Page 22 - Making things move_ DIY mechanisms for inventors, hobbyists, and artists

Chapter 1 Introduction to Mechanisms and Machines 3

3. Multiply and/or change direction of force A system of pulleys can lift a
heavy box up while you pull down with less effort than it would take to lift the
box without help.

4. Multiply speed The gears on a bicycle allow the rider to trade extra force
for increased speed, or sit back and pedal easily, at the expense of going
slower.

It turns out that all complicated machines are made of combinations of just six classic
simple machines: the lever, pulley, wheel and axle, inclined plane, screw, and gear.
These machines are easy to spot all around us once you know what to look for.

1. Levers

You can consider a lever a single-mechanism machine. It’s a mechanism, by our
definition, because it has moving parts. It’s a machine because it helps you do work.
A lever is a rigid object used with a pivot point or fulcrum to multiply the mechanical
force on an object. There are actually three different classes of levers. Each kind of
lever has three components arranged in different ways:

1. Fulcrum (pivot point)

2. Input (effort or force)

3. Output (load or resistance)

First Class Levers
In a first class, or simple, lever, the fulcrum is between the input and output. This is
the classic seesaw most people think of when they hear the word lever, as shown in
Figure 1-1.

Things can balance on a seesaw in three ways:

1. The two things can weigh exactly the same amount, and be spaced exactly the
same distance from the fulcrum (the way it looks in Figure 1-1).

2. You can push down on one side with the same amount of force as the weight
on the other side. Your parents may have done this with you on seesaws
when you were a kid.