How to enable Screw pitch

[jamesp]

Hi,

Really sorry if I'm missing something obvious, but I can't seem to find a way to add a Screw joint.
Add->Joint only has Revolute, Prismatic, and Spherical.
Revolute joints have a Screw pitch parameter set to 0.0, however it's greyed out so I can't change it there.

Having the same issue in 3.5 and 3.6.1.

Any help would be appreciated.
Thanks!

[fferri]

Hello,

you can't have a screw joint in torque/force mode. Use another mode.

See Joint types and operation.

[jamesp]

Thanks for the reply!

Is that some kind of global parameter that needs to be set?
I had added a Resolute joint and played with its mode settings under Scene object properties, but the screw pitch field remained greyed out.

[fferri]

You have to deselect "Position is cyclic" as well.

[coppelia]

If you need a screw-type actuator in force/torque mode, then do something like:

revoluteJoint --> auxiliaryShape --> prismaticJoint

Then add a non-threaded child script to one of the two joint, and use a joint callback function that links the position of one joint to the other. This will give you a position-controlled screw.
If you need the force/torque to be able to travel from one joint to the other (and the other way round), then you'll have to use the Vortex engine, and link the two joints via the Vortex joint dynamic properties (Joint dependency-item).

Cheers