Car Tutorial Part 5 - Wheel openings, Rims and Tires continued
Ed Ferguson, CascadiaDesignStudio.com
In front view select the green cutting solid and Perform Transform > Array > Circular using 5 for the Item Count. Note: Due to the taper in the green cutting objects, the spokes will be larger than they appear below.
Select the pink rim, perform Boolean > Difference, and select all five green objects to subtract.
Notice below that we have nice single-surface inside corners and large radius features to help insure the fillet process in the next step goes well. You don’t want small slivers of surfaces and curves with non-tangent kinks. Again, starting with a well-made cutting object is the key.
Select all the green surfaces and Fillet 0.4” Circular.
The rim looks good from the inside as well.
Let’s add some detail to the spokes next.
Make a pocket on the spokes to add some interest. This is a challenge because we want to pocket a complex object, with the bottom of the pocket matching the curvature of the top surface. I tried various methods using extrusions, trims, insets, lofts, blends with limited success.
So, after experimentation I ended up using the following pocketing technique for complex shapes:
Make a closed curve to define the shape of the pocket. I drew one straight line at an angle, Mirrored it, and used Blend at Bulge = 0.7, Continuity = Tangent (G1) to form the rounded ends. Select and Join all four line segments into a closed curve.
Position the cyan closed curve over the spoke.
Perform Construct > Curve > Project to map the closed curve onto the spoke.
We need to produce a surface for making the pocket. To do so, select the wheel and perform Trim, using the projected curve as the cutting object.
I assigned a cyan style to the trimmed surface for visual clarity.
Select the cyan surface and Construct > Offset Shell. I used a 0.8” shell. Just be sure to use a value that doesn’t puncture through the back of the spoke.
The resulting shelled object with the wheel hidden for clarity.
Now, we need to keep the cyan object while reversing the Trim operation we made in the prior step. So, select the cyan object and press Ctrl-C to save it to the clipboard. Then hit the Undo button (4 times in my case) until the wheel reverts back to a solid object. ( I tried to Join the wheel back into a solid after the Trim, but without success, thus the Ctrl-C and Undo trick).
Ctrl-V to paste the cyan object back. (Hide the wheel and you’ll see it.) Select the cyan object and Circular Array to duplicate it onto each spoke.
Boolean > Difference the wheel while selecting all five cyan objects as the objects to subtract (you may need to hide the wheel to select the five cyan objects).
Pocketed spokes:
Select the top edges around all five pockets and Fillet 0.2” with Shape = Circular
Note: There were several very short edge pieces, so be sure to zoom in when selecting edges.
Filleted spoke pockets are shown below. I’ll leave them cyan Style so I can assign a unique material in the render program, such as a dark rough cast surface, to set this feature apart from the rest of the wheel.
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