May 20, 2013 1 Comment
Bicycle have lots of karma and charm. A collection of gem-like devices, individually clever and, when connected, produce a mechanism that's brilliant. Like a skilled acrobat, its accomplishments seem like tricks.
Among these devices, I'm partial in the extreme to wheels. Puzzling through the years over this irresistible attraction, I've discovered some clues. The wheel is not singular. It's a multi-function event whose complexity defies simple analysis. Like "flames dancing" (Duchamp) it is difficult to take in all these facets at once.
This is the hypnosis of a crafted diamond. Brilliant light shapes project in multiple directions. Move and you see something new. No two-eyed human can take it in at once. By the way, diamonds are one of the four forms of pure carbon* found in nature, and carbon is the sixth element.
Where are we going? The wheel does at least six independent tasks at once (not including its attraction of fools like me and Duchamp).
(1) A wheel: rotating about its center, enabling terrestrial mobility like nothing humans have yet devised. Due to a highly tensioned design, the bicycle wheel is unique and represents perhaps the apogee of wheel functionality. That story goes back thousands of years.
(2) A tire interface: half the pneumatic tire system. Much of wheel design concerns the dimensional and force requirements of this challenge. When the pneumatic tire appeared, wheels got a supercharge.
(3) Brake system component: for bikes with rim brakes (the vast majority), the rim is actually the disk of a disk brake system. Torque, abrasion, pressure, area, straightness, and heat involved in braking amount to a tremendous demand on the wheel's structure and material options. Hub brake forces are also key drivers of design.
(4) Transmission element: at least half your gears live on the rear wheel. The internal or external gears of the hub define much of this zone of the wheel. Consequent torsional forces must be addressed with many specific design features.
(5) Suspension: the spoked structure is resilient and flexible. Without some give, neighboring components (forks, in particular) would need to be much stronger. Seat posts and handlebars would break, not to mention extra vibration to the rider. The amount that a wheel flexes is a necessary element affecting the design of all other parts.
(6) Steering system: the front wheel is the gyroscopic part of a single track vehicles's stability. This feature (spinning mass creating strong directional forces) explains how bikes can be ridden by 4 and 80 year olds alike, learned by any person who can walk.
These diverse requirements of a bicycle wheel are the design demands that govern cost, weight, dimension, material choice, and force management. They define the wheel. It evolved to do these things. I want you to see them all when you behold or work on a wheel.
Let's explore these facets. I'll devote a blog post to each. So, with minimal interruptions, look for six episodes that illuminate this gem-like complexity.
BTW, "20 Tips" may interfere from time to time, but my aim is to cover these six dazzling tricks as swiftly and interestingly as possible.
* #1 - amorphous (pencil lead, charcoal), #2 - 2D (carbon fiber), #3 - 3D (diamond), #4 - Nanostuff (Bucky balls, etc.).
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