A
lever is a device that applies force or transfers it. They are simple mechanisms
that usually consist of a stiff length of wood or metal which pivots round a
fixed point called a fulcrum.
Most
machines will employ some form of lever and you will find that they are used
a lot in Automata. It is useful therefore to understand how they work and how
to use them in your own designs.
Levers work on the principle of “mechanical advantage” which can be
worked out in a simple equation and is used to compare the effort applied to
the load moved. We will look at this formula a little later on.
Archimedes established the Law of the levers in his book “On the equilibrium
of planes” .
He formulated that there were three separate types (or orders as they are referred
to) which have their fulcrum, effort and load arranged in different ways.
A
little bit of theory
A lever can produce a small output motion from a large input force such as when
using a crow bar. A lever can also be used the other way round. A small input
movement can be increased by a lever to create a larger output movement.
Moving the fulcrum point, the effort or load points can affect the effectiveness
of a lever. For example if you move the fulcrum point on a class 1 lever towards
the effort, the load travels further but takes more force to move it. The opposite
happens when you move it towards the load.
In engineering terms, you are experimenting with the “Mechanical advantage”
of the lever.
There is a price to pay for gaining mechanical advantage. When a small effort
moves a larger load the smaller effort has to move a much greater distance
than the larger load. At the scale we normally work with Automata, much of
this will not really affect you. The important thing about levers is the way
that they can be used to transmit, amplify or decrease movement.
First
order levers.
A first order lever has its fulcrum point between the load and effort. A good
every day example of a first order lever is a pair of scissors.
Second
order lever.
A second order lever has its fulcrum and effort at opposite ends and the load
some where between the two. A good every day example of a second order lever
is a wheelbarrow.
A
third order lever
This has the fulcrum and load at opposite ends with the effort some where between
the two. A good every day example of a third order lever is a shovel
Large
movement of effort
Small
movement of load
