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### Author Topic: Length of a helix vs composition of forces  (Read 7138 times)

#### activ25

• Full Member
• Posts: 158
##### Length of a helix vs composition of forces
« on: September 21, 2018, 07:24:11 AM »
roll up a spring
« Last Edit: September 21, 2018, 06:15:19 PM by activ25 »

#### activ25

• Full Member
• Posts: 158
##### Re: Length of a helix vs composition of forces
« Reply #1 on: September 21, 2018, 09:30:30 PM »
The device
« Last Edit: September 22, 2018, 07:46:34 AM by activ25 »

#### activ25

• Full Member
• Posts: 158
##### Re: Length of a helix vs composition of forces
« Reply #2 on: September 22, 2018, 04:17:22 PM »
My logic:

1/ I suppose the device conserved the energy without the spring (the center of gravity of the helix moves).

2/ I add the spring, compared to the case 1/, I have the works from the torques from F on the axis 'x' and 'y' and I win the difference of the length of the spring: I give these calculations in the image.

I drew it but, note the disk has inside it a nut (fixed on the disk), when the screw thread rotates (relatively to the disk) then the screw thread moves up (60°)
« Last Edit: September 22, 2018, 10:14:15 PM by activ25 »

#### activ25

• Full Member
• Posts: 158
##### Re: Length of a helix vs composition of forces
« Reply #3 on: September 23, 2018, 09:37:40 AM »
I updated the images
« Last Edit: September 23, 2018, 02:16:39 PM by activ25 »

#### activ25

• Full Member
• Posts: 158
##### Re: Length of a helix vs composition of forces
« Reply #4 on: September 23, 2018, 11:15:06 PM »
I can cancel the centripetal forces and ONLY them. My spring don't use the centripetal forces, it uses the rotation of the screw-thread relatively to the disk.

My device don't use the centripetal forces but at least with the device to cancel the centripetal forces I can compare :

1/ without the spring, the energy is conserve, the SUM = 0

2/ with the spring, I gave all the new energies the NEW_SUM = SUM + new energies I gave. Like the SUM = 0, the additional energies must be at zero if the energy is conserved, it seems here it is not

#### activ25

• Full Member
• Posts: 158
##### Re: Length of a helix vs composition of forces
« Reply #5 on: September 28, 2018, 10:15:01 AM »
I corrected the sum of work

#### activ25

• Full Member
• Posts: 158
##### Re: Length of a helix vs composition of forces
« Reply #6 on: September 30, 2018, 11:32:01 AM »
the calculations

#### activ25

• Full Member
• Posts: 158
##### Re: Length of a helix vs composition of forces
« Reply #7 on: October 06, 2018, 10:52:20 AM »
I updated the calculations. No external gravity. No friction (to simplify the calculations). No external motor. The bolt doesn't turn around itself before I start to count the sum of energy.

#### activ25

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• Posts: 158
##### Re: Length of a helix vs composition of forces
« Reply #8 on: October 07, 2018, 11:39:27 AM »
with a torus helix composed of multiple segments join by cardan shaft. The nut must pivot around 90°, the pivot can be small if the number of segments is big.
« Last Edit: October 07, 2018, 05:56:24 PM by activ25 »

#### activ25

• Full Member
• Posts: 158
##### Re: Length of a helix vs composition of forces
« Reply #9 on: October 12, 2018, 09:10:57 PM »
To prevent to move the center of mass of the bolt I can move the nut down and more closer to the axis A1. The bolt rotates only relatively to the nut (no translation). Like that it is easier to the calculation AND for the real device.

The cycle:

The device has reach its angular velocity and it is like I drew. I can set OFF/ON the helix of the nut.

1/ The nut is set ON and just after the nut moves down and more closer to the axis A1, in the same time I set ON the motor between the nut and the bolt (the motor M in previous message) I need an energy for that, in the same time I recover an energy from the axis A1 and from the movement of the nut
2/ I set OFF the helix of the nut, just after I recover the energy from the rotation of the bolt around itself (the motor rotates the bolt around itself not only relatively to the nut)
3/ I move the nut up and farther to A1 (it must be like I drew at the image at start)

LOOP STEP 1/

2 images: first: at start, second: at final
« Last Edit: October 13, 2018, 08:17:59 AM by activ25 »

#### activ25

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• Posts: 158
##### Re: Length of a helix vs composition of forces
« Reply #10 on: October 13, 2018, 11:27:43 AM »
I redrew the device, the nut is circular in top view. When I said the center of mass of the bolt don't move, I mean, its radius ! The center of mass of the bolt rotates because the bolt is inside the nut and because the nut is fixed to the black arm and because the black arm rotates around A1. But, the radius is always the same, like that for the calculations and for the real device it is easier. The energy recover is very few in comparison with the energy needed to rotate the bolt around A1, it is not a problem IF friction = 0, but in reality it is not possible, so I need to reduce the looses from the rotation of the bolt around A1, reduce air pressure and take ceramic rolling gears.
« Last Edit: October 13, 2018, 01:53:14 PM by activ25 »

#### activ25

• Full Member
• Posts: 158
##### Re: Length of a helix vs composition of forces
« Reply #11 on: October 19, 2018, 08:12:59 AM »
I don't need the nut. I drew like the cylinder is transparent. All the motors are fixed inside the cylinder. The bolt never rotates around itself, I brake it from the green brake fixed on the cylinder. The motors inside the cylinder are fixed of the cylinder. The cylinder has no helix, only the bolt has an helix. On the helix are fixed magnets of electromagnets. The violet support is fixed on the cylinder. I recover an energy from the translation of the motor. I recover an energy from the rotation around A1. I need an energy for the motor.
« Last Edit: October 19, 2018, 05:53:05 PM by activ25 »

#### activ25

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• Posts: 158
##### Re: Length of a helix vs composition of forces
« Reply #12 on: October 20, 2018, 09:37:32 AM »
I drew the device in 2 positions. The center of mass is always at the same radius except for the motor but the size of the motor is in relation of the force F so directly link to the energy recovered. Remember the energy recovered is less than 1% of the kinetic energy inside the rotation around A1, so the device must be build to reduce all the friction, especially from air and rolling-element bearings.

I took simplifications to simplify the calculations but it is possible to have an external gravity, to have friction, w not constant, another angles phi and theta, and even the bolt can rotate around itself even the efficiency is lower, etc. all the geometry is an example.

For an angle of rotation δ (around A1) the sum of energy during the step1 is:

(+√3/2-√3+3/4*√3)*δRF

δ could be 2pi or more. δ is the angle of rotation of the helix relatively to the cylinder.

With R the radius of the bolt (or the radius where the force is applied) and F the force.
« Last Edit: October 20, 2018, 07:51:01 PM by activ25 »

#### activ25

• Full Member
• Posts: 158
##### Re: Length of a helix vs composition of forces
« Reply #13 on: November 09, 2018, 12:39:28 PM »
With a 3d multibody simulator, the sum of energy is not conserved, exactly like my calculations proved it. But I'm force to move the motor in the longitudinal axis of the bolt. That device is impossible to test in reality, except, maybe, in a lab, but it is possible to simulate it. And the equivalent electric must be possible to build and test in real. The advantage with the electricity, it costs nothing to have an alternative current, but here, in mechanics, it increases so much the losses that it is not thinkable to reverse the rotation of the bolt around A1, even 1 time each second. With electricity, it is possible to have a 10 Mhz signal without any problem.

#### activ25

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• Posts: 158
##### Re: Length of a helix vs composition of forces
« Reply #14 on: December 18, 2018, 09:35:13 AM »
2 cylinders