moving machine part.

$ost commonly seen in automotive suspension

!lso seen as the undercarriage legs on some light aircraft.

Info $ilitary Catapult and 2adlocs also using the leaf spring.



FLAT / LEAFSPRING

*tress concentrates in one point (centre%

his can be improved by adding extra leafs at this point.

Leaf Spring

Load Test

How toinstalled

Leafspring

http://var/www/apps/conversion/tmp/scratch_7/video/leaf%20spring%20load%20test.avi

http://var/www/apps/conversion/tmp/scratch_7/video/Super%20Springs%20-%20Leaf%20Spring%20Support%20For%20Your%20Chevy%20Truck%20With%20Strutmasters.avi







FLAT / LEAFSPRING

*tress concentrations can also be improved by increasing the width of

the spring at this point.

hese spring are nown as Diamond Spring



HELICALSPRING

The most common type of spring.

*ometimes termed a coil spring

Is essentially a wire or bar wound into a helix

Designed to act under compression' extension'but rarely both' which would be detrimental to the

spring3s life

! spring used in compression tends to shorten in action

4hile a tension spring lengthens in action.



A common application for helical springs on aircraft is a

eli!"oil thread insert / used to strengthen or repair threads

HELICALSPRING



COMPRESSION SPRING

5pen-coil helical spring that offers resistance to a

compressive force applied axially.

he pitch or spacing between the coils can beconstant or variable.

6sually coiled as a constant-diameter cylinder.

1 2 3 4 !

Fee len!t"

WieDia#ete

Pit$"

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ise)

Ri!"t Hand&Clo$'(ise)

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O*tside

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Go*nd S*%a$e



COMPRESSIONSPRING

7ound wire is predominant shape used because it is readily available and

adaptable to standard coiler tooling.

he spring shape is also available as

Conical ( apered %

Convex ( "arrel %

Concave ( 1ourglass %

,arious Combination of these



Helical"#mpression

"onical "onstant$itch

%arrel

&ariable$itchHourglas

s

COMPRESSIONSPRING



E+TENSION SPRINGSPRING

elical springs in extension wor very

much lie those in compression 0 except for

the obvious difference in direction.

Extension *prings absorb and store energy

by offering resistance to a pulling ( tension %

force.

,arious types of ends are use to attach the

extension spring to the source of the force .



SPIRAL SPRINGS

The two types of spiral are the :

lat *piral or !rchimedes *piral

Conical orm *piral



FLAT SPIRAL SPRING

he flat spiral can absorb force at a tangent to its axis / it can be

wound up to close the space between its coils.



CONICAL SPIRALSPRING

he conical form can be compressed or stretched' and also reacts to forces at

right angles to its axis.

he advantage of spiral springs is the ability to be deflected in a combination of

ways.

Sto'eo

De,e$tion

A--liedFo$e



TORSION SPRING

elical torsion springs are different from other helical springs

because they are loaded in torsion' which results in bending

(rather than shear % stresses in the wire.



TORSION SPRING

orsion springs have a variety of different ends which are manufactured in

con8unction with the design application of the spring .

TORSION SPRING



TORSION SPRING

or example'

orsion spring are used to assist the opening of 4D passenger entry

door on "9:9-;<<=9<<=><<

TORSION SPRING



TORSION SPRING

TORSION .ARS



TORSION .ARS

he torsion bar spring is essentially a shaft of uniform cross-section that stores

energy when twisted.

5ne end of the bar is fixed and the other is free to twist. he bars resistance to

twisting causes springing action.

TORSION .ARS



! straight laminated torsion bar' instead of thrust bearings' is used to contain

centrifugal forces in the tail rotor system of some helicopters.

TORSION .ARS

TORSION .ARS



TORSION .ARS

TORSION .AR TORUE WRENCH



TORSION .AR TORUE WRENCH

he s?uare drive in the torsion bar tor?ue wrench acts as a torsion bar

spring which activates some gears to show tor?ue on an indicator.



DISC SPRINGS



DISC SPRINGS

his classification of springsincludes a large family of spring

types ' such as

+ *ingle disc

+ $ultiple disc

+ "ellevillie spring

+ @oc washer

+ Diaphgram

DISC SPRING



DISC SPRING

+ Dis$ s-in!s are shallow conical rings that can besub'ected to a(ial loads.

+ )is* springs may be used where space is limited andlarge forces are present.

+ +he single dis* handles small de,ections .

+ Sta$' o #*lti-le dis' springs is used for greaterde,ection.

DISC SPRING

http://var/www/apps/conversion/tmp/scratch_7/video/Disc%20springs%20are%20used%20for%20high%20force%20and%20short%20spring%20travel.avi

http://var/www/apps/conversion/tmp/scratch_7/video/Belleville%20Disc%20Spring%20Stacking%20Demo.avi

http://var/www/apps/conversion/tmp/scratch_7/video/Belleville%20Disc%20Spring%20Stacking%20Demo.avi





DISC SPRING

4ell-nown dis spring applications include the diaphragm spring in the

automotive clutch.

DISC SPRING



DISC SPRING

!nother common dis spring varieties are

finger washers' wave spring washers and

the shae proof washers which provide lightlocing of nuts and bolts.



TERMINOLOGY



TERMINOLOGY

#nside $iameter measurement between inner surface across centre

Outside $iameter measurement across the outer surface across centre

TERMINOLOGY



TERMINOLOGY

%ean $iameter!$easurement between

opposite wire centre

Free &ength!

@ength of a spring when not underload

TERMINOLOGY



TERMINOLOGY

'ire $iameter ( diameter of wire used in the spring.

TERMINOLOGY



TERMINOLOGY

&ength #nside ooks !$easurement between

inside surfaces of

hoos.

&ength Over "oil !

@ength of the wound

wire

TERMINOLOGY



TERMINOLOGY

"oils ( 4ound wire in a spring

)itch ( Distance between ad8acent coil centres.

Space *etween "oils ( Distance between ad8acent coil surfaces.

TYPE OF ENDS



TYPE OF ENDS

Compression springs can have closed and ground ends to

sit s?uare on surfaces to apply pressure evenly' or the ends

can be open.



TYPE OF ENDS



5pen Ends ' )round

5pen Ends ' Not )round



TESTING



Inspection and testing of springs is carried out according to the maintenance

manual applicable to the ma8or assembly the spring is part of.

*prings are inspected for

+ *lueing ( Discoloration which indicates overheating

+ )itting ( *urface defects caused by corrosion

+ "ompression Strength ( to ensure spring has sufficient recoil strength

+ Free &ength ( to ensure spring is the same length as when new

+ $istortion ( to ensure spring is the same shape as when new

TESTING



TESTING

$easurement of the compression

strength of a spring is performed

with a spring tester.

he spring is compressed to a

specified height ' and the forced

re?uired to do so is measured to

ensure it is within tolerance.

TESTING



ree Compressed

!nother chec which may be

performed is spring free

length to ensure the spring

is not buckled or distorted.

his chec measures the length of the spring in the relaxed position

against a straight edge

*pring distortion affects the control the spring exerxises over a mechanism

TESTING



!lways replace a spring with the correctly identified part. In somesystems a range of springs may be available these could be

identified by a coloured paint mar to indicate their particular range.

Correctly operated and maintained' a spring can be expected to

have a long life however' their operating envionment and the

nature of their tas exposes them to the ris of failure.

TESTING



!ny +ick or Scratch will concentrate stress and lead to a fracture .

Overheating, in a hot environment ' can change the heat treatment

and temper of the spring steel. his will cause loss of tension or

fatigue failure.

"orrosion, in an environment exposed to the atmosphere or

corrosive elements will lead to surface deterioration and add to stress

or fatigue failure.

he nature of spring steel maes it vulnerable to corrosion' andprotective surface treatments are easily damaged.

spring (material n hardware)

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