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I have a quick question about torque.

If I had a long shaft that was turning a screw and the screw was not turning due to a lack of torque, would making the modification in the picture (without increasing the power of whatever is turning the shaft) increase the torque at the bottom of the shaft?

i.e. would incorporating a crossbar of some sort increase the amount of torque at the bottom of the shaft? Thanks in advance!

enter image description here

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  • $\begingroup$ Why should that work? Remember you can't get free energy. $\endgroup$ May 17, 2020 at 5:12
  • $\begingroup$ Welcome to perpetuum. Please send me your personal details so I get get the contract ready. $\endgroup$
    – user257090
    May 17, 2020 at 7:43
  • $\begingroup$ Where is the force being applied on each object in the drawing? $\endgroup$ May 18, 2020 at 2:44

3 Answers 3

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I'm assuming that you're turning it around the square bit? That increases the distance from the pivot which I'm assuming is the middle of the circular arrow so it should.

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  • $\begingroup$ no still it just increases output force.. torque doesn't increase $\endgroup$ May 17, 2020 at 7:58
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You have to use gears to increase torque. If the shaft's input end is rotated by $\Delta\theta$, the output end also rotates by the same amount $\Delta\theta$. If the input torque $\tau$ did a work $\tau\Delta\theta$, conserving energy gives

$\tau_{out}\Delta\theta = \tau\Delta\theta$

Thus $\tau_{out}=\tau$

By changing the shape you have actually increased the moment of inertia and thus it makes harder for the motor to produce an acceleration. So now you have the same torque but a decreased acceleration.

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You are actually asking two questions, in the first you have constant torque from a motor, and in the second, when you use a crossbar, you have constant force, which is what we humans can do. In the second case the torque you can do increases with the length of the bar so you can unscrew the screw.

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