The ratio in a drive system is represented in reference to the number 1.
A ratio of 2 to 1 would be signified by 2:1.
A ratio of 1/4 to one would be signified by .25:1.
To find the total ratio, use the
Ratio = (Radius of Driven Sprocket) / (Radius of Drive Sprocket)
Example: On a bicycle, the sprocket that is attached to the pedals is the
drive sprocket and is 4 inches in radius. The driven sprocket at the rear
wheel is 2 inches in radius. What is th total ratio?
Ratio = 2 / 4
Calculated out this drive has a .5:1 ratio. For every full revolution
of the pedals, the rear wheel turns 2 revolutions.