In Praise of Underloved Aluminum

LeifUK

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I was thinking of this as well, I wonder why it is chosen over aluminum for this application? Perhaps the quality of the finish it takes? I also know of a few laptop computers produced that had a magnesium alloy chassis.

Me too. I have a macro rail for photography which is made from magnesium, not aluminium, and I have no idea why. Aluminium would be perfectly fine.

In the case of titanium I don't think the main problem is the cost, given that 500g costs about $20, compared to $1 for aluminium. Ti is not easy to machine and form and I think that is the real cost.

Another possible material is ceramic, which has been used in watch cases. It is extremely resistant to scratching, but it is not easy to manufacture. I think it would make a fantastic torch casing. The thermal conductivity of a ceramic such as alumina is 6.3 W/(m*K) compared to about 22 for titanium. Okay, not so good, but much better than plastic, so it would be fine for lower power lights.

Mmmm. Just Googled, and it seems that some ceramics are quite good conductors, much better than titanium.
 
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brandocommando

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Ceramics could be great, when I was a kid some NASA people came to my school with a ceramic tile like the ones on the bottom of the space shuttle. They held a blowtorch to it until it was red hot, then they removed the blowtorch, waited about 2 seconds and touched it with their bare hands, and it was totally cool (temperature.) So, ceramics can be an excellent conductor of heat.
The only problem is ceramics do not conduct electricity so there would be no ground path without some sort of metal insert.
 
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flashflood

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Ceramics could be great, when I was a kid some NASA people came to my school with a ceramic tile like the ones on the bottom of the space shuttle. They held a blowtorch to it until it was red hot, then they removed the blowtorch, waited about 2 seconds and touched it with their bare hands, and it was totally cool (temperature.) So, ceramics can be an excellent conductor of heat.

That demonstration actually shows the opposite. Those ceramic tiles are such good insulators (poor conductors of heat) that even if you heat one to 1000 degrees, you won't get burned touching it because the heat will not move from the tile to your hand.
 

Chrontius

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Depends on the ceramic they're using - the shuttle tiles are some kind of high-resistivity foamed ceramic.

And why not magnesium?
Wikipedia said:
Magnesium is flammable, burning at a temperature of approximately 3,100 °C (3,370 K; 5,610 °F),[7] and the autoignition temperature of magnesium ribbon is approximately 630 °C (903 K; 1,166 °F) in air.

Air Safety Week said:
* The molten lithium burned explosively, spraying white-hot lithium to a radius of several feet as the batteries bounced around.

* The duration of the peak temperature increased with the number of batteries, reaching as high as 1,400 degrees F [760°C] (as a matter of interest, the melting temperature of aluminum is around 1,200 degrees F [649°C]).

This would be fine for a gadget produced by Q branch, which is expected to have a spectacular self-destruct function to prevent capture, but not for EDC.

Edit: Celsius conversions in [brackets] mine, courtesy of albireo.ch
 

brandocommando

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That demonstration actually shows the opposite. Those ceramic tiles are such good insulators (poor conductors of heat) that even if you heat one to 1000 degrees, you won't get burned touching it because the heat will not move from the tile to your hand.

Yes, you are correct. Thanks for the clarification!

"Much of the shuttle is covered with LI-900 silica (ceramic) tiles, made from essentially very pure quartz sand. The insulation prevents heat transfer to the underlying orbiter aluminum skin and structure. These tiles are such poor heat conductors that one can hold one while it is still red hot."
 
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beerwax

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rising on the awsome scale. holding a ceramic tile heated to HOT and not getting burned.

which ceramics would have the look and feel to impress as a torch. ive only seen knives and bearings. something translucent might impress.
 

ma_sha1

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One more vote for Magnesium: The best racing wheels are made out of Magnesium alloy, because it is very lightweight but tough, so the wheels can be made lighter than Alu. with same strength.

Some of the DLP projector cases are made out of or Magnesium alloy. I cut some of them them open while modding, they are brittle, perhaps requires different machine tools & skills that flashlight maker haven't tried?

Why Titanium being popular in flashlight business? One word: Marketing!
 

UnderTheWeepingMoon

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Endeavour once made a very small quantity of magnesium CR2-Ions, one of which is shown here. He warns that "although magnesium is very light, it is not an inert metal and is capable of corroding over the course of many years". Still, it's proof that lights can be made of Mg.
 

Tana

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When you look at it, magnesium alloy casting was long time avoided due to Mg being more reactive than Aluminum (there has been incidents in car racing where cars would catch on fire - Mg parts - and burn like a matches when that happens)... with latest alloys, the possibility of this is reduced to minimum and there is really not much reason why someone wouldn't replace Al with Mg alloys and make a flashlight out of it. But thermal conductivity is less than aluminum, can't confirm on electrical, too lazy to google. With different (and yet still unestablished like Aluminum) finishings, it's common sense that majority of brands will pick aluminum alloys as much widely explored area.
There will be someone who will try Mg first, though... but not in high powered lights as that slightly thermal conductivity difference can make a huge difference in reliablity of the whole light.

Titanium for flashlight ??? For me, no thanks... Extra price only for "bling" efect is not my road... but lot of people would surely disagree... we gotta love differences in people and different points of views and learn to respect that...
 

LeifUK

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I like the natural aluminium colour, and my silver and blue maglites still look nice. Okay the type II anodising is not as thick or hard as type III, but type II does not chip, and in my book the slight scratches it picks up are not a problem. Frankly type II is as good as type III in my subjective opinion and it has the advantage of allowing nice colours, not just military ones. Unfortunately I think marketing has convinced us that type II is inferior.
 

beerwax

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if you dropped a magnesium flashlight i suspect it might crack.

i have seem magnesium in fishing reels, salt and magnesium having quite a party.
the guys with mg camera bodies are any of them underwater type cameras ?
 

Saint_Dogbert

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I like the natural aluminium colour, and my silver and blue maglites still look nice. Okay the type II anodising is not as thick or hard as type III, but type II does not chip, and in my book the slight scratches it picks up are not a problem. Frankly type II is as good as type III in my subjective opinion and it has the advantage of allowing nice colours, not just military ones. Unfortunately I think marketing has convinced us that type II is inferior.

Quality Mil spec type III really is better, but some manufacturers don't apply proper anodizing quality control. I've found Type II to be mostly aesthetic; it scratches and dings quite easily with moderate use. Granted so will Type III, especially at sharp machined edges. But experience has shown me that it has an advantage over Type II. I especially like the quality of Type III anodized threads.
 

beerwax

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yeah type III can be lovely.

thermal conduction - lets look at the data.
there are many examples of titanium , stainless steel and aluminium flashlights where drive levels are high and heat generated is comparable. (take a walk in the field of AAAs)
and while all these lights all get hot none of them fail and the heat levels in the hand feel similar (to me).

this may be because the copper/brass heatsink close to the led has done its job and wicked the heat to a larger area of torch body. and the larger the area the less the conductivity matters.

and so thermal conductivity of a torch body dont matter much.

cheers
 

kromeke

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Magnesium does not accept a nice corrosion resistant finish. It does not anodize like aluminum. There is a dichromate finish that is supposed to provide some corrosion protection, but it is available in one color, brown. It doesn't compare to type III or type II aluminum anodize.

I've made a forebody for a novatac out of Mg. I haven't finished the entire light, but by the time I am done, the previously completed parts will have dulled to a matte grey finish. I suppose I could keep it polished, but that takes too much work.
 

IMSabbel

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About burning magnesium: Its A LOT harder than it looks.
Bought once a few kg of magnesium scrap on ebay to make some nice fire, and had trouble getting it going even with a welding torch.

Powder=Wooosh. Solid blocks: Nothing
 

kitman22

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Ti has the cool factor, hence why makers use it and we buy it. Ti is not that easy to work with either compared to other metals but in our age cool factor often over comes function and form. I would choose an aluminum light over a Ti one of the same model due to the better heat conduction but I would still by a McGizmo Ti light, well because they are cool and I want one :naughty:
 
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