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Why no spinners?

Engines Discuss Why no spinners? in the Technical forums; Why is it, that certain radial engined fighters, esp. American ones, don't have spinners? Seems to be the case with ...

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    Why no spinners?

    Why is it, that certain radial engined fighters, esp. American ones, don't have spinners? Seems to be the case with most (all?) R-1830 and R-2800 engined fighters.



    Russian, British and German radials usually all had spinners.

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    Quote Originally Posted by riacrato View Post
    Why is it, that certain radial engined fighters, esp. American ones, don't have spinners? Seems to be the case with most (all?) R-1830 and R-2800 engined fighters.

    Russian, British and German radials usually all had spinners.
    Good question. I'd think that the spinners would be added if they gave the plane another 10 or 20 m.p.h. speed.

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    Might have screwed with the airflow. Those later engined aircraft of WW2, especially the second gen stuff, had all sorts of problems with Air Flow to the back set of cylinders. Seems it was the biggest problem with them.

    Still a problem today. Have IO-540 (I think that's the number, it's a continental) and the two cylinders up against the back wall are always running hotter than the front ones. And that engine is air cooled too (with nowhere near the HP, around 310).

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    Senior Member Aaron Brooks Wolters's Avatar
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    I'm with you Tim. I think they were trying to get all the airflow they could get into the opening to cool the engine. I could be wrong though.

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    Senior Member davparlr's Avatar
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    The only production radial aircraft in WWII that I could find with a spinner were two, the Brewster Buffalo and the P-61. Several experimental and pre-production planes had one. Since all liquid cooled aircraft had spinners, they must have been an aerodynamic advantage so I would guess it was for cooling. It is noted that the one of the fastest radials in the war, the P-47M did not have a spinner. The experimental, and faster, XP-47J had one. The XP-47J had other aerodynamic clean-ups, so a direct comparison cannot be made.

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    All the above were correct answers. Aerodynamics, cooling, lack there of were all reasons why we seen spinners appear and disappear from some WW2 aircraft. Additionally maintainers may have left off the spinners because of an addition maintenance process that brought no value added to the aircraft's performance. Take a good look at some aircraft spinners and see how many screws hold them on. It's very time consuming removing and installing spinners.

    Another point is when they get damaged, they set up some pretty undesirable vibrations and technically you really can't repair a prop spinner as any repair to a spinner will upset its natural dynamic balance designed into it.

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    Bit of reading here, though might be speculative, about the spinners causing over-heating problems.

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    Glock Perfection Matt308's Avatar
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    Inhibit airflow to the radial cylinders while taxiing/idle.

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    Quote Originally Posted by Matt308 View Post
    Inhibit airflow to the radial cylinders while taxiing/idle.
    In some cases it was the opposite. the area around the hub and roots of the blades was a low pressure area and on some aircraft the air was going in the cowling by the edge and flowing back out near the hub without going through the cooling fins of the engine.
    some planes were fitted with blade root cuffs to help solve this problem, others with spinners and a few with flat disks (or nearly so) mounted to the front of the engine.

    See: http://yolo.net/~jeaton/fsmforum/307/001307.jpg

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    My guess is that the larger engines utilized by the USAAF required a sufficient amount of cooling, particularly in climbs.
    Considering that the top speeds of these planes were already higher than their contemporaries, it may have been a design niche to help preserve engine heat for performance in climb. The cuffs later fitted to props were said to also improve cooling with out consequence to performance.
    Id say definitely an air flow issue.

    Bill

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    Quote Originally Posted by FLYBOYJ View Post

    Another point is when they get damaged, they set up some pretty undesirable vibrations and technically you really can't repair a prop spinner as any repair to a spinner will upset its natural dynamic balance designed into it.
    That is a really good point that I forgot about. Thinking more so the prop than the actual spinner but they're part of the same system. But when your prop gets out of balance, it's annoying (possible fatal in some circumstances but it rarely gets to that point). Had it happen once with wood warping. One blade was ok, the other wasn't.

    It was a drag (pun intended).

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    Interesting points, thank you.

    Cooling and aerodynamics, or the trade-off between were probably the obvious answers. It's interesing how many non-US designs with the R-1830 seem to have a spinner (Saab 17 / 18, LeO 451, MB.176), whereas the US ones don't (but also the Fokker, for example).

    If I look at the R-1830 I also notice the era of the engine block (?) where the propeller connects to the drive shaft is round in shape probably to direct airflow to the cylinders.

    A spinner in front of that shape might mess with the airflow concept?

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    Quote Originally Posted by riacrato View Post
    If I look at the R-1830 I also notice the era of the engine block (?) where the propeller connects to the drive shaft is round in shape probably to direct airflow to the cylinders.
    Actually that is not the engine block but the propeller gear box and although takes a rounded shape really has nothing to do with airflow. What IS controlling airflow and cooling are those black baffles behind the cylinders.

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    Quote Originally Posted by davparlr View Post
    The only production radial aircraft in WWII that I could find with a spinner were two, the Brewster Buffalo and the P-61.
    There were more US types, such as: Douglas SBD-1 to -3, Curtiss SB2C-1, -4, and Lockheed C-69. The Helldiver case is of particular interest here, because on SB2C-3 and -5 variants spinners were omitted.

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    Benevolens Magister Airframes's Avatar
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    They were also on the early B26 'Marauder', and omitted on later production, I believe due to restricted airflow, and engine over heating.





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