@Dr-Sassi
Hi Dr. Sassi,
Thanks so much for taking a look at this. I can see your example works - but this is driving the user data of the matrix object, not the user data of an object within a cloner.
I attach an example that shows the problem. With the user data cloner if I switch it off the rectangle changes height. If you turn it on the changes stop. it does not seem to make a difference if I move the field driver tag to the cloner object.
user-data-xpresso-cloner_001.c4d

Hi,
I have cloner, cloning Xpresso rigs that drive Tracer objects (think animated Spirographs). The rig has user data to control the wheel size and pen position. I want to use Field drivers and Random Fields to make every cloned rig unique.

I am trying to use a field driver on user data I have set up for my rig. The user data is connected to my Xpresso setup for the rig. This does not seem to work.

It allows me to add the user data into the field driver parameter but the changes to the user data don't seem to affect the Xpresso or objects.

Is this a limitation of Field Drivers?

many thanks in advance!