Sprocket Selection

Overview

  • The amount of tension in the chains is largely effected by sprocket size
  • Assuming torque is fixed, a larger sprocket is equivalent to a longer moment arm, and therefore less force (tension)
    • Max torque is dependant on the amount of friction, which is a fixed value
  • To minimize tension, choose the largest sprocket that provides enough ground clearance between the playing surface and chain

Tension

  • The smaller the d2/d1 ratio, the less tension there will be
  • d1 = d2 − ground clearance
  • If tension is a concern, assuming the desired ground clearance is independent of wheel size, it is best to use a larger wheel size to reduce the above ratio
  • Note: the ground clearance used above may be less than the clearance between the base of the robot and the ground. This is because the chain is driven and may be able to free itself if it contacts an obstacle.