Gears and Gear Trains:
Student Learning Goal
The student will be able to identify and describe, in
quantitative and qualitative terms, the operation
and applications of gears (C3.1).
Gears and Gear Trains
SPH4C
Gears
Gears are toothed wheels on axles and are
therefore members of the lever family.
The teeth prevent slippage.
Purpose
Gears are used to transfer or change rotational
speed.
Example:
The load gear will turn at 1/3 of the rotational
speed of the effort gear (driver).
Gear Ratio
This ratio of the number of teeth of the effort gear
to the number of teeth of the load gear is called
the gear ratio.
Gear Ratio
This ratio of the number of teeth of the effort gear
to the number of teeth of the load gear is called
the gear ratio which is equal to the IMA.
IMA
Why would one want to use gears with an IMA of
less than 1?
IMA
Why would one want to use gears with an IMA of
less than 1?
The trade-off is that when you reduce speed, you
increase torque.
Example
What is the IMA of the following set of gears?
Example
What is the IMA of the following set of gears?
IMA = 4 (or the gear ratio = 4:1)
Gear Trains
To create larger gear ratios, gears are often
connected in gear trains, for example:
Each gear turns at twice the speed of the one to its left, which
means that the red gear turns at 2 x 2 x 2 = 8 times the speed
of the blue gear.
Planetary Gear Trains
Planetary gear trains allow the output shaft to be
along the same axis as the input shaft:
Such a gearing system would be used in a device
such as an electric screwdriver.
More Practice
Construction with Gears Lab Activity