Question |
| Asked by: |
J. Viklund |
| Subject: |
Eccentric masses |
| Question: |
Vibratory hammers use contra-rotating eccentric masses and can generate a centrifugal force of up to 4 000 kN. The maximum displacement amplitude can exceed 30 mm.
http://www.geoforum.com/info/pileinfo/view_process.asp?ID=22
If you could brake the movement at 270 degrees (90 for the other rotor) where the counterrotating forces anyway cancles each other, and accelerate them at 90 degrees (270 for the other rotor). Wouldnt that give a greater movement at 180 degrees than 0? If you built an array of couter routating pairs with a suitable offset, would you get a (almost) continous force?
Can you restrict the forces to 2 vectors of different amplitude? Or must they be equal to obey "the laws"? |
| Date: |
4 May 2004
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Answers (Ordered by Date)
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| Answer: |
Ram Firestone - 04/05/2004 16:02:41
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| | The short answer is no (unless you can prove Newton wrong). Without any outside force the center of mass always stays in the same place. This is conservation of momentum. It is even true under Einstein. However from what I read he added this to his theory because he thought it was elegant. I'm not sure there is any actual proof that it is true at relativistic speeds, but don't take my word for it.
Ram
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| Answer: |
Nitro MacMad - 04/05/2004 18:17:00
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| | Dear J. Viclund,
I am sorry to say that Ram is right (sorry because such a device would be a darn sight simpler than the gyro nightmare that is the only way I've found round "the third"). there are loads of means of producing a momentary impulse, the problem lies in repeating the cycle without closing the loop (the old equal and opposite loop) and ending with zilch. In the case of eccentric masses you even have to throw away loads of energy to obtain zilch. No deity exists that says such things must obey "the laws" but eccentrics (masses that is) certainly would seem to.
Kind regards
NM
P.S. Although I have described above that the mechanism required to produce a useable driving force (the fast repeater) as a gyro nightmare the principle can be seen cheaply with a toy gyroscope. Ironically this is the only missing gyro demonstration in the video clips on this site. I shall ask the webmaster if he would like to put such a demo video here.
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