Sorry Ron, I have been away on my hols and have only just seen your post… :rolleyes:

I would also say animation nodes - you can use the Expression node for complex mathematical calculations in a single node with multiple inputs. However, some functions are not available in raw form just yet - like **sqrt( )**, but you can use **math.sqrt( )** instead - also math.sine, etc. For Pythogorean calcs this works in a single expression node:

**math.sqrt( (x **2) + (y **2) ) **- where x and y are two inputs from other nodes.

Which produces the square root of x[SUP]2[/SUP] + y[SUP]2[/SUP] rather than use lots of Math nodes. I understand from the developer that more functions will be available with version 2, obviating the need for the **math. **bit. I am currently investigating rigging my train - two bogies - using animation nodes rather than drivers, it seems to be a better option, but will take me some time I think. I will post it on my Animation Nodes WIP https://blenderartists.org/forum/showthread.php?434089-Animation-Nodes-A-Thread-For-All when I have done it. I want to port all my complex drivers over to Expression nodes in time. :spin:

I haven’t looked at your file yet - later today is an option and if I get any more bright ideas, I will let you know.

Cheers, Clock.

PS. Just PM me if you don’t see quick responses from me for mathematical questions, I am ultra-busy just now with my new glider, new ISP, new email system, new website, blah blah blah…:yes: I know there are not too many mathematicians on this site, but I will always help and a PM will nudge me.