The term Windage can apply to several things.
For example, electric motors are affected by friction between the rotor and air. Large alternators have significant losses due to windage. To reduce losses, hydrogen gas may be used, since it is less dense.
There are two causes of windage:
The term can refer to:
There is a hydrodynamic effect similar to windage.
In firearms parlance, the word windage refers to the sight adjustment used to compensate for the horizontal deviation of the projectile trajectory from the intended point of impact due to wind drift or Coriolis effect. By contrast, the adjustment for the vertical deviation is the elevation. Kentucky windage refers to the practice of aiming to one side of the target to adjust for wind, without changing the existing settings on the gunsight.
Windage also refers to the difference in diameter between the bore and the ball, especially in muskets and cannons. The gap allows the shot to be loaded quickly, but reduces the efficiency of the weapon, as it allows gas to escape. It also reduces the accuracy, as the ball takes a zig-zag path along the barrel, emerging at an unpredictable angle.
In automotive parlance, windage refers to parasitic drag on the crankshaft due to sump oil splashing on the crank train during rough driving, and/or dissipating energy in turbulence from the crank train moving the crankcase gas and oil mist at high RPM. Windage may also inhibit the migration of oil into the sump and back to the oil pump, creating lubrication problems. Some manufacturers and aftermarket vendors have developed special scrapers to remove excess oil from the counterweights and windage screens to create a barrier between the crankshaft and oil sump.