Questions about modeling car rim

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  10 October 2013
Questions about modeling car rim


I have started the Austin-Healey Sprite tutorial at nevercenter and ran into a problem creating the car rims in an efficient way.
As creating round objects with recurring geometry is certainly an everyday task, I assume it is a good idea to learn how to do this efficiently and as precisely as possible instead of creating similar (not identical, like it should ideally be) geometry several times.

So I created the basic shape of the rim as well as I could (my first model).
Then I created cylinders with the radius of the wholes in the rim with intention to use those to cut out the wholes with a bool operation.
Now I have been told several times that using bool operations is a quick and dirty approach because you can`t control the outcome and often you get problems in the mesh.
However, I`d like to use the cylinders as references displayed in shaded mode in the background while I would be cutting the wholes manually.

But I failed rotating the cylinders correctly as you can see on the attached screenshots.

It`s been a few weeks when I interrupted creating the model, so it`s possible that I can`t recall exactly what I did but I am confident that I can remember 95% of it.

I created one cylinder.

I created an array instancing the cylinder 12 times in a circle and positioned those over the rim.

A photo of the rim:

The first array of cylinders I created:

Bool substract did not work.
I assume, the green highlighing color indicates, that it`s still an array. That may be the reason that the bool operation did not work.
I therefore searched for a function to make the array into one single object.
I could not find such a function. This should be helpful in other situations, even if I don`t need it in this case. So, if you know where I have to look for it, let me know...

Then I noticed that the way the cylinders were oriented would actually not be accurate to tell me where I would have to cut for the wholes in the rim
So I created new cylinders and tried rotating them correctly but failed:
I devided 360 by 12 rotating each new cylinder by 30.
But each cylinder was contorted instead of rotated in a single axis.

Screenshots of my second attempt to create the cylinders. Incorrect rotation:

I am pretty certain that the problem is, that center of the rotation operation would have to be the exact center of the rim.

That means setting the manipulator for all cylinders in the center of the rim (or array of cylinders, which should be the same) and rotating cylinders based on that manipulator, correct?
I was not able to set the manipulator at the center of the rim (checked the manual).

Then, I imagine, it I should be able to create the intended outcome by rotating the first cylinder by 360/12 (on 1 single axis), the second cylinder by 2*(360/12) and so forth.
Yes, no?

As I mentioned, I have looked in the manual but found it was all not very detailed.

I am open to doing this differently, too. But I think there will be other situations where I the approach described makes sense.
  10 October 2013
I would probably model just one segment and manually construct the hole; then duplicate and rotate to complete the whole object.

Boolean subtractions will not be much help if you plan to subdivide the model.
Some basic silo tutorials
  10 October 2013
Originally Posted by Cinnsealach: I would probably model just one segment and manually construct the hole; then duplicate and rotate to complete the whole object.

Boolean subtractions will not be much help if you plan to subdivide the model.

I had something like that in mind. However I`d still like to know (and probably have to know that for this and other projects) how I can combine an array of objects to one single object and how I can move the manipulator so rotation operations for example have the intended results.

I haven`t found those questions answered in the manual.
  10 October 2013
you can edit the manipulator position in manipulator edit mode and place it where required manually or by selecting a component (selection menu). You may need to disable manipulator repositioning (selection - auto orient menu).

for the array, select the instances and de-instance them then combine. create menu.
Some basic silo tutorials

Last edited by Cinnsealach : 10 October 2013 at 03:52 PM.
  10 October 2013
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