Constructing Custom Helmet Visors

[gambitq72]

Hello all, at the risk of reigniting a somewhat tired and frustrating debate, I was hoping to get some feedback on a couple ideas I had to possibly construct that holy grail of armor, the perfectly accurate visor for all the helmet variations.

From what I've been able to research it seems that most all half-mirror finishes are created by a certain metal (or metal alloy) is vaporized in a vacuum and deposited onto the desired surface, and the whole process is carefully stopped before the layer becomes too thick to allow any light through.

So I understand that if you placed some window tint film on Plexiglas and tried to vacuform it the whole sheet would probably delaminate; however, is it possible to vacuform a dispersion-tinted motorcycle visor?
Theoretically the only thing that could potentially delaminate would be the scratch resistant coating/film, and this could potentially allow for more angular visors like the ODST or even smaller visors for the Hyabusa or the Scout helmets to be more accurately formed, and allow for the normal helmet to accurately show the lines and patterns on the visor itself.

My second thought for the larger visors (specifically the EVA visor) is that it should be theoretically possible to construct a dispersion machine. The biggest challenge to construct such a beast would be to find a decent vacuum pump (I just don't think a shop-vac would cut it) as well as an effective way to reliably channel about 3,000 degrees C into a graphite crucible. That temperature should allow for the vaporization of either gold or silver to get a really nice mirrored tint with a little experimentation. I've been working on rough plans for a while, but I am stuck to theory as my current living arrangements don't really allow for machines involving combustion or large amounts of current inside.

Any thoughts? Advice? Comments?

-DK

 

[brychang]

well, not sure about most of it, but after 8 years of chemistry i can tell you one sure fire way of cheaply getting those high temps (it is however leathal if you screw up) you hook the termials of a 12v car battery up to 2 graphite electrodes, and with heavily insulated gloves, hold them together and short the circuit on the metal you are trying to vaporise.

alternatively, i'm fair certain a gas axe, arc welder or plasma cutter could get the temps you are looking for...but are costly, and just as dangerous (in different ways!)

 

[gambitq72]

well, not sure about most of it, but after 8 years of chemistry i can tell you one sure fire way of cheaply getting those high temps (it is however leathal if you screw up) you hook the termials of a 12v car battery up to 2 graphite electrodes, and with heavily insulated gloves, hold them together and short the circuit on the metal you are trying to vaporise.

alternatively, i'm fair certain a gas axe, arc welder or plasma cutter could get the temps you are looking for...but are costly, and just as dangerous (in different ways!)

I figured running a high amp low voltage arc between two tungsten non consumable electrodes could possibly do the trick, but the biggest hurdle I've run into is how to get the electrodes into the crucible without creating some sort of jacob's ladder and getting an effective seal between the electrode wires and the vacuum chamber walls. I thought that placing a battery or the transformers inside a vacuum would probably create additional gasses within the chamber and mar the coating.

I know the proper blend of acetylene and oxygen can easily reach 6000 degrees F which should do the trick but getting the heat transferred into the vacuum chamber once again becomes the biggest problem. I thought about somehow sealing a large ring around the crucible and directly heating it from below, but was unsure how a airtight seal would hold up to that much heat. I also think that making the entire bottom surface of the vacuum chamber one large graphite sheet may be a bit cost prohibitive.

I do believe that using a DC arc would have a benefit of allowing for more of the coating to reach the part, as you could put a mild opposite charge through the surface in question to attract more of the vaporized metal, but using oxy-acetylene may ultimately be easier construction-wise.

-DK

 

[brychang]

all are good points...but hey, i'm just the ideas guy! your the one who has to make it work.......now hop to it! just kidding


the idea of poking the crucibles ass out of the chamber would be best, and there are seals that can take the heat (eg the o-rings used in the SRBs on the space shuttle) but they are beyond just aerospace grade, so may be hard to get hold of!

 

[Loess]

Small-scale commercial vacuum metalizers use tungsten filaments (think light bulb filaments) to hold and melt the metal being vaporized.

Here's a guy that has a hobby rig.

 

[NZTK]

getting the heat transferred into the vacuum chamber once again becomes the biggest problem.

Yeah, you'd also be violating known physical laws. the energy heats the crucible, which transfers heat to the metal via contact alone, you cant heat a vacuum (as you probably know)
Unfortunately, it would be virtually impossible for you to build you own vacuum chamber. If you don't believe me, ring up an electro-chemistry specialist, and ask him/her. Maintaining a vacuum of over 15 Torrs is something even professional labs have trouble with and even with professional equipment it can take days to achieve the vacuum required, and that's not even mentioning the sophisticated equipment you need to detect leaks.
The "holy grail" for those working in their garages, you refer to (in my opinion at least), is a process called "Flow Coating" it is practised by 14 year olds in science classes all around the world. Probably daily. The chemical process involves a tinning solution on a hygroscopic (wettable) substrate then applying silver nitrate (or gold) to deposit atoms on the surface. The substrate is then sealed with a clear lacquer to protect the metal particles while maintaining translucency. The technique is very old and only compatible with certain substrates. The tinning solution is quite poisonous and has to be disposed of correctly because if it gets into waterways, it kills most things.

 

[BFDesigns]

Vapor deposition is generally industrial for the specific reason that the coating has to be done on an atomic level; the metal powder has to be atomized to stick. Theoretically it is possible to do vapor deposition on any material, however with the cost of gold nowadays I don't think I would wanna run a vapor dep lab at the moment. It is possible to make a vacuum chamber very easily and powerfully with a 1 ft. ID x 2 ft. section of steel sewer piping, silicone, and 1 inch clear acrylic. And you can make it incredibly powerful with just a bike pump and easily reach the levels that are needed for vapor dep, so long as the chanber is 100% sealed. The only problem lies in atomizing the metal.

EDIT: Just read the article that Loess linked to. The set up using boats looks extremely cheap and simple! Might have to make one

 

[CPU64]

There's a place down near me that I worked at for 2 days..
They make replicas of space and aviation stuff. Including the space suits with the mirrored visors. They send them out to a place in CA and they cost about $300 to get plated, if I remember correctly.

I looked them up and the address is www.guard-lee.com