Hello, I have multiple gears in my design. Using "gear mates" I can mate them, but if you've used this, you know that though the gears "rotate' relative to each other correctly, they do not mesh while rotating. I've looked at the documentation extensively, as well as "physical dynamics" and "collision" detection, but haven't found a way to make the gears mesh while rotating. Has anyone come up with a good way to do this. I am using SW 2004 - perhaps 2005 has better mates than this? Any help is appreciated. I did look at "mikejwilson.com" - he has an example of this, but it's for 2001+, and it "breaks" during conversion to 2004 such that I can't tell waht's going for the mates. Mike Tripoli mtripoli - at - hell dot com BTW - "GearTrax" from Camnetics ([URL="http://www.camnetics.com"]www.camnetics.com[/URL]) is excellent for working on gears. It provides not only everything you could want for gear design, but you can generate an Excel spreadsheet, it generates the solid model that you then do whatever you want with, etc. No, I do not work for them, I paid the 0.00 for it, and it was worth every penny.