Hilsch Tubes Revisited

Let me amend that: I ran a photo of a stack of ceramic and steel blocks wrung together. No carbide.

Tungsten carbide doesn't wring very well. Chromium carbide gage blocks wring better. Tungsten carbide blocks are usually the square ones with the hole in the middle, for a clamp screw. But regular ones are available, or they were.

The last I read - years ago - was the attraction theory seemed to be about all that was left after the other ideas had been proved wrong, but at the time no one had demonstrated any definitive proof of the theory..... but they were still working on it :-)

Here is an abstract of the modern theory:

A method is presented for calcg. van der Waals forces in systems with nonlocal cond. The fluctuating fields in the electromagnetic stress tensor are obtained by applying the fluctuation-dissipation theorem to the response of the system to an external polarization. As an example, the method is used to calc. the contribution of conduction electrons to the interaction of 2 blocks of metal. When the electrons are described in a simple hydrodynamic approxn. keeping only the lowest order nonlocal terms, the interaction force is the same as that obtained by Lifshitz assuming local cond. At sepns. large compared to the London penetration depth c/wp the interaction is due to electromagnetic waveguide, modes, while at distances small compared to c/wp, the force is due to surface plasmons. As a 2nd example, the method is applied to the interaction of 2 graphitelike blocks. With a quantum mech. derived description of the electron motion, the resulting force differs from Lifshitz expression both because of the anisotropy of the system and because of the nonlocal cond.

By the way, machining all those tiny gecko feet is going to be a bitch.

-- Cheers,

John B.

John B. fired this volley in news: snipped-for-privacy@4ax.com:

Been done... but machined by electron beams.

They're using the materials for experimental applications, but I know of no practical ones, yet.

LLoyd

A robotic fly catcher, perhaps?

:-)

O.K. That eliminates the need for cohesion, but adhesion is still a possibility.

Thanks, DoN.

Over here they sell some stuff called "Tokay feet". I believe y'all call it velcro :-)

"Tokay" (I believe they may be called "Tokay Geckos by foreigners) are about 12 inches long, walk up walls, and eat other lizards, small birds, etc., as opposed to the smaller geckos that eat bugs.

-- Cheers,

John B.

We have self duplicating, mobile, bug catchers over here. We call then chinchoks you may call them geckos :-)

-- Cheers,

John B.

Probably excellent smoked, or slow-roasted on a spit....