sentences:  The backlash of a gear train equals the sum of the backlash of each pair of gears, so in long trains backlash can become a problem.For situations that require precision, such as instrumentation and control, backlash can be minimised through one of several techniques.For instance, the gear can be split along a plane perpendicular to the axis, one half fixed to the shaft in the usual manner, the other half placed alongside it, free to rotate about the shaft, but with springs between the two halves providing relative torque between them, so that one achieves, in effect, a single gear with expanding teeth.