Car Tutorial Part 4 - Wheel openings, Rims and Tires

Ed Ferguson, CascadiaDesignStudio.com



Wheel Openings:
In side view draw a closed curve for the wheel opening. I started with a 15” radius circle and modified its points to make the curve below.



Extrude the curve (with Cap Ends checked) to the depth of the wheel well. Make three copies and position in place for the remaining wheels.



Perform Boolean > Difference to make the wheel opening.
Select the outer edges of the wheel opening and Fillet 0.3”.



Rims and Tires:
There are tutorials in the MoI forum and elsewhere on the web for making Nurbs car rims. A great one by Majik Mike is here: http://moi3d.com/forum/index.php?webtag=MOI&msg=5470.1

My method below is pretty straightforward and I’ve included my 3DM file below for those who want to try it. The shape and contour of the spokes is easily changed by modifying one or two curves.

Draw a profile curve for the top half of the rim. There are wheel blueprints on the web to use as a guide, or use the curve in my attached 3DM file.

Draw the profile 10” high by 10” wide. This profile curve will get revolved into a 20” diameter rim after a few steps. When completely finished, we’ll resize our finished wheel / tire combination to the exact desired diameter and width via the Edit Size window.



Next we’ll draw the cutting object to define the spokes from the front view. Think of this object as the negative space between the spokes.

Draw a 9.1” radius circle and a 12.3” x 9.1” triangle and arrange as follows:
Perform Boolean > Isect, selecting the triangle then the circle.
Select the resulting “slice of pie” closed curve and Fillet 1.0”.



Tip: We will instruct MoI later to perform a single, yet complex, fillet operation on the spokes. For cutting objects like this I find it’s best to construct them with Boolean operations and fillets rather than hand-draw the curve. A complex fillet operation works much better when curves and radius corners are constructed with precision.

Arrange the rim profile curve and the green cutting profile above as follows.



We will sweep the green profile closed curve into a solid cutting object. To do so, add two rails (green curves) to guide and shape the sweep.



Sweep the cutting profile using the two rails (Auto Profile, Maintain Height = un-checked, Cap Ends).



Select the pink rim profile and perform Construct > Revolve, picking two points on the bottom straight line when asked to pick the revolve axis start and end points.

The result is our 20” diameter rim. Note that because we Revolved a closed curve, our rim is a solid object.

I attached the car_wheel.3dm file below containing the construction curves to give a head start making your own wheel.