On 02/18/2010 12:26 PM, Harry Veeder wrote: > > > > > ----- Original Message ---- >> From: Stephen A. Lawrence <[email protected]> To: >> [email protected] Sent: Wed, February 17, 2010 3:43:49 PM >> Subject: Re: [Vo]:latest from Naudin on the Orbo >> >> >> >> On 02/17/2010 12:14 AM, Harry Veeder wrote: >>> >>> I did some googling on magnetic saturation... (some parts of the >>> post have been removed) >> >> No prob, I snip all over the place, myself. >> >> >> ... >> >> [sal] >>>> The distinction you're drawing between a "cloak" and a "shield" >>>> is interesting but I think it hides the fundamental >>>> similarities between this design and all magnetic shield >>>> perpmos. >>> >>> My terminology is meant to illuminate the difference between the >>> orbo and all other magnetically shielded perpetual mobiles. >> >> OK, I can see that. >> >> [sal] >>>> They *all* share the very important trait of drawing no power >>>> (to operate the motor) while the shield is stationary; only >>>> the effects during shield motion really matter. >>> >>> Since there is relative motion between the putative shield and >>> the rotor, you can't say it requires no power once it is "in >>> place". >> >> I don't follow this. There's always relative motion between some >> magnet and the 'shield'; in fact, that's the point of the shield: >> it lets you move some external magnet without resistance from the >> one behind the "shield". > > yes, but the shield and the external magnet will interact > (action-reaction) as they sweep past each other. The shield will be > heated and the magnet will slow down.
But no -- if the shield is truly a "shield" then it will block the B field of the external magnets but won't itself interact with them. Anyhow that's what I think of as a "shield". More on this below. ... > The shield interaction with the permanent magnet should obey Newton's > third law, otherwise I think it is a misnomer to call it a shield. > Here is an example of a putative perpetual mobile where the shielding > moves with the rotor. > > http://www.lhup.edu/~dsimanek/museum/cheng2.htm > > Of course this won't work, because as the author notes a shield must > obey newton's third law. The only reason that's an issue is that the shield material is assumed to be magnetic, itself. A proper shield must be non-magnetic. :-) At least, IMO. The problem with *that* is that there is *no* *such* *thing* as a magnetic shield. In fact, this isn't just a matter of semantics, despite my strong statements as to what constitutes a "shield". In fact there is no material which will actually act as a magnetic shield, for any definition of the word "shield" which captures the common meaning. Any shield, to be worthy of the name, must *block* the external field from entering the shielded area. And that's not what happens when real materials are used. The magnetic field of the external magnets, in fact, goes right through the material of any "shield" you care to construct. What any physically realizable "shield" actually does is produce a magnetic field of its own which cancels the field of the magnets against which you're trying to shield something. And that, right there, makes it obvious that the artist who drew this image: http://www.lhup.edu/~dsimanek/museum/magmot.gif wasn't thinking in terms of real-world materials. Real-world so-called "shields" *all* operate on the principle of the Fenton Silencer, or, perhaps more to the point, any set of noise-cancelling headphones, like, for example, the Bose QuietComfort series. A "real shield", on the other hand, would be like earplugs. And there is no such thing, because a static B field (which is what we're talking about) doesn't propagate and hence can't be blocked. Changes to the field, like EM radiation, propagate; a static field just "is". Steorn's coils, which cancel the external field within the torus, are classic examples of real world "shields", even though the material of which they're constructed is active (wires carrying current) rather than passive (ferromagnetic material). ... >> >> For that to be (nearly) the case, the coil's field, within the >> torus, must be vastly stronger than the magnet's field. Otherwise >> the field lines of the core would stick out of the torus and the >> core would not be fully shielded. >> ... > > Yes, I realized this I after went to bed and woke up the next > morning. > > Anyway, what I am getting at is that if orbo is truly OU, the shield > is not really a shield, if that makes any sense. ;-) If I understand what you're using the word "shield" to mean, then yes, it makes sense.
