# Dyson vacuum cleaner claim? T or F?

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A TV ad for Dyson vacuum cleaners claims the dirt is separated from the air by a force 100,000 times the force of gravity. Off the top of my pointed head, that seems way overstated.

Anyone care to calculate that for a grain of sand? I bet a 1/4" nut (metal content) would have it bouncing off the walls.

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Hmm. I think one would have to compare the drag force on a small particle in an airflow, vs the gravitational force.

The gravitational force could be a pretty small number, I could imagine a dust bit weighing less than a milligram.

Jim

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Our Dyson certainly stuffed a local large spider when it was sucked up. It just went THUD in the container!!!!!!!and did not move again.

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On Wed, 27 Oct 2004 22:42:42 GMT, Andy Asberry calmly ranted:

I've seen those commercials and gasped when I heard it, too. I made it a point to pay attention the second time to verify the fallacy they were spewing. Those are obviously "The New Math, Brit style" calculations.

IANAE, but my pointy head says their "force" is up to 2 times that of gravity if the beasties can suck 15 inches of merc.

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It's obvious that it's sears force being used. ERS

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The important figure is not for big bits, but small ones. For small ones, where the dust falls at maybe 1mm/s, in normal gravity, if it's inside the cyclone for .05 seconds and needs to be made to fall 5cm in that time, then you need it to fall 50 seconds worth in

1/20th of a second, so you need it to go 1000 times as fast. I suspect that if you put the centrifuge at 1000G, it's not going to make it, as the flow might get turbulent, so you'll need a larger force.

On another tack, is it likely?

1Mm/s^2, and 250m/s. A=v^2/r (for circular motion). So, v^2 = 1/16th million. And r = 1/16m, or 6cm. Sounds possible.
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Not sure about the claim but there was a recent test of vacuum cleaners done..can't remember who did it. Anyway, the Dyson was considered only fair to middlin becuase it didn't really suck dirt all that well. Had large suction (like the HEPA filter models by eureka and others) but just didn't pull gunk out of the carpet.

Soo......not worth the premium price. Same for the Orec (sp?). I guess there's more to cleaning than suction power.

Koz

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The Wall St. Journal had a comparison of a half dozen "Dyson-like" vacuums recently, possibly earlier this week. In any event, the Dyson out performed all the other vacuums for the range of tests they did. Some of the others (Sears?) did OK, but cost half to a third as much. They didn't compare them with any regular bag-type vacuums (canister or upright).

Doug White

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the claim but there was a recent test of vacuum cleaners

So who was on top?

JW

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I believe it was the Eureka with the dust canister and round filter inside. Can't remember the exact model. I have one of those and it's always amazing just how much crap they suck out of the carpets. Filters are expensive and you really need to clean all the dust from the filter leaves after almost every use. It's a bit of a pain but they really do pick up an amazing amount of crud.

Koz

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Unless I got my sums wrong, I figure the centripetal acceleration at a radius of 2" at 41967 RPM to be 100,000G. The velocity would be

732 ft/sec or about 500 MPH. That's below sonic velocity, so I suppose it's possible though there would be a lot of drag.

With a radius of 1" the spin rate becomes 59336 RPM but velocity goes down to 353 MPH. At r = 0.5", 83913 RPM and 250 MPH.

Leaf blowers claim an air velocity of > 200 MPH straight flow, d>A TV ad for Dyson vacuum cleaners claims the dirt is separated from

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"Don Foreman" wrote: Unless I got my sums wrong, I figure the centripetal acceleration at a radius of 2" at 41967 RPM to be 100,000G. The velocity would be 732 ft/sec or about 500 MPH.(clip) ^^^^^^^^^^^^^^ What would be the pressure developed in a blower running under those conditions?

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There have been several "no clog" vacuums in the past.

The Rainbow sucks the incoming airflow through a vat of water, trapping the dirt. It doesn't clog up, but the dirty water must be disposed of after every use or it will sour and stink to high heaven. Generally a pain in the ass to use.

The best, in my opinion, was the Compact, now called Tri-Star, I believe. It had patented "Cyclonic action" that swirled the dirt in the bag preventing it from clogging. The only time mine has lost suction is when it was too full to spin the dirt. Their patent recently expired, spawning the rash of cheap plastic imitators. The bad thing about the compact is it is a canister. The good thing about the Tri-Star is it has a high-low switch that will allow it to run quieter. It still seems to suck just as well when using the power head on carpet. Compacts and Tri-Stars last a long time and are available used, if you look. Parts are available, should yours need a new hose or whatever.

Ron Thompson On the Beautiful Florida Space Coast, right beside the Kennedy Space Center, USA