Hello all,

 Just to add some extra to this discussion for other creators facing the same problem.

 The pivot approach of lesbentley is the right solution. The rocking chair motion is exactly similar to a wheel rolling without slipping. In this case, the translation (To be more precise, the pivot axis translation) should be equal to the length of the arc. Mathematically, the length is equal to:

Arc length = Length of the radius x rotation angle (radian)

Length of radius is the distance between the floor and the pivot axis when the rocking chair is on the floor.

 Rotation angle is the rocking angle given in radians. Why to use radian instead of degree (Poser unit are degree)? Simply because it is the direct way to link the arc of a circle to the radius. However, as one radians equal 57.3 degrees, the transformation is very simple:

 Radian value = Degree value / 57.3

 Working example (lesbentley model)

 The pivot is at 0.268 Poser unit from the floor.

The rocking chair rotate by 22 degrees in both direction

 Arc of circle = 0.268 x (22/57.3) = 0.1029 Poser unit

 0.1029 is the translation value to keep in mind

 

Now, we can compute directly the Delta value to insert in the translation channel

 Delta = Slave / Master = Translation / Rotation = 0.1029 / 22 = 0.004677

 Remember that Delta value calculation is with Poser Native unit.

 Note: The value of 0.004677 is near the value of lestbently which is after some transformation is 0.00445

 

For those of you that work with Poser 8 and above, you teach the rotation channel as:

 First key

          Master (rotation channel) = -22

          Slave (translation channel) = -0.1029

Second key

          Master (rotation channel) = 22

          Slave (translation channel) = 0.1029

 The translation value of the slave channel is given in Poser native unit, but can be in the unit that you set in the general preference. In this case, the arc of circle (the translation value) should be calculated with the same unit.

 The above calculations are very precise (It is math) but the location of the pivot point is not. You should be careful to set correctly this point.

Keppel: If you need more help, sent a e-mail via this site, but lesbentley is better than me for all the ERC coding.