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Tuesday, 26 December 2017

how does gear ratio affect speed?

Image Courtesy : Google
          The Gear ratio tells us how briskly one gear is rotating compared to different when two or more gears are interlocked. In general, when we connect two gears of different dimensions, consider the drive gear (which is connected to motor) is larger than driven gear then the driven gear rotate more quickely, viceversa.

Determining gear ratio of gear train:
          To form a gear train atleast two gears must be enguaged with each other, the one which is attached to the motor drive is called drive gear, and the which is attached to the load shaft is called driven gear. To transmit power some times we use any number of gears between the driver and driven gears. These gears are called "Idler gear".
         To findout the gear ratio take two gears of different dimensions, count the number of teeth on both driver and driven gear manually or some times this information is present on gears itself.
          Let us say that, our drive gear (Input gear) have 20 teeth and driven gear (Output gear) having 50 teeth. divide the output gear teeth by drive gear to determine the Gear ratio. Based on teeth number we may get gear ratio as a decimal, a fraction or in ratio form. In this case, divide 50 teeth of driven by 20 teeth of driving gear, it gives us the gear ratio as 50/20 = 2.5 (or) 5/2 (or) 2.5:1.
         This shows that if our input gear (having 20 teeth) is to rotate two anf half rotations to get one complete revolution of driven gear.
Determining speed of gear train:
          If our input gear (having 20 teeth) is rotating at 100 rpm, and it is connected to our output gear (50 teeth), based on this we can say that our output gear will rotate at 40 rpm.
Why?
Our gear ratio is T2:T1 = 50:20 ..... Or 2.5:1
          If our smaller gear rotates 100 rpm, our large gear solely rotates 5/2. It takes 2.5 rotations of our small gear to 1 complete rotation of our large gear. So our large gear is rotating at 5/2 the speed i.e., 40 rpm. If the number of teeth of smaller gear increases the speed of bigger gear decreases and viceversa.

What if our gear ratio where 1:4?
          In the above case our input gear is 4x larger as our output gear. If our input gear is rotating at 20 rpm ... each rotation, would result in 4 rotations of our output gear. Thereby our output becomes 80 rpm. 

By this we can say that Gear Ratio will affect the Speed of a gear train.

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