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Crank Shaft Effect


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Does the spinning of the crank shaft add gyro forces that add to the overall forces to overcome (or aid in some way) when cornering?

 

I've heard one reason 600's are easier to turn is because of the crank. So thought I'd through this out for some clarification,.

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Yes, it affects handling, and the heavier it is, the greater the impact. Which is why many two-stroke racers over the years ran counter-rotating cranks. Not that it helped all that much against the Hondas, which used a shared crank :lol:

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Does the spinning of the crank shaft add gyro forces that add to the overall forces to overcome (or aid in some way) when cornering?

 

I've heard one reason 600's are easier to turn is because of the crank. So thought I'd through this out for some clarification,.

 

it is true that the crankshaft is another gyro that you must force into another plane when turning, the wheels being the others. yes 600s have less gyro from the crank at a given rpm, however the effect is directly proportional to RPM and if you are one of those guys who who likes to spin the motor to the moon on a 600 entering a turn then you will kill the advantage that may have been there.

 

I have read riders talk about being able to feel the difference between an 03 RR (ZX600)and an 03 R (zx636). I did some research and found out the crank casting was the same and it was just offset ground to get the 1.4 mm / .055". Needless to say I fired off a letter to the editor that was not responded to. In all my riding and racing I have never felt that the engine gyro was perceptible when turning. I would add to that I am entering corners(turning)between 7 and 9,000 rpm.

 

Even with the S 1000 RR I don't feel the engine gyro and it is easy to spin and likes to rev like a 600. It may be my size at 200+ lbs, or the timing of my steering input (with the forks compressed from braking) but if I had to guess why a 600 seem easier to turn it would be weight in general.

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Yes, it affects handling, and the heavier it is, the greater the impact. Which is why many two-stroke racers over the years ran counter-rotating cranks. Not that it helped all that much against the Hondas, which used a shared crank :lol:

 

I believe the reason to counter rotate the crank was to try and keep the front wheel down by reversing the effect of the engine torque, much like a car rotates to one side when you rev it bikes want to rotate the opposite direction of engine rotation, most bikes spin forward lifting the front.

 

Gyroscopic precession will not be effected by counter rotation of the motor, it is generated when the axis of a gyro changes plane, not matter the direction of rotation. and No it doesn't counter balance the precession of the wheels, the counter rotation would have to be on the same axis to produce a neutralizing effect.

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I believe the reason to counter rotate the crank was to try and keep the front wheel down by reversing the effect of the engine torque, much like a car rotates to one side when you rev it bikes want to rotate the opposite direction of engine rotation, most bikes spin forward lifting the front.

 

 

 

That could easily be countered by turning the crank in the opposite direction, no? I think everything was tried and tested back then. Honda also tried counter-rotating cranks and found benefits, but refused to use it because it wasn't the Honda way.

 

Personally, I cannot feel the difference between a full and an empty fuel tank, but German magazine MOTORRAD tested a litre bike (Gixxer 1000 from memory) in a high speed slalom run with low and high rpm and there was a significant difference in speed. So there is little doubt that it will have an impact in how quickly a motorcycle will change direction, but what level it takes to notice I cannot say.

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I believe the reason to counter rotate the crank was to try and keep the front wheel down by reversing the effect of the engine torque, much like a car rotates to one side when you rev it bikes want to rotate the opposite direction of engine rotation, most bikes spin forward lifting the front.

 

 

 

That could easily be countered by turning the crank in the opposite direction, no? I think everything was tried and tested back then. Honda also tried counter-rotating cranks and found benefits, but refused to use it because it wasn't the Honda way.

 

Personally, I cannot feel the difference between a full and an empty fuel tank, but German magazine MOTORRAD tested a litre bike (Gixxer 1000 from memory) in a high speed slalom run with low and high rpm and there was a significant difference in speed. So there is little doubt that it will have an impact in how quickly a motorcycle will change direction, but what level it takes to notice I cannot say.

 

As for fuel load I have only really noticed when I made a 7 gallon tank for my 636 to do the Toyota 200 at Willow Springs. Having another 20 lbs right on top was very noticeable and killed the front grip for quite a few laps. The experiment worked however as it was a one stop race for me and I was in 7th overall first 600 when I pitted on lap 45. I couldn't wait for that fuel light to come on!

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  • 2 weeks later...

I rode a BMW boxer R1200S which is a sports tourer with an inline crank, and it does indeed seem easy to flick around. Difficult to describe but you get the sensation that the quick change of direction isn't down to insanely fast steering geometry. I also rode GSXR750 and 1000 recently (window shopping) and I thought the 1000 was harder to get turning, it felt as though it were heavier though in reality I don't think there are many kg in it.

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Wasn't the crankshaft gyroscopic effect the reason behind the MotoCzysz C1's longitudinal design and counter rotating crankshaft halves? I have to admit the depth and breadth of my knowledge on this comes from the documenatary "Birth of a Racer" from a few years ago. Can I assume that this design has not panned out since MotoCzysz seems to be focused on electric sportbike development? Or is this something that is still being worked on?

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