The Bicycle

http://www.cyclesportandfitness.com/the_varsity.htm

Some personal history:

Schwinn made the Varsity from 1959 to 1987.

Bicycle sales soared in the 1970’s 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 kid’s 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.

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 rider’s feet.

http://www.karl-drais.de/rubrik.htm

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”.

Tambora

Krakatoa

Idea borrowed from ice skates

• Hybrid of inline ice skates and roller skates.

• Uses largest muscles in the body (legs)

1858 – Central Park - NYC

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.php

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://old-photos.blogspot.com/2007_06_01_archive.html

http://www.branfordbike.com/crank/crank1.html

http://www.kansas-tours.net/tours

In 1868 pedals are added to the front wheel similar to tricycle

http://www.veloparis.com/web/velocipede_michaux.php

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”

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/Image:Ordinary_bicycle02.jpg

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

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.

HowStuffWorks

City of Vancouver Archives collection

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.

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

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.

Solid Rubber Tires mountedon Steel wheels

http://pennyfarthing.org/

1886 Los Angeles

wikipedia

Finally a chain and sprockets are added in 1885 by

John Starley of England

http://www.makingthemodernworld.org.uk

http://www.bicyclegifts.com/johnplayer.html

A sprocket (a gear driven by a chain) is added.

The teeth on the sprockets gripped the chain

The rotating chain then drove the rear sprocket which was connected to the back wheel.

Two wheels of the same size and the use of the chain made this bicycle much safer than it’s predecessors, thus is was called the Safety Bicycle. Rider is centered over the two wheels

Solid rubber tire

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.

Rear Sprocket Front Sprocket

Balloon Tires introduced in 1888 by John Boyd Dunlop

http://www.dunlop-tires.com

Pressurized Air-filled or Pneumatic tires

The Bicycle speeds the evolution of women’s fashion

http://library2.usask.ca/herstory/bike.html http://www.sewingcentral.com

http://info.detnews.com/history/

New Found Mobility and Freedom

Early bicycles were expensive,So most owners were wealthy.

http://www.victoriana.com/postcard/images/81-Victorian-Bicycle-1895.jpg

http://www.bicycleapparel.com

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.

State of the Bicycle Today

In 2003, 105,000,000 bicycles were produced, compared to 42,000,000 cars in the same year

Amersterdam

Bike Freeways in Denmark

China New Dehli, India

UC Davis

How does a modern bicycle works…?

By converting power in legs to rotary power in the wheels

&Using two cranks to apply torque to

the front sprocket which in turn drives the rear wheel

http://www.maffoo.net/cycling.html

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

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

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.

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 = F * dForce/Tension on chain is lowest but chain is moving fastest because it is farthest from the center of the sprocket.

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.

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.

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.

Reducing Drag (wind resistance)Altering position to reduce air resistance

Constructing streamlined shapes

http://tptherapy.wordpress.com

http://www.machinehead-software.co.uk/bike

Recumbent with Front Fairing

Linear Pull or V Brakes

Center Pull – Caliper Brakes

Dual Pivot Caliper Brakes

Answers.com

Levers as Brakes

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.

Belts are similar to chains

Belts were used to power factory equipmentprior to the use of electricity.

http://engineeringjohnson

Briggs and Stratton website

Resources

• http://bicycling.about.com/od/thebikelife/ss/History.htm