Sum of torque

[dieter]

I would have to make them, with wood and saw, and a couple of inline-skate ballbearings, probably I go and get some plywood this evening


Can your simulation software export animations? That would help a lot. Also, looking foward to see your build!


BR

[EOW]

Like I saw my simulation, the angular velocities must not be w, 2w and 4w but w, 2w and 6w. With 2 supports, the motor and the Support1 need -6FRwt, the Pulley2 recover 6FRwt. But with one support, the motor and the support need -6FRwt and the Pulley2 recover 6FRwt, but there is the torque on the support, that torque gives the energy 2FRwt. It's necessary to check the sliding of the belt with w (support),2w(Pulley1) and 6w (Pulley2), if the sliding is 0 this could say the case with one support must give an extra energy to the support.

[EOW]

For explain the forces F1 and F2 in my last example. Take another simple example, I renamed forces, with one pulley. Apply a force F1 to the rope, that force is transmitted to F2 along the rope. F2 want to move the pulley to the left, so F2 apply a force F3 to the axis, the fixed axis reply and give the force F4. F1/F4 is a torque that turn the pulley but the support receive the force F3. With 2 pulleys there are 2 forces, and if the size of the pulley is not the same there is a torque. Do you understand ?

[EOW]

I made a mistake with the force with one support. If I brake the Pulley2 on the support, you're right there is no torque (first image shows all forces, grey color -> to the pulley, magenta color -> to the support and black colo -> to the belt).

Now, second image, I don't brake the pulley2, imagine it with a mass. I accelerate more and more the Pulley2, the energy is in the kinetic energy in the pulley. The sum of forces are like I drawn, no ? And the support decelerate because it receive a counterclockwise torque from force F1 / F2, no ?

[dieter]

Hi EOW,


I would say yes, as long as the pulley is accellerating, the inertia of the mass will give an opposite torque to the support. I guess this happens due to an imbalance of centrifugal force on the pulley shaft. Not sure tho.


BR