Car Tutorial Part 18 - Fuel Door

Ed Ferguson, CascadiaDesignStudio.com

Fuel Door Assembly:

Let’s make a round fuel door 5” in diameter with a flange 7” in diameter.

Draw a profile curve 3.5” x 0.5”. Make sure the left end has a radius. Select the curve and revolve. The resulting solid is the basic fuel door flange.



Draw a 2.5” radius circle and two rectangles (2” x 0.8”). Arrange per the top drawing.

Make a copy and Trim / Join to create the closed curve shown at the bottom. Select the curve and Fillet 0.25”. This step of rounding all eight corners is very important.



Center the curve over the blue solid and Boolean > Merge. The result is two solid objects.



Assign a unique Style (color green) to the center object (cap). Fillet 0.1”.

Select the inside edges on the blue flange and Fillet 0.1”.

Select the green cap and move it slightly above the blue flange.

Shrink the green cap proportionally by changing its Z dimension in the Edit box (with Maintain Proportions checked) from 0.5” to 0.49”. The result is a small clearance between the fuel cap and the flange.



Next we’ll make the recessed mounting screw heads. Draw a circle with a 0.26” radius. Draw Curve > Polygon and make a 6 sided polygon inside the circle. Duplicate the hex curve and move it back. Draw a slightly larger circle and move it forward to define the bevel. Loft the four curves using Loft Style = Straight, Profile = Exact, and Cap Ends = Un-checked. Select the rear hex curve and perform Planer to cap it off. Select the entire object and Join.



Position the screw head at the 12 o’clock position on the blue flange. Rotate the screw head axis as necessary so it is tangent with the curvature of the flange. Position the screw head so it sets just above the surface of the flange. Select the screw head and perform Array > Circular using Item Count = 6 to place six screw heads around the flange.

Boolean Difference the blue flange with the screws. Select the blue assembly, the orange screws, and Join.

Here’s the final Fuel Door assembly which will be recessed into the car body. It has more detail than found in most other parts of the car model. But because it will be added to the car body in an area used for some close up render shots, the level of detail here will pay off.



Position the Fuel Door assembly where you want it on the car body. Rotate as needed to make it tangent with the body in top and back views.

Select the edge that makes the front of the blue flange). Ctrl+C Ctrl+V to copy / paste. When you copy / paste an edge this way, the “paste” becomes an independent curve object which is automatically selected. Select all the segments of this new curve and Join (shown in yellow below). Enlarge the curve radius 0.5” to produce the larger circle shown in yellow below.



Select the body panels that surround the Fuel Door assembly and Trim with the large yellow curve (circle). Delete the sections of the body that were trimmed. The result is an air gap around the assembly. In back view, move the Fuel Door assembly so all parts of it are slightly inside the car body.



Select the edges just below the fillet on the blue flange, and the edges around the car body hole. Perform Blend with G2 Continuity and Bulge= 0.8. Assign the car body Style to the blended surface.



Hide the blue flange, select the inner edges of the car body opening and perform Planer to close the bottom. This insures we can make the car body a solid again. Because of the prior Trim operation, the car body is no longer a solid. Select the entire body, Join, and verify it’s now a solid.

Unhide the Fuel Door assembly and render. I applied a spun metal material.