The Bicycle

1
The Bicycle
Some personal history Schwinn made the Varsity
from 1959 to 1987. Bicycle sales soared in the
1970s in part due to a rise in oil prices. I
paid about 100 in 1975 to own my very own 10
speed. It was not a kids bike it was so cool
and sophisticated. It had multiple sprockets
(chain rings). The Varsity was a tank, heavy
and indestructible. In a flat place like UC
Davis, it was perfect in every way.
http//www.cyclesportandfitness.com/the_varsity.ht
m
2
Wheel is invented 5500 years ago but the bicycle
emerges in 1817
German Baron Karl Von Drais invented a
walking machine to help him get around the
gardens. The Hobby Horse as it was called was
pushed forward by the riders feet.
http//www.karl-drais.de/rubrik.htm
3
Why the Hobby Horse?

• In 1815, Indonesian Volcano, Tambora, explodes
  releasing the greatest known mass of dust into
  the atmosphere.
• An explosion seven times more massive than
  Krakatoa in 1883.
• 1816 is known as the year without a summer
• Many horses were killed or died due to lack of
  fodder, causing a shortage of horses, leading to
  the development of a human powered running
  machine.

Krakatoa
Tambora
4
Idea borrowed from ice skates

• Hybrid of inline ice skates and roller skates.
• Uses largest muscles in the body (legs)

1858 Central Park - NYC
5
Pedals introduced in 1839
Kirkpatrick Macmillan, a Scottish Blacksmith
added pedals. The pedals were attached to rods
that were connected to rotating cranks that
powered the back wheel. Lack of bike development
for 20 years possibly due to railway craze
http//www.veloparis.com/web/velocipede_michaux.ph
p
6
What is a crank?

• 1.
• A device for transmitting rotary motion
  consisting of an arm perpendicular to the
  rotating shaft.
• 2.
• A device that translates back and forth motion
  into rotational motion
• (as seen with cars and trains)

http//www.branfordbike.com/crank/crank1.html
http//old-photos.blogspot.com/2007_06_01_archive.
html
http//www.kansas-tours.net/tours
7
In 1868 pedals are added to the front wheel
similar to tricycle
Invented by French carriage makers, Pierre and
Ernest Michaux Wheels are made of iron with
wooden spokes and the frame is iron. The bike
requires strength to ride. Popular where roads
were paved and more suitable to bicycles. Called
the Boneshaker
http//www.veloparis.com/web/velocipede_michaux.ph
p
8
In 1871 the high wheel bike, or penny-farthing is
invented
The large front wheel with metal spokes allows
the bicycle to move farther with each turn of the
pedals. The seat had to be mounted over the
front wheel for stability. This design is
similar to a unicycle with a small back wheel.
http//commons.wikimedia.org/wiki/ImageOrdinary_b
icycle02.jpg
9
Large Front Wheel gives Penny-farthing better
range

• If the wheel has a diameter of 60, one rotation
  of the pedal propels the bike forward by over 15
  feet.
• Speed and Distance is achieved
• Pedaling at 60 rpm produced a speed of 942
  feet/minute or 10.7 mph

10
Other Penny-Farthing Design Improvements Metal
wheels with metal spokes and ball bearings.
Solid rubber tires to cushion the ride. Ball
bearings reduced the friction making The
Penny-farthing easier to ride. DaVinci is
credited with sketching ball bearings around 1500.
City of Vancouver Archives collection
HowStuffWorks
11
What is a bearing?

• Roller or Ball Bearings allow an axle or shaft to
  rotate freely with limited friction.
• A connector (usually a support) that permits the
  connected members to move relative to one another.

12
Natural Rubber

• Few applications exist for rubber in its natural
  state because natural rubber is sticky at high
  temperatures and brittle at low temperatures.
• Charles Goodyear had been working for seven years
  trying to make a useful rubber.

Wikipedia
13
In 1839 Charles Goodyear makes an trial and
error discovery

• Some Rubber and Sulfur are mixed on a hot stove.
  This causes the rubber to become vulcanized.
• The Sulfur helps link the long polymer chains
  together so that rubber is more durable and able
  to hold shapes over a wide range of temperatures.
  This is called curing.

14
Solid Rubber Tires mounted on Steel wheels
wikipedia
1886 Los Angeles
http//pennyfarthing.org/
15
Finally a chain and sprockets are added in 1885
by John Starley of England
http//www.bicyclegifts.com/johnplayer.html
http//www.makingthemodernworld.org.uk
16
The rotating chain then drove the rear sprocket
which was connected to the back wheel.
A sprocket (a gear driven by a chain) is added.
Solid rubber tire
The teeth on the sprockets gripped the chain
Two wheels of the same size and the use of the
chain made this bicycle much safer than its
predecessors, thus is was called the Safety
Bicycle. Rider is centered over the two wheels
17
The large front sprocket and the small rear
sprocket eliminate the need for an oversized
front wheel

• One rotation of the pedals can produce 3
  rotations on the rear wheel, if the front
  sprocket has 3X the number of teeth as the rear
  sprocket.

Front Sprocket
Rear Sprocket
18
Balloon Tires introduced in 1888 by John Boyd
Dunlop
Pressurized Air-filled or Pneumatic tires
http//www.dunlop-tires.com
19
The Bicycle speeds the evolution of womens
fashion
http//info.detnews.com/history/
http//library2.usask.ca/herstory/bike.html
http//www.sewingcentral.com
20
New Found Mobility and Freedom
By 1896, one third of all American cyclists were
women. The "rational dress" movement picked up
speed, and by the end of 1890s, corsets were
loosened, skirt hems were raised, and even
non-cycling women began to wear this bold new
style of clothing.
http//www.bicycleapparel.com
Early bicycles were expensive, So most owners
were wealthy.
http//www.victoriana.com/postcard/images/81-Victo
rian-Bicycle-1895.jpg
21
State of the Bicycle Today
In 2003, 105,000,000 bicycles were produced,
compared to 42,000,000 cars in the same year
22
New Dehli, India
China
UC Davis
Bike Freeways in Denmark
Amersterdam
23
How does a modern bicycle works?By converting
power in legs to rotary power in the
wheelsUsing two cranks to apply torque to the
front sprocket which in turn drives the rear wheel
24
The cranks are powered by the feet and legs. The
front sprocket pulls the chain. Torque d X
Force Torque is a rotational or turning
force. Force is applied by the feet. d distance
from the sprocket axle to the pedal.
d
crank
axle
http//www.maffoo.net/cycling.html
25
The crank and front sprocket creates tension on
the chain. The chain turns the rear wheel
sprocket. Multiple front sprockets allow the
rider to select the chain speed. The farther the
chain is from the center, the faster the chain
moves, but the lower the tension (pulling force)
will be on the chain.
http//storage.zcubes.com
26
The free wheel at rear has numerous different
sized sprockets. If the chain is on the largest
rear sprocket, greater torque is applied to the
rear wheel axle, but the rear wheel will be
rotating more slowly. Good for going uphill. If
the chain is on the smallest rear sprocket, a
smaller torque is applied to the rear wheel axle
but the wheel will be rotating more quickly.
Good on flat land or going downhill. Changing
gears allows the cyclist to trade force for speed
and vice versa.
27
Highest Gear Chain moves fastest, rear wheel
moves fastest, but with the lowest torque on rear
wheel. Can also say that legs are moving slow
compared to wheels.
Torque on back wheel is low because the chain is
close to the center of the wheel. However back
wheel is turning fast because chain does not have
far to travel to make ½ rotation of the sprocket.
Torque F d Force/Tension on chain is lowest
but chain is moving fastest because it is
farthest from the center of the sprocket.
28
Lowest Gear Slowest chain but with the highest
torque on rear wheel. Can also say that legs are
moving fast compared to wheels.
Tension on chain is high because chain is close
to the center of the chain wheel. This is
similar to using a winch to wind something over a
narrow spool. Chain is moving slowly compared to
legs.
Torque on rear wheel is maximized because chain
is farthest from the center. Back wheel is
turning slowly because chain has to travel a
longer distance to rotate the wheel.
29
Bicycle Efficiency

• Very efficient 20-30
• Bike rider is a fuel cell conversion of
  chemical potential energy directly into work
• Heat dissipation (from cool air) helps rider
  effectively release 75 of his/her waste energy
  enabling the rider to sustain top power output
  without overheating.
• Multiple gears allow for greater efficiency.

30
Reducing Drag (wind resistance)

• Altering position to reduce air resistance
• Constructing streamlined shapes

http//www.machinehead-software.co.uk/bike
Recumbent with Front Fairing
http//tptherapy.wordpress.com
31
Levers as Brakes
Linear Pull or V Brakes
Dual Pivot Caliper Brakes
Center Pull Caliper Brakes
Answers.com
32
Relationship between gears and tire rotation

• Put the bicycle in low gear. Turn the pedal one
  complete circle. Record the number of rotations
  the tire makes.
• Put the bicycle in high gear. Record
  observations for this gear.

33
Belts are similar to chains
http//engineeringjohnson
Belts were used to power factory equipment prior
to the use of electricity.
34
Briggs and Stratton website
35
Resources

• http//bicycling.about.com/od/thebikelife/ss/Histo
  ry.htm