This can not be key framed!
I have a gear, crankshaft and piston.
the piston motion needs to be explicitly in the X axis

I made the gear rigid with initial spin velocity and constrained with nail. (It spins fine and stays in place)
I constrain the crankshaft to the gear with a pin constraint.  ( it stays attached to the gear )
I have used a parent constraint on the piston between the crankshaft on X axis only . ( piston X translate works great on Y or Z motion.)
the problem is the end of the crankshaft does not stay attached to the piston.
When I add another constraint from crankshaft to piston (hinge constraint for example), the piston now moves in X,Y,Z.
It is now a rigid body and I cant figure out how to control Y and Z translate.

I need to point constraint the crankshaft to the piston and lock Y and Z translate.
how can I constrain the end of my crankshaft to the piston keeping x axis translation only?

I have tried to use barrier constraints on the piston to keep it from moving in Y and Z but no luck.

Thanks

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looks like a double-transformation problem
make sure your pivots are centered where they should be…

might also need to freeze geometry on your objects before rigging it up…

Alternatively, you should be able to set this up with a skeletal system with kinematics

n8skow [FA]