A REVIEW ON HELICAL COMPRESSION SPRING TO DESIGN A SHOCK ABSORBER OF BIKE

Journal for Research| Volume 01| Issue 11 | January 2016 ISSN: 2395-7549

A Review on Helical Compression Spring to Design a Shock Absorber of Bike Mr Amol Vikas Joshi PG Student Department of Mechanical Engineering J.T.M. College of Engineering, Faizpur

Mr Kundan K. Chaudhari Associate Professor Department of Mechanical Engineering SSSIST, Sehore

Abstract A spring is an elastic object used to store mechanical energy. A shock absorber is a mechanical device designed to smooth out or damp shock impulse & dissipate kinetic energy. In this paper there is reviewed some papers on suspension system. The aim of this review paper is to represent a general study on the analysis of spring to fulfil the requirement of suspension system.

Keywords: Allowable Stress, Compression spring, Design, Suspension _______________________________________________________________________________________________________

I. INTRODUCTION The automobile frame and body are mounted on the front and rear axle not directly but through the springs and shock absorbers.

The assembly of parts, which perform the isolation of parts from the road shocks, may be in the forms of bounce, pitch and roll is called suspension system.

Functions of suspension system 1. It prevents the vehicle body and frame from road shocks.

2. It gives stability of the vehicle.

3. It safeguards the passengers and goods from road shocks.

4. It gives the good road holding while driving, cornering and braking.

Requirements of suspension system 1. There should be minimum deflection.

2. It should be of low initial cost.

3.It should have low maintenance and low operating cost.

5. It should have minimum tyre wear.

Fig.1: Suspension System

To fulfil the requirement of suspension system this paper focused on spring features, applications, selection of material, design procedure etc.

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A Review on Helical Compression Spring to Design a Shock Absorber of Bike (J4R/ Volume 01 / Issue 11 / 04)

II. SPRING A spring is an elastic object used to store mechanical energy. A spring is a flexible element used to exert a force or a torque and, at the same time, to store energy. The force can be a linear push or pull, or it can be radial, acting similarly to a rubber band around a roll of drawings.

Functions of spring 1) To cushion, absorb or control energy due to either shock or vibration as in car spring, railway buffers, shock absorbers & vibration dampers.

2) To apply forces, as in brakes, clutches and spring loaded valves.

3) To measure forces, as in spring balances and engine.

4) To store energy, as in watches, toys etc 5) To control motion by maintaining contact between two elements.

6) To change vibration characteristics of a member as in flexible mounting of motors.

Classification of spring

Fig.2: Classification of Spring

(a)Compression spring

(b)tension spring (c) Torsion spring Fig.3: (a, b, c, d) Types of Spring

(d) Belleville spring

Helical spring: It is made of wire coiled in the form of helix having circular, square or rectangular cross section. The load applied on the helical spring is along the axis of helix here, the major stress is induced is shear stress due to twisting. Depending on the load acting on the helical spring, the spring is further classified as compression and tension spring. Helical compression spring is generally used in bike rear suspension so this paper is more focussed on helical compression spring.

Helical compression spring The coils of helical spring are separate from each other. Depending on the type of end the helical compression spring is classified as follows

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A Review on Helical Compression Spring to Design a Shock Absorber of Bike (J4R/ Volume 01 / Issue 11 / 04)

(a)Plain end

(b)plain & ground end (c)squared end Fig.4: (a, b, c, d) shows types of compression spring

(d)squared & ground end

Design of Helical Springs The design of a helical compression spring involves the following considerations: 1) Modes of loading – i.e., whether the spring is subjected to static or infrequently varying load or alternating load.

2) The force deflection characteristic requirement for the given application.

3) Required life for springs subjected to alternating loads.

4) Environmental conditions such as corrosive atmosphere and temperature.

5) Economy desired.

Considering these factors, the designer selects the material and specify the wire size, spring diameter, number of turns spring rate, type of ends, free length and the surface condition.

Selection of material One of the important considerations in spring design is the selection of the spring material. In general, the material of the spring should have high fatigue strength, high ductility, high resilience and should be creep resistant. Springs are often grouped into classes according to the service condition e.g. light service, average service and severe service. Light service includes spring subjected to loads that are static or very infrequently varied such as those used in safety valves springs. Average service is applicable to the stress range as for the sever service. It is meant for intermittent operation for example in engine governor, automobile suspension springs. Severe service covers rapid continuous loading. Selection of material for the helical spring is with the help of following table.

Table - 1

Material and its allowable stress Sr No.

1

2 3 4 5

-

Material Carbon steel Diameter 2.125mm Diameter 2.125 to 4.625mm Diameter 4.625 to 8.00 mm Diameter 8.00 to 13.25mm Diameter 13.25 to 24.25mm Diameter 24.25 to 38.00 mm Music wire Oil tempered wire Hard drawn spring wire Stainless steel wire

Allowable Shear Stress (N/mm2) Light

Average

Severe

651 595 525 455 392 350 612 525 437.5 437.5

525 483 420 364 315 280 490 420 350 350

420 385 336 294 252 224 392 336 280 280

Modulus of Rigidity(G) KN/mm2

Modulus of Elasticity(E) KN/mm2

80 80 80 80 80 80 80 80 80 70

210 210 210 210 210 210 210 210 210 196

Terminology of helical spring: d = wire diameter of spring Di = inside diameter of spring coil Do =outside diameter of spring coil D = mean coil diameter C= Spring index G= Modulus of rigidity E= Modulus of Elasticity NT = total no. Of coil NA = Active turn

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A Review on Helical Compression Spring to Design a Shock Absorber of Bike (J4R/ Volume 01 / Issue 11 / 04)

Fig. 5: helical compression spring

III. STRESS IN HELICAL COMPRESSION SPRING The axial load tends to produce twisting moment in the wire, so torsional shear stress induced in the wire.

8đ?‘Šđ??ˇ Ď„1 = 3 _ _ _ _ _ _ _ _ _ (neglecting curvature effect) đ?œ‹đ?‘‘ In addition to this torsional stress direct shear(Ď„2) and stress due to curvature effect of wire.

8đ?‘Šđ??ˇ direct shear, (Ď„2)= 2 đ?œ‹đ?‘‘

resultant shear stress, Ď„ = Ď„1 + Ď„2 8đ?‘Šđ??ˇ đ?‘‘ 8đ?‘Šđ??ˇ 1 8đ?‘Šđ??ˇ Ď„ = 3 (1+ ) = 3 (1+ ) = Ks 3 đ?œ‹đ?‘‘

2đ??ˇ

đ?œ‹đ?‘‘

2đ??ś

đ?œ‹đ?‘‘

1

where shear stress factor=Ks= (1+ ) 2đ??ś when stress due to curvature effect is considered then, 8Kcđ?‘Šđ??ś Maximum shear stress Ď„= đ?&#x;? đ?›ąđ???

Whal’s stress concentration factor = Kc =

4đ??śâˆ’1 4đ?‘?−4

+

0.615 đ??ś

IV. DEFORMATION OF HELICAL COMPRESSION SPRING Deformation of spring is due to action of force applied on it. It may be δ=

8đ?‘Šđ?‘? 3 đ?‘ đ??´ đ??şđ?‘‘

V. CONCLUSION In this study the helical compression spring in shock absorber is to resist the shocks obtained from the irregularities and bumping from road. Also by studying the selection procedure which material is best for helical compression spring to sustain the shocks come from the road irregularities. Also this study concluded selection of coil and wire diameter to reduce the stress on the helical compression spring.

VI. REFERENCES [1] [2] [3]

J.M. Gallardo, L. Soria, E.J. Herrera Investigation of service failures in automobile shock absorbers Engineering Failure Analysis 14 (2007) 355–363 Machine Design by V.B. Bhandari Tata Mcgraw Hill Education Private Limited Publication Third Edition 2007 Machine Design by R.S. Khurmi Eurasia Publishing House (Pvt.) Ltd. Publication Fourteenth Edition 2005

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