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Author Topic: Sum of torque  (Read 173889 times)

dieter

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Re: Sum of torque
« Reply #90 on: January 01, 2015, 12:31:25 PM »
Hi EOW,


I watched #92 10 minutes, I still do not understand it, sorry.  :-[


BR


dieter

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Re: Sum of torque
« Reply #91 on: January 01, 2015, 12:41:31 PM »
Still studying it... wait a minute, do you mean the friction / no friction axles are bearings with no friction in clockwise rotation and much friction in counterclockwise rotation?


BR

EOW

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Re: Sum of torque
« Reply #92 on: January 01, 2015, 12:44:27 PM »
Quote
Still studying it... wait a minute, do you mean the friction / no friction axles are bearings with no friction in clockwise rotation and much friction in counterclockwise rotation?
I'm not sure to understand. My goal is to slow down the disk (or sprocket) in the support frame reference WITHOUT return a torque on the support. Slow down the disk in the support frame reference = accelerate the disk in the labo frame reference.

1/ Forget the chain, it's possible to use only stems and a disk. The disk is on a support. If a disk don't turn in the labo frame reference, its angular velocity is -w if the support turns at w, ok ?

2/ Now, if I slow down the disk in the support frame reference, the angular velocity goes from -w to -0 in the support frame reference, the disk accelerates in the labo frame reference, ok ?

3/ The disk has magnets and can attrack the stem (steel), but there is friction in the axis between the stem and the disk. The friction gives heating (it's an energy). This energy come from the kinetic energy of the disk: the disk slow down in the support frame reference.

4/ I use the centrifugal force for eject the stem. I need to give an energy for eject the stem, the energy can come only from the angular velocity of the disk, so the angular velocity of the disk increases in the labo frame reference.

The only thing to verify is: the support musn't receives a torque, and if the axis of rotation of the disk has no friction, it's not possible to return a torque I think

Tell me if you don't understand, I can explain more

EOW

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Re: Sum of torque
« Reply #93 on: January 01, 2015, 01:04:01 PM »
All could be fine with one disk, but in the labo frame reference the disk don't turn, so there is no centrifugal force, it's for that I would like to use 2 sprockets and a roller chain. But without return a torque on the support.

dieter

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Re: Sum of torque
« Reply #94 on: January 01, 2015, 01:34:45 PM »
I even don't know what "Labo" means, I tried babelfish translation, not found.
I made some gears, like planetary gears, but basicly this is not really my field of expertise, so I hope you don't mind if I seem rather stupid  ???
I will read it again after some sleep. I didn't sleep since last year ^_^
BR

EOW

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Re: Sum of torque
« Reply #95 on: January 01, 2015, 07:41:05 PM »
labo frame reference: when you are in the laboratory and you look at the device turn, http://en.wikipedia.org/wiki/Laboratory_frame_of_reference

support frame reference: when you are in the support and you look at the disk

maybe I can use a massless roller chain like that it's easy to straigth the chain.
« Last Edit: January 01, 2015, 10:12:39 PM by EOW »

EOW

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Re: Sum of torque
« Reply #96 on: January 02, 2015, 10:21:56 AM »
If I use a massless roller chain with friction, I can roll up the chain around the red disk, friction will slow down the red disk (in the support frame reference) = accelerate the red disk in the lab frame reference. The red disk has a mass.

Cycle:

1/ The red disk don't turn in the lab frame reference, launch the support at w. The roller chain is all around the support. The energy needed is the energy for turn the support at w
2/ Roll up the chain around the red disk, at final the roller chain is all around the red disk, not on the support
3/ Slow down all the support. The energy recover is the energy from the support and the energy from the red disk.
Repeat
« Last Edit: January 02, 2015, 09:09:28 PM by EOW »

dieter

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Re: Sum of torque
« Reply #97 on: January 02, 2015, 10:28:21 AM »
I think I am beginning to understand slooowly  :) .  In the next weeks I won't have much time to hang around in forums  :-\ . This was interesting. Maybe you should build one of these devices?
What I usually do is:
1 have the idea
2 draw it in 2D
3 simulate it in 3D in the Computer (here I often discover flaws in my thinking!)
I'm using Blitz3D, but any flexible 3D engine will do. Making use of an attached physics engine may be useful, maybe not always.
4 make a crude model, eg. of wood.


Kind Regards

EOW

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Re: Sum of torque
« Reply #98 on: January 02, 2015, 10:42:07 AM »
Thanks for the software, I will simulate. It's difficult to start with Blitz3d ?

Regards

EOW

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Re: Sum of torque
« Reply #99 on: January 02, 2015, 11:18:19 AM »
I think it's better with a straigth roller chain to roll up on the red disk (the chain turns at w). Like (in theory) the roller chain has no mass there is only the friction that need a force. Like there is only one disk maybe it gives a force to the support, imagine the forces is like the first image, the support receives a counterclockwise torque but in this case I can place the red disk like in the second image. So, I think there is no force on the support. But there is friction and the red disk is accelerating.

dieter

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Re: Sum of torque
« Reply #100 on: January 02, 2015, 11:19:06 AM »
Hi EOW,
Blitz3D is a basic compiler with an embedded 3D engine for DirectX. It is rather easy when you know a bit about programming. But it is not for free. Some years ago there was a free version with a 1000 lines of code limitation, but now I guess there is only a 30 days trial version.


There is also freebasic with some 3D extensions, but I  not sure if it has all the important features, like parenting one object to an other.


There may be other solutions, including Blender, although Blender is very unintuitive and hard to learn.


BR

dieter

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Re: Sum of torque
« Reply #101 on: January 02, 2015, 11:23:54 AM »
CORRECTION!!! BLITZ3D is now Freeware!!!


www.blitzbasic.com/


Totally reccommended! I paid 100$ and never regreted a thing!


BR


Edit: BTW, here you should find several physic engine extensions, like Physix, Bullet and others:
www.blitzbasic.com/Community/topics.php?forum=94


The blitz3D compiler allows to use those 3rd party DLLs with a "wrapper".


Basicly it may be useful to search the forum using the word "physic"

EOW

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Re: Sum of torque
« Reply #102 on: January 02, 2015, 12:08:04 PM »
With Blitz it's possible to have the sum of forces, the energy, etc ?

dieter

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Re: Sum of torque
« Reply #103 on: January 02, 2015, 12:16:33 PM »
You have to add one of the physic engines (see my last posting), and then yes, to some degree they try to simulate physics. Some are really good, probably even with friction parameters.


Ok, this is not the best, because the best physics simulations usually cost $$$. But it is interesting and may be very useful.


BR


EOW

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Re: Sum of torque
« Reply #104 on: January 02, 2015, 03:01:08 PM »
With a stem with mass, the left half fixed circle can stop the stem. With a fixed spiral, the stem can have a massless, the spiral gives always a prependicular force to the stem. There is friction between the stem and the red disks. Forces F1 and F2 are forces from friction between the red disk and the purple stem. Forces F3 and F4 force the purple stem to be on the disk, F3 and F4 cancel themselves, the spring never move, it don't lost energy.

It's ok because S<pi*R
« Last Edit: January 02, 2015, 08:27:19 PM by EOW »