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Author Topic: WM2D Problem, cant find simple error in CF rotator.  (Read 3600 times)

mindsweeper

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WM2D Problem, cant find simple error in CF rotator.
« on: January 12, 2009, 07:43:55 PM »
Hi all, 1st post in this section and after working with pendulums for many years in clocks I have had many a thought on using centrifugal force and an offset mass to produce usable rotational acceleration, After some time working on the problem I find myself here seeking inspiration and guidance.

This model has been bugging me like mad and I have been scratching my head over this one for a while now.

Please have a look at the model and let me know what I'm doing wrong. It's quite a basic concept but I've not seen it done like this before, that's not to say it's not been done a million times before and proved not to work. I'm sure I have all the setting correct.

Anyhow I'd appreciate if someone could point out my schoolboy error.

hansvonlieven

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Re: WM2D Problem, cant find simple error in CF rotator.
« Reply #1 on: January 12, 2009, 08:34:58 PM »
G'day mindsweeper,

You are applying torque to the system via that rotational damper of yours, that is why it keeps rotating.

Hans von Lieven

mindsweeper

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Re: WM2D Problem, cant find simple error in CF rotator.
« Reply #2 on: January 12, 2009, 10:48:23 PM »
G'day mindsweeper,

You are applying torque to the system via that rotational damper of yours, that is why it keeps rotating.

Hans von Lieven

Hi Hans,

Thanks for looking at my sim, I thought I'd add that for resistance. If I set it as a damper NO?

It should be 1 n-m-s resistive force, I know if I use a pin joint on the offset mass it accelerates faster.

EDIT: Attached the same with just a pin joint and no rot damp.

EDIT 2: Also If you look at the 1st sim, the dampers force is acting opposite to the direction of rotation and picks up speed, I have been able to set this to 2.1 N-m-s and it will just overcome it but acceleration is slow..
« Last Edit: January 12, 2009, 11:27:14 PM by mindsweeper »

hansvonlieven

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Re: WM2D Problem, cant find simple error in CF rotator.
« Reply #3 on: January 13, 2009, 03:31:53 AM »
G'day Mindsweeper,

The problem with your simulation is a programme bug. In some simulations using the polygon tool in a kinetic element results in unexpected behaviour. In the attached simulation I have substituted the polygon with two rectangles of the same combined weight. The programme now works as expected.

Hans von Lieven

mindsweeper

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Re: WM2D Problem, cant find simple error in CF rotator.
« Reply #4 on: January 13, 2009, 10:11:00 AM »
Ahh,  I'll be steering clear of polygons from now on, damn there handy.

Hans, you are a true jewel in the rough.

Many thanks,

sweep