130 likes | 480 Views
GEAR RATIOS. Putting Gears to Work. Reverse direction of rotation Increase or decrease the speed of rotation Move rotational motion to a different axis Keep rotation of two axes synchronized. Understanding Gear Ratio. Circumference of a circle – Diameter multiplied by Pi
E N D
Putting Gears to Work • Reverse direction of rotation • Increase or decrease the speed of rotation • Move rotational motion to a different axis • Keep rotation of two axes synchronized
Understanding Gear Ratio • Circumference of a circle – Diameter multiplied by Pi • 1.27” x 3.14 = 4.0” • Circle with 0.635 diameter has a 2” circumference • Smaller gear rotates twice for each rotation of larger gear, gear ration is 2:1
Gear Teeth • Prevent slippage between gears – synchronizes • Counting teeth on each gear determines exact gear ratio • If one has 60 teeth & the other has 20, the ratio is 3:1 • Slight imperfection in gear diameter doesn't matter, ratio is controlled by number of teeth
Gear Trains • To create large gear ratios, several gears are connected together
Worm Gear • Creates very high gear ratio • Threaded shaft engages teeth on a gear • For each turn of shaft the gear moves one tooth, if gear has 40 teeth, 40:1 gear ratio is achieved
Planetary Gear Train • Say you want gear ration of 6:1 with input & output gears moving in same direction • Planetary gears are very compact & produce the same effect
Planetary Gear Train • Different gear ratios can be achieved depending on which gear is the input & output & which one is held still • Automatic trans use this gear set to achieve different ratios for each gear range. • Using clutches & brake bands to hold different parts of the gearset stationary & change inputs & outputs
Gear Synchronizing • To have two gears that are far apart rotation in the same direction, put a big gear between them • Or use two small gears between them • A more practical approach is to use a toothed belt or chain