[ODE] AMotors and Universal joints

[luca regini]

I have a chain made of universal joints. I need to rotate the chain along
its main axis.
Attaching an AMotor between the last bodies on the chain and setting the
velocity on the chain axis doesn't work ( pheraps because the joint forces
the relative orientation about this axis to be fixed). I tried other
approached but they didnt' work. Someone can give me a suggestion???

Greets,
Luca

P.S: Since i am working on a research project my boss can also consider a
paid consultancy if someone is interested.

Greets
Luca