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ME1352 : DESIGN OF TRANSMISSION SYSTEMS

M.Puviyarasan, Senior Lecturer

Department of Mechanical Engineering

Panimalar Engineering College, Chennai

1Pec / DoME / MP / Design of Transmission Systems/Contents

by

Types

Adaptive Design

Developed / Innovative Design

Inventive / New Design

Pec / DoME / MP / Design of Transmission Systems/Contents 2

OBJECTIVE To gain knowledge on the principles and procedure

for the design of Power Transmission components.

To understand the standard procedure available

for Design of Transmission sip terms

To learn to use standard data and catalogues


Unit - IDESIGN OF TRANSMISSION SYSTEMS

FOR FLEXIBLE ELEMENTS 9

Selection of V belts and pulleys

selection of Flat belts and pulleys

Wire ropes and pulleys

Selection of Transmission chains and Sprockets

Design of pulleys and sprockets.


Unit – I Cont….Flexible Machine Elements – Belts, Ropes, Chains Belts Pulleys are mounted on Shafts Continuous belt or rope is passed over them Amount Power transmitted depends upon several

factors For example Velocity of belt, Tension in the belt, Mass

of the belt, Arc of Contact between the belt & Smaller pulley


Belts Cont….

Types of Flat Belt DrivesOpen Belt Drive

Shafts Parallel & Rotating in same direction

Open Belt Drive with one idler Small angle of contact on smaller pulley To increase Idler pulleys are provided

Open Belt Drive with many idlers Used to transmit motion from one shaft to several parallel

shafts

Crossed / Twisted Belt DriveCompound Drive


Pulley

Velocity Ratio depends on pulley diameter

Should be selected very Carefully


Belt Drive . . .

V- Belts and Pulleys Mostly used with electric motors to drive

blowers, compressors, appliances (like Mixer,

grinder), Machine Tools

Run in Sheaves

V - belts made of Trapezoidal section

Power transmission due to wedging action

between the belt & the V - groove in the Pulley

(Sheave).

V- Belts and Pulleys Cont . . .

Groove angle in sheave is less than

Belt section Angle

Clearance at bottom to prevent bottoming

Multiple V-Belts can be used to increase the

power capacity

High Velocity Ratio

Can operate in any position

Construction of V- grooved pulley is complicated

& CostlierPec / DoME / MP / Design of Transmission Systems/Contents 10

Pulley Material Cast iron

Economical, Stable, Durable

Steel Pressed steel, Formed steel

Die cast Aluminium

V- Belts and Pulleys Cont….

Belt Drives

Belt Drives Cont…. Advantages

Low initial cost Easy, flexible equipment design, as tolerances are not

important. Used for connecting shafts that are apart by large distance Drive is protected against overloads Isolation from shock and vibration between driver and

driven system. Driven shaft speed conveniently changed by changing

pulley sizes. Belt drives require no lubrication. Maintenance is relatively convenient Very quiet compared to chain drives, and direct spur gear

drives

Belt Drives Cont….

Disadvantages Occupies more space It is not possible to get accurate velocity

ratio, because of slip Efficiency is less than that of gear drive Shorter life

Belts are subjected to repeated (fatigue) loading i.e., repeated flexing, as they pass over pulley

Belt Drives Cont…. Belt Types

Based on belt cross section Flat-belt drive V- belt drive Round belt drive

Flat belt Drive Open belt drive Crossed belt drive Quarter turn drive Fast and loose pulley drive Stepped pulley drive Belt drive with an idler pulley

Belt Drives Cont…. Belt Materials

LeatherCotton and canvasRubberNylon core BeltsBalata Belts

Design by Manufacturer’s Data / Standard Procedure

Design by Basic Equations

Wire Ropes Used whenever large power is to be transmitted over

long distances

Used in elevators, oil well Drilling, Mine hoists, cranes

conveyors, tramways, Bridges(Suspension)

Material handling equipments

Lighter weight & high strength to weigh ratio

Silent operation even at high working speeds

Less Danger for damage due to jerks

Material: Wrought iron, Cast steel, Alloy Steel

Wire Ropes Sheaves & Drums

Wire Ropes Cont…

Construction and specification

Wire Ropes Cont…

Wire Ropes Cont…

Wire rope construction"

is designated 6x19 FC

RH OL FSWR

Wire Ropes Cont…

6 Number of strands that make up the rope

19 Number of wires that make up each strand

FC Fibre core

RH Right hand lay

OL Ordinary lay

FSWR Flexible steel wire rope

Designated as 6x19 FC RH OL FSWR

Chain Drives Between Belt & Gear Drive Has the adv. Of both Belt & Gear Drive Velocity Ratio less than 10, 25m/sec,125kW Popularly used in Transportation, Agriculture,

Building construction, Material handling equipment.

One chain can be arranged to drive several sockets

Can be operated under adverse temp. & atmospheric conditions

Chain Drives Cont…

Require precise alignment of shafts than the belt drives

Require take-up devices Types

Link Chain / WeldedTansmission / Roller chainSilent Chain

Chain Drives Cont…

Unit – I

For Exam

V-Belt & Chain Drive

Unit – I ISPUR GEARS AND PARALLEL AXIS

HELICAL GEARS (9)Gear Terminology

Speed ratios and number of teeth

Force analysis

Tooth stresses

Dynamic effects

Fatigue strength

Factor of safety

Unit – I I Cont….

Gear materials

Module and Face width

Power rating calculations based on strength and wear

considerations

Parallel axis Helical Gears

Pressure angle in the normal and transverse plane

Equivalent number of teeth-forces and stresses.

Estimating the size of the helical gears

Spur Gears

Toothed wheels used for transmitting Motion &

Power

Constant Velocity Ratio

Can operate at high speeds & Can be used

where precise timing is required

Large Power

Spur Gears Cont… Advantages

No Slip, Exact velocity Ratio is obtained Can transmit motion at very low velocity

Limitations Manufacturing needs special tools & equipments Manufacturing and Maintenance costs are

comparatively high

Material Steel, Cast Iron, Bronze, Non metallic

Spur Gears Cont…

Helical Gears Initial contact upon meshing is a line contact –

Spur gears Produces shock effect Results in reduced load capacity Noisy in operation

Initial contact is a point Becomes a line of increasing length as contact continuous

Simple modification of ordinary spur gears

Teeth in form of helix around the gear

Helical Gears Cont…..

End thrust in addition to tangential and radial loads

To avoid we can use Herringbone gears

Helical gears of opposite hands are mounted in pairs on a shaft.

Noise , Load carrying capacity

Automobiles, Turbines & high speed applications

Noise , Load carrying capacity

Helical Gears Cont…

Gears ! ! !

THANK YOU

39Pec / DoME / MP / Design of Transmission Systems/Contents

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