Creating A 3D Sopwith Pup, Part one: The Engine - Jeff Matheson - Page 4
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Here we have a piece that is a bit more complicated, with curves in two planes, an inset middle and a slot in the middle. Time for a ProBoolean! First, I set up a simple Box primitive, 6 segments and 5 wide. By converting this to an Editable Poly and editing the sides and end in vertex mode, I created the central narrow section and the fork at the end (where it will attach to the pushrod) (SCREENSHOT).
For the curved outline, create an Ellipse spline, and convert it into an Editable Spline. Edit it at the vertex level to stretch one side out to give the ellipse a long, egg shape (based upon the photographic reference). Extrude it, so that it cuts all the way through the previous object (SCREENSHOT). Once you are satisfied with the intersection of these two objects, create a ProBoolean compound object, and choose the Intersection option (SCREENSHOT). Viola! A fairly complex geometry in a few easy steps.
Continue to work with the ProBoolean object to cut the holes in the center, using a combination of a thin flat Box and a long square box (rotated 45 degrees). Add a simple Lathed spline object for the pushrod pin. The locking nut at the top and the bolt head at the bottom are simple Cylinders (with only 6 sides), with a ChamferCylinder for the bolt shaft itself (SCREENSHOT).
The final piece of the cylinder to be modeled was the spark plug. Since I was unable to find a good image of a period-correct spark plug, I kept this a bit more generic than I normally would have. To model the spark plug, I chose to Lathe a Line spline, even though the actual plug is made up of three different materials (a steel head, a ceramic middle, and a steel base. Once modeled, I converted the plug into an Editable poly, and using the Polygon editing mode, I selected the polygons for the head and gave them a Material ID of 1. For the middle ceramic part, I specified a Material ID of 2, and a Material ID of 3 for the base. By specifying different Material IDs for different sections of a single object, the textures applied can appear as to be multiple objects (SCREENSHOT).
STEP 2 - CREATING THE MAIN CRANKCASE
After reviewing the photographic reference, it was clear the that the main crankcase shape was that of a 9-sided, faceted cylinder. Each cylinder was mounted on an octagonal face, with smaller triangular faces separating the front sections. Basically, the main crankcase shape is similar to a big gemstone.
Begin by creating a simple Cylinder primitive, with only 9 sides. Use the background image to get the size and position correct for your cylinder. I compared a number of photos to make sure that the size I chose was accurate, even if the background image was a bit off due to perspective (SCREENSHOT).
To create the extra facets, convert the Cylinder to an Editable Poly and enter vertex editing mode. Select all the vertices, and using the Chamfer operator, adjust the object until all the octagonal faces appear to be symmetric (SCREENSHOT).
CYLINDER LOCK RING AND CYLINDER MOUNT
Each cylinder is attached to the main crankcase by a large lock ring, which encircles the base of the cylinder. The lock ring has a number of slots along its perimeter, which allows the mechanic to turn it with a large hook spanner. To model the lock ring, I chose to begin with another simple Cylinder, sized appropriately, and create the slots by extruding certain polygons. How many sides should this Cylinder have? The photographic reference shows that there are 8 slots on the ring, and that the proportion of slot to ring is about 1/5 (that is, each slot is only 1/5 the length of the section of ring next to it). This gives me 48 sides for my Cylinder (8x(1+5)) (SCREENSHOT).
After converting the new Cylinder to an Editable Poly, I select the Polygons that I intend to extrude (leaving the 8 equally spaced slots alone) (SCREENSHOT), and use the Extrude operator (in Polygon editing mode) to increase these sections by about 1/8"? (SCREENSHOT).
I also add a simple Cylinder to the bottom of the Lock Ring where the cylinder meets the crankcase (SCREENSHOT). This is the cylinder mount.
CRANKCASE FRONT AND CENTRAL SHROUD
The main crankcase also has a circular front part, where the pushrods and intake pipes attach. Bolted to the front of the main crankcase is a smooth, conical shroud which ends in the shaft for the propeller attachment. The crankcase front is half of a simple ChamferCylinder primitive (SCREENSHOT), and the central shroud is a Lathed spline (SCREENSHOT). To model the bolt heads, I used a combination of a 6-sided ChamferCylinder (for the nut) and a smoother 24-sided ChamferCylinder (for the bolt shaft). To reduce the number of polygons, I cut the second cylinder in half (since the vertices inside the nut would not be visible) (SCREENSHOT). Once 1 bolt head was finished, simply clone another 17 instances around the outer edge of the shroud (review the method used above to clone the ball bearings) (SCREENSHOT).
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