Bicycle mechanics and repair decal mechanical engineering 98 198 spring 14 lecture 7
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Bicycle Mechanics and Repair Decal Mechanical Engineering 98/198 spring 14 Lecture 7. Components. Nipples. Rims. Hub. Spokes. Types of Wheels. Rims. “Clincher” tire. Tensions spokes uniformly. Provides surface for brake pads. Spoke holes. Braking Surface. Hook. Increases

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Bicycle mechanics and repair decal mechanical engineering 98 198 spring 14 lecture 7

Bicycle Mechanics and Repair DecalMechanical Engineering 98/198spring 14Lecture 7


Components
Components

Nipples

Rims

Hub

Spokes



Rims

  • “Clincher” tire.

  • Tensions spokes uniformly.

  • Provides surface for brake pads.

Spoke holes

Braking

Surface

Hook


Increases

Wheel Strength

And integrity

Tubular

(tubie, tubs,

sewups)

Vs

Clincher

(hook-rim,

wire-bead)


Hubs

Freehub body

Holes for spoke elbows

  • Tensions spokes uniformly.

  • Provides axis in which wheels rotate.

  • Rear hubs are threaded for a freewheel or contain a freehub body for a cassette.


Spokes

  • Tensioned uniformly throughout the wheel.

  • Connected to the hub and rim.

  • Supports weight and other forces placed on the rim.

  • Threaded end connects to rim.

  • “Elbow” end connects to hub.

  • Different lengths, gauges, butted

Elbow

Threads


Compression

Tension

Concrete

Rope

Good in compression

Poor in tension

Good in tension

Poor in compression


Spoke in tension and compression
Spoke in Tension and Compression

Good in Tension

Poor in Compression


Spoke pretension
Spoke Pretension

If the spoke is pretensioned, the tension has to be overcome when the spoke is compressed

Pretension > Applied Compression

Pretension

+

Applied Compression

=

Sum

Pretension < Applied Compression

Pretension

+

Applied Compression

=

Sum

Spoke Collapses

The greater the pretension, the greater the applied compression can be


Nipples

  • Connects spokes to the rim.

  • Allows for tensioning of spokes.

Spoke

Nipple

Spoke Wrench

Rim


A wheel stands on its spokes
A Wheel Stands on its Spokes

The wheel does not hang from the top part of the rim

High Tension

Lower Tension

Compressive force from road

Only works because the spokes have been pretensioned

http://www.astounding.org.uk/ian/wheel/


Advantages of high spoke tension
Advantages of High Spoke Tension

The greater the spoke tension, the greater the

compressive forces the wheel can withstand

Carry greater loads

Take bigger hits


A true wheel
A True Wheel

  • Wheels with no or very little imperfections such as wobbles or hops.

    • New, or like-new


An untrue wheel
An Untrue Wheel

  • Wheels with a slight amount of wobbles or hops that prevents even rotation.

    • This DOES NOT include wheels that have broken joints, sandwiched, squashed, dinged, broken hubs etc.


Spoke wrench
Spoke Wrench

  • Different shapes but perform same function

  • Make sure it is fully on the spoke or you risk stripping it


Spoke and nipple
Spoke and Nipple

Loosen

As you are looking from the outside of the wheel into

the rim, clockwise (righty) to tighten spoke.

As you are looking into the rim, counterclockwise

(lefty) to loosen spoke


Righty tighty lefty loosey

Righty-tighty, Lefty-loosey




Dish (centering)

  • wheel must be centered between dropouts

http://thebiketube.com/wheel-building/how-to-dish-bike-wheel

http://www.youtube.com/watch?v=N1C2dZnUvuM


Truing basics
Truing Basics

  • Check the damage

  • Nut-Bolt

    Spoke nipple - nut

    Spoke – screw/bolt

  • Check tension of all spokes


How to fix a wobble nick
How to Fix a Wobble-Nick

  • Find your wobble

  • Know what is “center”

  • Spoke adjustment

    Tightening pulls rim

    Loosening pushes rim


Serious problems
Serious Problems

  • If wheel has multiple wobbles, fix worst problem areas first and repeat with other problem areas.

  • Check the wheel again and make sure all spokes are properly tensioned.


How to replace spokes
How to Replace Spokes

  • Remove broken spoke and rim tape

  • Replace nipple if needed

  • Pull spoke through hub

  • Cross spokes like other spokes

  • Thread into nipple and tighten

  • Remove cogs if necessary

  • Grease the threads!!!


Riding on a bent or broken spoke
Riding on a Bent or Broken Spoke

  • Spokes provide the tension that pushes against the ground. Without spokes, the wheel will be very weak and will easily warp.

  • Replace missing/broken spokes ASAP and check spoke tension regularly.


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