Thickness of aircraft grade aluminium used in flashlights over the years (Fenix)

Hello guys!

I was just playing with all my new Fenix flashlights and also some old ones (back from 2008 when I bought them). And I have noticed a very visible difference in the thickness of aircraft grade alumunium used in body of these flashlights from the past and the recent days. I took some pictures with Fenix L2D Q5 (back from 2008) and LD22 (2015) and compared it to each other, as well as TK10 (2008) and TK09 (2016) and there is a clearly thicker layer of aluminium used in the older Fenix flashlights...

Here are those 2 pictures I took http://jirizak.rajce.idnes.cz/Fenix_2008_2015_16#DSC06681.jpg

What do you guys think of that? I understand it is a marketing, not to use too much non-essential material so the company can save as much money as they can on the amout of material used, also the policy can be to make the flashlights as lightweight as possible, but do you think it will effect the durability of these recent Fenix flashlights compared to the older ones? And have someone of you noticed the similar changes in thickness of your flashlights over the years also with other companies that use Aircraft grade aluminium?

Thank you very much!

I prefer the thinner lights personally.

Your pictures aren't viewable on either a iPhone or iPad.

Manufacturers using the term "aerospace grade" aluminum is bogus. They play into the hype that if used in aerospace that it must be good.

Most manufacturers would never use 2000 series aluminum so for flashlights, but that's what a large number of aircraft parts are made of. Forging are typically 7000 series aluminums.

6061 aluminum is a basic aluminum. It's weldable, but only possesses a tensile strength around 42,000 psi. 7075 aluminum on the other hand isn't recommend to be welded but in raw form has over 80,000 psi tensile strength.

So, just how strong does a cylinder one inch in diameter with a .075 " wall thickness really need to be for use as a flashlight?

NoNotAgain said:

Your pictures aren't viewable on either a iPhone or iPad.

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Interesting. The pics are showing fine on both my 6s Plus and Air 2.

NoNotAgain said:

Your pictures aren't viewable on either a iPhone or iPad.

Manufacturers using the term "aerospace grade" aluminum is bogus. They play into the hype that if used in aerospace that it must be good.

Most manufacturers would never use 2000 series aluminum so for flashlights, but that's what a large number of aircraft parts are made of. Forging are typically 7000 series aluminums.

6061 aluminum is a basic aluminum. It's weldable, but only possesses a tensile strength around 42,000 psi. 7075 aluminum on the other hand isn't recommend to be welded but in raw form has over 80,000 psi tensile strength.

So, just how strong does a cylinder one inch in diameter with a .075 " wall thickness really need to be for use as a flashlight?

Click to expand...

Thanks! That is really interesting reading... I had no idea...

NoNotAgain said:

So, just how strong does a cylinder one inch in diameter with a .075 " wall thickness really need to be for use as a flashlight?

Click to expand...

Its not all about strength. Thicker tubes got more mass, and will soak up more heat.
My dqg 18650 with ultra thin walls, will heat up instantly, and after one minute, its relly hot. Its driven at 1,5A.
My more beefy solarforce l2t with a edc+ x60l wont heat up that fast. It takes ages even before i feel the heat in my hand. Also driven at 1,5A. Same story with a chunky malkoff md-2. The heat spreads out better with a thick walled tube. And more mass means its room for more heat.

jorn said:

Its not all about strength. Thicker tubes got more mass, and will soak up more heat.
My dqg 18650 with ultra thin walls, will heat up instantly, and after one minute, its relly hot. Its driven at 1,5A.
My more beefy solarforce l2t with a edc+ x60l wont heat up that fast. It takes ages even before i feel the heat in my hand. Also driven at 1,5A. Same story with a chunky malkoff md-2. The heat spreads out better with a thick walled tube. And more mass means its room for more heat.

Click to expand...

I somewhat tend to agree with your comment. All things being equal, the more mass, the more material to dissipate heat.

If you look at older light styles, they don't use any fins on the head. Newer lights, from reputable manufacturers now are almost completely designed using computer models, incorporate fins and internal heat pads/sinks.

Few lights today depend on the body to dissipate the heat generated by the LED. Both Fenix and Nitecore use active heat management that scales power down once a light reaches a certain temperature.

The TK10 in this case made a whopping 225 lumens on turbo. The TK09 makes 960.

Im aware of the temprature controlled lights that electronicly steps down. But that is just a workaround to the real problem. The light needs to transfer the heat away from the led die, and get rid of the heat just as fast as it's generated. Or the led will overheat and loose preformance, and lifetime. The more areal to radiate, the more mass to soak up and tranfer heat throug , the less bottlenecks, the better the light will preform. We dont really want any light to trottle down


Any light will still preform better if the head can transfer lots of heat through the tube really well. Using lots of fins adds surface areal. The more areal radiating heat, the better cooling. Thats just about the only thing that gets rid of the heat in the end. Areal that is hotter than the surroundings. (+ your hand acts like a effective water cooling system if the tube allows to heat up properly.) Having a beefy tube might make the head transfer more of the heat better to the whole tube, the same way as a 4 lane highway can handle more traffic than a road with a single lane. That is if there are no huge bottlenecks for the heat to hit into, jumping from the head to the body. If the heat can spread effortlessly all the way to the back of the tube, you get more areal radiating heat than just the finned head. Every little thing that helps the heat spread out is good. Zebralight uses a unibody, so the heat wont have a bottleneck in the area where the head is normally threaded to the body. Malkoff's md2 is beefed up in the area where the head meets the tube. Every little bit that helps heat spread is welcomed in my book

^^^ Nice explanation by Jorn!

Surface area is what dissipates heat. Mass does not. Increased mass means increased heat capacity. That is an increased ability to store heat. Increased mass means that it takes longer for a flashlight to get hot. Once it gets hot, however, it also takes longer for it to cool down.

Wait until you see a Gerber Infinity or Inova X5; flashlight circuits carved into slabs of aluminum..

You are absolutely right: I remember comparing specs of the orginal TK11 and the TK09 that came out in 2014 and the TK11 was much heavier. The price of the TK09 was also somewhat cheaper taken into account flashlights prices have been increasing.

Even the old TK12 which was released a few months after the TK11 wasn't as thick. I think the TK10 and TK11 were flagship flashlights at the time so they really put the best materials. I'm unsure why the TK15, TK21, TK22, and TK09 never had flashlight body as rugged as the TK11. I think the flashligths market has evolved and the 1x18650 was not the definite model setting the benchmark anymore as in 2009 or 2010. Other possibilities are that Fenix decided to reduce weight to lower weight, keep prices competitive, or simply improve margins.

I have seen something similar happen in the outdoor clothing industry where some manufacturer keep removing features from newer models claiming to simplify and reduce weight even from their non-ultra-light or non-light-weight collections. I suspect that lowering weight in many cases, especially if at the expense of useful features, is only a sales pitch and by reducing materials they simply want to keep prices competitive and improve margins. All companies in all sectors have to do that, I wouldn't expect the flashlight industry to be any different.

I prefer heavier, physically stronger lights. A little extra mass on a light with all thinks other wise being equal is a good thing. More mass to absorb heat, or to stay cooler as it never hits the hot level. Yes, surface area bleeds out the heat but mass allow for more of it. Extra mass also allows for thicker, deeper threads. Granted these aren't hammers, it just gives me more confidence in my tools if I know the tools are far tougher than needed.