Gryroscopic or flywheel effect
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Thread: Gryroscopic or flywheel effect

  1. #1
    Senior Member Draxsr's Avatar
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    Gryroscopic or flywheel effect

    Oddball question - As most are well aware, when doing slow maneuvering with a v-twin motorcycle, some stability can be generated by revving the engine and applying some trailing brake while playing in the friction zone. Very slow speeds are achieved with the help of the forces created by the spinning parts of the engine (the flywheel?).

    Now, I'm an operator, not a maintainer and can't really speak to the accuracy of the parts involved, but know it does work. I wonder though, if the flat-6 in the F6B (or any Goldwing for that matter) gains similar benefits at higher RPMs. Or is the engine oriented differently?

    Any thoughts on this would be appreciated.
    2016 F6B Deluxe with goodies.

  2. #2
    Senior Member 53driver's Avatar
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    That's a great question!

    By design the HD V-Twin has "more" stuff spinning in the North-South plane than a flat 6 - flywheel, crankshaft, plus the primary and clutch plates.
    However, I think that most physicists will agree that stuff spinning in ANY plane will stabilize as much as long as it is equivalent mass at equivalent speed as long as that plane is not messed with too greatly.
    At slow speeds, almost no angle of bank, dragging the rear brake (or as close to that as we can come with linked brakes) I would say that any RPM increase that you can maintain steadily will help.
    Cheers,
    Steve
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  3. #3
    Senior Member shortleg0521's Avatar
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    Also there is what's called Fud,s 2nd law.
    That is to say , If an object is pushed with surfactant force it will
    become horizontal.

  4. #4
    Senior Member Travelor's Avatar
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    I think the gyroscopic forces developed by a spinning mass are applied at 90 degrees to the "axle" of the spinning mass. Hence, a spinning wheel remains vertical. If you hold a bicycle wheel by the axle and spin it, it resists an attempt to rotate the axle either in a horizontal or vertical rotation. But if you are holding it vertical (axle horizontal) straight out in front of you and raise your arms, there is no effect on the wheel. Likewise with a "V" twin - the mass of the flywheel is spinning in the same plane as the wheels (axle side to side) and thus provides stability in a vertical plane (helping to keep the bike from falling over). However, a flat six, with the "axle" of the rotating mass (flywheel, crankshaft, alternator and trans gears) in a longitudinal direction (front to back) does not provide any gyroscopic stability along its axis so there is no vertical stability provided as the bike leans from side to side. If all the rotating parts of the flat six are spinning in the same direction (which Honda does not do), you get a torque twist when twisting the throttle or down shifting. This has always been the issue with BMW Boxer twins until the latest engine iteration in 2014 where the redesigned engine rotates the alternator and clutch counter to the flywheel, greatly reducing the torque effect.

  5. #5
    Senior Member 53driver's Avatar
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    WELL PUT! Great example with the bicycle tire!
    So, if anything is spinning there will be stability, but the issue is 'along which axis.' Got it.
    Since the bike doesn't tip forward or backward, but rather to the left or right, the flat 6 gives no stability whereas the HD design does.
    It also means the HDs are more resistant to leaning over...lol.

    Thanks Travelor!
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    Saorla - 1995 FLSTN Heritage Special


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  6. #6
    One of the basic principals of the gyroscope is they remain stable in space. This is the reason they are used in air craft instruments so level flight can be maintained when the natural horizon is not visible.

    Riding a Goldwing is like opening a can of testosterone.
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  7. #7
    Senior Member Travelor's Avatar
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    Quote Originally Posted by 53driver View Post
    WELL PUT! Great example with the bicycle tire!
    So, if anything is spinning there will be stability, but the issue is 'along which axis.' Got it.
    Since the bike doesn't tip forward or backward, but rather to the left or right, the flat 6 gives no stability whereas the HD design does.
    It also means the HDs are more resistant to leaning over...lol.

    Thanks Travelor!

  8. #8
    Senior Member 53driver's Avatar
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    Quote Originally Posted by Retired Army View Post
    One of the basic principals of the gyroscope is they remain stable in space. This is the reason they are used in air craft instruments so level flight can be maintained when the natural horizon is not visible.
    That's exactly the approach I was coming from! The gyros in aircraft utilize 3 axes (or more) to keep a balanced reference for instruments and pilots.
    However, Travelor made me recall that while aircraft tilt in all three axes, our bikes tilt (fall over) in only one, so as long as the axis of rotation is perpendicular to the path of travel of the bike, that axis of rotation would apply to motorcycles.
    I think I need more coffee, I burned through all the brain cells awakened by the first cup...lol

  9. #9
    Senior Member P.Sutton's Avatar
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    On all my previous bikes, both dirt and street, I was able to “creep” forward as opposed to coming to a stop by increasing rpm and sliding the clutch against the brake. Even coming to a complete stop for a moment or intermittently without putting down my feet. With the F6B I immediately noticed how much harder this was when I first started riding it. I attributed this to the gyroscopic effect as all the other rotating assemblies were transversely oriented. I have learned on the B, not to focus just ahead (for instance, on the red light about to turn green) but to look as far down the road as I can and focus on a fixed point. This helps with balance and keeps me from having to put my feet down in some situations.

  10. #10
    Senior Member DaWadd's Avatar
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    This is all great reading
    2013 F6B in black of course

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