http://static.howstuffworks.com/gift/transmittion-reverse.gift Which of the following statements
gives the most correct description of the system? Because the idler gear is smaller each tooth
will go through more cycles in a given period than the teeth on of the other gears Also, because
the idler gear is loaded in two directions, each tooth will see a foil reversal of the Sending stress
Tins combination of more cycles and full reversal means that the idler gear will fatigue before
the other gears Power and torque are the same for all gears (assuming no faction) However the
idler gear will fail first due solely to the fact that it is smaller, and thus the teeth go through more
cycle If there is no friction then all gears transmit the same power Power dictates the energy that
is put into the gear teeth and how Quickly fatigue will occur Therefore, despite the fact that they
are all different sizes, each gear can be expected to have the same life (given the statistical nature
of material properties The idler gear has to transmit for force because the power is the same, but
the issue is that it is smaller This means mote force is required to provide the same torque to
ensure the same power is transmitted
Solution
Statement 1 gives the most correct explanation. - The tangential velocity at the
contact points will be same for all the gears. Otherwise there will be tooth slip. Hence, the
smaller gear will rotate faster than the bigger gears. The idler gear is driven by one gear and
drives the other gear. Hence, the teeth encounter the reversal of bending stress which causes
fatigue. - Power transfer will be same for all the gears but not the torque transfer. This is so
because the gears rotate at different speeds. - Power does not dictate the energy that is put into
the gear teeth but the rate of energy transfer. The torque transfer capacity dictates the fatigue life.
- For same power transfer, smaller gear will transfer lesser torque because it rotates faster. Power
is proportional to the product of torque and rotational speed.