Why don't inline 4's use this type of crank?

Why don't inline 4's use this type of crank? Balances primary forces like normal but without fricked rocking couples?

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  1. 10 months ago
    Anonymous

    You're just shifting the problem to another aspect.

    • 10 months ago
      Anonymous

      How?

      • 10 months ago
        Anonymous

        Fortnine did a nice video on it recently. Motorcycles, but engines are engines.

        • 10 months ago
          Anonymous

          Can you please post the link, just for clarification I'm not talking about a crossplane online four I'm talking a flatplane but in that configuration

  2. 10 months ago
    Anonymous

    Yamaha R1 uses a crossplane I4.

    • 10 months ago
      Anonymous

      I'm not talking about a crossplane, the picture I posted is a up down up down FLAT plane

    • 10 months ago
      Anonymous

      Whereas in the Yamaha it's TDC middle middle BDC

  3. 10 months ago
    Anonymous

    The primary forces will be worse, you are creating two rocking couples because pistons traveling the same direction are a different distance away from the center of mass.

    • 10 months ago
      Anonymous

      >pistons traveling the same direction are a different distance away from the center of mass
      This is the reason regular I4s have a perfect primary balance, it's secondary forces that are the problem because momentum of pistons and whatnot and IIRC that's a problem that can't really be fixed with four cylinders without greatly negatively affecting primary balance

    • 10 months ago
      Anonymous

      like said, the primary balance will be worse. the engine would rock back and forth due to the center of gravity for each piston pair having been offset

      • 10 months ago
        Anonymous

        See

        I know what a rocking couple is but the two rocking couples in this situation cancel out because two rotational forces going in the same direction but connected to each other cancel each other this is why two gears meshed together can't be spun in the same direction because the right side of the first rocking couple is trying to rotate the crankshaft down while the left side of the second crankshaft is trying to rotate it up it should have BETTER balance because in the up down down up crankshaft the two rocking couples are BOTH exercising a downward pressure on the inside of the crank and and upwards pressure on the ends

        • 10 months ago
          Anonymous

          [...]
          [...]

          the red line i put on your original image marks the center of the engine, now look at the rocking couples that i outlined in squares in relation to the center line.

      • 10 months ago
        Anonymous

        I know what a rocking couple is but the two rocking couples in this situation cancel out because two rotational forces going in the same direction but connected to each other cancel each other this is why two gears meshed together can't be spun in the same direction because the right side of the first rocking couple is trying to rotate the crankshaft down while the left side of the second crankshaft is trying to rotate it up it should have BETTER balance because in the up down down up crankshaft the two rocking couples are BOTH exercising a downward pressure on the inside of the crank and and upwards pressure on the ends

        The primary forces will be worse, you are creating two rocking couples because pistons traveling the same direction are a different distance away from the center of mass.

    • 10 months ago
      Anonymous

      I know what a rocking couple is but the two rocking couples in this situation cancel out because two rotational forces going in the same direction but connected to each other cancel each other this is why two gears meshed together can't be spun in the same direction because the right side of the first rocking couple is trying to rotate the crankshaft down while the left side of the second crankshaft is trying to rotate it up it should have BETTER balance because in the up down down up crankshaft the two rocking couples are BOTH exercising a downward pressure on the inside of the crank and and upwards pressure on the ends

      • 10 months ago
        Anonymous

        As I said, the distance of (pistons traveling in the same direction) from the center of mass is different
        This means that the levers are unequal, therefore the resulting forces are unequal and won't cancel themselves out. This is literally high school physics

        And if that doesn't convince you, don't you think that over the last 100 years, car manufacturers who spend billions on r&d wouldn't come up with and adopt this configuration if it was any good?

        • 10 months ago
          Anonymous

          What the frick are you talking about the centre of a rocking couple is at the centre of the next closest piston moving down lmfao, both situations have two distinct rocking couples at the exact same position

          • 10 months ago
            Anonymous

            jesus christ anon. if you can't see why the engine wouldn't rock back and forth in that pic then i can't help you any more.

          • 10 months ago
            Anonymous

            except it does dude, you can't just say it doesn't. This is why every single makers have 1 and 4 opposing 2 and 3

          • 10 months ago
            Anonymous

            i'm talking about the lower half where 1 and 3, and 2 and 4 are paired.
            why do you think straight 6s have opposing pistons paired?

          • 10 months ago
            Anonymous

            I thought we were talking about i4's

          • 10 months ago
            Anonymous

            just pretend cylinders 1 and 6 don't exist. the point is to show the opposing pistons cancelling each other out. if it was paired 1-4, 2-5, 3-6, there'd be crazy vibrations.

          • 10 months ago
            Anonymous

            Take two gears try spinning them disconnected in the same direction then change direction now mesh those gears and try to do the same thing, you can't because the rotational forces cancel out and there's no back and forth motion lmfao

          • 10 months ago
            Anonymous

            except it does dude, you can't just say it doesn't. This is why every single makers have 1 and 4 opposing 2 and 3

            Take two gears try spinning them disconnected in the same direction then change direction now mesh those gears and try to do the same thing, you can't because the rotational forces cancel out and there's no back and forth motion lmfao

            fml. i meant if you can't see why the engine WOULD rock back and forth in the bottom pic.

      • 10 months ago
        Anonymous

        >the first rocking couple is trying to rotate the crankshaft down while the left side of the second crankshaft is trying to rotate it up
        Ok, a little practical exercise, since you don't seem to get this
        Stand up straight and put your arms out to your sides, like a crucifix position
        First, try to move your arms up and down, both in the same direction. Like a bird would flap its wings, do it as fast as you can
        Second, try to move them in opposite directions. Move one arm up while moving the other down. Again, as fast as possible
        Now compare, in which of the two did your torso move less?

        This is exactly what primary forces are, your configuration would cause the engine to shake from side to side because the forces try to make it rotate

        • 10 months ago
          Anonymous

          That's fricking moronic situation because in that situation the second situation that is a single rocking couple and the first situation it's two

  4. 10 months ago
    Anonymous

    I'm getting a feeling that this is simply premium quality bait because no one can actually be *this* moronic
    Like, even actual downies have some inherent, instinctual understanding of balance

    In case it's not bait, well, you're wrong OP, you should've paid attention in high school physics but don't worry about it, not everyone is built to be an engineer

    • 10 months ago
      Anonymous

      judging by OP's latest response, i don't think this is bait at all now.
      godspeed in your engineering adventures OP

  5. 10 months ago
    Anonymous

    Couples prevent the pistons from stressing the crank.

    • 10 months ago
      Anonymous

      Ok maybe this is an actual answer that makes sense, up down up down would prevent rotational vibration but result in a increase of stress at the crankshaft where the rocking couples connect

      • 10 months ago
        Anonymous

        The couples balance each other during combustion stroke.

  6. 10 months ago
    Anonymous

    The Mustang GT350 does that, but with 2 of them in a flat plane V8. It requires massive dampers to deal with the primary imbalance, and it would only be worse on an I4.

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