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Gyroscopic forces in motorbikes.

  1. May 31, 2010 #1
    Just a quick problem for you guys that goes a little bit further than my high school physics education.

    In recent years dirt bike manufactures have been trying to negate the effects that the crankshaft, through gyroscopic effect has over the motorbike. To take one example; the 2010 KTM 400exc. This bike is exactly the same as the 450exc apart from the engine. They have reduced the displacement from 449.3 to 393.4. They have done this by reducing the stroke of the engine.

    They have reduced the stroke (and therefore the diameter of the crank) from 63.4mm to 55.5mm. Now my question is would this have a large impact on the bikes handling through reducing the gyroscopic forces or would it be a perceptive effect by reducing and changing the power output of the engine and making it more ‘manageable’.
    I know that to figure out this properly you would need more weights and measurements but I don’t have access to them. I have tried but not luck. Any light that you guys could shed on this topic would be GREATLY appreciated.

  2. jcsd
  3. May 31, 2010 #2


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    Considering the engine is centrally located near the roll axis of the bike and rider, and that it is a 400cc single cylnder engine, I doubt it would have much effect on the rate of lean on a dirt bike.
    Last edited: Jun 1, 2010
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