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Thread: SBD Dauntless

  1. #371
    Imperial Guard kevjon's Avatar
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    Engine looks great, looking forward to seeing it with its final details.

  2. #372
    Here's a beautifully restored Wright R-1820...

    https://www.youtube.com/watch?v=H5uRUt0Jww8

  3. #373
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    Tu Fun, thank you for this video!
    It was an earlier R-1820F version (mine are the R-1820G100 or R-1820G200), so I could not use it as the direct reference.
    Fortunately it confirmed some of my assumptions about the rear oil slump and other obscured details.

  4. #374
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    In this post I will finish my model of the R-1820-52 “Cyclone”. (This is the continuation of the subproject that I started reporting in the previous post). Figure below shows the oil sump, used in this engine:



    Oil sump shape vary even within the same G100 family: I observed different proportions of the front “barrel” and its forward pipe in the early and the later of these “Cyclone” models. This particular oil sump (Figure "a", above) was used in the later G100s engines, like the R-1820-52. Apart from the forward pipe, it was also attached to the front crankcase via a “chin” (Figure "c", above).
    To avoid eventual confusion, I would like to clarify the multiple naming conventions of the same engine: In the further text I will also use the internal Wright name for this “Cyclone” family: R-1820G100, or simply “G100”. The R-1820-52 engine is one of its members. (A month ago I finished a model of one of the later “Cyclone” versions: R-1820-60, which represents another, the “G200” family). I explained details of these nomenclature in this post.
    While I have a few photos of the forward part of the oil sump, I have not any evidence of the shape of its rear part. (Because of the different shape of the intake pipes, I do not think that it forms the “Y-shaped” fork, like in the G200 series). All what I had found is a single, poor quality photo of the damaged engine recovered from Lake Michigan (Figure "a", below):



    There is “something” at the bottom of this crankcase: it has a trapezoidal shape and (probably) two inner (oil?) ducts inside. I decided that this is the rear base of the oil sump (Figure "b", above). It is quite thin (no more than 1 in), fitted between the crankcase main section (cylinder bases) and the intake pipe (Figure "c", above).
    As you can see, I have made lot of various assumptions about the rear part of this oil sump. Well, in every model you can always find some elements that have such a “hypothetical shape”. However, this is the last resort, when all my photo queries brought nothing.
    Fortunately, the video from TuFun's post confirmed these assumptions.

    As I described in my post about "Cyclone" versions, the R-1820G100 and R-1820G series used the same deflectors. Thus I recreated the upper deflector (the “rectangular” version) using photos of a restored R-1820G engine, from the F3F-2:



    I recreated the sheet metal frame and the flexible (rubber?) tip (Figure "a", "c", above). The photos from the recovered SBD-1 show, that there were some variations in the shape of the deflector rear part, around the spark plug. In the R-1820-32 from the SBD-1 I can see a kind of additional cut-out for the ignition cable, which is missing in this F3F-2. (F3F-2 had a different ignition harness – compare the deflectors in Figure "b" and "d", above).

    The top cylinder in the SBD-2…-4 had the elastic tip removed. (Because of the fitting the engine to the “Duntless” NACA cowling – I will show it later n this post). Thus I defined this deflector as another group instance, named F.G11.Deflector. (In the R-1820-60 model the top deflector is the part of the cylinder group).

    In similar way I modeled the side deflector:



    This deflector also has a flexible tip. As you can see, I skipped here some details (Figure "a", above) that do not appear on every object instance. Note the characteristic “bat-like” fitting in the front of this deflector (Figure "b", above). (The R-1820-60 deflectors had different fittings).

    The last remaining details are the spark plug harness and the oil scavenge pipe:



    As in the previous case, I am leaving the invisible, rear part of this engine in the simplified, “block” form.

    Finally, I imported the NACA cowling from the main model and placed the engine inside. Fortunately, it fits very well:



    In the R-1820-52 (and -32 in the SBD-2) the deflector on the cylinder 1 top was mounted without the flexible tip, to fit below the air intake duct of the upper cowling (Figure "b", above). Both of the cylinder 1 side deflectors also had their flexible tips removed, to fit below the gun troughs.

    In the R-1820-60 and -66 (used in the SBD-5 and 6) the cylinder 1 featured the full top deflector. (It was possible, because, as I explained in this post, SBD-5 and -6 had two filtered air intakes, used for takeoffs. For the higher airspeeds there was enough “fresh” air for the air intake hidden behind the cylinder row). The R-1820-60 had different fittings on the cylinder 1 side deflectors that fit the gun troughs (Figure "c", above).

    The R-1820-52 is now complete, for the assumed level of details. You can download the model presented in this post from this source *.blend file. I think that it can be also useful for the models of the other aircraft that featured the geared R-1820G or R-1820G100 engines. (Like Brewster “Buffalo”, DC-2 and some versions of the DC-3, or Curtiss “Hawk” 75). The exhaust stacks are not included, because this is an aircraft-specific detail (as the eventual air intake filters in the SBD-5 and SBD-6). I will recreate these details in the next post, for both of my ‘Cyclone” models.
    Last edited by wjaworski; 09-01-2018 at 6:48 PM.

  5. #375
    I'll have to model an R-1820-97 soon, so thank you very much for all this info. I hope it will help me pay attention to the right features.
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  6. #376
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    Quote Originally Posted by Skyraider3D View Post
    I'll have to model an R-1820-97 soon, so thank you very much for all this info. I hope it will help me pay attention to the right features.
    You are welcome!
    From this document it seems, that he R-1820-97 was (nearly?) identical to the R-1820-60.
    (You can find my R-1820-60 model in the *.blend file linked to my last post, in the scene named "R-1820-60").

  7. #377
    General Mark06GT's Avatar
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    Wow wow wow. You're attention to detail and accuracy is mind blowing.

  8. #378
    Thanks!!
    Did you see this document yet?
    http://www.enginehistory.org/Piston/...sAfter1930.pdf
    Last weekend I took a lot of photos of the 1100-hp GR-1820G102A, if you're in need of any reference for this version.
    Oddly enough there is no military model number specified for these, according to the document above, yet it powered many military aircraft.
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  9. #379
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    Excuse me for late answer, during last two months I was deeply engaged in another project (nothing special, just a boring, financial reporting stuff ).

    Mark06GT: thank you!
    Quote Originally Posted by Skyraider3D View Post
    Did you see this document yet?
    http://www.enginehistory.org/Piston/...sAfter1930.pdf
    Last weekend I took a lot of photos of the 1100-hp GR-1820G102A, if you're in need of any reference for this version.
    Oddly enough there is no military model number specified for these, according to the document above, yet it powered many military aircraft.
    Thank you! This PDF is a kind of the "Rosetta stone" for interpreting the "military" and "factory" symbols of the US aircaft engines. It shows clearly, that in fact R-1820-32 and R-1820-52 could be even the same engine (their specs are identical: even the weight). Just the R-1820-52 has a strange manufacturer symbol (N-765C9GA1). While the prefix "N-765" appears on this list for the first time, the rest of this symbol ("9GA1") match the "new" Curtiss nomenclature, introduced in the '40s. Later on this list there are more R-1820 engines with similar manufacturer symbols. Maybe they were the same engines, but produced on license by Studebaker?
    I would be grateful for the pictures of the of the GR-1820G102A, especially:
    • the propeller governor and its base (especially the rear sections of the base, between the governor and the cylinder row)
    • deflectors,
    • intake pipe bases on the crankcase,
    • the Stromberg-Bendix carburetor. (if it was used in this model).
    • oil sump (especially the middle and rear sections, and its base on the crankcase)
    Last edited by wjaworski; 10-27-2018 at 5:41 PM.

  10. #380
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    In my previous post I have finished the second variant of the R-1820-52 “Cyclone” engine, which was used in the SBD-3 and -4. (It looks like the earlier R-1820-32 model, mounted in the SBD-1 and -2). In the resulting Blender file linked at the end of that post you will find two “Cyclone” versions: the R-1820-52 (for the earlier SBD versions, up to SBD-4) and the R-1820-60 (for the SBD-5 and -6). Each of these engines has its own “scene”.

    To “mount” these engines into my SBD models, I imported both scenes to the main Blender file. I defined each engine variant as a group, to facilitate placing them in the aircraft models as the group instances. I also added the firewall bulkhead and updated the shape of the cowling behind the cylinder row. (I will refer to this piece as the “inner cowling”). So far I did not especially care for the shape of its central part, hidden below the NACA ring. Now I updated it for the real size and shape of the engine mounting ring (as in figure "a", below):



    On the photos I noticed a kind of bulges, extruding from the both sides of the inner cowling (figure "b", above). I assumed that they are shaped around small triangle plates welded on the sides of the mounting ring. (I have no photo to proof this assumption). Anyway, I modified the shape of the inner cowling in the SBD-5 to match this feature. I assumed that the inner cowling in the earlier SBD versions (SBD-4, SBD-3,…) also had such “bulges”.

    In Figure "b", above, you can see three openings for the intake air in the SBD-5 and SBD-6: a rectangular one in the middle and two round holes on the sides. These side openings are for the air filters, intended mainly for the takeoff and landing:



    The idea is that the during the dusty conditions on the airfield the direct intake door (1) is closed, while the doors for the filtered air: (2) and (3) are open. When the aircraft climbs higher, its pilot flips positions of these doors, closing the filtered air input (2), (3) and opening the direct input (1).

    There was no such a thing in the earlier SBD versions. It seems that the alternate filtered air input was introduced to many US aircraft in the same time: between 1942 and 1943. (You can also see the filter intakes in the P-40 starting from the M version, and in the P-51, starting from the B version). Maybe it was a general suggestion from the Army, after several months of the airfield war experience?
    I added these two filters and their intakes to the R-1820-60 engine:



    As you can see, these intakes are tightly fitted between cylinders 2-3 and 8-9 (Figure "a", above), so they have a quite complex shape (Figure "b", above). I do not have a photo for such an obscure detail, but the location of the filter determines, that the mixture intake pipes of Cylinder 3 and Cylinder 9 went through the corresponding intake body. (In principle, it is technically possible). I did not make holes in the deflectors between cylinders 2-3 and 8-9. (They would not be visible anyway, because both elements: the deflector and the intake are covered with black enamel).

    The next aircraft-specific element is the exhaust collector. In the SBD-4 and earlier versions its outer contour had a circular shape (Figure "a", below). However, in the SBD-5 (and -6) it went around the air filters, so it had a slightly different shape around this area (Figure "b", below):



    I built these collectors from simple tubular segments. Each of these segments is first tapered by the Simple Deform modifier (1), then bent along its shaping curve by the Curve modifier (2):



    The offset of the original tube object from the curve object determines the origin of the resulting shape on the curve. Small gaps between subsequent tubular segments are hidden under the joining rings (as in the real collector). 95% of this collector is closed inside the NACA ring, so I decided to not recreate the fillets along the edges of the individual outlet pipes. (Joining all these tubular meshes would be a time-consuming task).

    I used some photos to compare proportions of the exhaust collector, circular reinforcement and the cross section behind the NACA cowling in the SBD-3. The findings led me to the conclusion that I should modify the bottom part of the engine cowling:



    Many months ago I found that the cross-section of the lower inner cowling in the SBD-5/SBD-6 had a non-elliptic shape (shown in Figure "b", below). I also assumed, that such a cross-section also occurs in the earlier SBD versions. Now I can see that I was wrong: the photo above shows that in the SBD-1.. SBD-4 it was a regular ellipse (as in Figure "a", below):



    It seems now that Douglas designers modified a little the bottom part of the engine cowling in the SBD-5, shaping its circular “chin” (Figure "b", above). Maybe they did it because of the larger oil cooler used in this version? (It was required by the more powerful engine). If in the SBD-5 they shifted whole engine 3.5” forward, such an additional modification is also possible. (There was no any bulkhead at this station, and this cowling piece was already shaped anew).

    To determine the exact location of the engine along the fuselage centerline, I used the high-resolution reference photo of the SBD-5 (Figure "a", below):



    I shifted the engine along the fuselage centerline, until its crankcase matched the crankcase visible on the photo. Then I measured the f distance (Figure "a", abve) and applied it to the SBD-3 and SBD-1 models. (In the SBD-5 the engine together with the NACA cowling was shifted forward, thus in the SBD-1 and SBD-3 I could not simply apply the absolute location of the engine origin).

    Finally, I applied the materials to the engine models, copied the environments from the SBDs to the R-1820-52 and R-1820-60 scenes, and made test renders:



    On these renders I placed the engines “in the middle of the air” just to be able to evaluate all their materials in the full light conditions. Due to relatively small size of most of the engine elements, I used here only the procedural textures. I did not apply to this engine models any oils stains or other dirt. The historical photos show that the blue enamel on the crankcase was kept surprisingly clear, even in the worn-out aircraft. The other parts of the engine are obscured under the NACA cowling, so there is no need for additional “dirt” textures. You can see it in the test render of the R-1820-60 “Cyclone” inside the SBD-5 NACA cowling:



    You can download the model presented in this post from this source *.blend file.

    In the next two posts I will work on the details of the cowling behind the cylinder row.
    Last edited by wjaworski; 10-27-2018 at 7:34 PM.

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