A

PROJECT REPORT

ON

KINEMATICS WALKER

Submitted in partial fulfilment of the requirements for the award of the degree of

bachelor of engineering

IN

MECHANICAL ENGINEERING

R.P.INDERPRASTHA INSTITUTE OF TECHNOLOGY

BASTARA,KARNAL

Session 2011-2014

Under the Guidance of: Submitted by:

Er. Digvijay Rana Ankush Sharma-5710754

Submitted to:

H.O. D. Kapil Monga

ACKNOWLEDGEMENT

Words are inadequate and out of place at times particularly in the context of expressing sincere

feeling in the contribute of this work,is no more than a more ritual.It is our privilege to

acknowledgement with respect and gratitude, the keen valuable and ever available guidance

render to me by Er. Digvijay Rana without the wise counsel and able guidance. It would have

been impossible to complete the thesis in this manner.

We shall always be highly great full to H.O. D. Kapil Monga sir for providing this opportunity to

carry out the present research work. The constant guidance and encouragement received from the

Head Department of Mechanical Engineering has been of great help in carrying out the present

work and is acknowledged and with reverential thanks.

We express gratitude to other faculty member of Mechanical Engineering Department R.P.I.I.T.

for their intellectual support throughout of this work.

Finally, we are indebted to our family and for their ever available help in accomplishing this task

successfully.

Above all we are thankful to the almighty god for giving strength to carry out the present work.

1. Saurabh Gupta-5710733

2. Aman Kundu-5710730

3. Ravikant Rana-5710734

4. Ankush Sharma-5710754

5. Santokh Singh-5710763

CERTIFICATE

Certified that Saurabh Gupta (5710733) Aman Kundu (5710730) Ravikant Rana (5710754) Ankush Sharma (5710754) Santokh Singh (5710763) are students of B.Tech Mechanical Engineering. They have done their project on “KINEMATICS WALKER” under my guidance.

Students have put their sincere efforts and I wish them all the best for the future.

Er. Digvijay Rana

CONTENTS PAGE NO.

ACKNOWLEDGEMENT 1

CERTIFICATE 2

ABSTRACT 4

CHAPTER-1 5-20

INTRODUCTION

1.1 INTRODUCTION 1.2 PRACTICALITY AND COMPLEXITY OF CONSTRUCTION

1.3 HARDWARE

1.4 COMPONENT DETAIL

1.4.1 CHASSIS 1.4.1.1 FRAME

1.4.1.2 LEGS

1.5 D.C GEAR REDUCTION MOTOR

1.6 SPECIFICATION

1.7 TIMING GEAR

1.8 TIMING CHAIN

1.9 BEARINGS

1.10 CRANKSHAFT 1.11 FASTENERS

1.12 INFUSION SET

1.13 MOVEMENT

1.14 OPERATION

CHAPTER-2 21-31

CHAIN DRIVES

2.1 INTRODUCTION

2.2 CHAIN

2.3 EFFICIENCY

2.4 MAINTENANCE

2.4.1 REMOVAL

2.4.2 WEAR

2.4.3 SIZES

2.4.4 WIDTH

2.4.5 LENGTH

2.5 VARIATIONS

2.6 MANUFACTURERS

2.7 CHAIN TOOL

2.8 APPLICATIONS OF CHAIN DRIVES

2.9 MOTORISED CHAIN PULLEY SYSTEM

2.10 ADVANTAGES OF CHAIN DRIVE

2.11 DISADVANTAGES OF CHAIN DRIVE

2.12 RELATION BETWEEN PITCH AND PITCH CIRCLE DIAMETER

CHAPTER-3 32-43

BELT AND PULLEY

3.1 INTRODUCTION

3.1.1 BELT AND PULLEY SYSTEMS

3.1.2ROPE AND PULLEY SYSTEMS

3.2 TYPES OF SYSTEMS

3.3 HOW ITS WORKING

3.4 II WORK AND MECHANICAL ADVANTAGE

3.5 III PULLEY SYSTEMS

3.6 A BLOCK AND TACKLE

3.6.1 BLOCK AND TACKLE

3.7 OVERVIEW

3.8 MECHANICAL ADVANTAGE

3.9 FRICTION

3.10 RIGGING METHODS

CONCLUSION 44

LIST OF FIGURES PAGE NO.

TOP VIEW OF FRAME 7

VIEW OF LEGS 8

TOP VIEW OF DC GEAR MOTOR 9

DIMENSIONAL VIEW OF DC GEAR MOTOR 10

GRAPH OF DC GEAR MOTOR 11

TIMING GEAR 12

TIMING CHAIN 13

BEARING 14

CRANKSHAFT 16

FASTENERS 17

INFUSION SET 18

MOMENT MECHANISM 19

WORKING ANALYSIS 20

CHAIN DRIVE 22

SCREW NUT 27

MOTORIZED CHAIN PULLEY 29

FIXED PULLEY 34

BLOCK AND TACKLES 40

ABSTRACT

This project involves the design and fabrication of a kinematics walker. This kinematics walker

is eight leg machines that can walk on any surfaces. It is arrangement of eight linkages that are

power together by a single motor. This device is analogues to a eight legged insect such as

spider. The motor can either be powered by mains or battery. The kinematics walker comprises

eight legs that move simultaneously to provide motion. Each of these eight linkages are made of

a four bar mechanism.

CHAPTER-1

INTRODUCTION

1.1 INTRODUCTIONThe concept of a mission capable legged robot is acquiring an ever increasing interest in the field

of explorative robotics. On one hand legged robots would possess clear advantages over wheeled

robots like obstacle climbing capability and mechanical graceful degradation, on the other hand

their development has been hampered by the challenging task of actually implementing an

efficient structure and designing an effective four bar mechanism.

1.2 PRACTICALITY AND COMPLEXITY OF CONSTRUCTIONThe design process used in developing the parts of the hexapod considers the level of difficulty

associated with building the different sections of the hexapod robot. Cost, complexity and

functionality were thoroughly considered during the design in order to keep the built product

practical. The scope and design for the project has been scaled to fit the budget that is outlined in

the budget section of this report.

The design uses common, available materials for the machined components along with

purchased parts such as electronics and robotics available from supply stores. It is an innovative

and practical design, which improves on previous hexapod designs. By using shapes that can be

easily manufactured we have decreased the machining time needed. Simple fasteners such as

glue/epoxy and standard sized screws/bolts will be used to assemble the finished product.

1.3 HARDWAREDC Gear motor will provide the moving force for this robot. Single DC Gear Reduction motor

has been used to determine their suitability. Weight, torque, and power consumption have been

measured and compared. The ideal DC Gear Motor for our application is readily available and

has been selected to be sourced.

The basic requirement of this robot is low speed and high torque which is been accomplished by

using this DC Gear Motor.

For pick and place mechanism (Robotic Arm) a principal of Hydraulics is used. Here the

combination of injections and infusion set is used in place of Hydraulic

Cylinder, Pistons and Gear Pumps etc.

1.4 COMPONENT DETAILA brief explanation of the robots key components is provided below.

1.4.1 CHASSIS

1.4.1.1 FRAMEThe frame of the robot consists of four Iron plates that are bolted together using one shaft and

two crankshafts as illustrated in Figure 1. All metal strips are of equal lengths and are placed

parallel to each other. These metal strip are equispaced and two crankshafts are placed at two

ends and between these crankshafts a central shaft is placed to help the metal strip to be

equispaced.

Fig 1

TOP VIEW OF FRAME

1.4.1.2 LEGSEach of the six legs are connected by the two crankshafts placed between the chassis as shown in

Figure 2. These legs are made up of wood and are rectangular in shape three legs are placed at

each of the crankshafts. Out of three, one has the backward motion whereas remaining two

consists of the forward motion. So the four legs will move in one direction and the centered two

legs will move in the opposite direction so as to stabilize the balance of a robot.

Fig 2

VIEW OF LEGS

1.5 D.C GEAR REDUCTION MOTORA gear motor’s purpose is to act as a power transmission component. As such, the two most

important factors at the gearbox output shaft are its speed (in rpm) and how much work it can do,

as determined by the amount of torque it produces. Typically, gearboxes serve to take motor

power, reduce its speed, and magnify its torque. However, when attempting to size a gear motor

for a specific application, focus on the speed and available torque at the gearbox’s output shaft

Fig 3

VIEW OF D.C GEAR MOTOR

Know the basics: The gear sets (or gear train) inside a gearbox provide a mechanical advantage

that multiplies torque from the input side to the gearbox output shaft. This mechanical advantage

is called the gearbox ratio, and is the number used to determine the torque multiplication from

input to output. For example, a gearbox ratio of 30:1 means that the output side is about 30 times

more forceful than the input side. So, if a gearmotormust generate 30 in.-lb full load

Torque at its output shaft, then input torque must be 1.0 in.-lb. (This simple example does not

account for the gear train’s internal losses as measured by its overall efficiency.) Once input

torque requirement is known, it’s easy to calculate the required motor input hp needed, based on

motor input speed.

1.6 SPECIFICATION

TABLE NO. 1

Torque Speed

25 kg-cm 22 rpm

TABLE 1: SPECIFICATION OF D.C GEAR MOTOR

Fig 4

DIMENSIONAL FIG. OF D.C GEAR MOTOR

N

P

I

η

Fig 5

12V-24V

Graph of D.C Gear Motor Where N = SPEED

P = POWER

I = CURRENT

η = EFFICIENCY

1.7 TIMING GEAR

A gear is a rotating machine part having cut teeth, or cogs, which mesh with another toothed part

in order to transmit torque. Two or more gears working in tandem are called a transmission and

can produce a mechanical advantage through a gear ratio and thus may be considered a simple

machine. Geared devices can change the speed, magnitude, and direction of a power source. The

most common situation is for a gear to mesh with another gear, however a gear can also mesh a

non-rotating toothed part, called a rack, thereby producing translation instead of rotation.

Fig 6

TIMING GEARS

The gears in a transmission are analogous to the wheels in a pulley. An advantage of gears is that

the teeth of a gear prevent slipping.

When two gears of unequal number of teeth are combined a mechanical advantage is produced,

with both the rotational speeds and the torques of the two gears differing in a simple relationship.

In transmissions which offer multiple gear ratios, such as bicycles and cars, the term gear, as in

first gear, refers to a gear ratio rather than an actual physical gear. The term is used to describe

similar devices even when gear ratio is continuous rather than discrete, or when the device does

not actually contain any gears, as in a continuously variable transmission

1.8 TIMING CHAINTiming chain, flexible series of connected links used in various ways, especially for the

transmission of motive power, for hoisting and for securing or fastening. Commonly, mechanical

energy from a motor or other source applied to a sprocket wheel is conveyed by means of an

endless chain to another sprocket wheel for driving a mechanism. Examples of such an

arrangement are found in bicycles, motorcycles, and conveyor belts. The chain in this application

is so designed that each consecutive link fits over a sprocket, the distance between links being

called the pitch. The relative speed of the wheels varies according to their relative

circumferences and, thus, the number of sprockets on each. There are several types of chain for

the transmission of power. A detachable-link chain has links that are simple rectangles, each with

a connecting hook at one end by which it is attached to the next link. A pintle chain has links that

are approximately U-shaped. The closed end of each link fits into the open end of the next one; a

pin holds the two links together. A block chain consists of metal blocks that are joined together

by side plates and pins to form links.

Fig 7

TIMING CHAIN

A roller chain has links consisting of side plates with hollow cylindrical rollers between them.

Pins pass through the rollers and side plates to hold the links together. A silent, or inverted-tooth,

chain has links made of toothed metal plates. A number of these links are placed side by side to

form a group. Each group is joined to another one by meshing the ends of the links of both

groups and inserting a pin there. By repeating the process a chain can be formed. Its width can be

varied by varying the number of links in a group. Although not completely silent, this type of

chain is quieter than other power transmission chains. The coil chains used in hoists and for

locking or fastening purposes are of the open-link type, comprising solid interlocked rings, or of

the stud-link type, in which a stud, or bar, across the link keeps the chain from kinking.

1.9 BEARINGSBearing, machine part designed to reduce friction between moving parts or to support moving

loads. There are two main kinds of bearings: the antifriction type, such as the roller bearing and

the ball bearing, operating on the principle of rolling friction; and the plain, or sliding, type, such

as the journal bearing and the thrust bearing, employing the principle of sliding friction. Roller

bearings are either cylindrical or tapered (conical), depending upon the application; they

overcome frictional resistance by a rolling contact and are suited to large, heavy assemblies. Ball

bearings are usually found in light precision machinery where high speeds are maintained,

friction being reduced by the rolling action of the hard steel balls. In both types the balls or

rollers are caged in an angular grooved track, called a race, and the bearings are held in place by

a frame, commonly called a pillow block or Plummer block. Ball bearings or roller bearings

reduce friction more than sliding bearings do. Other advantages of antifriction bearings include

ability to operate at high speeds and easy lubrication.

Fig 8

BEARING

A journal bearing usually consists of a split cylindrical shell of hard, strong metal held in a rigid

support and an inner cylindrical part of soft metal, which holds a rotating shaft, or journal. A

self-aligning journal bearing has a spherically shaped support that turns in a socket to adjust to

movements of the shaft. Slight misalignment of the shaft can be accommodated in the ordinary

journal bearing by wearing of the soft bearing material, often an alloy of tin or lead. Less

frequently used are aluminum alloys, steel, cast iron, or a thin layer of silver covered with a thin

coating of a soft bearing material. Ideally, a film of lubricant, normally oil, separates journal and

bearing so that contact is prevented. Bearings that are not split are called bushings.

A thrust bearing supports an axial load on a shaft, i.e., a force directed along a shaft's length. It

may be a plate at the end of a shaft or a plate against which the collar on the shaft pushes. Large

thrust bearings, such as those used to transmit the motive force of a ship's propeller from the

shaft to the hull, have blocks that are separated from the collar on the shaft by wedge-shaped

spaces filled with oil. Graphite bearings are used in high-temperature situations. Certain plastics

make satisfactory self-lubricating bearings for low speeds and light loads and, if additionally

lubricated, work at higher speeds and carry greater loads. Rubber and a naturally oily wood,

lignum vitae, are used in water-lubricated bearings. Watches and other precision instruments

have glass or sapphire pivot bearings. In gas-lubricated bearings a film of gas separates the

bearings from the moving machine parts. Magnetic bearings employ magnetic repulsion to

separate journal from bearing, reducing friction still further.

1.10 CRANKSHAFTHere the crankshaft is used to convert motion from rotary to oscillatory motion. The legs are

mounted with the crankpin which is required for the movementt of robo

Fig 9

CRANKSHAFT

1.11 FASTENERSIn fabrication, connectors between structural members. Bolted connections are used when it is

necessary to fasten two elements tightly together, especially to resist shear and bending, as in

column and beam connections. Threaded metal bolts are always used in conjunction with nuts.

Another threaded fastener is the screw, which has countless applications, especially for wood

construction. The wood screw carves a mating thread in the wood, ensuring a tight fit. Pins are

used to keep two or more elements in alignment; since the pin is not threaded, it allows for

rotational movement, as in machinery parts. Riveted connections, which resist shearing forces,

were in wide use for steel construction before being replaced by welding. The rivet, visibly

prominent on older steel bridges, is a metal pin fastener with one end flattened into a head by

hammering it through a metal gusset plate. The common nail, less resistant to shear or pull-out

forces, is useful for cabinet and finishing work, where stresses are minimal.

Fig 10

FASTENERS

Flanges, grunions, and/or clevises are mounted to the cylinder body. The piston rod also has

mounting attachments to connect the cylinder to the object or machine component that it is

pushing.

A hydraulic cylinder is the actuator or “motor” side of this system. The “generator” side of the

hydraulic system is the hydraulic pump which brings in a fixed or regulated flow of oil to the

bottom side of the hydraulic cylinder, to move the piston rod upwards. The piston pushes the oil

in the other chamber back to the reservoir. If we assume that the oil pressure in the piston rod

chamber is approximately zero, the force F on the piston rod equals the pressure P in the cylinder

times the piston area A:

.

The piston moves instead downwards if oil is pumped into the piston rod side chamber and the

oil from the piston area flows back to the reservoir without pressure. The pressure in the piston

rod area chamber is (Pull Force) / (piston area – piston rod area)

1.12 INFUSION SETHere the infusion Set is used to transmit pressurized fluid from one injection to another instead

of fluid pipelines.

Fig 11

INFUSION SET

1.13 MOVEMENT

It consists of the assembly of following components:

Crankshaft

Wooden Legs

Fixed Link

Hinged Link

Gear Chain Assembly

Gear Motor

Fig 12

MOVEMENT MECHANISM

1.14 OPERATION

The diagram below shows the leg numbering system for the robot.

Fig 13

WORKING ANALYSIS

Each leg has two muscles, one to pull it back and one to lift it.

A standard walking pattern has been designed which is built into the software. This is the

walking pattern used when the 'Move Data' method of control is selected.

In order to walk a whole series of muscle control instructions is given. The pattern for walking

forwards normally is as follows:-

Lift legs 0, 2 and 4.

Pull back legs 1, 3 and 5 to push robot forwards.

Lower legs 0, 2 and 4.

Lift legs 1, 3 and 5.

Move legs 1, 3 and 5 forward to reset them.

Pull back legs 0, 2 and 4 to push robot forwards.

Lower legs 1, 3 and 5.

Lift legs 0, 2 and 4.

Move legs 0, 2 and 4 forward to reset them.

Lower legs 0, 2 and 4.

CHAPTER-2

CHAIN DRIVES

2.1 INTRODUCTION

The chains are made up of rigid links which are hinged together in order to provide the necessary

flexibility for warping around the driving and driven wheels. The wheels have projecting teeth

and fit into the corresponding recesses, in the links of the chain as shown in fig.

The wheels and the chains are thus constrained to move together without slipping and ensures

perfect velocity ratio. The toothed wheels are known as sprocket wheels.

These wheels resemble to spur gears. The chains are mostly used to transmit the motion and power from one shaft to another, when the distance between the centres of shaft in short such as in bicycles, motor cycles, agricultural machinery, road rollers etc.

2.2 CHAIN

A bicycle chain is a roller chain that transfers power from the pedals to the drive-wheel of a

bicycle thus propelling it. Most bicycle chains are made from plain carbon or alloy steel, but

some are chrome plated or stainless steel to prevent rust or simply for aesthetics.

Fig 14

2.3 EFFICIENCY

A chain as used on a bicycle can be very efficient. Efficiencies of 98.6% have been measured [1]

Surprisingly, lubrication of the chain didn't affect efficiency of the chain much; "The role of the

lubricant, as far as we can tell, is to take up space so that dirt doesn't get into the chain".[1] A

larger sprocket will give a more efficient drive (reduces the movement angle of the links).

Surprisingly, higher chain tension was found to be more efficient; "This is actually not in the

direction you'd expect, based simply on friction".[1]

2.4 MAINTENANCE

Fig 15

Chain lubrication is a common problem for cyclists. Liquid lubricants penetrate to the inside of

the links and are not easily displaced, but quickly attract dirt. "Dry" lubricants, often containing

wax or Teflon, have poor penetrating qualities unless carried in an evaporating solvent, but stay

cleaner in use. The cardinal rule for long chain life is never to lubricate a dirty chain, as this

washes abrasive particles into the rollers. Chains should be cleaned before lubrication. The chain

should be wiped dry after the lubricant has had enough time to penetrate the links. An alternative

approach is to change the (relatively cheap) chain very frequently; then proper care is less

important. Some utility bicycles have fully-enclosing chain guards which virtually eliminate

chain wear and maintenance. On recumbent bicycles the chain is often run through tubes to

prevent it from picking up dirt, and to keep the cyclists leg free from grease and dirt.

2.4.1 REMOVAL

On most upright bicycles, the chain loops through the right rear triangle made by the right chain

stay, right seat stay, and seat tube. Thus a chain must be “broken” with a chain tool or at a master

link (also known as a connecting link), which typically has one pin held by a C clip, allowing it

to be inserted or removed with simple tools, to be removed for cleaning or replacement.

2.4.2 WEAR

Chain wear, or chain stretch, becomes an issue with extensive cycling. Although the overall

effect is often called "stretch", chains generally wear through attrition of the bushings (or half-

bushings, in the Sides design) and not by elongation of the side plates. The tension created by

pedaling is insufficient to cause the latter. Because an old chain is longer than needed, its links

will not precisely fit the spaces between teeth in the drive train, making gear shifts a problem and

possibly resulting in a 'skipping' chain that reduces power transfer and makes pedaling very

uncomfortable.

Twenty half-links in a new chain measure 10" (254 mm), and replacement is recommended

before the old chain measures 256 mm (0.7% wear). A safer time to replace a chain is when 24

half-links in the old chain measure 121/16 inches (0.4% wear). If the chain has worn beyond this

limit, the rear sprockets are also likely to wear, in extreme cases followed by the front chain

rings. Replacing worn sprocket cassettes and chain rings after missing the chain replacement

window is much more expensive.

2.4.3 SIZES

The chain in use on modern bicycles has a 1/2” pitch, which is ANSI standard #40, where the 4

indicates the pitch of the chain in eighths of an inch, and metric #8, where the 8 indicates the

pitched in sixteenths of an inch.

2.4.4 WIDTH

Chain comes in either 3/32”, 1/8”, 5/32” or 3/16” roller widths: 5/32” is used on cargo bikes and

tricks, 1/8” with the common low cost coaster (back pedal brake) bike, hub and fixed gearing and

on track bicycles, and 3/32” with the derailleur gears most commonly fitted on racing, touring

and mountain bikes.

The Wiki book “Bicycle Maintenance and Repair” explains that the difference between

derailleur chains commonly labeled 8-speed, 9-speed, and 10-speed is in its external width (all

are 3/32” chains).

2.4.5 LENGTH

New chains usually come in a stock length, long enough for most upright bike applications. The

appropriate number of links must be removed before installation in order for the drive train to

function properly. The pin connecting links can be pushed out with a chain tool to shorten, and

additional links may be added to lengthen.

In the case of derailleur gears the chain is usually long enough so that it can be shifted into the

biggest front chain ring and the biggest rear cog without jamming, and not so long that, when

shifted into the smallest front chain ring and the smallest rear cog, the rear derailleur cannot take

up all the slack. Meeting both these requirements is not always possible.

In the case of single-speed bicycle and hub gears, the chain length must match the distance

between crank and rear hub and the sizes of the front chain ring and rear cog. These bikes

usually have some mechanism for small adjustments such as horizontal dropouts, track ends, or

an eccentric mechanism in the rear hub or the bottom bracket. In extreme cases, a chain half-link

may be necessary.

2.5 VARIATIONS

In order to reduce weight, chains have been manufactured with hollow pins and with cut-outs in

the links.

2.6 MANUFACTURERS

Bicycle chains are made by companies such as:

Campagnolo

Rohloff AG

KMC

Shimano

SRAM

2.7 CHAIN TOOL

A chain tool is a small mechanical device used to "break" a bicycle chain in such a way that it

can be mended with the same tool. A bicycle chain has links and plates that are pinned together;

these pins can be pushed partway out with the chain tool.

This tool is required for removal and installation of some types of chains on a bicycle, for

maintenance or replacement. Some chains used on bicycles with a single front chaining and rear

sprocket, for example bicycles with hub gears or coaster brake hubs, do not require this as they

have a master link on the chain which holds the pin in place with an easily removable c-clip; this

protrudes, however, and would interfere with the smooth operation of a derailleur system. Some

recent derailleur chains have a special link which does not protrude that could be used to break

the chain without tools. However, this tool is needed should it be necessary to lengthen or

shorten any type of chain.

Fig 16

2.8 APPLICATIONS OF CHAIN DRIVES

As can be seen, the chain tool has two positions where a chain can be inserted perpendicular to

the tool, one close to the movable screw portion, and one lower down just above the fixed end. In

each position, there are a pair of protruding "ears"; one fits into the centre of one link of the

chain, the other fits into the centre of the next link, holding the pin between the links aligned in

the centre of the groove running down the centre of the tool, so that the tip of the movable screw

can press vertically on the end of the pin. The end of the screw is slightly narrower than the pin,

so that it can press the pin through the link. Often the end of the screw is a removable piece

which can be replaced when worn.

In use, the chain is first placed into the lower position of the tool and the screw is turned in,

pressing the pin through the top plate of the outer link and almost all the way through the centre

of the roller on the inner link, leaving just enough pin protruding that the inner link can be

snapped free with a bit of pressure. This leaves the pin still aligned firmly vertical by the bottom

plate; the pin should never be totally pushed through the bottom plate because it is then no longer

fixed in the vertical axis and becomes almost impossible to re-insert. Even if the pin is merely

pressed flush with the bottom plate it becomes more difficult to work with, as the chain now has

to be held in alignment during reassembly, in contrast to leaving just enough of the pin

protruding into the inner link to allow it to be snapped together by hand.

To reassemble, the chain is placed in position on the bicycle and the inner link snapped over the

pin as described; the screw on the tool is now backed almost all the way out, and the chain is

once more placed on the lower position of the tool, but reversed: this time with the pin

protruding upwards, towards the screw. Now the screw is turned in again, pressing the pin down

but this time inwards through the roller and back into the other outer plate, leaving the chain

assembled as it was in the first place. Examination of the relative amount of protrusion of the pin

on either side of the outer links of the chain determines when to stop.

Now, the upper position of the tool, with the chain held next to the screw, comes into play. The

previous reassembly procedure usually leaves the outer plates of that link of the chain pressed

tightly against the roller of the inner plates; these results in a "stiff link" which will tend to skip

when shifting. To relieve this condition, the screw is backed almost all the way out once again,

and the link of chain with the just-inserted pin is moved to the upper position of the tool. The

screw is now advanced again, but only slightly, to press the pin forward just a tiny amount. Since

the lower outer plate is not supported in this position of the chain on the tool, the pin is not

pressed through the lower plate but only through the upper plate. Instead, the lower plate moves

with the pin, relative to the upper plate, creating a larger separation; a very small movement is

enough to release the pressure of the outer plates against the inner plates, freeing the "stiff link".

This procedure can be used to free any "stiff links" which occur spontaneously, as well.

Some chain tools lack the "ears" in the upper position. Stiff links can sometimes be loosened

without a chain tool, by bending the chain left and right.[1]

The tool is used similarly either to remove a segment of chain to shorten it, or to join two

segments of chain to make a longer one. If neither piece to be joined has a pin protruding from

one side to enable it to be joined in this fashion, then one inner link must be removed, leaving

that pin protruding for use to join to the other segment of chain.

The design pictured here is for chains where the links have flat plates. For chains with

complicated shaped plates designed to facilitate smooth shifting, specific chain tools are

available which are identical in design and operation, but have the ears protruding into the chain

shaped in cross section to fit the links of the particular chain in question precisely, so as to hold

the pin in the all-important vertical alignment with the screw of the tool.

If you do push the pin too far and it comes completely free of the chain, you can re-insert it into a

flat plate by putting the flat plates against a hard surface with an appropriately sized Allen

wrench between the holes in the plates, then tapping the pin into the top plate with a small

hammer.

2.9 MOTORISED CHAIN PULLEY SYSTEM

A pulley (also called a sheave or block) is a wheel with a groove between two flanges around its

circumference. A rope, cable or belt usually runs inside the groove. Pulleys are used to change

the direction of an applied force, transmit rotational motion, or realize a mechanical advantage in

either a linear or rotational system of motion.

FIG 17

2.10 ADVANTAGES OF CHAIN DRIVE

1. As no slip takes place during chain Drive, hence perfect velocity ratio is obtained.

2. Since the chains are made of metal, therefore they occupy less space in width than a belt.

3. The chain drive may be used when the distance between the shaft is less.

4. The chain drive gives a high transmission efficiency up to 98 %.

5. The chain drive gives less load on the shafts.

6. The chain drive has the ability to transmitting motion to several shafts by one chain only.

2.11 DISADVANTAGES OF CHAIN DRIVE

1. The production cost of chains is relatively high.

2. The chain drive needs accurate mounting and careful maintenance.

3. The chain drive has velocity fluctuations especially when unduly stretched.

2.12 RELATION BETWEEN PITCH AND PITCH CIRCLE DIAMETER

Since the links of the chains are rigid, therefore pitch of the chain does not lie on the arc of the

pitch circle. The pitch length becomes a chord. Consider one pitch length AB of the chain

subtending an angle at the centre of sprocket.

Let d = dia. Of the pitch circle and=4cm

T = No. Of teeth on the sprocket=10.

Pitch of the chain,

P=AB=2AOsin(ᶱ/2)=2* d/2sin(ᶱ/2)= d sin(ᶱ/2)=1.23

We know that ᶱ=360/T

P= d sin(360/2T)= d sin(180/T)=1.25

Or d= p cosec(180/T)=1.18

And length of the chain,

L=π(r1+r2)+2x+((r 1−r 2 ) 2/ x)

L=72cm.

CHAPTER-3

BELT AND PULLEY

3.1 INTRODUCTION

3.1.1 BELT AND PULLEY SYSTEMS

Belt and pulley system A belt and pulley system is characterized by two or more pulleys in common to a

belt. This allows for mechanical power, torque, and speed to be transmitted across axes and, if the pulleys

are of differing diameters, a mechanical advantage to be realized.

A belt drive is analogous to that of a chain drive, however a belt sheave may be smooth (devoid of

discrete interlocking members as would be found on a chain sprocket, spur gear, or timing belt) so that

the mechanical advantage is given by the ratio of the pitch diameter of the sheaves only (one is not able to

count 'teeth' to determine gear ratio).

Belt and pulley systems are systems that can be very efficient, with stated efficiencies up to 98%.

3.1.2ROPE AND PULLEY SYSTEMS

An easy pulley is a rope around a tree. Rope and pulley systems (the rope may be a light line or a strong

cable) are characterized by the use of one rope transmitting a linear motive force (in tension) to a load

through one or more pulleys for the purpose of pulling the load (often against gravity.) They are often

included in the list of simple machines. In a system of a single rope and pulleys, the mechanical

advantage gained is ideally the number of pulleys in the system (if one pulley is used only to change the

direction of the load). The tension in the rope is reduced by the mechanical advantage, while the distance

(that is, the length of rope) is increased by the same proportion. Since a slender cable is more easily

managed than a fat one (albeit shorter and stronger), pulley systems are often the preferred method of

applying mechanical advantage to the pulling force of a winch (as can be found in a lift crane).

In practice, the more pulleys there are, the less efficient a system is. This is due to sliding friction in the

system where cable meets pulley and in the rotational mechanism of each pulley.

It is not recorded when or by whom the pulley was first developed. It is believed however that

Archimedes developed the first documented block and tackle pulley system, as recorded by Plutarch.

Plutarch reported that Archimedes moved an entire warship, laden with men, using compound pulleys and

his own strength.

3.2 TYPES OF SYSTEMS

These are different types of pulley systems:

Fixed pulley

Movable pulley

Fixed A fixed or class 1 pulley has a fixed axle. That is, the axle is “fixed” or anchored in place. A fixed

pulley is used to change the direction of the force on a rope (called a belt). A fixed pulley has a

mechanical advantage of 1. A mechanical advantage of one means that the force is equal on both sides of

the pulley and there is no multiplication of force.

Movable A movable or class 2 pulley has a free axle. That is, the axle is “free” to move in space. A

movable pulley is used to multiply forces. A movable pulley has a mechanical advantage of 2. That is, if

one end of the rope is anchored, pulling on the other end of the rope will apply a doubled force to the

object attached to the pulley.

Compound A compound pulley is a combination fixed and movable pulley system.

Block and tackle – A block and tackle is a compound pulley where several pulleys are mounted on each

axle, further increasing the mechanical advantage.

FIG 18

3.3 HOW ITS WORKING

Diagram 1 – A basic equation for a

pulley: In equilibrium, the force F on

the pulley axle is equal and opposite

to the sum of the tensions in each line

leaving the pulley, and these tensions

are equal.

Diagram 2 – A simple pulley

system – a single movable

pulley lifting weight W. The

tension in each line is W/2,

yielding an advantage of 2.

Diagram 2a – Another

simple pulley system

similar to diagram 2, but in

which the lifting force is

redirected downward.

FIG 19

The simplest theory of operation for a pulley system assumes that the pulleys and lines are weightless,

and that there is no energy loss due to friction. It is also assumed that the lines do not stretch.

A crane using the compound pulley system yielding an advantage of 4. The single fixed pulley is

installed on the crane. The two movable pulleys (joined together) are attached to the hook. One end of the

rope is attached to the crane frame, another – to the winch. In equilibrium, the total force on the pulley

must be zero. This means that the force on the axle of the pulley is shared equally by the two lines

looping through the pulley. The situation is schematically illustrated in diagram 1. For the case where the

lines are not parallel, the tensions in each line are still equal, but now the vector sum of all forces is zero.

A second basic equation for the pulley follows from the conservation of energy: The product of the

weight lifted times the distance it is moved is equal to the product of the lifting force (the tension in the

lifting line) times the distance the lifting line is moved. The weight lifted divided by the lifting force is

defined as the advantage of the pulley system.

It is important to notice that a system of pulleys does not change the amount of work done. The work is

given by the force times the distance moved. The pulley simply allows trading force for distance: you pull

with less force, but over a longer distance.

In diagram 2, a single movable pulley allows weight W to be lifted with only half the force needed to lift

the weight without assistance. The total force needed is divided between the lifting force (red arrow) and

the “ceiling” which is some immovable object (such as the earth). In this simple system, the lifting force

is directed in the same direction as the movement of the weight. The advantage of this system is 2.

Although the force needed to lift the weight is only W/2, we will need to draw a length of rope that is

twice the distance that the weight is lifted, so that the total amount of work done (Force x distance)

remains the same.

A second pulley may be added as in diagram 2a, which simply serves to redirect the lifting force

downward, it does not change the advantage of the system.

A crane using the compound pulley system yielding an advantage of 4. The single fixed pulley is installed

on the crane. The two movable pulleys (joined together) are attached to the hook. One end of the rope is

attached to the crane frame, another – to the winch.

Diagram 3 – A simple

compound pulley system –

a movable pulley and a

fixed pulley lifting weight

W. The tension in each line

is one W/3, yielding an

advantage of 3.

Diagram 3a – A simple compound

pulley system – a movable pulley

and a fixed pulley lifting weight W,

with an additional pulley redirecting

the lifting force downward. The

tension in each line is one W/3,

yielding an advantage of 3.

Diagram 4a – A more

complicated compound pulley

system. The tension in each line

is W/4, yielding an advantage of

4. An additional pulley

redirecting the lifting force has

been added.

FIG 20

The addition of a fixed pulley to the single pulley system can yield an increase of advantage. In

diagram 3, the addition of a fixed pulley yields a lifting advantage of 3. The tension in each line

is W/3, and the force on the axles of each pulley is 2W/3. As in the case of diagram 2a, another

pulley may be added to reverse the direction of the lifting force, but with no increase in

advantage. This situation is shown in diagram 3a.

This process can be continued indefinitely for ideal pulleys with each additional pulley yielding a

unit increase in advantage. For real pulleys friction among rope and pulleys will increase as more

pulleys are added to the point that no advantage is possible. It puts a limit for the number of

pulleys usable in practice. The above pulley systems are known collectively as block and tackle

pulley systems. In diagram 4a, a block and tackle system with advantage 4 is shown. A practical

implementation in which the connection to the ceiling is combined and the fixed and movable

pulleys are encased in single housings is shown in figure 4b.

Other pulley systems are possible, and some can deliver an increased advantage with fewer

pulleys than the block and tackle system. The advantage of the block and tackle system is that

each pulley and line is subjected to equal tensions and forces. Efficient design dictates that each

line and pulley be capable of handling its load, and no more. Other pulley designs will require

different strengths of line and pulleys depending on their position in the system, but a block and

tackle system can use the same line size throughout, and can mount the fixed and movable

pulleys on a common axle.

3.4 II WORK AND MECHANICAL ADVANTAGE

To lift any object, a person must do some work. Work is the product of the effort, or force,

applied to an object multiplied by the distance the force is applied. The relation of work to force

and distance can be shown as an equation:

Work = Force × Distance

A pulley makes work easier by increasing the distance over which effort is applied. Pulleys

increase distance by requiring additional rope to be pulled to lift an object. Increasing the

distance reduces the amount of force needed for the job. By changing the direction of a force,

pulleys make it easier to apply the force because it is more convenient to pull down than to pull

up. Combining pulleys increases the amount of rope needed to lift an object, so heavy loads can

be lifted with even less effort.

Mechanical advantage (MA) is a term that describes how much a machine magnifies effort. The

greater the MA, the less the effort needed to lift a given load. There are two types of MA:

theoretical and actual. Theoretical MA is the MA most commonly referred to. It is the MA a

machine would have if it were perfect. The actual MA, which is always less than theoretical MA,

takes into account imperfections in simple machines. The main source of imperfection is friction,

the result of two bodies rubbing against each other. Friction always opposes motion, and is

present to some degree in almost every machine. Friction is a major problem in pulleys because

of the weight on the rope and the movement of the rope on the pulley. Lubricants and bearings

are often used in pulleys to reduce friction.

MA is generally determined by dividing the distance the effort travels by the distance the load

travels. The higher the MA, the easier it is to do work. A single fixed pulley, such as that at the

top of a flagpole, has a theoretical MA of 1, which means for each distance of rope the user pulls

in, the flag rises the same distance. Effort is not magnified in this case. The load that can be lifted

is equal to the force that is applied by the user. The primary benefit of a single pulley is to

change the direction of the force or to move a load to a point (such as the top of a flagpole) that

cannot be reached by the user. In reality, the actual MA is slightly less than 1 because of the

friction of the rope against the pulley and the friction between the pulley and the axle on which it

turns.

Pulleys can offer MAs of greater than 1 if they are movable. A movable pulley is one that is

attached to the load to be lifted and therefore moves with the load as the rope is pulled. Even a

single pulley, when placed on the object to be moved, provides an MA of 2, meaning that twice

the load can be lifted with the same amount of effort. The MA of a movable pulley (or a system

of pulleys with a movable part) equals the number of strands of rope coming from the movable

part (the load being lifted).

A movable pulley can be used to lift a heavy load from the bottom of a cargo ship up to the deck.

For a single movable pulley to work, one end of the rope is tied to a fixed anchor on the deck.

The rope leads from the anchor down through the pulley (which is attached to the load), and back

up to the user. Since both strands of rope coming from the pulley equally support the load, any

effort applied is doubled. Since a pulley system with an MA of 2 increases the force by a factor

of 2, the pulley system must also double the distance the effort travels. Therefore, in order to

raise a load a given distance, the user must pull and take in twice as much rope.

3.5 III PULLEY SYSTEMS

Systems of pulleys have been used for centuries to move loads. Two common types of pulley

systems are the block and tackle and the chain hoist. Chain hoists are usually operated by hand,

while a block and tackle system is often used with an engine or motor.

3.6 A BLOCK AND TACKLE

When several movable and fixed pulleys are used together, the entire system is usually called a

block and tackle. Block and tackle systems are commonly used on sailing ships to lift heavy

sails. The term block refers to the case that houses the pulleys side by side and holds the axle of

the pulleys in place. Tackle is a term traditionally used to refer to a sailing ship’s rigging, which

was usually made of rope. Thus the block and tackle consists of a system of pulleys in their

housings and a rope used to apply the forces. The MA of a block and tackle is equal to the

number of strands of rope coming from the moveable set of pulleys attached to the load.

A block and tackle typically houses several pulleys, and can increase MA considerably. On

sailing ships, a block and tackle is used to apply forces to another block and tackle to gain an

even greater MA. This is often necessary because of the large friction losses in such systems,

which are usually made of wood with some metal parts. By using these devices, sailors can exert

large forces. They will, however, have to pull a greater length of rope to accomplish this Chain

Hoist

A chain hoist is a pulley system joined together by a closed loop of chain that is pulled by hand.

Chain hoists are sometimes used to lift automobile engines out of cars. The pulleys on a chain

hoist have teeth that hold the chain, much like the sprockets that hold a bicycle chain in place. A

chain hoist is made up of two sections. The top has a large pulley and a small pulley joined side

by side on the same axle. The large and small pulleys turn together as a unit. The bottom section

of a chain hoist is a movable pulley attached to the load.

The chain hangs down from the large pulley on one side, and then threads back up around the

small pulley, down through the movable pulley, and back up to the large pulley. When a user

pulls on the chain hanging down from the large pulley, that pulley pulls in chain from the

movable pulley. The chain threading through the movable pulley is fed from the small pulley on

top. When the chain is pulled, the large pulley brings in more chain than the small pulley lets out,

and so the load is raised. Since the effort travels a greater distance than the load, the chain hoist

multiplies force. The MA of a chain hoist depends on the diameters of the large and small

pulleys.

3.6.1 BLOCK AND TACKLE

Block and tackle [1] is a system of two or more pulleys with a rope or cable threaded between

them, usually used to lift or pull heavy loads.

FIG 21

3.7 OVERVIEW

This block and tackle on a davit of the Mercator is used to help lower a boat.

Seamen aboard the now-defunct USNS Southern Cross freighter rigged this block and tackle to

make heavy lifts during cargo operations.Although used in many situations, they are especially

common on boats and sailing ships, where motorized aids are usually not available, and the task

must be performed manually. The block and tackle pulley was invented by Archimedes.

A Block is a set of pulleys or "sheaves" all mounted on a single axle. When rope or line is run

through a block or a series of blocks(this generally reduces lift force) the whole assembly is

called a Tackle. It usually is a compound machine.

The most common arrangement of block and tackle is to have a block attached to a fixed position

(the fixed or standing block), and another block left to move with the load being pulled or lifted

(The moving block).

FIG 22

3.8 MECHANICAL ADVANTAGE

The mechanical advantage of a block and tackle is equal to the number of parts in the line, that

either attach to or run through the moving block, or the number of supporting ropes. For

example, take a block and tackle with 2 sheaves on both the moving block and the fixed block. If

you compare the blocks, you will see one block will have 4 lines running through its sheaves.

The other will have 4 lines running through its sheaves (including the part of the line being

pulled or hauled), with a 5th line attached to a secure point on the block. If the hauling part is

coming out of the fixed block, your block and tackle will have a mechanical advantage of 4. If

you turn the tackle around, so your hauling part is coming from your moving block, the

mechanical advantage is now 5.

The mechanical advantage of a tackle is relevant, because it dictates how much easier it is to haul

or lift your load. A tackle with a mechanical advantage of 4 will be able to lift 100 lbs with only

25 lbs of tension on the hauling part of the line.

Mechanical advantage correlates directly with velocity ratio. The velocity ratio of a tackle refers

to the relative velocities of the hauling line to the hauled load. A line with a mechanical

advantage of 4, has a velocity ratio of 4:1. In other words, to raise a load at 1 meter per second, 4

meters of line per second must be pulled from the hauling part of the rope.

FIG 23

3.9 FRICTION

The increased force produced by a tackle is offset by both the increased length of rope needed

and the friction in the system. In order to raise a block and tackle with a mechanical advantage of

6 a distance of 1 metre, it is necessary to pull 6 metres of rope through the blocks. Frictional

losses also mean there is a practical point at which the benefit of adding a further sheave is offset

by the incremental increase in friction which would require additional force to be applied in

order to lift the load. Too much friction may result in the tackle not allowing the load to be

released easily[2], or by the reduction in force needed to move the load being judged insufficient

because undue friction has to be overcome as well.

3.10 RIGGING METHODS

A tackle may be "Rigged to advantage" - where the pull on the rope is in the same direction as

that in which the load is to be moved. The hauling part is pulled from the moving block.

"Rigged to disadvantage" - where the pull on the rope is in the opposite direction to that in which

the load is to be moved. The hauling part is pulled from the fixed block.

While rigging to advantage is obviously the most efficient use of equipment and resources, there

are several reasons why rigging to disadvantage may be more desirable. The decision of which to

use depends on pragmatic considerations for the total ergonomics of working with a particular

situation. Lifting from a fixed point overhead is an obvious example of such a situation.

CONCLUSION

It’s a project based on the principle of kinematics 4-Bar Mechanism and the principle of

Hydraulics. Its main quality is that it can move on the irregular surface (i.e. hilly areas, sandy

areas etc.) and is self balanced. This model can also be very helpful for future perspective as it

can be used in Defence sector for any of the mission works or in Remote Areas. This is very

simple in construction and is highly cost effective.