bicycle mechanics and repair decal mechanical engineering 98/198 spring 14 lecture 4
DESCRIPTION
Bicycle Mechanics and Repair Decal Mechanical Engineering 98/198 Spring 14 Lecture 4. Components. Shifter. Cable. Front Derailleur. Gear Basics. Cassette/Freewheel. Front Chain Rings. Gear Ratios. A gear ratio = number of teeth on the front chain ring - PowerPoint PPT PresentationTRANSCRIPT
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Bicycle Mechanics and Repair DecalMechanical Engineering 98/198
Spring 14
Lecture 4
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ComponentsShifter
Cable
Front Derailleur
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Gear Basics
• Cassette/Freewheel • Front Chain Rings
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Gear Ratios
• A gear ratio =
number of teeth on the front chain ring
number of teeth on the back sprocket
• Lower ratios make it easier to pedal
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Proper Shifting
• Shift only when pedaling forward.• Avoid “crossing” the chain as much as
possible.• Do not shift when pedaling hard (up a hill).
Crossed Chain
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What are shifters?Shifters are devices on your handlebars, stem or
downtube that allow you to change gears
Downtube shifters
STI shifters
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Types of Shifters
Stem-mounted shifters
Index shifter with integrated brake lever
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Types of Shifters
Bar-end shifter
Twist-style shifters
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How shifters work• 2 functional types of shifters– Indexed (Preset positions, “click” shifting)– Friction (Undefined positions, analog)
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Friction Shifters
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Index Shifters
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Shifter Cables
http://harriscyclery.net/product/ejac-french-gear-shift-cable-2367.htm
Cable head can be cylindrical(modern)
Cable head can be a disc(vintage)
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Shifter Housing
• Necessary for indexed shifting
• Can be used for tension shifting
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Front Derailleur Types
Top Pull Bottom Pull
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Front Derailleur Types
Double(also clamped)
Triple(also braze-on)
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How does it work?!
Pushes the chain to a different chainring
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Chain jumps to a larger chainring
Chain falls to a smaller chainring
Campy EPS http://www.youtube.com/watch?v=j9SgACoEQoE
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Shifting Mechanism
Possible cable directions Limit screws
=
Chain
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Installation
Align the bottom of derailleur cage to be lightly above the largest chainring
Angle cage by a couple degrees toward the rear of the bike
Source: parktool.com
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Initial Set Up-Upper Limit Screw
Source: techdocs.shimano.com
Step 1: set gears as shown above
Step 2: turn HIGH adjustment screw until a small gap on the right side is achieved
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Initial Set Up-Lower Limit Screw
Source: techdocs.shimano.com
Step 1: set gears as shown above
Step 2: turn LOW adjustment screw until small gap is achieved as shownStep 3: tension and secure cable
to derailleur
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Initial Set Up-Upper Limit Screw
Source: techdocs.shimano.com
Step 1: set gears as shown above
Step 2: turn HIGH adjustment screw until a small gap on the right side is achieved
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Initial Set Up – Adjusting Shifting
Source: techdocs.shimano.com
Step 1: set gears as shown above
Step 2: turn the barrel adjuster counter-clockwise until a small gap on the left side is set. Go through all gears and fine-tune.
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Source: techdocs.shimano.com
Set gears as shown above
Turn LOW adjustment screw until small gap is achieved as shown
Turn HIGH adjustment screw until a small gap on the right side is achieved
Set gears as shown above
Setting Limit Screws
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Fine Adjustment (trim)
• A properly tuned derailleur will shift between all front gears and not throw the chain off the chainrings.
• Even a well-adjusted derailleur may rub in some gear combinations
Clockwise = screws adjuster in = loosens cable tension = Moves derailleur inward
Counterclockwise = screws adjuster out = increases cable tension = Moves derailleur outward
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PROBLEM #1
• Max has a problem. Recently, he found that it was much harder to pedal than usual. What could be wrong with his bike?
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PROBLEM #2
• Austin has a problem. He tells us that he hears noises from his chain. What could be wrong?
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PROBLEM #3
• Chris has a problem. He has trouble braking! The brake levers are hard to pull and the bike has no stopping power. What could be wrong?