piston help ( or fun with nulls not)

[rexnoctu]

Ok I am doing (what I thought was) a simple piston setup. I haev one lower upper null parented to an arm with its target set as null 2. Null 2 is parented to a base with its target as null 1. What I want to happen is for the nulls to align in the pitch level only. What is happening is that as soon as number 1 passes over number 2, the heading spins 180 on #2.
I tried turning heading from follow target to KF and it follows until #1 passed over then it starts moving the wrong direction.
I am sure there is something ease that I am missing, but it is late and my mind isn't at it best.
Thanks for any suggestions or thoughts.

[richpr]

Try this link (http://www.lightwaveoz.org/brainiac.php) for Lightwave Oz...

At the bottom there seems to be something you could use...
Crankshaft tut... (http://www.abfk89.ukgateway.net/)

[jimnokc]

Hopefully I'm not steering you towards something I've downloaded as other content, but I am pretty sure it's on the LW CD.

Look and see if you have a scenes/_features/InverseKinematics folder, under there is a file called IK_Piston that should help you sort out the setup.

Again, I hope this was part of the shipping version and not something I've copied for a plug-in!

Jim