66.
When bevel gears having equal teeth and equal pitch angles connect two shafts whose axes intersect at right angle, then they are known as

69.
In order to have a connecting rod equally strong in buckling about X-axis and Y-axis, the moment of inertia about X-axis should be __________ the moment of inertia about Y-axis.

70.
The connecting rod bolts are tightened up so that tightening stress