presentation by G.RAMPRASAD

1. POWER SKATE BOARD BY USING CHAIN DRIVE
Mini project
UNDER THE GUIDENCE OF BATCH MEMBERS::
U.HARIBABU sir 15495A0304
MECHANICAL ENGINEERING 14491A0340
QIS COLLEGE OF ENGG& TECHNOLOGY 14491A0357
14491A0312
14491A0356
QIS COLLEGE OF ENGINNERING AND TECHNOLOGY
Dept. of mechanical engineering
2017-18

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The History of Skateboarding
1958: The skateboard is made from roller skates attached to a
board. This is really where it all starts. As surfing becomes more
popular, skating becomes a way to surf when there are no waves
—"sidewalk surfing."
1959: "Roller Derby" mass produces a skateboard with metal
wheels.
1963-66: Surfboard companies like Makaha and Hobie start
making better-quality skateboards with clay wheels and trucks that
are made for skating. The first skate contest is put on in Hermosa
Beach, California, in 1963.
In 1964, the musical group Jan and Dean appear on Dick Clark's
American Bandstand and sing "Sidewalk Surfing." Dean does a
few simple tricks and rides the board across the stage.
1973: With the invention of urethane wheels, new possibilities emerge. What once was a noisy, bumpy ride is
now smooth and silent. Banks and ditches become skateable, as these new wheels can grip the concrete.
Surfers like Larry Bertlemann inspire a new and radical form of skating, as surfing begins to turn toward a
shorter board with more fluid moves. From this point on, skating will never be the same.
1973-75: Fiberglass boards made by surf shops out of fin material become popular with the surf crowd.
Companies experiment making skateboard decks, using everything from wood to aluminum. The first full-length
skate movie, Spinnin' Wheels, is released.
1976-78: The California drought forces homeowners to drain their pools. Though skaters have been riding
swimming pools since the introduction of urethane wheels the previous year, they now view the empty pools as
territory to be conquered. New tricks are invented daily—aerials, inverts, and the ollie. Many concrete parks are
also being built, and the first professional skaters begin to receive notice. However, many skate parks are forced
to close because of low attendance and high insurance rates.
1980s: Street skating turns handrails and walls into free skate parks. Skater-owned companies become more
and more common.
1990s: Skateboarding takes a giant step into the mainstream with the 1995 ESPN's Extreme Games, becoming
more of a spectator sport. By the late 90s, skating appears in commercials for everything from soft drinks to
phone companies. Fashion trends begin to reflect the influence of the skating crowd.
2000: Skating can now be enjoyed by children as young as two, but the majority of skaters range from early
teens to twenties. Many cities have built high quality skate parks, and a number of camps and lessons are
available to young people. Some families even enjoy skating as a family activity.
2006: This brings us to today. Scholastic News Online launches a special report dedicated to skateboarding
—"Kids On Board."

3. 2
PARTS OF SKATE BOARD::
The following descriptions cover skateboard parts that are most prevalent in popular and modern forms of
skateboarding. Many parts exist with exotic or alternative constructions. A traditional complete skateboard
consists of the deck (often with grip tape applied on top to enhance traction), trucks (with urethane bushings),
wheels (with sealed bearings), bushings, nuts and bolts to fasten the truck and wheel assembly to the bottom of
the deck. Older decks also included plastic parts such as side, tail, and nose guards.
Modern decks vary in size, but most are 7 to 10.5 inches (18 to
27 cm) wide. Wider decks can be used for greater stability when
skateboarding. Standard skateboard decks are usually between 28
and 33 inches (71 and 84 cm) long. The underside of the deck can be
printed with a design by the manufacturer, blank, or decorated by any
other means.
"Long" boards are usually over 36 inches (91 cm) long. Plastic
"penny" boards are typically about 22 inches (56 cm) long. Some
larger penny boards over 27 inches (69 cm) long are called "nickel"
boards.
The longboard, a common variant of the skateboard, is used for
higher speed and rough surface boarding, and they are much more
expensive. One of the first deck companies was called "Drapped" taken from Jonny's second name. "Old school"
boards (those made in the 1970s–80s or modern boards that mimic their shape) are generally wider and often
have only one kicktail. Variants of the 1970s often have little or no concavity, whereas 1980s models have
deeper concavities and steeper kicktails.
Grip tape
Grip tape is a sheet of paper or fabric with adhesive on one side and a surface similar to fine sand paper on the
other. Grip tape is applied to the top surface of a board to allow the rider's feet to grip the surface and help the
skater stay on the board while doing tricks. Grip tape is usually black, but is also available in many different
colors such as pink, red, yellow, checkered, camo, and even clear. Often, they have designs die-cut to show the
color of the board, or to display the board's company logo. Grip tape accumulates dirt and other substances that
will inhibit grip, so use of a grip eraser or rubber eraser is necessary after riding through mud or with dirty shoes.
Trucks
Attached to the deck are two metal (usually made of aluminum alloy)
trucks, which connect the wheels and bearings to the deck. The
trucks are further composed of two parts.
The top part of the truck is screwed to the deck and is called the
baseplate, and beneath it is the hanger. The axle runs through the
hanger. Between the baseplate and the hanger are bushings, also
rubbers or grommets, that provide the cushion mechanism for turning
the skateboard. The bushings cushion the truck when it turns. The
stiffer the bushings, the more resistant the skateboard is to turning.
The softer the bushings, the easier it is to turn. Bushings come in
varying shapes and urethane formulas as well as durometers, which
An Independent brand skateboard truck
may affect turning, rebound and durability. A bolt called a kingpin holds these parts together and fits inside the
bushings. Thus by tightening or loosening the kingpin nut, the trucks can be adjusted loosely for better turning

4. 3
is being ridden. Trucks that are too small can be hard to maintain stability and can cause wheel bite to occur
when turning.
Longboard specific trucks are a more recent development. A longboard truck has the king pin laid at a more
obtuse angle (usually between 38 and 50 degrees) to the deck, giving a greater degree of turning for the same tilt
of the deck. Many longboard specific trucks also have a reverse kingpin arrangement with the kingpins facing
outward.
Wheels
The wheels of a skateboard are usually made of polyurethane, and come in many different sizes and shapes to
suit different types of skating. Larger diameters (55–85 mm) roll faster, and move more easily over cracks in
pavement and are better for transition skateboarding. Smaller diameters (48–54 mm) keep the board closer to
the ground, require less force to accelerate and produce a lower center of gravity which allows for a better
response time, but also make for a slower top speed and are better for street skateboarding. Wheels also are
available in a variety of hardnesses usually measured on the Shore durometer "A" scale. Again like car tires,
wheels range from the very soft (about Shore A 75) to the very hard (about Shore A 101). As the A scale stops at
100, any wheels labeled 101A or higher are harder, but do not use the appropriate durometer scale. Some wheel
manufacturers now use the "B" or "D" scales, which have a larger and more accurate range of hardness. Modern
street skaters prefer medium-sized wheels (usually 51–54 mm), as small wheels with lighter trucks can make
tricks like kickflips and other flip tricks easier by keeping the center of gravity of the skateboard closer to the
deck, thus making the deck easier to spin. Street wheels are harder (A 100/A 101). Vertical ramp or "vert" skating
requires larger wheels (usually 55–65 mm), as it involves higher speeds. Vert wheels are also usually slightly
softer (A 98/ A 99), allowing them to maintain high speed on ramps without sliding. Slalom skating requires even
larger wheels (60–75 mm) to sustain the highest speeds possible. They also need to be soft and have better grip
to make the tight and frequent turns in slalom racing. Even larger wheels are used in longboarding and downhill
skateboarding. Sizes range from 65 mm to 100 mm. These extreme sizes of wheels almost always have cores
of hard plastic that can be made thinner and lighter than a solid polyurethane wheel. They are often used by
skateboard videographers as well, as the large soft wheels allow for smooth and easy movement over any
terrain.
Bearings
Each skateboard wheel is mounted on its axle via two bearings. With few exceptions, the
bearings are the industrial standard "608" size, with a bore of 8 mm (or 10mm depending
on the axle), an outer diameter of 22 mm, and a width of 7 mm. These are usually made
of steel, though silicon nitride, a high-tech ceramic, is sometimes used. Many skateboard
bearings are graded according to the ABEC scale. The scale starts with ABEC1 as the
lowest, followed by 3, 5, 7, and 9. It is a common misconception that the higher ABECs
are better for skateboarding, as the ABEC rating only measures tolerances, which do not
necessarily apply to skateboards. Bearing performance is determined on how well
maintained the bearings are. Maintenance on bearings includes periodically cleaning and
lubricating them . Bearings that are kept unmaintained have their performance greatly
lowered and will soon need to be replaced. Bearing cleaning kits are commonly available
on the market. The ABEC rating does not determine the speed or durability of a
An animation of the
working principle for a
ball bearing. N.B. The
diagram shows an 8-
balled-bearing
whereas a skateboard
bearing is typically 7-
balled
skateboard bearing. In particular, the ABEC rating says nothing about how well a bearing handles axial (side-to-
side) loads, which are severe in most skateboard applications. Many companies do not show the ABEC rating,
such as Bones Bearings, which makes bearings specifically for skateboarding, often marketed as "Skate Rated".
Each bearing usually contains 7 steel or ceramic bearing balls, although other configurations are used as well.
Hardware
Mounting hardware is a set of eight 10-32 UNF bolts, usually an Allen or Phillips head, and matching nylon
locknuts. They are used to attach the trucks (and any type of risers) to the board. Some sets have one different

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Colored bolt to show which side is the nose of the skateboard. Hardware is available in various lengths for
mounting trucks with or without risers.
A bicycle wheel is a wheel, most commonly a wire wheel, designed for a
bicycle. A pair is often called a wheelset, especially in the context of ready
built "off the shelf" performance-oriented wheels.
Bicycle wheels are typically designed to fit into the frame and fork via
dropouts, and hold bicycle tires.
Construction
The first bicycle wheels followed the traditions of carriage building: a wooden
hub, a fixed steel axle (the bearings were located in the fork ends), wooden
spokes and a shrink fitted iron tire. A typical modern wheel has a metal hub,
wire tension spokes and a metal or carbon fiber rim which holds a pneumatic
rubber tire.
Hub
A hub is the center part of a bicycle wheel. It consists of an axle, bearings
and a hub shell. The hub shell typically has two machined metal flanges to
which spokes can be attached. Hub shells can be one-piece with press-in
cartridge or free bearings or, in the case of older designs, the flanges may be
affixed to a separate hub shell.
Axle
The axle is attached to dropouts on the fork or the frame. The axle can attach
using a:
Bicycle wheel with wooden rim
Nipples
Quick release - a lever and skewer that pass through a hollow axle
designed to allow for installation and removal of the wheel without any
tools (found on most modern road bikes and some mountain bikes).
Nut - the axle is threaded and protrudes past the sides of the fork/frame.
(often found on track, fixed gear, single speed, BMX and inexpensive
bikes)
bolt - the axle has a hole with threads cut into it and a bolt can be
screwed into those threads. (found on some single speed hubs,
Cannondale Lefty hubs)
Thru axle - a removable axle with a threaded end that is inserted through
a hole in one fork leg, through the hub, and then screwed into the other
fork leg. Some axles have integrated cam levers that compress axle
elements against the fork leg to lock it in place, while others rely on pinch
bolts on the fork leg to secure it. Diameters for front thru axles include
Spokes
Rim
20 mm, 15 mm, 12 mm, and 9 mm. Rear axles typically have diameters of 10 or 12 mm. Most thru axles
are found on mountain bikes, although increasingly disc-braked cyclocross and road bikes are using
them. Thru axles repeatably locate the wheel in the fork or frame, which is important to prevent
misalignment of brake rotors when using disc brakes. Unlike other axle systems (except Lefty), the thru
axle is specific to the fork or frame, not the hub. Hubs/wheels do not include axles, and the axle is

6. 2/12
generally supplied with the fork or frame. Adapters are usually available
to convert wheels suitable for a larger thru axle to a smaller diameter,
and to standard 9mm quick releases. This allows a degree of re-use of
wheels between frames with different axle specifications.
Female axle - hollow center axle, typically 14, 15, 17, or 20 mm in
diameter made of chromoly and aluminum, with two bolts thread into on
either side. This design can be much stronger than traditional axles,
which are commonly only 8 mm, 9 mm, 9.5 mm, or 10 mm in diameter.
(found on higher end BMX hubs and some mountain bike hubs)
Modern bicycles have adopted standard axle spacing: the hubs of front
wheels are generally 100 mm wide fork spacing, road wheels with freehubs
generally have a 130 mm wide rear wheel hub. Mountain bikes have adopted
a 135 mm rear hub width,which allows clearance to mount a brake disc on the
hub or to decrease the wheel dish for a more durable wheel. Freeride and
downhill are available with both 142 and 150 mm spacing.
Bearings
A Shimano Dura-Ace freehub style hub
The bearings allow the hub shell (and the rest of the wheel parts) to rotate freely about the axle. Most bicycle
hubs use steel or ceramic ball bearings. Some hubs use serviceable "cup and cone" bearings, whereas some
use pre-assembled replaceable "cartridge" bearings.
A "cup and cone" hub contains loose balls that contact an
adjustable 'cone' that is screwed onto the axle and a 'race' that is
pressed permanently into the hub shell. Both surfaces are
smooth to allow the bearings to roll with little friction. This type of
hub can be easily disassembled for lubrication, but it must be
adjusted correctly; incorrect adjustment can lead to premature
wear or failure.
In a "cartridge bearing" hub, the bearings are contained in a
cartridge that is shaped like a hollow cylinder where the inner
surface rotates with respect to the outer surface by the use of
ball bearings. The manufacturing tolerances, as well as seal
quality, can be significantly superior to loose ball bearings. The
cartridge is pressed into the hub shell and the axle rests against
the inner race of the cartridge. The cartridge bearing itself is
Freehub vs freewheel hub
generally not serviceable or adjustable; instead the entire cartridge bearing is replaced in case of wear or failure.
Hub shell and flanges
The hub shell is the part of the hub to which the spokes (or disc structure) attach. The hub shell of a spoked
wheel generally has two flanges extending radially outward from the axle. Each flange has holes or slots to
which spokes are affixed. Some wheels (like the Full Speed Ahead RD-800) have an additional flange in the
center of the hub. Others (like some from Bontrager and Zipp) do not have a noticeable flange. The spokes still
attach to the edge of the hub but not through visible holes. Other wheels (like those from Velomax/Easton) have
a threaded hub shell that the spokes thread into.
On traditionally spoked wheels, flange spacing affects the lateral stiffness of the wheel, with wider being stiffer,
and flange diameter affects the torsional stiffness of the wheel and the number of spoke holes that the hub can
accept, with larger diameter being stiffer and accepting more holes. Asymmetrical flange diameters, tried to

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mitigate the adverse effects of asymmetrical spacing and dish necessary on rear wheels with many sprockets,
have also been used with modest benefits.
Rim
The rim is commonly a metal extrusion that is butted into itself to form a
hoop, though may also be a structure of carbon fiber composite, and was
historically made of wood. Some wheels use both an aerodynamic carbon
hoop bonded to an aluminum rim on which to mount conventional bicycle
tires.
Metallic bicycle rims are now normally made of aluminium alloy, although until
the 1980s most bicycle rims - with the exception of those used on racing
bicycles - were made of steel and thermoplastic.
Rims designed for use with rim brakes provide a smooth parallel braking
surface, while rims meant for use with disc brakes or hub brakes sometimes
lack this surface.
The Westwood pattern rim was one of the first rim designs, and rod-actuated
brakes, which press against the inside surface of the rim were designed for
this rim. These rims cannot be used with caliper rim brakes.
The cross-section of a rim can have a wide range of geometry, each
optimized for particular performance goals. Aerodynamics, mass and inertia,
stiffness, durability, tubeless tire compatibility, brake compatibility, and cost
are all considerations. If the part of the cross-section of the rim is hollow
where the spokes attached, as in the Sprint rim pictured, it is described as
box-section or double-wall to distinguish it from single-wall rims such as
the Westwood rim pictured. The double wall can make the rim stiffer.
Triple-wall rims have additional reinforcement inside the box-section.
Aluminum rims are often reinforced with either single eyelets or double
eyelets to distribute the stress of the spoke. A single eyelet reinforces the
spoke hole much like a hollow rivet. A double eyelet is a cup that is riveted
into both walls of a double-walled rim.
Clincher rims
Westwood rim as fitted to vintage
roadster bicycles with rod/ stirrup
brakes, today being used in
contemporary “drum brake” traditional
utility bicycles
Endrick Rim as fitted to sports bicycles
from the 1930s, 40s and 50s,
forerunner of modern-day rim brakes
Most bicycle rims are "clincher" rims for use with clincher tires. These tires have a wire or aramid (Kevlar or
Twaron) fiber bead that interlocks with flanges in the rim. A separate airtight inner tube enclosed by the rim
supports the tire carcass and maintains the bead lock. If the inner part of the rim where the inner tube fits has
spoke holes, they must be covered by a rim tape or strip, usually rubber, cloth, or tough plastic, to protect the
inner tube.
An advantage of this system is that the inner tube can be easily accessed in the case of a leak to be patched or
replaced.
The ISO 5775-2 standard defines designations for bicycle rims. It distinguishes between
1. Straight-side (SS) rims
2. Crochet-type (C) rims
3. Hooked-bead (HB) rims

8. 4/12
Traditional clincher rims were straight-sided. Various "hook" (also called "crochet") designs emerged in the 1970s
to hold the bead of the tire in place, allowing high (6–10 bar, 80–150 psi) air pressure.
Tubular or sew-up rims
Main article: Tubular tyre
Some rims are designed for tubular tyres which are torus shaped and attached to the rim with adhesive. The rim
provides a shallow circular outer cross section in which the tire lies instead of flanges on which tire beads seat.
Tubeless
A tubeless tire system requires an airtight rim — capable of being sealed at the valve stem, spoke holes (if they
go all the way through the rim) and the tire bead seat — and a compatible tire. Universal System Tubeless
(UST), originally developed by Mavic, Michelin and Hutchinson for mountain bikes is the most common system
of tubeless tires/rims for bicycles. The main benefit of tubeless tires is the ability to use low air pressure for
better traction without getting pinch flats because there is no tube to pinch between the rim and an obstacle.
Some cyclists have avoided the price premium for a tubeless system by sealing the spoke holes with a special
rim strip and then sealing the valve stem and bead seat with a latex sealer. However, tires not designed for
tubeless application do not have as robust a sidewall as those that are.
The drawbacks to tubeless tires are that they are notorious for being harder to mount on the rim than clincher
tires, and that the cyclist must still carry a spare tube to insert in case of a flat tire due to a puncture.
French tire manufacturer Hutchinson has introduced a tubeless wheel system, Road Tubeless, that shares many
similarities to the UST (Universal System Tubeless) that was developed in conjunction with Mavic and Michelin.
Road Tubeless rims, like UST rims, have no spoke holes protruding to the air chamber of the rim. The flange of
the Road Tubeless rim is similar to the hook bead of a standard clincher rim but is contoured to very close
tolerances to interlock with a Road Tubeless tire, creating an airtight seal between tire and rim. This system
eliminates the need for a rim strip and inner tube.
Increasingly common are tubeless tires conforming to the UST (Universal System Tubeless) standard pioneered
by French wheel manufacturer Mavic in conjunction with tire manufacturers Hutchinson and Michelin.
In 2006, Shimano and Hutchinson introduced a tubeless system for road bikes.
Spokes
The rim is connected to the hub by several spokes under tension. Original bicycle wheels used wooden spokes
that could be loaded only in compression, modern bicycle wheels almost exclusively use spokes that can only be
loaded in tension. There are a few companies making wheels with spokes that are used in both compression
and tension.
One end of each spoke is threaded for a specialized nut, called a nipple, which is used to connect the spoke to
the rim and adjust the tension in the spoke. This is normally at the rim end. The hub end normally has a 90
degree bend to pass through the spoke hole in the hub, and a head so it does not slip through the hole.
Double-butted spokes have reduced thickness over the center section and are lighter, more elastic, and more
aerodynamic than spokes of uniform thickness. Single-butted spokes are thicker at the hub and then taper to a
thinner section all the way to the threads at the rim. Triple-butted spokes also exist and are thickest at the hub,
thinner at the threaded end, and thinnest in the middle.
Apart from tubeless wheels, which do not need them, tubed bicycle wheels require rim tapes or strips, a flexible
but tough liner strip (usually rubber or woven nylon or similar material) attached to the inner circumference of the

9. 1/3
wheel to cover the ends of the nipples. Otherwise, the nipple ends wear a hole in the tube causing a flat tire.
In 2007, Mavic introduced their R-Sys, a new bicycle spoke technology that allows the spokes to be loaded in
both tension and compression. This technology is promised to allow for fewer spokes, lower wheel weight and
inertia, increased wheel stiffness, with no loss of durability. However, in 2009 Mavic recalled R-Sys front wheels
due to spoke failures leading to collapse of the entire wheel.
Cross section
Spokes are usually circular in cross-section, but high-performance wheels may use spokes of flat or oval cross-
section, also known as bladed, to reduce aerodynamic drag. Some spokes are hollow tubes.
Material
The spokes on the vast majority of modern bicycle wheels are steel or stainless steel. Stainless steel spokes are
favored by most manufacturers and riders for their durability, stiffness, damage tolerance, and ease of
maintenance Spokes are also available in titanium, aluminum, or carbon fiber.
Chain drive is a way of transmitting mechanical power from one place to another. It is often used to convey
power to the wheels of a vehicle, particularly bicycles and motorcycles. It is also used in a wide variety of
machines besides vehicles.
Most often, the power is conveyed by a roller chain, known as the drive chain or transmission chain
passing over a sprocket gear, with the teeth of the gear meshing with the holes in the links of the chain. The gear
is turned, and this pulls the chain putting mechanical force into the system. Another type of drive chain is the
Morse chain, invented by the Morse Chain Company of Ithaca, New York, United States. This has inverted teeth.
Sometimes the power is output by simply rotating the chain, which can be used to lift or drag objects. In other
situations, a second gear is placed and the power is recovered by attaching shafts or hubs to this gear. Though
drive chains are often simple oval loops, they can also go around corners by placing more than two gears along
the chain; gears that do not put power into the system or transmit it out are generally known as idler-wheels. By
varying the diameter of the input and output gears with respect to each other, the gear ratio can be altered. For
example, when the bicycle pedals' gear rotate once, it causes the gear that drives the wheels to rotate more
than one revolution.
Chains versus belts
Roller chain and sprockets is a very efficient method of power transmission compared to (friction-drive) belts,
with far less frictional loss.
Although chains can be made stronger than belts, their greater mass increases drive train inertia.
Drive chains are most often made of metal, while belts are often rubber, plastic, urethane, or other substances.
Drive belts can slip unless they have teeth, which means that the output side may not rotate at a precise speed,
and some work gets lost to the friction of the belt as it bends around the pulleys. Wear on rubber or plastic belts
and their teeth is often easier to observe, and chains wear out faster than belts if not properly lubricated.
One problem with roller chains is the variation in speed, or surging, caused by the acceleration and deceleration
of the chain as it goes around the sprocket link by link. It starts as soon as the pitch line of the chain contacts the
first tooth of the sprocket. This contact occurs at a point below the pitch circle of the sprocket. As the sprocket
rotates, the chain is raised up to the pitch circle and is then dropped down again as sprocket rotation continues.

10. In other words, conventional roller chain drives suffer the potential for vibration, as the effective
radius of action in a chain and sprocket combination constantly changes during revolution
("Chordal action"). If the chain moves at constant speed, then the shafts must accelerate and
decelerate constantly. If one sprocket rotates at a constant speed, then the chain (and probably all
other sprockets that it drives) must accelerate and decelerate constantly. This is usually not an
issue with many drive systems; however, most motorcycles are fitted with a rubber bushed rear
wheel hub to virtually eliminate this vibration issue. Toothed belt drives are designed to avoid this
issue by operating at a constant pitch radius.
Chains are often narrower than belts, and this can make it easier to shift them to larger or smaller
gears in order to vary the gear ratio. Multi-speed bicycles with derailleurs make use of this. Also,
the more positive meshing of a chain can make it easier to build gears that can increase or shrink
in diameter, again altering the gear ratio. However, some newer synchronous belts claim to have
"equivalent capacity to roller chain drives in the same width".
Both can be used to move objects by attaching pockets, buckets, or frames to them; chains are
often used to move things vertically by holding them in frames, as in industrial toasters, while
belts are good at moving things horizontally in the form of conveyor belts. It is not unusual for the
systems to be used in combination; for example the rollers that drive conveyor belts are
themselves often driven by drive chains.
Drive shafts are another common method used to move mechanical power around that is
sometimes evaluated
in comparison to chain drive; in particular belt drive vs chain drive vs shaft drive is a key design
decision for most motorcycles. Drive shafts tend to be tougher and more reliable than chain drive,
but the bevel gears have far more friction than a chain. For this reason virtually all high-
performance motorcycles use chain drive, with shaft- driven arrangements generally used for non-
sporting machines. Toothed-belt drives are used for some (non- sporting) models.
Chain Drive Systems
Chain drives, gear drives and belt drive systems are all effective power transmission choices.
Each offers advantages and disadvantages with respect to the other.
The advantages of chain drive systems are as follows:
1. Shaft center distances are
relatively unrestricted. Whereas
gear drive center-to-center
distances are restricted to
specific dimensions for a given
set of gears, the center distances
between two chained sprockets
can vary anywhere from 50% to
300% or more of their pitch
diameters.
2. Chain Drive are relatively easy
to install. Assembly tolerances
are not as restrictive as those for
gear drives. Chain drives are a

11. better choice for less experienced builders working with a minimum of machine tools.
3. Chain drives can be readily redesigned and reconfigured in comparison to gear drive
systems.
4. Chains perform better than gears under shock loading conditions.
5. Chain drives spread operating loads over many teeth whereas the operating loads acting
on gear drives are concentrated on one or two teeth.
6. Chain drives do not require tension on the slack side (Belt drives do) thus bearing loading
is reduced.
7. Chain drives require less space for a given loading and speed condition than pulleys and
belts.
8. Chain drives systems are (usually) less costly to build and maintain than an equivalent
gear drive.
While chain drives offer many advantages, there are good reasons to choose a gear drive system,
particularly when:
1. Compact drive requirements
demand the shortest possible
distance between shaft
centers.
2. High speed ratios are
required.
3. High rotating speeds (RPM)
are required.
4. High horsepower AND high
speed loading is required.

12. Belt and pulley systems also offer design advantages with respect to either chain or gear drives.
These advantages include:
1. Belts slip, chain and gears drives do not. This is a useful advantage for drive systems that
do not require positive speed
ratios to be maintained.
Momentary overloading
loading conditions may cause
a belt to slip over the pulleys
whereas a chain may break or
a gear tooth may shear. Belts
offer built in “Clutching”. Of
course sustained overloading
will cause premature wear and
“Burned out” belts.
2. Belt drives are not as noisy as
chain or gear drive systems.
3. Belt drives can operate over
longer center distances than
chain drives.
Belts are better suited to extremely high-speed ratios.
Engineering is the process of making the best decisions within the given parameters of
knowledge, time, budgets and other available resources. Within a given set of constraints, the
best engineers make the best decisions. Clearly, no single drive system is ideal for all
applications. Experience and knowledge guide the best engineering decisions with respect to
drive selection. This lesson will help young engineers gain drive system experience and
knowledge by analyzing, calculating, drawing and designing chain and sprocket drive systems.
Roller Chain Construction
Roller chains are assembled using link plates, pins and rollers and connecting them in an endless
chain using a connecting link.
Note: The GEARS-IDS kit makes
use of 25 (pitch) Nylatron plastic
chain. Plastic chain does not
require the use of master links to
connect the chain into endless
loops. for directions on assembling
Nylatron plastic chain.
Chain sections are made up from
two separate assemblies called the
Roller Link and the Pin Link.
Fig. 4 Roller Chain Components
Note: Smaller pitch chains (1/4 and
less) do not have rollers.

13. Chain Size (Pitch)
Chains are sized according to their pitch. The center-to-center distances of the link pins
determine pitch. The plastic chain used in the GEARS-IDS kit is an industry standard pitch size.
The center-to-center distance of the pins is 0.250 inches. The pitch of chain drive components is
specified by a 2 digit number.
The first digit
specifies the
center –to-
center
distance of
the chain link
pins in 1/8ths
of an inch,
the second
number
specifies the
chain style.
Fig. 5 Roller Chain Pitch
#25 chain
means:
Chain pitch =
2 x 1/8 or ¼”
pitch
Chain style =
5 = rollerless
chain.
Chain style specifications are as
follows:
0 = Standard proportion roller
chain
1 = Light weight roller chain
5 = Rollerless chain
Examples:
The plastic chain in the gears kit is
a #25 plastic chain
2 = 2 x 1/8” or ¼ “ pitch
5 = Rollerless chain
Roller Links and Pin Links
Roller Links and Pin Links
Chains are made up using two types of link assemblies; Roller links (Inside links) and pin links
(outside links). Roller links and pin links are assembled in a continuous loop using a
connecting link.

14. 1/2
Connecting Link
Connecting Link
A connecting link is a special purpose pink link assembly designed for easy and rapid replacement.
Standard Chain
Dimensions
The dimensions of roller chain and sprockets are governed by American National Standards Institute or ANSI.
ANSI standards are used to ensure the interchangeability between chains and sprockets produced by different
manufacturers.

15. 2/2
PRINCIPAL OF DC MOTOR::
A DC motor is any of a class of rotary electrical machines that converts
direct current electrical energy into mechanical energy. The most common
types rely on the forces produced by magnetic fields. Nearly all types of
DC motors have some internal mechanism, either electromechanical or
electronic, to periodically change the direction of current flow in part of the
motor.
DC motors were the first type widely used, since they could be powered
from existing direct-current lighting power distribution systems. A DC
motor's speed can be controlled over a wide range, using either a
variable supply voltage or by changing the strength of current in its field
windings. Small DC motors are used in tools, toys, and appliances. The
universal motor can operate on direct current but is a lightweight motor
used for portable power tools and appliances. Larger DC motors are
used in propulsion of electric vehicles, elevator and hoists, or in drives
for steel rolling mills. The advent of power electronics has made
replacement of DC motors with AC motors possible in many
applications.
Electromagnetic motors
Workings of a brushed electric motor with a
two-pole rotor (armature) and permanent
magnet stator. "N" and "S" designate
polarities on the inside axis faces of the
magnets; the outside faces have opposite
polarities. The + and - signs show where the
DC current is applied to the commutator
which supplies current to the armature coils
A coil of wire with a current running through it generates an electromagnetic field aligned with the center of the
coil. The direction and magnitude of the magnetic field produced by the coil can be changed with the direction
and magnitude of the current flowing through it.
A simple DC motor has a stationary set of magnets in the stator and an armature with one or more windings of
insulated wire wrapped around a soft iron core that concentrates the magnetic field. The windings usually have
multiple turns around the core, and in large motors there can be several parallel current paths. The ends of the
wire winding are connected to a commutator. The commutator allows each armature coil to be energized in turn
and connects the rotating coils with the external power supply through brushes. (Brushless DC motors have
electronics that switch the DC current to each coil on and off and have no brushes.)
The total amount of current sent to the coil, the coil's size and what it's wrapped around dictate the strength of the
electromagnetic field created.
The sequence of turning a particular coil on or off dictates what direction the effective electromagnetic fields are
pointed. By turning on and off coils in sequence a rotating magnetic field can be created. These rotating
magnetic fields interact with the magnetic fields of the magnets (permanent or electromagnets) in the stationary
part of the motor (stator) to create a force on the armature which causes it to rotate. In some DC motor designs
the stator fields use electromagnets to create their magnetic fields which allow greater control over the motor.
At high power levels, DC motors are almost always cooled using forced air.
Different number of stator and armature fields as well as how they are connected provide different inherent
speed/torque regulation characteristics. The speed of a DC motor can be controlled by changing the voltage
applied to the armature. The introduction of variable resistance in the armature circuit or field circuit allowed
speed control. Modern DC motors are often controlled by power electronics systems which adjust the voltage by
"chopping" the DC current into on and off cycles which have an effective lower voltage.
Since the series-wound DC motor develops its highest torque at low speed, it is often used in traction
applications such as electric locomotives, and trams. The DC motor was the mainstay of electric traction drives

16. 1/3
on both electric and diesel-electric locomotives, street-cars/trams and diesel electric drilling rigs for many years.
The introduction of DC motors and an electrical grid system to run machinery starting in the 1870s started a new
second Industrial Revolution. DC motors can operate directly from rechargeable batteries, providing the motive
power for the first electric vehicles and today's hybrid cars and electric cars as well as driving a host of cordless
tools. Today DC motors are still found in applications as small as toys and disk drives, or in large sizes to
operate steel rolling mills and paper machines. Large DC motors with separately excited fields were generally
used with winder drives for mine hoists, for high torque as well as smooth speed control using thyristor drives.
These are now replaced with large AC motors with variable frequency drives.
If external mechanical power is applied to a DC motor it acts as a DC generator, a dynamo. This feature is used
to slow down and recharge batteries on hybrid car and electric cars or to return electricity back to the electric grid
used on a street car or electric powered train line when they slow down. This process is called regenerative
braking on hybrid and electric cars. In diesel electric locomotives they also use their DC motors as generators to
slow down but dissipate the energy in resistor stacks. Newer designs are adding large battery packs to recapture
some of this energy.
Speed Control Methods of a DC Motor
Speed of a DC motor can be varied by varying flux, armature resistance or applied voltage. Different speed
control methods for different DC shunt and series methods are there.
Speed Control of Shunt Motors
Flux control method
Armature and Rheostat control method
Voltage control method
1. Multiple voltage control
2. Ward Leonard system
Speed Control of Series Motors
Flux control method
1. Field diverter
2. Armature diverter
3. Trapped field control
4. Paralleling field coils
Variable Resistance in series with motor
Series -parallel control method
Flux Control Method
In this flux control method, speed of the motor is inversely proportional to the flux. Thus, by decreasing flux and
speed can be increased vice versa. To control the flux , he rheostat is added in series with the field winding will
increase the speed (N), because of this flux will decrease. So, the field current is relatively small and hence I2R
loss is decreased. This method is quite efficient.

17. 2/3
Flux Control Method
So in this method, the speed can be increased by reducing flux, it puts a method to reducing flux with this
method, it puts a method to maximum speed as weakening of flux beyond the limits will adversely affect the
commutator.
Armature Control Method
In the armature control method, the speed of the DC motor is directly proportional to the back emf (Eb) and Eb =
V- IaRa. When supply voltage (V) and armature resistance Ra are kept constant, the Speed is directly
proportional to armature current (Ia). If we add resistance in series with the armature, the armature current (Ia)
decreases and hence speed decreases.
This armature control method is based on the fact that by varying the voltage across the required voltage. The
motor back EMF (Eb) and Speed of the motor can be changed. This method is done by inserting the variable
resistance (Rc) in series with the armature.
Armature Control Method

18. 3/3
SPECIFICATION OF SKATE BOARD
 Dimension of Skate board::100*31*3 cm
 Cycle diameter ::Ø 48 cm
 Gap between the wheel ::65 cm
 Dia of skate wheel ::Ø 8 cm
 Distance between socket :: 18 cm
 Max .dia of drilling machine:: 10-12 cm
 Capacity of motor :: DC motor ,12 v,speed:0-750rpm

19. 4/3
ADVANTAGES::
 Low cost
 Low weight
 Flexible design
 Easy to change the speed
 Easy to take turns while using brakes
 Eco friendly

20. 5/3
DISADVANTAGES::
 Board can breaking if the weight more
 Injuries occur at un balancing, over speed turnings
 Required special skate roads
 Problem of lubrication on chain drive
 Noise produced while metal to metal contact

21. 6/3
APPLICATIONS::
 School/college
 Industries
 Parks /streets
 Airports
 Railway station