THE
WAY GEARS WORK
Gears are very versatile and can help produce a range of movements that can
be used to control the speed of action.
In basic terms, gears are comparable to continuously applied levers, as one
tooth is engaging, another is disengaging. The amount of teeth each gear wheel
has affects the action on the gear wheel it engages or meshes with. The gear
wheel being turned is called the input gear and the the one it drives is called
the output gear.
Gears with unequal numbers of teeth alter the speed between the input and out
put. This is referred to as the Gear Ratio.
Gears
also alter the direction of rotation. In the above example gear wheel A is rotating
clock wise but as it turns, gear wheel B is moved anti-clockwise.
The
drive gear (A) is known as the input gear.
The
gear that is being turned (B) is referred to as the output gear.
CALCULATING
RATIOS
The following example shows how the ratios are calculated.
If the input gear
(A) has 10 teeth and the output gear (B) 30 teeth, then the ratio is termed
3 to 1and is written down as 3:1
Ratio = number of teeth on the output gear B (30)
number
of teeth on the input gear A (10)
= 3 and is written down as 3:1
1
The first figure (3)
refers to how many turns the input gear (1) must turn in oerder to rotate
the out put gear 1 full revolution.
Simply divide the
amount of teeth from the input by the output gear to work out the ratio.
The principle behind gears is also very simple. In the above example, for
every complete revolution of the input gear the out put turns 1/3 of the way
round. This means you are slowing down the action and is referred to in engineering
terms as “Stepping Down”. If we reverse everything then the opposite
happens and we “Step Up”. Know it takes 1 turn of the input gear
to turn the output gear 3 revolutions and the ratio is now 1:3.
10
teeth
30
teeth
10
teeth
30
teeth
Output
gear
Input
gear
Stepping
down has the advantage of producing more power although at a slower rate. This
is often a big advantage with Automata as some of the mechanism can get stiff
or are under tension and it makes turning the handle easier.
Stepping
up produces a much faster output speed, but mechanically delivers less power.
Be aware of this as you may find that your Automata doesn’t work properly
or the handle is very hard to turn. However it is useful if you want something
to move more quickly in relation to other things or just to go very fast.
This
Automata has gear ratio of 3:1. So for every 1 turn of the handle the drive
shrft turns1/3 of a revolution
INPUT
OUTPUT
INPUT
OUTPUT
