Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

My Tungsten Cube (2019)

thume.ca

Post reply on HN
Print view View original

241–250 of 336 posts

Re: My Tungsten Cube (2019)

#241

Post by anonporridge »

moftz wrote: post #218
BurningFrog wrote: post #185

Earlier quoted context omitted.

Metals also survive pretty much anything, including catastrophic fires.

Gold can easily melt in a house fire. A diamond ring can turn into a puddle of gold and no diamond because it burned off

Melted gold is just as valuable as gold jewelry, since they melt it down anyway when you sell it. It might be worth marginally less than an intact piece of gold bullion that can be resold without processing.

Diamonds don't have resale value anyway. They're literally a scam.

Re: My Tungsten Cube (2019)

#242

Post by learc83 »

jacquesm wrote: post #233
learc83 wrote: post #229

Earlier quoted context omitted.

Just confirmed with my wife (ER doctor) that there is no situation where an EMT amputates your finger because they can’t get a ring off.

I don't think I ever said that an EMT would amputate your finger. I said that you might get further injuries. For instance: embedded Tungsten fragments or in case of a prolonged problem removing the ring further tissue damage.

The main point of the person you were replying to was that the finger amputation thing is an urban legend because you can shatter a tungsten ring. And the point of my reply was that an EMT won’t amputate your finger. I just assumed that your reply was refuting that point.

Re: My Tungsten Cube (2019)

#243

Post by anonporridge »

lacksconfidence wrote: post #157
anonporridge wrote: post #131

Earlier quoted context omitted.

It's not like that money disappears. Just think of it like buying gold bullion. Unlike say, a $9000 motorcycle impulse purchase, a block of raw metal should hold it's inflation adjusted value relatively well for decades and you can sell it whenever to recoup the money.

Gold bullion has a healthy market to sell back into though.I don't know the numbers, but i wouldn't be surprised if I could easily sell gold for 80% of "market" value, whereas probably closer to 20% for something like Iridium that has a very small adressable market unless I were to expend considerable effort finding someone willing to pay what it's worth.

You could probably sell it to just about any gold dealer, as a lot of them sell iridium bars anyway. The tools they have to verify the purity of gold also work for other metals. If not, then they would certainly have connections to find someone who will buy it.

Also, you generally buy/sell on a 5-10% spread from the "spot" market price of the metal, depending on the quanitity you're dealing with. Dealers generally offer a closer price to spot when dealing with larger dollar value amounts of metal.

Re: My Tungsten Cube (2019)

#244

Post by anonporridge »

alasdair_ wrote: post #184

I bought a cube of aerogel and feel the same way about it, with the obvious distinction of it being insanely light not heavy.

I have a cube of aluminum the same size as my 1kg cube of tungsten. It's weird feeling the insane difference between two solid blocks of metal.

Re: My Tungsten Cube (2019)

#245

Post by kragen »

jacquesm wrote: post #237
kragen wrote: post #231

Earlier quoted context omitted.

I don't really understand what the limiting factors on ECM speed are. There's electrolyte heating, cathode heating, bulk electrolyte resistance, formation of salt boundary layers on both the cathode and the anode, and so on. But one thing I do know is that MRR is proportional to the area of the interelectrode process gap: twice the area gives you twice the MRR at the same current density, whether the current density…

That Fresnel reflector idea sounds super interesting. Has anybody tried that?

Not that I've heard of; it's possible that someone tried it and it doesn't work for some reason that isn't obvious to me, and then they didn't publish their negative result. I published the idea in 02019 in https://dercuano.github.io/notes/mechano-optical-vector-disp..., but I haven't actually tried it, and not many people read Dercuano, in part because most of it is ideas I thought up but haven't tried.

Reading I've done since then explains that, when anodizing, the anodized layer grows up out of the surface roughly as far as the surface gets depressed, and the anodized layer has a higher refractive index than air, so, for many purposes, you don't need to etch nearly as much metal. (The anodized layer is thin enough that it would be adequate in many applications that normally require a first-surface mirror, though not all.)

It's well known that if you're instead anodizing silicon you can fabricate a rugate filter by varying the anodizing current to vary the density of the anodized layer, that when anodizing titanium you get brilliant iridescence due to the high refractive index of the oxide and consequent strong single-layer dichroic filtering effect, and that there's a negative feedback on the current from the oxide layer thickness in all of these cases, requiring higher voltage to get a thicker oxide; this should also tend to even out small surface asperities, and is not the same effect as anodic leveling. The possibility of including such dichroic filters on the surface of the holographic reflective optics, with wavelength response tailored at a submillimeter or even submicron X-Y resolution, could be interesting for fabricating a wide variety of optical systems.

If you end up trying it, I'd love to hear about the results! If I'm not dead by then. Though I'm sure you have a long list of ideas of your own that you can't wait to try, like everyone else capable of trying this sort of thing.

All this seems to me like a crucial enabling technology for feedback control of machine tools, because light waves don't distort or change their dimensions much when the temperature in the room changes or there's a side load on your gantry.

Re: My Tungsten Cube (2019)

#247

Post by GravitasFailure »

tyingq wrote: post #238
TeMPOraL wrote: post #226

Earlier quoted context omitted.

And, as divbzero's Quora link points out, it's going to kill you by oxidizing into a toxin when exposed to open air.

That seems to be a concern with osmium powder, ground osmium, etc. I don't think that a cube has any handling requirements more exotic than lead solder.

Less than that even. It's a noble metal and doesn't like to react under normal conditions, though hitting it with a blowtorch might ruin your day.

Re: My Tungsten Cube (2019)

#250

Post by tohnjitor »

ISL wrote: post #149
jacquesm wrote: post #140

Earlier quoted context omitted.

That I readily believe, but to face a sheet is a different matter, which I believe was the application the OP intended. You can also cut tungsten with water jets loaded with abrasives, I've seen a 2" thick block cut like that, it was quite impressive. But that won't get you a surface. You'd need to start with a sheet of the right thickness.

True. I bet a quick call to Rembar would put you on your way to a source if you just need sheet. Tungsten foil/sheet isn't that hard to come by.

Rembar and Plansee are consistently good.
Post reply on HN