Bicycles and Simple Machines for Dummies

a bicycle crank arm is a class two lever

Over the Labor Day weekend that just ended, most of our staffers who are also cyclists took to the roads and trails around AN HQ to get some sun, fresh air, and sweat. As is often the case, they traveled at least a few miles on a popular local rails-to-trails path. One road warrior swears that he could double his income by offering to teach the riders there how to shift their mountain bikes at a couple of bucks a pop. It appears that they have no clue about "Bicycles & Simple Machines" – but neither did Cameron Deskins when he posted his Prezi,com slideshow of that title.

It's hard telling where Cameron might have been in his school career: kids usually study simple machines in about grade five, but this is probably a high school "communications" assignment, mostly because Deskins seems to know how to use a spell-checker. Whatever the case, Cameron seems to done fairly well with his little presentation; but, sadly, oversimplified his subject. We'll save the worst for last:

• Cameron gave far more emphasis to screws than necessary, since most bicycles have a surprisingly small number of screws. The frames are (usually) one-piece construction, after all. 
• He seemed to think that there are only two wheel and axle combinations on a bike. He was wrong: there are no fewer that four, and he carefully avoided mentioning the one that most people have problems with: the gear system (he reduces it to a pulley). He also seemed to forget that the cranks and chainring(s) form a wheel and axle.
• Deskins said that there is one lever on a bike, the handlebars. Kudos to Cameron for that, because the handlebars are a class one lever. Unfortunately, he didn't mention that the fulcrum of that lever is the axle of a wheel and axle system, the headset. Without that rotating axle, you couldn't steer!

Cameron's most glaring omission, however was his failure to recognize that the crank arms ("pedals") are also levers. They're class two levers, in which the load is between the fulcrum and the force (see image). Cameron is far, far, far from the only person who doesn't seem to understand the physics of a bicycle drivetrain. You only need to get out on a popular multiuse trail on a summer weekend to see that many people still don't understand that the whole reason for those gears is to reduce the amount of work necessary to get a bicycle up to speed and keep it there. They're all worthy of a Dumbass of the Day award, but this guy's the only one to put his name on the work. Sorry, Cameron, you're it.

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