# Motor RPM

Document Sample

```					Gear Ratios

Calculations
The most used drive system on a
FIRST robot uses sprockets and
chains. It is vital to the success of a
robot to properly adjust the size of
sprockets in order to obtain the
maximum speed and power.
Balancing speed versus power can
be daunting but with a few basic
guidelines it can be made easy. Let‘s
examine a couple things to keep in
mind while choosing the right gear
ratio . . .
Types of
Sprockets
a) Driver Sprockets are directly
driven by a motor
b) Driven Sprockets mesh with
the driven sprocket
Gear Ratio Velocity
First, notice which sprocket has the
most teeth. This will be the sprocket that
completes one revolution. Take the
number of teeth on the driven sprocket
and divide that number by the amount
of teeth on the driver sprocket.
Driver Sprocket:   30 Teeth
Driven Sprocket:   10 Teeth
30/10   = 3:1 Ratio
Revolutions per Minute
Ex. 1:
To calculate the Motor RPM (60 rpm) x gear ratio (3:1)
RPM output of                 = 180 rpm
a given gear
ratio, take the   Ex. 2:
velocity ratio    Motor RPM (100 rpm) x gear ratio (1:4)
and multiply                   = 400 rpm
that number
by the RPM
output of the
motor source.
RPM with a Compound Gear
• The easiest way to calculate RPM on a
compound system is to split up the
problem into two equations or pairs
depending on the amount of gears
involved.
• After finding the ratio for each pair,
multiply them together with the motor
RPM to get your final RPM.
• see next slide for examples
Ex. 1: This example involves 4 gears. Gear A-
Driver Sprocket, Gear B and Gear C are
Fixed, and Gear D. The motor RPM in this
example will be 100 RPM.
Driver Sprocket-Gear A (30 teeth) / Gear B (10 teeth) = 3:1 Ratio
Gear C (20 teeth) / Gear D(50 teeth) = 2:5 Ratio

3:1 Ratio x 2:5 Ratio x 100rpm = 120 rpm

Ex. 2: This example also involves 4 gears. Gear A-
Driver Sprocket, Gear B and Gear C are Fixed,
and Gear D. The motor RPM in this example will
be 60 RPM.
Driver Sprocket-Gear A (20 teeth) / Gear B (15
teeth) = 4:3 Ratio
Gear C (50 teeth) / Gear D (10 teeth) = 5:1 Ratio
4:3 Ratio x 5:1 Ratio x 60rpm = 400 rpm

```
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
 views: 0 posted: 4/14/2013 language: Unknown pages: 7