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Thread: How many "G's" do you pull?

  1. #16
    apriliaforum prov-nov Vee Twin Pilot's Avatar
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    A Japanese I4 machine would be the G winner, lateral G's might be equal to the Eyetalian bros

  2. #17
    apriliaforum Junkie samnavy's Avatar
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    EvilEagle, I'm an E-2 Hawkeye NFO. I sit back in the tube look out my little window, but believe me, sometimes it's scarier than being up front!

    break

    VEE TWIN PILOT, you've just made no sense. Two bikes that accelerate at the same rate, ie... 0-60 in 3sec, would have the same forward acceleration coefficient regardless of engine.
    As for lateral G's, they really don't exist for a motorcyle. As a bike rounds a corner, the rider leans into the turn and the "G's" are absorbed by compressing the suspension, not accelerating the rider sideways off the bike as you are pressed to the side of a car while rounding a corner.
    NFO's do it in the back seat!

  3. #18
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    Originally posted by samnavy
    EvilEagle, I'm an E-2 Hawkeye NFO. I sit back in the tube look out my little window, but believe me, sometimes it's scarier than being up front!
    I can imagine! I don't think I could sit in the back seat all the time, I'd probably get airsick. I've got to sit in the backseat of one of our tubs on Wed night because the vice wing king wants to fly with NVG's; so they need an experienced NVG guy to watch him.

  4. #19
    apriliaforum expert RVZoo's Avatar
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    Originally posted by samnavy
    As for lateral G's, they really don't exist for a motorcyle. As a bike rounds a corner, the rider leans into the turn and the "G's" are absorbed by compressing the suspension, not accelerating the rider sideways off the bike as you are pressed to the side of a car while rounding a corner.
    Lateral Gs exist in a motorcycle as well... Otherwise you'd go straight... They may not be 100% 'lateral' to you, the rider. But you are changing direction laterally (on the road) so you are laterally accelerating.
    How does the rider feel the 'lateral' Gs? Similar to a plane pilot: the resulting vector of adding gravitational attraction (weight) to lateral acceleration seems to point 'down' in the pilot/rider reference system. Therefore, when cornering real hard on a motorcycle your apparent 'weight' increases. The effect is very exaggerated on a banked turn like those at Daytona.
    I feel too lazy now to do the math, but you just need speed and radius of turn to find lateral acceleration.
    Avoiding danger is no safer in the long run than outright exposure... Life is either a daring adventure or nothing.

  5. #20
    apriliaforum Junkie GeneS's Avatar
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    a=v2/r

    Lateral acceleration equals the velocity squared divided by the radius. Doesn't matter if you on an V2, I4 or even an E2.

    GeneS

  6. #21
    apriliaforum Junkie samnavy's Avatar
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    RVZoo, of course the laws of physics still apply to motorcycles and yes, lateral G's do exist to a certain extent manifested in the form of "down"... but then wouldn't this be vertical "g's" and not lateral... debatable and semantical.
    I can't ever recall a situation on my bike or my plane where I though I was going to slide sideways off the seat, in fact I think it would be nearly impossible in any controlled riding situation.
    My point was that lateral g's don't apply on a bike the same way they do in a car. When was the last time you saw a skidpad number for a motorcycle?
    NFO's do it in the back seat!

  7. #22
    apriliaforum Junkie GeneS's Avatar
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    The way lateral g's are sensed by the operator are different on a bike or in an airplane from in a car going around an unbanked turn. But as far as the action at the contact patch, the forces are identical.

  8. #23
    apriliaforum expert azmotogirl's Avatar
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    Separete an object in motion (car/bike, aircraft or watercraft- for 3 quite different types of conditions) from an object INSIDE this moving object (on this case a human inside moving unit).
    The combination and result of outside forces acting toward moving object are substantially different (air, water, ground), and according to the existing tehnologies parctically are the highest in the case of aircraft. The impact of g-forces is a result of a result of acting forces outside the system, (horizontal or verical- the same g=9.8 kg=32#).
    I don't think this forum is a good place to draw vector diagram or to spread equations- I don't want to make it too boring for everyone.

  9. #24
    apriliaforum prov-nov Vee Twin Pilot's Avatar
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    Originally posted by samnavy

    VEE TWIN PILOT, you've just made no sense. Two bikes that accelerate at the same rate, ie... 0-60 in 3sec, would have the same forward acceleration coefficient regardless of engine.
    As for lateral G's, they really don't exist for a motorcyle. As a bike rounds a corner, the rider leans into the turn and the "G's" are absorbed by compressing the suspension, not accelerating the rider sideways off the bike as you are pressed to the side of a car while rounding a corner.
    But a prilla and say a ZX10 do not have the same 0-60 times so an I4 machine will pull more G's when the fun knob is turned. Regarding lateral G's, the relation between theta (lean angle), velocity and radius of curvature (keeping center of mass constant), comes out as Vmax = 45 degree theta. The resultant force on the contact patch is acting away from the center of curvature. Kinda need some engineering background to understand all this

  10. #25
    apriliaforum Junkie samnavy's Avatar
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    "But a prilla and say a ZX10 do not have the same 0-60 times so an I4 machine will pull more G's when the fun knob is turned. "

    VeeTwinPilot, I'm not sure what you're trying to say here. You've basically just said that all I4's are faster than all Vtwins. A ZX10 is faster than a Mille for example because it has a lot more power... but not because it has four cylinders in a line. It is true that the current crop of I4 Jap litrebikes are faster than the current Italian Vtwins, but that's not a function of power, not engine type.
    And yours and GeneS comments regarding the contact patch are correct, but we've been talking about what the rider feels(right?) The G's felt by the rider!!! Who cares how much fun the tire is having!
    NFO's do it in the back seat!

  11. #26
    apriliaforum Junkie GeneS's Avatar
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    Got it, try this. The maximum lateral acceleration for a street tire on asphalt is about 1G. On a flat skid pad, a corvette will do about 1G laterally.

    The rider on a bike cornering with a 45 degree lean angle, will feel 1G divided by sin45 which is 1.41G.

    Some rubber compounds can generate more than 1G, that's why the motogp guys can lean more than 45 degrees.

  12. #27
    apriliaforum expert navydevildoc's Avatar
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    I suppose we need to get someone with an accelerometer on their bike and have a go at it... would be interesting to see the results.

  13. #28
    apriliaforum expert Bill in OKC's Avatar
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    Would this help?

    http://www.escortradar.com/gtimer.htm

    Says it has a built-in accelerometer.

    Nevermind, I found this in the FAQs:

    Can the G-Timers be used on motorcycles?


    We have done no testing on motorcycles. The cornering G-force reading will definitely not work, due to the way motorcycles lean into turns. The acceleration, braking, and timed run modes may work, providing the motorcycle does not lift its front wheel during acceleration.
    Last edited by Bill in OKC; 11-15-2004 at 05:30 PM.

  14. #29
    apriliaforum expert RVZoo's Avatar
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    ‘Lateral acceleration’ is just a term. As far as I know, it means how fast (at what rate) a given object can change direction laterally. The fact that the rider/driver/pilot can or cannot feel it or can feel it in this or that subjective direction is irrelevant. If the rider/driver/pilot is seating foot forward, upside down or backwards that’s irrelevant to the ability of a given object (self propelled or otherwise) to change direction laterally. Yes, it is usually used by car guys to talk about how fast a car can go around a skidpad, but nothing limits the term to that particular application.

    ‘G’s are just a measure of acceleration and one of the reasons it is used is because it relates to something we all have experienced: the gravitational attraction of the rock we call Earth.

    As a mere measure of acceleration, Gs could therefore be used to quantify any acceleration. Be it of cars, motorcycles, planes, boats or subatomic particles (Gs are not used for particles because of a matter of scale, not because quarks are not driven around a skidpad). Under these premises, it does make sense to talk about ‘how many Gs a motorcycle can pull’ so to speak. Be that acceleration in a straight line (doing the quarter mile or breaking, for example) or to change direction.

    The term was probably ‘made known’ by aviation for the simple reason that resulting forces usually point in the subjective direction the pilot calls ‘down’ therefore causing a sense of increased weight of his own body. Are you twice as heavy? Two Gs then…

    Oh, and if the conditions are right you don’t need a MotoGP bike with full race slicks to lean further than 45º. As a mere reference, you can go to: Motorcycle Design and Technology (Motorbooks Workshop) by Gaetano Cocco.

    Cheers.
    Last edited by RVZoo; 11-15-2004 at 07:08 PM.
    Avoiding danger is no safer in the long run than outright exposure... Life is either a daring adventure or nothing.

  15. #30
    apriliaforum Junkie 1-G'_rider's Avatar
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    the name speaks for itself lol had too sorry

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