Reminds me of

Another of those Natl Assn of Mfrs films. This one is mainly about uses of ultrasonics. Many of them are familiar now, detecting flaws in aluminum or embryos, and cleaning surfaces.

Here’s a use that didn’t seem to go anywhere, but the experiment is dramatically effective:

Ultrasonic sound breaks up fog and smog. Reminds me of hail cannons, which I was mentioning earlier today in a comment at Substack.

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Last week I ran across these strange devices while looking for something else, as usual.

On further reading, it turns out that hail cannons were a big business for about 20 years. French and Italian farmers were convinced that the cannons made a difference. Like cloud seeding, they didn’t halt the weather every time, but they dissipated hail often enough to save massive amounts of money and trouble. Unlike cloud seeding, there was no downside. Seeding is a zero-sum procedure, depriving one location of rain to favor another location. Deicing the hail doesn’t move the precip, it just avoids the damage.

Major agricultural implement companies made hail cannons along with plows and seeders and cream separators. Genuine scientific conferences were held annually, showing off the latest experiments and inventions.

The French called them canons contre grèle or grelifuges, and the Italians called them Grandinifughi. A word you can chew on!

The cannons broke the updrafts that encouraged hail, and left a heavy rain.

Here’s my attempt to capture the scene.

Polistra is at the controls of CANNONE FORMIDABILE, a full-fledged artillery piece with azimuth and altitude adjustments:

Happystar is supervising a cannon built into its own cozy shed, with a separate inner room where the tireur could sit and wait for the storm while sipping the products of the vineyard he was protecting.

An automatic acetylene cannon is in the background, developed by Maghiora and Blanchi.

Did the cannons make sense? We know from wind-tunnel studies of streamlining that a vortex breaks up smooth airflow. The purpose of streamlining is twofold: First avoid flat surfaces directly pushing the air; second, avoid vortices. You want the air to split smoothly around the car or plane, and rejoin smoothly afterward.

The end of the Grandinifughi era isn’t clear. Did the farmers decide that the Grandinifughi weren’t worth the effort? Or did insurance companies make damage more profitable than prevention? Flood insurance works that way.

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Happy ending! Grelifuges are STILL USED in France and Italy, and STILL MADE in Spain, and they look about the same as the 1902 versions! The new cannons use acetylene, continuing the tech invented by Maghiora and Blanchi. Video of a modern grelifuge. Live action with a visible and audible whirlwind-ring at 4:14. The old description wasn’t lyrical, it was accurate!

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The ultrasonic experiment also recalls the Lodge electrostatic dust collector, which I was also mentioning in the same comment. Lodge was using electrostatic charge, not ultrasonics. His sons tried a similar-looking experiment on London fog and smog.

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Lodge’s sons, who ran the Lodge Fume Deposit Company profitably for many years, also tried to control weather with static charge. This miniature experiment was successful, but they quickly gave up attempts to apply the same technique to parts of a city. One ‘active lightning rod’ on a building managed to clear out a few cubic feet around it. There was no way to multiply the effect enough to clear a house, let alone a neighborhood.

This bell jar was similar to the one above, except that the positive charge is a single point in the middle and negative charge is on the metal base. The bell jar contained water vapor similar to a London fog.

When charge was applied, the water vapor COHERED in radial patterns, following the electrostatic lines of force.

The real thing:

This coherer-like behavior was the interesting part. Coherers are a basic and general type of device, with a range of uses that have only been partly explored.

If a coherer-like effect could create charged ‘nuclei’ for pollution, it could possibly agglomerate and precipitate large masses of smoke and smog.

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