[img:6fd2e2374a]http://img12.imageshack.us/img12/5534/dumbgears.th.jpg[/img:6fd2e2374a]' alt='' /> huamin, It depends on what you want to do. Do you want to rotate the gears through large angles and see other parts of the machine move with them, or do you want to move very slightly to see the surface contact as one tooth advances? In either case, the Mechanism module can be helpful, but there are other possibilities, especially if you don't have Mechanism or haven't learned how to use it. One way is to use
Relations. For example, in the attached image you see 2 crude (straight-sided teeth) gears for illustration purposes. When you assemble the gears align each gear with an
Assembly Datum Plane that can rotate by means of its offset angle from one of the Default planes. Then write a relation such as the following:
$D4:1=-(1/K*(D1:1))+J In this example
D1:1 is the Datum Plane angle controlling the first gear,
D4:1 the angle controlling the second.
K is the respective ratio of the two gears' pitch diameters, and
J is a correction angle if necessary to establish initial mesh. The "
$" is necessary to allow negative values. It is also possible to write a series of
IF-THEN relations that will "exercise" your gear set by marching through a series of incrementing angles, but that's another topic. David
