Recreating the Wright R-1820 “Cyclone” (5)

In this post I will finish the first cylinder of the R-1820 “Cyclone”. It will be the “template” object, which I will clone eight times around the crankcase when I finish the other parts of this engine.

Although in my previous post the cylinder head received the full set of its cooling fins, it still lacks some details. One of them are the reinforcements of the valve covers:

Figure 87-1 Asymmetric reinforcements of the valve covers

As you can see, these reinforcements break the symmetry of the left and right valve covers. Both of them resemble a thick plate, but one is oblique, while the other is vertical. They are not the most prominent features of this cylinder head, and it took me some hours to determine their probable shape. Finally I classified them as the secondary features of the covers, which I have to recreate, for the assumed level of details.

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Recreating the Wright R-1820 “Cyclone” (4)

The fins of the air-cooled cylinder heads are a state-of-art piece of metallurgy (Figure 86‑1):

Figure 86-1 Fins of the R-1820 cylinder head

At the first glance, it is hard to believe that they were cast as a single piece. But when you look closer, you will discover that these fins “grow up” from the solid parts of the head as naturally, as the hair from the head (Figure 86‑2):

Figure 86-2 Close-up of the fin details

Try to imagine the shape of molds used in the production of these parts, and the challenges faced by their manufactures! (There is an interesting post about this. It describes production of the R-1830 Twin Wasp cylinders). Basically, modern producers of the heads for the air-cooled aircraft engines use the same technology as eighty years ago.

In my model I will recreate these fins in a somewhat simplified form, as a few separate Blender objects. I will also skip some fine details of their shape (for example the small features that I marked in the figure above). Such a simplification conforms the moderate level of details that I assumed for this model. It is always possible to make a more detailed version of this object later.

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Modeling the Carburetor Scoop

The carburetor scoop passed significant evolution in the subsequent Dauntless versions. In the SBD-1 there was a rather large air duct placed on the top of the NACA cowling (Figure 45‑1a):

Figure 45-1 Evolution of the carburetor scoop in the first Dauntless versions

However, it was quickly discovered that it obscures one of the most important spots in the pilot’s field of view: straight ahead and slightly below the flight path. That’s why it was somewhat corrected in the next version (SBD-2). In this aircraft the designers lowered the scoop, increasing the field of view from the cockpit. Such a solution persisted in the SBD-3 and -4. In the SBD-5 they completely redesigned it, placing the carburetor scoops inside the NACA cowling (more about this — see in this post the paragraphs around Figure 11-6).

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Modeling the Fin Fairing

In the SBD Dauntless the fillet along the fin and the fuselage was formed from the bent bottom edges of the fin panels. I am showing it in Figure 36‑1:

Figure 36-1 Details of the fin fairing

(To make some of these panel seams more visible on thee photos, I sketched along them thin lines). You can observe that each fin panel overlaps the next one, starting from the tip stamped as the part of one of the fuselage doors (see Figure 35‑8 in the previous post). The outer contours of these panes are not perfectly aligned: you can see small overlaps on the photos (Figure 36‑1). Surprisingly, such a detail makes the modeling more difficult. However, the most difficult part will be the seam between the fin and the horizontal tailplane fairings (see Figure 36‑1). It runs along the fuselage longeron, across the fillet between the stabilizers and fuselage.

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Cutting Out the Landing Gear Bay

In this post I will cut out the opening of the landing gear bay in the wing. In the SBD Dauntless its shape consists a rectangle and a circle (Figure 19‑1):

Figure 19-1 Landing gear bay in the SBD Dauntless
Figure 19-1 Landing gear bay in the SBD Dauntless

However, when you look closer, you will notice that the contour of the main wheel bay is not perfectly circular. There is a small deformation of its shape on the leading edge (see Figure 19‑1). I think that it looks in this way because of the technological reasons. Another feature of this opening is the fragment “cut out” in the bottom part of the fuselage, below the wing. (We will make it when we will form the fuselage).

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Details of the Outer Wing Panel

In one of the previous posts I showed details of the aileron bay. Now I separated the corresponding wing mesh fragment into a new object. I bent its upper edge like it was depicted on the photo (Figure 17‑1):

Figure 17-1 Internal wall of the aileron bay
Figure 17-1 Internal wall of the aileron bay

On some photos I could see that this wall was built of two pieces of sheet metal. Their seam was located below the aileron pushrod.

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