# Help with constraint rotating - Wheel with different parts (objects)

Hey BA,

I’m in desperate need for some help with rotating a wheel. My wheel group is comprised of 9 objects, from air release valve stems to brake discs (not all have the same center point and they’re at different locations on the rim etc), and I’m looking to simply rotate the whole wheel group 360 degrees in around 20 frames. I intend on rendering a still at the 10th frame with motion blur enabled, as I want to generate some realistic spin. My goal is to achieve a realistic rotation without wobbling or anything. I’ve looked into group rotation and that does not exist, so, without joining all of the objects into one whole object with baking (prefer not to as there are different materials), how would I go about this? I’ve tried rotating the objects around an empty as the target using local space, but it gets a little weird with the smaller objects of the wheel such as air valve stems (the objects which aren’t circular like the rim, disc and tire).

Hopefully there’s a solution out there and I’m not being too choosy.

Thanks!

Quite simple, really. Pick one central object, like lets say, the rim, and make the other 8 objects childs of the rim via parenting.

What do you mean by this:

Because that would be my first choice on how to do this. AFAIK, you don’t have to bake any materials. But maybe I’m missing something…

Randy

Thanks Randy, I’ll definitely use those pieces of advice. In the meantime, I found out another solution yesterday; I simply ditched the valve stem (because it was so small anyways—would’ve got lost with the blur regardless) since I realized that was the only non-circular object. I also realized that the disc+caliper shouldn’t move (duh), so from there it was easy to rotate 5 objects with the same center point. One thing that I ran into though was the 3º camber setting I had on the whole wheel, which was causing a wobble after framing. After a bit of thinking I remembered that I hadn’t applied rotation and scale to some of the objects, so after everything was reset and reframed, it seemed to rotate flawlessly on a 3º angle/axis!

Thanks for the advice again, I’ll be sure to implement it next time. One question though, let’s say I have the 9 objects with all different materials etc, could I then join them all into one giant object even with the different attributes? I would’ve thought that would screw up the materials, does it just embed them all somehow?

OK, glad you got it to working!

I have a few random thoughtws and tips to share with you…

1st, the disc has to rotate with the wheel, the wheel is bolted to it. The caliper is bolted to the car, and doesn’t move. The calipher sqeezes the disc to stop the wheel, thereby stopping the car. Anyway

As you found out, in blender it’s always best to apply loc/rot/scale to objects. In your case, all your moving objects should have the same loc/rot/scale, ideally being the center of the rotation. Then all objects can be rotated just by selecting them and rotating them.

You can also join all the objects into one object, very simple really. Select the rim, then shift-select all the other objects and ctrl-J to join them into one object. An object can have multiple materials on it, materials are assigned on a per face basis. So yes, you can have multiple materials on objects. Joining several objects and materials together just give you one big object (vertex wise) with lots of materials.

My suggestion of parenting all the parts was only made because you wanted to avoid joining the objects. Just join them, easy and works.

Randy

Whoops, of course! I think I accidentally typed that since I had the disc and caliper joined as one object.

Thanks for the knowledge again, I’ll definitely join everything next time instead of individually rotating each object from the wheel group. Wish groups had more function, though!