A gear train is made up of five spur gears as shown in the figure. Gear $$2$$ is driver and gear $$6$$ is driven member. $${N_{2,}}{N_{3,}}{N_{4,}}{N_5}$$ and $${N_6}$$ represent number of teeth on gears $$2,3,4,5,$$ and $$6$$ respectively, The gear(s) which act(s) as idler(s) is/are

Which one of the following is used to convert a rotational motion into a translational motion?

The following are the data for two crossed helical gears used for speed reduction:
Gear $$I:$$ Pitch circle diameter in the plane of rotation 80mm and helix angle 30^o

Gear $$II:$$ Pitch circle diameter in the plane of rotation 120mm and helix angle 22.5^o

If the input speed is 1440 rpm. The output speed in rpm is

Tooth interference in an external involute spur gear pair can be reduced by