Law of gearing ( in very simple words)

for Power transmission between two shafts there are mostly two type of mechanisms are used 1) chain or belt drive 2) gear drive..

But where constant velocity ratio is required and for power transmission for shorter distance gear drives are used.

Gear drives also helps to increase or decrease RPM of driven shaft..

Law of gearing ' WHEN TEETH OF TWO DIFFERENT GEARS ARE MESSING WITH EACH OTHER AT THAT TIME COMMON NORMAL OF ANY TWO MESSING TEETH MUST PASS THROUGH  PITCH POINT.'

If common normal passes through pitch point then we can get constant velocity ratio.

=» Figure for law of gearing is as shown..

Formula for law of gearing is ( by figure)
w(2) / w (1) = O(2)P / O(1)P

FOR DERIVATION OF IT REFER TWO FORMULA SHOWN IN FIGURE.

LAW OF GEARING PROVES THAT GEAR DRIVE HAS CONSTANT VELOCITY RATIO.