Magnesium flashlights?

hIKARInoob · 2019-04-18T17:14:31.000Z

Agro:

Why? I knew nothing about it so I looked it up and the top few results claim it to be easy to machine, even easier than Alu….

I thought it can start a fire during machining. Mechanical properties of magnesium is sufficiently interesting to be superior to aluminium under certain conditions, but I hardly see machined magnesium products. If a product is made from magnesium, then it’s often injection molded or die cast.

slowtechstef · 2019-04-18T17:20:50.000Z

I found some info about magnesium flashlights on CPF:

StorminMatt in a 2012 CPF thread

Magnesium is, as you said, softer than aluminum. And it oxidizes easier. Yes, coatings can help. But how often do coatings remain completely intact on a flashlight that is actually used? Of course, another factor is flammability. After all, magnesium was used back in the day for, among other things, photographic flashbulbs. So a magnesium flashlight probably wouldn’t be something you would want to use for tactical use or as a firefighter. Another factor is cost. Aluminum is a clear winner here. And most of the time, cost is what determines whether one material is used vs another.

All in all, aluminum is just a better compromise when it comes to building the body of a flashlight. It is cheaper, stronger, harder, and more resistant to oxidation. For the average person, an aluminum flashlight is going to last alot longer and stand up to more abuse. The fact that it is slightly heavier isn’t too important in most situations, especially when the downsides of magnesium are considered.

As far as conductivity, this is a hard comparison to make. Thermal conductivity can vary WIDELY among the various aluminum and magnesium alloys out there. However, PURE aluminum is a much better thermal conductor than PURE magnesium.

In another 2011 CPF thread drmaxx explains:

Magnesium alloys are used in many applications for decades. My guess is that using Mg-alloys just don’t have any substantial benefit compared with Al, but require more unusual techniques and know-how. So why use something more difficult, if you can get very similar results easier?

Historical footnote, according to CPF in 2008 the Muyshondt Aeon CR2 was (also) available in magnesium, under the caveat that “Be aware that although magnesium is very light, it is not an inert metal and is capable of corroding over the course of many years.”

So this makes we wonder why Surefire and Fenix in these particular headlamp cases decided to choose magnesium over aluminum. I wonder if in these cases the die casting is an additional advantage for specific designs, in addition to weight saving.

hIKARInoob · 2019-04-18T17:31:07.000Z

I consider weight saving not so interesting with small flashlights as a large contributor to total weight is the battery itself.

Of course, a company can always promote how the magnesium light is x% lighter than the aluminium variant, or generally how much less dense magnesium is…

MtnDon · 2019-04-18T18:27:32.000Z

My son, a machinist, tells me that magnesium can be machined but has many hazards as it can be ignited so easily. So many shops will not even touch the stuff. Magnesium has the unique ability to react with things around it such as CO2 (Carbon Dioxide) or H2O (water) to extract Oxygen for burning. It cannot burn in an atmosphere of pure nitrogen though. So they have a special enclosed 5 axis machine for machining magnesiumand a few other dangerous metals.

Firelight2 · 2019-04-18T18:32:40.000Z

Sounds like dangerous stuff.

I’m not sure I’d want to make a flashlight with it. Especially a heavily driven li-ion powered light.

kat · 2019-04-18T18:36:37.000Z

I would like a flashlight made from tungsten carbide

MtnDon · 2019-04-18T18:39:46.000Z

In the form of a finished light it is not so dangerous. It is the machines spiral strips that ignite very easily and powder that explodes. The deck of my old lawn mower was magnesium and it was never considered a hazrd even with a hot gas enine bolted to it . FYI, magnesium is used as the igniter in thermite.

Agro · 2019-04-18T18:47:10.000Z

hIKARInoob:

I consider weight saving not so interesting with small flashlights as a large contributor to total weight is the battery itself.

Of course, a company can always promote how the magnesium light is x% lighter than the aluminium variant, or generally how much less dense magnesium is…

I disagree here. In all but few cases flashlight weighs more than battery. Even the lightest lights could be reduced by 10% (cell included) if they had mg shells, most would be close to 15-20%. Overall not a killer kind of feature but definitely nice to have.

Overall - I’m reading through the topic now.
The toughest Mg alloys (f.e. Elektron 675) are way tougher than 6061 and close to 7075, have adequate thermal properties and are much lighter. There are some advanced surface finishes available (like Plasma Electrolytic Oxidation) though I’m unsure how do they compare to anodized alu. Cost….is surely a factor but I believe a high end light could be very good when done with Mg.

Scallywag · 2019-04-18T18:54:37.000Z

I'm thinking Mg lights will have to start in the realm of expensive lights like Muyshondt. If they were popular, we might see them sometimes as we do Ti lights, but I don't really expect it. I don't even really see any fuss being made over the choice of aluminum alloys for lights. I didn't get my D25C Ti because I need titanium, but because titanium is cool. But maybe that's the point, here, too. A magnesium light would be pretty cool.

P.S. Doubles as a road flare in case of emergency. Just put your battery into thermal runaway and the light goes too!

Agro · 2019-04-18T19:06:33.000Z

Scallywag:

P.S. Doubles as a road flare in case of emergency. Just put your battery into thermal runaway and the light goes too!

Nah. It melts before it burns and that’s 650 Celsius. You won’t set it alight without external heat source.
So….tactical - maybe no, maybe a direct hit with a bullet could cause local heatup leading to ignition. But firefighters should be fine and regular users even more so.

jon_slider · 2019-04-18T19:22:59.000Z

en.wikipedia.org

Magnesium alloy

Magnesium alloys are mixtures of magnesium (the lightest structural metal) with other metals (called an alloy), often aluminium, zinc, manganese, silicon, copper, rare earths and zirconium. Magnesium alloys have a hexagonal lattice structure, which affects the fundamental properties of these alloys. Plastic deformation of the hexagonal lattice is more complicated than in cubic latticed metals like aluminium, copper and steel; therefore, magnesium alloys are typically used as cast alloys, but res...

cliff notes:
a 28 gram flashlight made of solid aluminium, would weight 18 grams if made of magnesium alloy, a savings about 1/3 the weight of the body.

magnesium alloy oxidizes, because it contains aluminium

magnesium burns:
it is used in firestarters

I can see it now… LiIon vents with fire, the magnesium flashlight body joins the thermal runaway

and we get a campfire:
“Water pisses it off!”

hIKARInoob · 2019-04-18T19:21:48.000Z

jon_slider:

a 28 gram flashlight made of aluminium, would weight 18 grams if made of magnesium…

This is if you keep dimensions identical; hence you’re looking at the density ratio of the two materials.

Caleb · 2019-04-18T19:56:37.000Z

kat:

I would like a flashlight made from tungsten carbide

Or just the bezel and maybe the tail cap… the parts that will bump unto things.

BlueSwordM · 2019-04-18T20:07:33.000Z

Guys, they are just going to be using a magnesium-aluminium alloy, like LG does with their LG Gram

slowtechstef · 2019-04-18T20:12:32.000Z

jon_slider:

Magnesium alloy - Wikipedia

magnesium burns:
it is used in firestarters

I can see it now… LiIon vents with fire, the magnesium flashlight body joins the thermal runaway

and we get a campfire:
“Water pisses it off!”

From the wikipedia article you linked:

Adding 2% of calcium by weight to magnesium alloy AM60 results in the non-combustible magnesium alloy AMCa602.[15] The higher oxidation reactivity of calcium causes a coat of calcium oxide to form before magnesium ignites. The ignition temperature of the alloy is elevated by 200–300 K. An oxygen-free atmosphere is not necessary for machining operations.

I guess Fenix knows what they are doing, and would not manufacture and sell a light that is inherently unsafe; especially in combination with an 18650.

By the way, Surefire already sells a magnesium headlight as well since 2017. I guess it all comes down to choosing the right alloy and right coating/finishing.

slowtechstef · 2019-04-18T20:28:43.000Z

BlueSwordM:

Guys, they are just going to be using a magnesium-aluminium alloy, like LG does with their LG Gram

Thanks for the pointer to the LG Gram notebook.
Interesting to see LG taking over Apple in the field of material innovation for notebook construction.

I think there might be a trend here of producers starting to use magnesium-alloy constructions for light-weight electronic/consumer devices because of the more premium look and feel (and lower weight) when compared to objects made of aluminum.

Spartan · 2019-04-18T20:57:28.000Z

Magnesium is an epically stupid choice for flashlights. Period. End of story.

hIKARInoob · 2019-04-18T20:59:09.000Z

^ Well I guess you’re not into cool white then…

Spartan · 2019-04-18T20:59:47.000Z

slowtechstef:

jon_slider:

Magnesium alloy - Wikipedia

magnesium burns:
it is used in firestarters

I can see it now… LiIon vents with fire, the magnesium flashlight body joins the thermal runaway

and we get a campfire:
“Water pisses it off!”

From the wikipedia article you linked:

Adding 2% of calcium by weight to magnesium alloy AM60 results in the non-combustible magnesium alloy AMCa602.[15] The higher oxidation reactivity of calcium causes a coat of calcium oxide to form before magnesium ignites. The ignition temperature of the alloy is elevated by 200–300 K. An oxygen-free atmosphere is not necessary for machining operations.

I guess Fenix knows what they are doing, and would not manufacture and sell a light that is inherently unsafe; especially in combination with an 18650.

By the way, Surefire already sells a magnesium headlight as well since 2017. I guess it all comes down to choosing the right alloy and right coating/finishing.

No they don’t. It’s just something different they can crow about.

It’s not the first or the last time manufacturers put sales ahead of safety.

Spartan · 2019-04-18T21:00:53.000Z

hIKARInoob:

^ Well I guess you’re not into cool white then…

I rather be alive then cool white….on my way to crispy brown.