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Relation btw angular acceleration of driveshaft and wheels.

This is a discussion on Relation btw angular acceleration of driveshaft and wheels. within the Mechanical & Civil Engineering forums, part of the CE : Technical Discussions category; Hello guys I read yesterday that angular acc at driveshaft is related to angular acceleration at wheels as: ang acc ...

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    Exclamation Relation btw angular acceleration of driveshaft and wheels.

    Hello guys
    I read yesterday that angular acc at driveshaft is related to angular acceleration at wheels as:
    ang acc (d) = ang acc(w) x N
    Where N is final drive ratio (differential)
    This shows ang acc at drveshaft is greater than wheels and therefore torque because,
    Torque = I (MoI) x alpha (ang acc.)
    How is this possible? Because diff amplifies the torque input i.e toque output of diff should be greater than input and so should angular acc.
    Last edited by rpower; 24th November 2009 at 01:10 AM.

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    CE - Apprentice BigOhm's Avatar
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    Default Re: Relation btw angular acceleration of driveshaft and wheels.

    You're jumping to an unwarranted conclusion. Consider for a minute a very artificial situation where a driveshaft rotates 4 times for each rotation of the wheel. Don't worry about what the differential is doing - this is a gendanken car. In order to get an acceleration of, say, 2 sec^-2 at the wheel, you must have an acceleration of 8 sec^-2 at the driveshaft.

    Now, the torque = I alpha formula is right, but you probably can't use it here since the driveshaft sees "reflected" I from the wheels. Look at this in terms of work and you'll see that, in the above situation, the driveshaft has only 1/4 the torque as the wheel.

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    Default Re: Relation btw angular acceleration of driveshaft and wheels.

    So u mean the driveshaft has greater ang acc but it has small moment of inertia as compared to differential gear, so it has less torque. IS it?

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