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Comment Re:A glass lathe? (Score 1) 270

Second lesson: don't believe everything you read posted by anonymous cowards...

Metal vacuum tubes have a glass vacuum tube enclosed by a metal cover. The tube itself is not metal. Glass vacuum tubes are connected to vacuum pumps and sealed off. The getter is there to pick up "stuff" that boils off the filament and out of the other metal parts in the tube, it does not create the vacuum.

Comment I'm not a tube fan, but electrostatics? Sure! (Score 1) 270

Electrostatic speakers/phones aren't especially hard to make, but sourcing the materials can be difficult. You need ultra thin polyester film for the diaphragms, and some sort of weakly conductive coating (Licron or similar antistatic spray works well). You also need a method of stretching the diaphragm film tight and then gluing it while stretched. I invented a pneumatic stretcher almost 30 years ago when I was into all this stuff. 4693H contact adhesive will stick to the polyester (not much else will)...

Have at it:

Comment Re:Making 26 YOs work 80 hour weeks is easier too. (Score 1) 244

My point about "refurbs" was that maybe they aren't really refurbs. Maybe they're a second pricing tier for new vacuums to be sold to the "poor" and cheapskates. Refurbs come with reduced warranty and probably less fancy packaging that makes for a "cheaper" user experience. If they sold as new the people who paid full retail would get pissed off and stop buying them for the premium price.

Comment Re:Making 26 YOs work 80 hour weeks is easier too. (Score 1) 244

I was recently shopping for a vacuum to replace a couple "brand name", upright, bagless machines acquired over the years from Walmart or similar vendors. My two main reasons for replacement were the bagless systems were very dirty- emptying them involved holding it at arm's length over a trash can, taking a deep breath, opening the trap door and dropping the dirt into the trash in a cloud of dust. The other main complaint was the noise. Jeez, those things were awful. I couldn't stand to be in the house when one of them was running. The upright design requires moving the weight of the whole machine while vacuuming- very tiring.

Given the Dyson's reputation for being a premium product, I checked into them. Bagless- ugh! And on-line reviews by both pros and consumers said they were noisy as all get-out. And then there were all those refurbs...

I eventually settled on a Miele C4. It's very quiet, cannister type (much easier to use because you don't have to keep moving the weight of an upright back and forth), uses bags that close themselves up when you take them out of the machine. The air rushing through the nozzles makes more noise than the motor unit. My cats will sit undisturbed while I vacuum until the nozzle is within 1 m of them, then they just move out of the way.

I've been doing a lot more vacuuming since I got the Miele. It is hard to believe it can move as much air as it does an be so quiet.

Comment Making 26 YOs work 80 hour weeks is easier too... (Score 2) 244

Observation: it seems there are more places to buy refurbed Dyson vacuum cleaners and fans than there are places to buy them new. To me that suggests that they have terrible manufacturing and/or design quality, or that Dyson's marketing people have decided to charge a high price to the biters who are willing to buy a "new" Dyson vacuum cleaner or fan, and then sell "refurbs" to the unwashed masses who can't or won't buy a "new" unit.

Whatever is going on, the availability of all those refurbs has left me with an impression of poor quality. No thanks.

Comment Re:Flossing now neutral? Negative next.... (Score 1) 257

Yes, some dentists have given up trying to convince people of the safety and advantages of amalgam fillings and do great business taking advantage of the fear mongering that is so common on the internet these days. Some guys even go as far as wearing hazmat suits while they take out amalgam fillings.
It's great theater! If they just took out all the silver fillings and replaced them, you might never mention it to your friends, but if they wear hazmat suits and respirators while they do it, it's all but guaranteed that you're going to tell everyone you know about it. That will get a few of your more easily influenced friends to start wondering, and pretty soon they are calling up your dentist.

If your filling fell out, it either broke (less likely) or you developed decay under it (more likely), or the tooth fractured (possible) or a combo of those (also possible).

Comment Re:Flossing now neutral? Negative next.... (Score 1) 257

Amalgam fillings work by sealing the tooth very tightly. They are held in mechanically, by the shape of the filling and the tooth. Amalgam is extremely strong in compression (as in when chewing food) and routinely last for decades (I have some that have been in my mouth >40 years). As amalgam fillings age, the surface corrodes a bit, and actually seals tighter than when it was initially placed. Contrary to popular mythology, they do not spontaneously decompose and release mercury any more than the coins in your pocket spontaneously decompose. If they did that they would get smaller and looser over time, but they don't.

Composite fillings (the tooth colored ones) bond to the tooth chemically and shrink as they harden, putting stress on the bond with the tooth. After thousands of thermal cycles (eating hot and cold food/drink) and mechanical cycling from chewing, the bond with the tooth fails and the filling "leaks". You get decay under the filling unless a dentist spots the failed bond and repairs it. Composite fillings typically have to be replaced in 5-10 years depending on the shape of the filling and which tooth it is in.

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