# Titanium vs Aluminum Thermally (IR Images)



## cmacclel

After looking at these images is quite clear to see how much better Aluminum (6061) is at transferring / dissapating heat over Titanium (6al-4v). Pay no attention to the Temp in the upper left hand corner as that only represents the temperature at the crosshairs.









*Thermal Images of Aluminum (Top) and Titanium (Bottom) Lights at Various Drive Levels using an SST-50 LED*


*Thermal Images at 2500ma Drive Level*

*Base / 1 Minute / 2 Minutes*













*3 Minutes / 4 Minutes*











*Thermal Images at 1000ma Drive Level*

*Base / 1 Minute / 2 Minutes*












*3 Minutes / 4 Minutes / 5 Minutes*












*6 Minutes / 7 Minutes / 8 Minutes*












*9 Minutes / 10 Minutes / 11 Minutes*












*12 Minutes*


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## gadget_lover

What's your interpretation of those results? 

Which did better at getting rid of heat?


Daniel


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## cmacclel

gadget_lover said:


> What's your interpretation of those results?
> 
> Which did better at getting rid of heat?
> 
> 
> Daniel


 

The Aluminum transferred the heat to the whole body where as 90% of the heat stayed right where the heatsink is on the Titanium light. Also the aluminum light showed 20f+ cooler throughout the test.


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## Ajay

Thank you cmacclel

Excellent work, results clear as day.


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## 65535

I realize these things are quite accurate. What about the difference emissivity of the surfaces? Obviously it gets the point across aluminum transfers heat far better. Just curious if the different emissivity can cause inconsistencies in the readings on a FLIR camera.


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## cmacclel

65535 said:


> I realize these things are quite accurate. What about the difference emissivity of the surfaces? Obviously it gets the point across aluminum transfers heat far better. Just curious if the different emissivity can cause inconsistencies in the readings on a FLIR camera.



Both lights where covered with kapton tape so there should be no difference in emissivity.

Mac


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## dudu84

At first I thought those images came from CFD simulations, very cool :thumbsup:

This answered heat-related questions about my Ti lights, Thanks a bunch! :goodjob:


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## easilyled

These pictures are very conclusive that Al. has far superior thermal conductivity to Ti.

Of course to drive a small light at 2500ma for any sustained length of time is inadvisable, particularly for Ti.

It would be interesting to see for Ti only, the comparison between this small light and a much bigger one (eg. your 1D Mag-sized Ti lights with SST-50),
to see if the greater bulk and volume makes it safer to drive the light at this sort of current level for longer.


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## hydrou

Just to add some numbers.

Electrical conductivity of Al: 37.7 * 10^6 A/(V*m)
Electrical conductivity of Ti: 2.5 * 10^6 A/(V*m)

Thermal conductivity of Al: 235 W /(K*m)
Thermal conductivity of Ti: 22 W /(K*m)

So, one can see easily, that there is a factor of more than ten between thermal as well as electrical conductivity between the pure substances. And higher values indicate a way better conduction of heat or current resulting in less hot spots or thermal problems.

And just for comparison pure Fe:
Electrical conductivity of Fe: 1.0 * 10^6 A/(V*m)
Thermal conductivity of Fe: 80 W /(K*m)

In general, alloys might have slight changes to these values, but the order of magnitude will not change.


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## karlthev

Thanks Mac--great piece of data here!


Karl


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## EngrPaul

Thanks for the post! 

This is exactly what I would expect to see. The average outside temperature of both flashlights is the same, but the local temperature of the titanium light is higher near the emitter heat source.

What onlookers should take away: If the temperature is this much higher on the surface near the emitter, imagine how much hotter the emitter is inside. Higher emitter temperature = dimmer LED, both now and over time.

Would it be possible to measure relative output over the same duration as the tests above? I bet the output of the titanium light would sag due to emitter temperature rising more quickly.


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## tino_ale

Would it be possible to aim the IR camera directly towards the emitters and read the actual die temperature?

These tests are very interresting and well done. Clearly the heat is better spread throughout the Al body. The Al body tail is hotter than the Ti tail.

Still IMO the only test to get a definite quantitative answer to how good Al and Ti are relative to each other would be to measure actual junction or at least emitter temperature (not just heatsink or body temperature) while both lights sitting on a table and repeat the test with both lights held in your hand. This very last measurement is in fact the only one I am interested in but unfortunately it doesn't seem easy to set up.

I guess a IR camera equipped with a macro lens could measure the phosphor temperature?


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## KowShak

I've a few questions....

Aside from the material, are the two lights identical in terms of dimensions / material thickness etc? Assuming that they are, the conclusion here is simple, TI is not as good a material for LED lights as aluminium is.

Do you think the difference would be as marked if the wall thicknesses were thicker / thinner?


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## cmacclel

tino_ale said:


> Would it be possible to aim the IR camera directly towards the emitters and read the actual die temperature?
> 
> These tests are very interresting and well done. Clearly the heat is better spread throughout the Al body. The Al body tail is hotter than the Ti tail.
> 
> Still IMO the only test to get a definite quantitative answer to how good Al and Ti are relative to each other would be to measure actual junction or at least emitter temperature (not just heatsink or body temperature) while both lights sitting on a table and repeat the test with both lights held in your hand. This very last measurement is in fact the only one I am interested in but unfortunately it doesn't seem easy to set up.
> 
> I guess a IR camera equipped with a macro lens could measure the phosphor temperature?




Tino your exactly right. The problem is when a light is assembled it is difficult to measure to measure the heatsink temp. as close as possible to the die unless you drill holes into the light  This was a quick and dirty simple test. I hope to set another test up tonight with a thermal coupling into the heatsink as close as possible to the LED. I will then re-run the same test with the same heatsink / LED in both bodies.


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## cmacclel

KowShak said:


> I've a few questions....
> 
> Aside from the material, are the two lights identical in terms of dimensions / material thickness etc? Assuming that they are, the conclusion here is simple, TI is not as good a material for LED lights as aluminium is.
> 
> Do you think the difference would be as marked if the wall thicknesses were thicker / thinner?



The lights are exactly the same just different body material.

Mac


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## cmacclel

easilyled said:


> These pictures are very conclusive that Al. has far superior thermal conductivity to Ti.
> 
> Of course to drive a small light at 2500ma for any sustained length of time is inadvisable, particularly for Ti.
> 
> It would be interesting to see for Ti only, the comparison between this small light and a much bigger one (eg. your 1D Mag-sized Ti lights with SST-50),
> to see if the greater bulk and volume makes it safer to drive the light at this sort of current level for longer.



Daniel I doubt it matters much the thickness or the size of the Titanium. The fact is it does not have good thermal properties so the heat stays in one general area.

Though like you said it would be ridiculous to expect a light of this size to sustain 10 watts to the emitter. The 2500ma level is basically a burst mode and should not be used for more than a couple minutes. 

Mac




Mac


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## hydrou

@tino_ale:

I am afraid it will be not that easy... On the one hand, the lenses used for theses types of cameras ususally do not work with normal glass. You will need special lenses built with special optics. And on the other hand, you need to know the so called emissivity of the object. This will vary between 0 for an ideal white body and 1 for an ideal black body. Therefore, it is not possible to calculate exact temperature values for surfaces with unknown composition or radiation properties.


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## Fulgeo

cmacclel said:


> Daniel I doubt it matters much the thickness or the size of the Titanium. The fact is it does not have good thermal properties so the heat stays in one general area.



Great stuff Mac. I found these images very informative and interesting. One thought thou which you probably already thought of, it seems that some of the short comings of the thermal properties of Titanium could be resolved with finning. Your images really do point to where the problem is. Maybe a few cooling fins cut into the head right where the heat is could make a difference? Also because the Titanium is so much stronger than Aluminum maybe you could make circular long horizontal thin fins. I know that thermal mass is important but maybe with Titanium less is better where there is heat? Anyway you have the tools to play and I am envious. Thanks for sharing.


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## MrGman

The differences in emissivity aren't going to be that great and in this comparison really doesn't mean much because the Titanium body showing the lack of transfer from head to tail across itself is the real issue. The Titanium body doesn't change in emissivity across itself and its not transfering the heat as well as it could plus we see the thermal transfer numbers published. This series of thermal graph points out something that should be stated to make it very obvious. Titanium body high power flashlights are a contradiction of purposes. They cost more money for the exotic materials but they are 10 times less effective in transferring the heat away from the LED/heatsink in the head which is what you don't want to do. So people pay more money for the exotic metal because its "cool" and may not scratch as easily yet its far less effective in thermal management for the high power flashlight they are buying then the Aluminum that is much cheaper in cost. If these were incandescent lights we wouldn't care but for an LED, especially the higher power ones, running more than 10 watts of power, Titanium alloy hosts are the wrong way to go if you want the best possible thermal transfer to keep the LED from overheating. Truth is Truth. Thanks to cmacclel it is now abundantly clear we shouldn't be wasting money on the expensive Titaniun flashlights in the high power units such as an SST-50 or 90 because it hurts thermal transfer and the LED may not last as long with continued use. ouch


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## cmacclel

MrGman I agree with you 

But

"It Don’t Mean a Thing If It Ain’t Got That BLING"

But seriously Titanium lights are completely usable at lower drive levels. As for the SST-50 even driven at 150ma as in this particular light on level one it produces plenty of light. The burst mode must be used with common sense 




Mac


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## precisionworks

MrGman - nice to see you in The Sandbox 



> we shouldn't be wasting money on the expensive Titaniun flashlights in the high power units such as an SST-50 or 90


Unless we want to, which many of us do 

For my use, which is 90 minutes a day of dog walking in the dark, the light body could be made of Al, Ti, or just about any metal, as heat generation is a non issue. A multi level driver, or a resistorized tail switch, gives the user the option of running a 1000 lumen emitter at 20-30 lumens, which is perfect for avoiding cracks in the sidewalk or low hanging limbs. Out of 90 minutes run time, the highest level might see 15-20 seconds of use, sometimes a little more or less. We saw some deer in the park this morning & high beam stayed on forever ... probably 30 seconds.

I'm sure that someone is running their light at 500 or 1000 lumens for long time periods, and that will shorten the useful life of the phosphor. Maybe it will take a 50,000 hour emitter down to 5,000 hours - a loss of 90%. Even then, running flat out for an hour a day, the emitter will run for 13.69 years. I'll be happy if my Mac's Custom Ti light lasts that long


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## McGizmo

cmacclel said:


> *The Aluminum transferred the heat to the whole body where as 90% of the heat stayed right where the heatsink is on the Titanium light*. Also the aluminum light showed 20f+ cooler throughout the test.



Hi Mac,

I too have a FLIR which I find quite valuable in evaluation of the thermal conditions of some of the designs. I am not clear on how you have determined that 90% of the heat has stayed right where the heat sink is on the Ti light.

In your first "base" image, there appears to be a temperature differential on the Ti light where the head seems to be warmer in the heat sync area than the rest of the body. Is this a result of the light recently being on?

I used to show people the thermal resistance and low conductivity of Ti by taking a foot long bar of it and holding it at one end in my bare hand while bringing the other end up to a visually glowing red from a torch. No way you would hold a bar of aluminum or copper and do the same thing. You had to be careful though after setting the bar down because as it cooled, it also did transfer some of the residual heat towards the other end! I stayed clear of using titanium for a few years when I got into these flashlights even though it is a material I happen to be quite obsessed with. My concern was in regards to thermal relief for the LED.

Ultimately, it comes down to the LED itself and its specs and recommended operating temperature. If a design places the LED in a thermal environment where it is at or beyond its recommended operating temperature, I would submit that the design has failed. This might be as a result of poor material selection, poor thermal management or any other considerations.

Do you think any of your images there were taken at a point where you had reached a steady thermal state?


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## cmacclel

McGizmo said:


> Hi Mac,
> 
> I too have a FLIR which I find quite valuable in evaluation of the thermal conditions of some of the designs. I am not clear on how you have determined that 90% of the heat has stayed right where the heat sink is on the Ti light.
> 
> Nothing Scientific in my calculation it's just how I interpreted the results. What is your interpretation?
> 
> In your first "base" image, there appears to be a temperature differential on the Ti light where the head seems to be warmer in the heat sync area than the rest of the body. Is this a result of the light recently being on?
> 
> Yes there was a 2-3 Degree difference between the body's as the Titanium Light was previously in my Hand. (I just assembled the head)
> 
> I used to show people the thermal resistance and low conductivity of Ti by taking a foot long bar of it and holding it at one end in my bare hand while bringing the other end up to a visually glowing red from a torch. No way you would hold a bar of aluminum or copper and do the same thing. You had to be careful though after setting the bar down because as it cooled, it also did transfer some of the residual heat towards the other end! I stayed clear of using titanium for a few years when I got into these flashlights even though it is a material I happen to be quite obsessed with. My concern was in regards to thermal relief for the LED.
> 
> Ultimately, it comes down to the LED itself and its specs and recommended operating temperature. If a design places the LED in a thermal environment where it is at or beyond its recommended operating temperature, I would submit that the design has failed. This might be as a result of poor material selection, poor thermal management or any other considerations.
> 
> Well Don I guess that all depends on what you where trying to accomplish in the first place. I know your light designs are conservative....mine on the other hand are the opposite. I like muli-level lights that I can use all day on low then if needed shift into a super bright mode. Of course with this type of setup you need common sense
> 
> Do you think any of your images there were taken at a point where you had reached a steady thermal state?
> 
> No but if i can find the time I hope to re-visit this soon.


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## wquiles

Mac - thanks for the pictures and data gathering. Very cool experiment :twothumbs


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## spellitout

Excellent post! :thumbsup:


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## romteb

Great thread, a welcomed step in the direction of having real data in the long and mostly unsubstantiated discussion about thermal behavior of Al vs Ti in flashlight use.

Plus those thermal imaging devices are quite expensive and not that common, it's always very cool to see some images it produces.

Thanks.


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## Wattnot

Excellent work!

I just got my first Ti light and the first thing I noticed was how hot it got in a VERY short time! Need I worry about ? :laughing:


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## precisionworks

> Need I worry about  ?


Not at all.

Ship that heat trap to me & I'll send a brand new ALUMINUM SureFire, even trade :thumbsup:


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## McGizmo

cmacclel said:


> Daniel I doubt it matters much the thickness or the size of the Titanium. The fact is it does not have good thermal properties so the heat stays in one general area.
> 
> ....



Mac,

I don't feel I have a sufficient handle on thermodynamics to make much comment here and I realize that anything I might say could be construed as biased on my interest and use of titanium. 

On the other hand, I do question some of your comments but not as any expert. I do think it is safe to state that to elevate titanium or any material above ambient temperature requires heat energy. The more material you have the more energy it requires to elevate it to any target temperature. Thermal mass is a significant consideration and likely dependent on its thermal connectivity to the surrounding environment (hand held VS in a water filled container or sitting isolated in the air). 

The primary issue here between aluminum and titanium is the difference in thermal resistance and how this results in a difference in the temperature of the LED die. Clearly from your images we can see that the LED will be warmer in the Ti host and that the thermal differential across the Ti light is greater than that of the Al one because of the thermal resistance.

If the LED is at an unsafe temperature, it is at an unsafe temperature. If in your examples the LED is at a safe temperature in both the Al and Ti lights one could argue that the LED is not generating enough heat to bring the tail of the Ti light to an uncomfortable level to hold. :nana: If the Al light has the LED at a safe temperature and the Ti has the LED beyond its thermal capacity then the Ti light is a poor solution.

In terms of 90% of the heat remaining at the heat sink, although I question the comment, I don't know how to determine the magnitude of energy or where its distribution might lie. To confirm your supposition, I would think you could reduce the light to just the area that you say contains this 90% of heat. If you then drove the light at 90% of the power as in the example you should have the same temperatures in both cases, if you follow my logic. I would imagine that if you reduced the mass and material down to just the "heat sink area" and drove the LED at 90% of the original power level that you would see much higher temperatures on the surface.

Again, I have no expertise on these matters and I defer to those among us who do.


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## cmacclel

Wattnot said:


> Excellent work!
> 
> I just got my first Ti light and the first thing I noticed was how hot it got in a VERY short time! Need I worry about ? :laughing:



I doubt it......the max temp for most LED's is around 140-150c which is around 300f.

Mac


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## jahxman

McGizmo said:


> If the LED is at an unsafe temperature, it is at an unsafe temperature. If in your examples the LED is at a safe temperature in both the Al and Ti lights one could argue that the LED is not generating enough heat to bring the tail of the Ti light to an uncomfortable level to hold. :nana: If the Al light has the LED at a safe temperature and the Ti has the LED beyond its thermal capacity then the Ti light is a poor solution.


 
This is of course the core issue. It really falls upon the makers of these lights to ensure that their design will not thermally exceed the specs of the emitter being used. However, if that requirement is being met at the maximum drive level of a light, I could imagine some advantage in having a light that will NOT become too hot to hold in your hand after an extended run on max, as opposed to one that becomes too hot to hold after 10 minutes. I would prefer this type of design to one which allows me to drive the emitter to levels that will exceed its thermal specs if I don't remember to turn it down or off in time.


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## cmacclel

jahxman said:


> This is of course the core issue. It really falls upon the makers of these lights to ensure that their design will not thermally exceed the specs of the emitter being used. However, if that requirement is being met at the maximum drive level of a light, I could imagine some advantage in having a light that will NOT become too hot to hold in your hand after an extended run on max, as opposed to one that becomes too hot to hold after 10 minutes. I would prefer this type of design to one which allows me to drive the emitter to levels that will exceed its thermal specs if I don't remember to turn it down or off in time.


 
As long as your holding a light in your hand you become a very large heatsink  The only time you would be under a time limit would be if you left the light unattended. Almost all of the current crop of 200+ Lumen lights would become to hot to hold if left on in "High" mode while not in your hand.

People prefer different things and *my* motto is "I'd rather have it and not need it than to need it and not have it. As long as the light has multiple modes and the person using the light has a little bit of common sense they should be fine.

Mac


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## TranquillityBase

Excellent post Mac! 

It's refreshing to see a side by side with two indentical lights, one of each flavor.

We buy Ti lights because they're cool, tough, and did I mention cool!


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## Justintoxicated

Great pictures, I would still prefer ti to aluminum on my key chain light due to wear, and ti lights are cool, just not as well designed in general as an aluminum counterpart, then gain it depends on the purpose of the light and where it will be used. Perhaps we will start to see some hybrids in the future for Hot LED's like SST50 / 90?

How would copper or brass compare in your photos, my old understanding is that aluminum can dissipate heat faster than aluminum, however copper will conduct heat faster.

Will the next step be a titanium light with heat pipes?


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## precisionworks

> ti lights are cool, just not as well designed in general as an aluminum counterpart


I should have known that. Surefire et al are of a more advanced design than anything from Mac, McGizmo, Cool Fall, etc. But I have to wonder why there are two McGizmo's in the upper right pocket, plus one on the keychain, plus one of Mac's vials and an Atwood Keyton.

I'll trade my Ti PD-S for an Al PD-S if there's anyone silly enough to take me up on that offer :nana:


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## Justintoxicated

precisionworks said:


> I should have known that. Surefire et al are of a more advanced design than anything from Mac, McGizmo, Cool Fall, etc. But I have to wonder why there are two McGizmo's in the upper right pocket, plus one on the keychain, plus one of Mac's vials and an Atwood Keyton.
> 
> I'll trade my Ti PD-S for an Al PD-S if there's anyone silly enough to take me up on that offer :nana:



Brag Much?


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## easilyled

McGizmo said:


> ..... I do think it is safe to state that to elevate titanium or any material above ambient temperature requires heat energy. The more material you have the more energy it requires to elevate it to any target temperature. Thermal mass is a significant consideration and likely dependent on its thermal connectivity to the surrounding environment (hand held VS in a water filled container or sitting isolated in the air).
> 
> 
> .........In terms of 90% of the heat remaining at the heat sink, although I question the comment, I don't know how to determine the magnitude of energy or where its distribution might lie. To confirm your supposition, I would think you could reduce the light to just the area that you say contains this 90% of heat. If you then drove the light at 90% of the power as in the example you should have the same temperatures in both cases, if you follow my logic. I would imagine that if you reduced the mass and material down to just the "heat sink area" and drove the LED at 90% of the original power level that you would see much higher temperatures on the surface.



I think what you are saying is that the thicker and the wider that the titanium cross section is, then the cooler the titanium casing will remain due to the larger thermal mass not heating up as much. 

However, does it also follow then that the junction temperature around the emitter will be less in a thicker, bigger Ti light because of this, all other factors being equal?

I'm guessing that it will, because even though Titanium is sluggish in conducting heat away in comparison to Aluminium, it is still not a perfect insulator by any means.

Therefore since heat flows from hot to cold, the cooler the casing around the led and heat-sink module, the more heat will continue to flow into the Titanium even if the rate of transfer is quite slow.

Is this what your understanding is?


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## precisionworks

> Brag Much?


Sorry if I offended. My Ti lights are all work tools, carried 40+ hours each week. Dropped every now & then into tanks of liquid that eat right through Type 304 stainless. Given to co workers who tend to be less than careful. Aluminum lights are not an option for what I do.

The keychain stuff is Ti because not much else does well in metal to metal contact. All of it looks used, in a nice way. The Leatherman has Ti scales, the Chris Reeves Sebenza has Ti liners, and my right hip has Ti cannulated screw fixation. It sort of grows on you (or in you)


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## fyrstormer

cmacclel said:


> The Aluminum transferred the heat to the whole body where as 90% of the heat stayed right where the heatsink is on the Titanium light. Also the aluminum light showed 20f+ cooler throughout the test.


What are the actual lights used in this test?


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## Anglepoise

I have enjoyed this thread. Thank you.

I can't wait to put an SST-90 into one of my Ti lights.
Every light I own has variable output so maximum power can be used easily for a limited time. Also as mentioned above, holding a light with the hand will get rid of huge amounts of heat, slower of course with Ti.

People will still want the combination of SST and Ti. Nothing will stop the use of Ti as it is the most marvelous metal for a flashlight.


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## KC2IXE

hydrou said:


> Just to add some numbers.
> 
> Electrical conductivity of Al: 37.7 * 10^6 A/(V*m)
> Electrical conductivity of Ti: 2.5 * 10^6 A/(V*m)
> 
> Thermal conductivity of Al: 235 W /(K*m)
> Thermal conductivity of Ti: 22 W /(K*m)
> 
> .



Heh - I have an idea - Sterling Silver lights - Look fancy, great thermal conductivity (like 400 W /(K*m) - pure silver is 430), of course, we could go to Diamond


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## precisionworks

As far as an inexpensive material goes, one with very light weight & great thermal properties, magnesium is most often overlooked. Easily machined (as long as the chips never ignite), easily welded (as long as the base metal never ignites), not bad looking, much lighter than Al.


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## cmacclel

fyrstormer said:


> What are the actual lights used in this test?


 

https://www.candlepowerforums.com/threads/242182


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## McGizmo

easilyled said:


> I think what you are saying is that the thicker and the wider that the titanium cross section is, then the cooler the titanium casing will remain due to the larger thermal mass not heating up as much.
> 
> However, does it also follow then that the junction temperature around the emitter will be less in a thicker, bigger Ti light because of this, all other factors being equal?
> 
> I'm guessing that it will, because even though Titanium is sluggish in conducting heat away in comparison to Aluminium, it is still not a perfect insulator by any means.
> 
> Therefore since heat flows from hot to cold, the cooler the casing around the led and heat-sink module, the more heat will continue to flow into the Titanium even if the rate of transfer is quite slow.
> 
> Is this what your understanding is?



I believe if you increase the thermal mass you will see a lower junction temperature when you have reached a steady state. The greater the thermal resistance, the greater the thermal differential across the mass but yes, it will be cooler as you increase this mass. Air and water really suck compared to titanium and I would guess even your hand doesn't conduct heat as well as the titanium. The big and full thermal picture is not restricted to the light and goes beyond it.


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## fyrstormer

Hey Don, out of curiosity, are the results shown in this thread the reason why you decided to integrate a heatsink into the head of the Haiku, so the heat would be drawn to the surface area of the heatsink to dissipate instead of needing to be slowly conducted through the battery tube? Also, did you integrate a heatsink into the Haiku and not the PD-S because the Haiku's emitter has higher heat output, or just because you didn't come up with the idea sooner?

Just in case anyone reads that and thinks I'm dissing on Don's earlier designs, I own several and I'm never selling them.


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## McGizmo

fyrstormer,
I don't want to hijack Mac's thread here. I also don't follow your question. The original PD lights (Al) had integral bulkheads which were the mounting spot for the LED and the head itself was the heat sync. The Ti PD's and LunaSols have the LED mounted on an aluminum MCPCB which would be the heat sync and this is clamped against a shoulder in the Ti head to provide for the thermal path. The latest line of Haiku and XR-U head clickie lights are host to a threaded light engine similar in concept to the LE's used in the Aleph series. These new LE's consist of an aluminum threaded can that hosts a MCPCB and when installed, the MCPCB is clamped between a shoulder in the Ti head as well as against the threaded can itself. The can provides a thermal path to the head though its threads and the MCPCB has its own compressed thermal path forward into the head.

Perhaps to better justify this post in this thread, I can add a couple FLIR images.

Below is a LunaSol 20:






Below is the light and test set up under normal illumination and photographed:






I used a extended life masking tape to provide a known emissivity surface for the FLIR to view and a copper penny attached to a thermal couple and covered with the same tape was used to verify the ambient temperature as well as the calibration of the FLIR. The FLIR image was recorded after 15 minutes and apparently after steady state had been reached.

Below is a FLIR image I took of an ARC 6 and it was after it throttled down because of the thermal conditions and the on board thermal protection circuit (as I recall)





The numbers shown refer to the temp measured in their associated cross hairs. The soft ware is cool in that it allows you to move the cross hair to an area of interest and you can add more measure points if you want. I used the egg crates as a cradle for the lights being tested because I wanted to isolate them as much as possible from any potential external heat sync and leave them to air cooling which is probably the worst case for thermal relief; especially with no air movement beyond convection initiated by the heat source itself.

Thermocouples are great for measuring heat provided you can attach them where you want and still have the assembly be a reasonable mock-up of the real world. The FLIR is really handy for measuring surface temp and seeing the distribution of the heat at the surface. You have to know the emissivity of the surface for absolute value reading but even if you don't, you can get some relative measures and see the differential across the surface.

I think thermal considerations are important given that the health of the LED and circuit are temperature dependent. The battery chamber and temperature of the battery(ies) is also a consideration that should not be overlooked. Batteries can benefit from a warm environment but at some point, excessive heat can become problematic and even unsafe. Ambient atmospheric temperature and humidity can play a significant role. A high powered dive light might have a tough time surviving in the desert heat where it is just fine underwater. Fortunately with today's technology, we can get plenty of light without approaching any danger zones.


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## Marduke

precisionworks said:


> As far as an inexpensive material goes, one with very light weight & great thermal properties, magnesium is most often overlooked. Easily machined (as long as the chips never ignite), easily welded (as long as the base metal never ignites), not bad looking, much lighter than Al.


Corrosion would become a large concern for handheld lights in that case.


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## McGizmo

Marduke said:


> Corrosion would become a large concern for handheld lights in that case.



When it comes to sacrificial anodes in galvanic corrosion systems, magnesium is wonderful. I believe this is why it is found in most water heaters. Aluminum is noble in comparison. I think magnesium is about at the bottom of the galvanic scale unfortunately. I believe it can be anodized for some protection but I know for a fact that it wouldn't cut the grade in the world I play in.


----------



## 65535

While we're on the subject of heat. I believe (correct me if I'm wrong) that Novatac's lights (120P) have thermal cutoffs built into the circuit.

Seems like a pretty good idea anyways, seeing as LED's are completely capable of self meltdown.


----------



## Illum

I've always wondered why people want titanium lights? the thermal conductivity certainly leaves alot to be desired:thinking:


----------



## PlayboyJoeShmoe

I for one don't actually WANT Ti lights...

But should I win a lottery or two I'll just soldier along with them.

Multi level rules!


----------



## McGizmo

Illum said:


> I've always wondered why people want titanium lights? the thermal conductivity certainly leaves alot to be desired:thinking:



Perhaps they have different priorities or desires than you? If titanium doesn't meet yours, there is actually an easy solution for you and one you have probably followed. Have you considered the possibility that in many designs and uses, thermal conductivity is really a non issue? If you really do wonder why people want titanium lights, have you read any of the many threads relating to the subject?


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## tino_ale

There are *many* threads already discussing "why would I want Ti instead of Al for my lights" and "which is better", I suggest some here make a search (no offense but I see no point in repeating what's been very well documented many times).
This thread is specifically about thermal properties and since Mac is sharing very informative info on this matter let's keep the thread on it's track.

I can't wait to see the results if Mac manages to post measurements taken at the heat-sinks. Mac if you do so, may I suggest that you make a measurement with the lights on unattended and repeat the test with both lights in your right and left hand. Maybe even test with leather gloves on? I realize running these tests are time consuming. :huh: I've been willing to take such measurements but I've never had the same light in both Al/Ti, plus it requires a good access to the heat-sinks.


----------



## tino_ale

Just out of curiosity maybe Mac and Don would let us know what IR camera you are using? I've used one in the pas in board design and they are very neat tools indeed...


----------



## easilyled

Illum said:


> I've always wondered why people want titanium lights? the thermal conductivity certainly leaves alot to be desired:thinking:



This is presumably because you've never had one.

If you had a Ti-PD-S, for example, you would probably wonder why you ever wanted Aluminium lights. 

At 500ma on high, the Ti-PD-S still provides more than enough illumination for EDC purposes and can be safely kept on high at this level, while
hand held for an extended period.

Its beautiful, very strong, doesn't show scratches, can be taken into the sea without fear of corroding, will last for ever and still look like new. etc.etc.etc.etc.

Yawn! Let's play a new record please. (or CD!)


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## precisionworks

> I think magnesium is about at the bottom of the galvanic scale unfortunately. I believe it can be anodized for some protection


There are many alloys of titanium, with differing resistance to corrosion, and there are many variations in magnesium ... some being highly corrosion resistant. And as you mentioned, there are protective coatings available:

Dow 1, chrome pickle dip
Dow 7, dichromate dip
Dow 17, hard anodizing, available in the lighter Class C or the heavier Class D (.0012" thickness)


----------



## outersquare

interesting thread, 
list of thermal conductivity;

http://en.wikipedia.org/wiki/List_of_thermal_conductivities
http://en.wikipedia.org/wiki/Thermal_conductivity

someone should make a light out of a billet synthetic diamond 

:nana:


----------



## strinq

Excellent test. Some simple, easy to read conclusions, and correct me if I'm wrong.

1. Ti does not conduct heat as well as Al (duh).
2. Not a serious matter if the lights are driven to points where the temperature is still below the safety limit for the LEDs (as mentioned by McGizmo) 
3. BUT, what about the safety limit for the user? A lot of Al lights on high/turbo become too hot to handle (but in my experience it will still not hot enough to 'injure' the user) if left for some time (as mentioned by the cmacclel). This brings about the question, what's the scenario with a Ti light? From the pictures, it is clear that the heat is concentrated near the emitter and not distributed well throughout the body AND it seems that the temperature at that point seems significantly higher than the same point on the Al. Will it be so hot that the owner might get burns?

4. Another point is that almost everyone holds the light at the battery tube which in the case of the Ti light is significantly cooler than the head. This actually lowers the effectiveness of the users hand as a conductor. Which again brings about the question, will it get so hot (without the knowledge of the user because he just can't feel it) that when he accidentally touches the head, he gets burned? This is all assuming the LED's in both lights are driven at the same level.

- one reason to McGizmo's question about reaching steady state temp (I think).
- I might conclude that with Al, u can drive some lights harder before they breach the safety level. With Ti lights, u'll reach it faster. The question is, how much faster?


----------



## PlayboyJoeShmoe

We can rest fairly well with knowledge that only flashaholics are going to actually own lights that cost like Ti lights do.

The person on the street thinks paying over 10 bucks for a flashlight is crazy.

So, as flashaholics I think we'll be able to handle it. I rarely use turbo for more than 10-20 seconds. Rarely use high for very long. The LED in a Ti light should outlive me used like that.

I think it;s gonna be all right String.


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## easilyled

strinq said:


> ........
> 3. BUT, what about the safety limit for the user? A lot of Al lights on high/turbo become too hot to handle (but in my experience it will still not hot enough to 'injure' the user) if left for some time (as mentioned by the cmacclel). This brings about the question, what's the scenario with a Ti light? From the pictures, it is clear that the heat is concentrated near the emitter and not distributed well throughout the body AND it seems that the temperature at that point seems significantly higher than the same point on the Al. Will it be so hot that the owner might get burns?
> 
> 4. Another point is that almost everyone holds the light at the battery tube which in the case of the Ti light is significantly cooler than the head. This actually lowers the effectiveness of the users hand as a conductor. Which again brings about the question, will it get so hot (without the knowledge of the user because he just can't feel it) that when he accidentally touches the head, he gets burned? This is all assuming the LED's in both lights are driven at the same level. ....



The number of Ti lights that have been distributed amongst CPF members must run into the mid thousands by now at a very conservative guess.

(if you count up the numbers in each wave of McGizmo Ti lights, Spy007 lights, Aleph-style Ti lights by custom machinists, production Ti lights by Olight, Jetbeam, Surefire (Titan) and now the Quarks and many other assorted manufacturers)

Yet there has not been one reported problem of anyone suffering heat burns or even pain from holding a Titanium light.

So it doesn't seem very likely, judging by those statistics, does it?


----------



## gadget_lover

McGizmo said:


> I believe if you increase the thermal mass you will see a lower junction temperature when you have reached a steady state. The greater the thermal resistance, the greater the thermal differential across the mass but yes, it will be cooler as you increase this mass. Air and water really suck compared to titanium and I would guess even your hand doesn't conduct heat as well as the titanium. The big and full thermal picture is not restricted to the light and goes beyond it.



I think you meant to say that "f you increase the thermal mass you will see a lower junction temperature UNTIL you have reached a steady state."

Before the steady state, the mass is soaking up the heat. Hence the term heat sink. Once it reaches steady state, the heat sink has to conduct it TO somewhere. If it can't shed the heat to somewhere, the temperature of the junction will eventually equal the temperature of the heat sink mass. When that happens, the heat sink might as well not be there.

Note that this is in relation to mass, not surface area or thermal path area.

Daniel


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## easilyled

gadget_lover said:


> I think you meant to say that "f you increase the thermal mass you will see a lower junction temperature UNTIL you have reached a steady state."
> 
> Before the steady state, the mass is soaking up the heat. Hence the term heat sink. Once it reaches steady state, the heat sink has to conduct it TO somewhere. If it can't shed the heat to somewhere, the temperature of the junction will eventually equal the temperature of the heat sink mass. When that happens, the heat sink might as well not be there.
> 
> Note that this is in relation to mass, not surface area or thermal path area.
> 
> Daniel



I think McGizmo's response was in relation to my initial question about whether the junction temperature would be lower in a much bigger Ti light than a much smaller one, everything else being equal.

So everything would be bigger, the mass, the surface area, the volume and the thermal path area.

The reason why I asked is because I have a *big* Mac custom Ti light (mag 1D-sized) which is direct-driving an SST-50. 

I would guess from the light output that its pulling about 2.8amps. 

It has one of Mac's very thick, chunky custom SST-50 aluminium heat-sinks inside.

I am sincerely hoping that the junction temperature of the SST-50 is considerably lower in this light than it would be in a light about the eighth of this size with the same current. (as in the FLIR diagrams in this thread)

Logic tells me that even once steady state is reached, there will be much less heat surrounding the heat-sink and the led than there would be in a smaller light.

This is because there is much more surface area for the heat to be drawn away to and then also to dissipate into the atmosphere or a hand holding it.

I just wanted someone with more knowledge than me to verify this assumption.


----------



## McGizmo

Easilyled,
I agree with your assumption based on the size of your light compared to a much smaller one. I don't claim competence in thermodynamics but it takes energy to heat a mass beyond the ambient temperature around it. The more mass, the greater the energy required to bring it to any target temperature. I learned in math a long time ago to consider taking a situation to its limits to get an idea of what might be going on in a situation where the differences were not so great as to be obvious. 

Consider a high power LED being driven at maximum design current. We all agree such a LED requires a heat sink and thermal relief to remain at or below its maximum operating temperature.

OK, now comes the heat sink. First we start with one molecule of aluminum stuck to the sink pad of the LED. Will it be OK? How about one molecule of titanium? Will that suffice? Does anyone disagree with me that one molecule of aluminum or titanium is not going to work here? How about a cubic yard of aluminum in a cube bonded to the sink slug of the LED? How about a cubic yard of titanium bonded to the sink slug of the LED?

Will the aluminum cube be satisfactory but the titanium cube not because the titanium has a higher thermal resistance? Now I would expect the junction temperature of the LED on the aluminum block to be less that it would be on the titanium block once steady state was reached in both cases but I don't know this for a fact nor do I know what the difference would be. My gut tells me that a larger cube of titanium could bring the steady state temperature of the LED junction to the same temperature as the smaller aluminum block would. In fact if the Ti block were large enough relative to the aluminum block, it could result in a lower junction temperature than that of the aluminum and actually be a better thermal solution, at steady state.

If I bond a tiny chip of diamond to the bottom of a LED is it a better solution than a large block of aluminum bonded to a like LED solely by virtue of diamond having a much lower thermal resistance than that of aluminum? 

Mass and surface area as well as the ambient surrounds are all significant elements in the thermal relief of these LED's and a difference in thermal resistance of one of the components in the thermal relief path for the LED is just part of the equation.

I don't know the answer to the question I will now pose but if you took a high power LED, drove it at its max current and submersed it in a swimming pool by its lead wires, would it over heat? Water's thermal resistance is ~ 30 times lower than that of air I believe. Is a swimming pool sufficient as a heat sink? If it is not sufficient as a heat sink at full power no doubt it would be sufficient at some reduced yet still viable drive level. A drop of water on the bottom of the LED would not be nearly as effective. I can't quantify it but water is pretty effective at cooling and yet its thermal resistance is 10 times higher than titanium.

I am in over my head so I will stay here only as long as I can hold my breath! :nana:

If an aluminum and titanium light such as the pair shown here by Mac were both operated in a vacuum, which would be the better solution? Clearly the aluminum has a lower thermal resistance so the heat generated can spread quicker and faster throughout the light but then what. How does it pass beyond through the vacuum? I believe the only means of escape would be through emission. I believe titanium typically has a greater emissivity than that of aluminum? Is it possible that titanium could pass the heat beyond itself better than that of the aluminum and steady state temp of the junction actually lower in the Ti than that of the Al? :shrug:

Thermal resistance is just one piece of a much larger and more complex picture.

If one stereo system uses monster cable to its speakers and has gold for all of its internal circuits is it a better radio than another that uses copper wire and zip cord to its speakers? Are there other considerations to factor in?

Aluminum has better (lower) thermal resistance than titanium. This is a known fact. Sterling silver has better (lower) thermal resistance than aluminum. This is a known and accepted fact. If aluminum is a better choice than titanium for a flashlight body by virtue of its thermal resistance alone then silver would be a better choice than aluminum for the same reason. I think there are other considerations and among them are cost, reliability, durability and ultimately functionality.

A design can succeed with marginal materials and fail with the best materials chosen. Success is not based on the materials as much as it is based on understanding them and using them well within their limitations. :shrug:


----------



## easilyled

Thanks very much for such a well thought-out and eloquent post Don.

It does provide me with some confirmation about my understanding as well as some re-assurance that my Ti lights are not just beautiful ornaments but capable of being functioning tools, provided that common sense is employed.


----------



## MrGman

Aluminum is basically 11 times better at thermal transfer than Titanium. Building a more massive Titanium heatsink in general is not nearly as good as simply using Aluminum. Why, because you cannot get all of that mass directly to the source of the heat. That is what thermal resistance and transfer rates are all about. The Titanium doesn't want to move the heat from the hotspot to the cooler areas because its molecules are all bound up better in different molecular structure. So making the heatsink 3 times as large with Ti. is still not nearly as good as simply having used Aluminum. Using the ultimate heat spreader such as black diamond substrate would still be better over Aluminum or copper than Titanium for the same reason. Once its in the Titanium it just doesn't want to keep traveling outwards to all extremities. 

Radiating energy in a "hand held" flashlight into the vacuum of space is king of meaningless here. Radiating it into air, the Aluminum host would still be better. There are a lot of Aluminum radiators made for cars and other applications in the world. 

The simple point is; it is now becoming painfully obvious that all of those ultra cool designs using Titanium for a "High Powered" flashlight were not actually good at "cooling" the sources of heat. They may be more rugged and scratch resistant but not really good for one of the main purposes they are needed in an LED type light with driver circuitry, that is to take the heat away from that LED and driver circuitry and move it out to the extremities to keep the electronics cool and provide longer life. If these were incandescent lights with no electronics in them this would be a moot point, but they are not. 

People can of course buy what they want for whatever reasons they want but the idea that they were getting the best possible LED driver and electronics with the most rugged and "robust" housing design in Titanium, we find in reality that they are not. Because its not the most "robust" in doing the job of spreading out the heat. It is contrary to that purpose by 11 to 1. In other words no matter how you slice it, its 11 times worse to have used Titanium as the total housing for these purposes of tranfering out the heat than Aluminum alloy. 

There is no amount of mental gymnastics that is going to change that. 

Making the lights with Copper or Aluminum or carbon fiber inner sleeve and then an outer Titanium shell for mechanical strength may be the way to go, but then who wants to pay for that level of mechanical packaging to make an 11 to 24 watt light work better and last longer with the self induced heat dissipation?

I for one don't want to buy a high powered light where I could only use it for a couple of minutes at a time. Its counter productive to the purpose of having the light. If I choose to only use it for 2 minutes that's one thing. But if I am limited by the design of the light that cost me a small fortune to only use it for 2 minutes (example time only) then I say that is ridiculous. 

To me its far more important that the light not die a premature death from heat than it didn't get scratched. Thicker Ti walls will be more expensive and still won't solve the original problem.


----------



## gadget_lover

While Gman is correct in his reasoning, he ignores the cases where aluminum is 11 times better than it has to be. In those cases, titanium will work just as well. It only need be "good enough" when it comes to keeping the LED junction within operating range.

Don's swimming pool analogy does not work well, since the mass of the water only serves to store the heat till it reaches the very large surface where it's exchanged with the air. A body of water in an insulated sealed container will heat up till it reaches the junction temperature.

1 watt is approximately 3.41 BTU/h. Since a BTU is the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit. Do the math (8 pounds in a gallon, etc) and you see that a 3 watt light will heat a pint of water 10 degrees in an hour, or a gallon 1.2 degrees. It will take a while, but eventually that sealed pint of water will boil, and eventually the lights electronics will fail from the heat.

So even if you have a swimming pool for a heat sink, it will overheat unless there is a way for the heat to go somewhere. It's just a matter of how many months it will take.



Daniel


----------



## McGizmo

If I have made any errors in my comments or stated opinions, I hope someone who understands the thermodynamics can correct them so no one leaves this thread with the wrong ideas. 

MrGman,
Can you cite a premature death of a LED due to its titanium host and if yes, do you have any particulars in size of light, drive curtent to LED and other design considerations.

My heat sinks are aluminum but the lights are titanium. I admit and agree that the titanium impedes the transfer of heat but then so does my hand and the air which is much worse than the titanium.

If aluminum is 10x better than titanium in terms of heat transfer but the design requires something 20x better than titanium you have failure. If aluminum is 10x better than titanium at heat transfer but you only need something with half the transfer ability of titanium then the titanium will be fine and if you switch to aluminum you have this great bounty and bonus of thermal capability and I am happy for you. :nana:

On this note, I leave this thread to Mac and my apologies to any who would have rather I stayed out of it all along. :wave:


----------



## McGizmo

gadget_lover said:


> .....
> Don's swimming pool analogy does not work well, since the mass of the water only serves to store the heat till it reaches the very large surface where it's exchanged with the air. A body of water in an insulated sealed container will heat up till it reaches the junction temperature.
> 
> 1 watt is approximately 3.41 BTU/h. Since a BTU is the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit. Do the math (8 pounds in a gallon, etc) and you see that a 3 watt light will heat a pint of water 10 degrees in an hour, or a gallon 1.2 degrees. It will take a while, but eventually that sealed pint of water will boil, and eventually the lights electronics will fail from the heat.
> 
> So even if you have a swimming pool for a heat sink, it will overheat unless there is a way for the heat to go somewhere. It's just a matter of how many months it will take.
> 
> 
> 
> Daniel



Daniel,
If I had intended the swimming pool be in a vacuum and not capable of passing the heat on to a larger surrounding I would have so stipulated. What happens if you stick your aluminum in a similar thermally isolated situation? If you are going to impose an isolation on the swimming pool, fine but impose it as well on any other thermal mass you wish to compare it to.

I said I was out of here in a post I made moments ago and now, for certain I am. My errors and false perceptions are mine and I don't wish to share any misinformation. I leave it to the experts among you.


----------



## easilyled

gadget_lover said:


> While Gman is correct in his reasoning, he ignores the cases where aluminum is 11 times better than it has to be. In those cases, titanium will work just as well. It only need be "good enough" when it comes to keeping the LED junction within operating range.
> 
> Don's swimming pool analogy does not work well, since the mass of the water only serves to store the heat till it reaches the very large surface where it's exchanged with the air. A body of water in an insulated sealed container will heat up till it reaches the junction temperature.
> 
> 1 watt is approximately 3.41 BTU/h. Since a BTU is the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit. Do the math (8 pounds in a gallon, etc) and you see that a 3 watt light will heat a pint of water 10 degrees in an hour, or a gallon 1.2 degrees. It will take a while, but eventually that sealed pint of water will boil, and eventually the lights electronics will fail from the heat.
> 
> So even if you have a swimming pool for a heat sink, it will overheat unless there is a way for the heat to go somewhere. It's just a matter of how many months it will take.
> 
> Daniel



But isn't the point that the swimming pool is not sealed and therefore even though air is a lousy conductor of heat, the very fact that there's such a vast surface area of the hot water exposed to the air, means that the water is going to cool quite quickly.

The point that McGizmo was making was that its all relative.

If the size of Ti is more than 11 times that of Al., then the fact that Al. is 11 times better at conducting heat is nullified.

In a Ti light that is the size of a Maglight, it doesn't matter if the heat doesn't even reach the tail for a long time.

The surface area is so much bigger that even if the heat stays around the head, neck and the beginning of the body, there is still much more surface area to dissipate it into the external environment than there is in a much smaller light where the heat is spread evenly all around it.


----------



## TranquillityBase

> McGizmo
> 
> 
> 
> OK, now comes the heat sink. First we start with one molecule of aluminum stuck to the sink pad of the LED. Will it be OK?
> 
> 
> 
> 
> Depends on the drive level
> 
> Is the pool filled with fresh water or salt water? :nana:
Click to expand...


----------



## precisionworks

> who wants to pay for that level of mechanical packaging


I'd buy one, especially if it had the carbon fiber internals. That would give the owner serious bragging rights. If you look at the SPY lights by Cool Fall, $1000+ is not a deal killer ... in fact, it seems to only motivate people. As would carbon fiber.

Something I've learned after more than 20 years in sales - People may not buy what they need, but they always buy what they want.


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## gadget_lover

I guess I should clarify.... 

Any material used as a heat sink (aluminum or titanium or gold or water) has to transfer the heat to somewhere else. The heatsink in a vacuum or insulated container is pretty useless after a few seconds/minutes.

Thermal mass is like a heat sponge. Once it's at full temperature, you can not add more without raising the temperature of the heat source. Big and heavy is not necessarily cooler.

Please note that I pointed out that there are many cases where you do not need the thermal conductivity of aluminum. Many early lights used the super thin copper of the plated circuit board for a heat sink. That's almost nothing, heat-wise. 

And no offense meant to Don. I like his work and his designs. I just did not like his analogy. 

Daniel


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## MrGman

easilyled said:


> But isn't the point that the swimming pool is not sealed and therefore even though air is a lousy conductor of heat, the very fact that there's such a vast surface area of the hot water exposed to the air, means that the water is going to cool quite quickly.
> 
> The point that McGizmo was making was that its all relative.
> 
> *If the size of Ti is more than 11 times that of Al., then the fact that Al. is 11 times better at conducting heat is nullified.*
> 
> In a Ti light that is the size of a Maglight, it doesn't matter if the heat doesn't even reach the tail for a long time.
> 
> The surface area is so much bigger that even if the heat stays around the head, neck and the beginning of the body, there is still much more surface area to dissipate it into the external environment than there is in a much smaller light where the heat is spread evenly all around it.


 

*These are not correct statements.* Especially having 11 times more Ti mass over Aluminum making it irrelevant. That is because you can't have all that mass right at where you need it at the base of the LED die and the electronic circuit board driving it. That mass is spread out away from the source of the heat in the shape of a flashlight housing. That is my whole point. The flashlights are not just big blocks of Titanium with a die in the middle.

In regards to whether or not the point is moot because the light in question doesn't need that much heat sinking. We are talking or at least this whole discussion got started by talking about high power lights running SST chips not little 1 watt lights. If we are sticking to the issue of running 10 to 24 or even higher wattage lights that have Titanium housings then my point that its not the best heat transfer material for such power levels especially for the extra cost is valid. 

Do I personally know of Ti housing flashlights that have failed, no I do not. Is there plenty of anecdotal evidence of flashaholics turning their lights off because they are getting toasty around the head and they don't want to risk it, yes there is. I haven't bought and have no intention of buying a Ti host flashlight as its not the optimum choice for a higher power heatsink.

In regards to air and the human hand holding the light. These are the final transfer mediums of heat in a hand held flashlight being used in normal circumstances on this planet. The Aluminum shell is the heat spreader to the air and person holding the light. If your hand is getting warm, guess what, its taking heat from the flashlight and the operator is part of the final thermal equation. 

If you want to talk about 3 to 5 watt lights using a big maglite size housing and they don't always run on high mode at that, that is not the thrust of my point. Yeah they may not need all that surface area to be in Aluminum. If you are going to run an SST-50 at 8 to 11 watts and try to get maximum light out of it for maximum electrical power it is allegedly rated to handle, putting it in a Titanium shell would be contradictory to that intention. It simply would not be the best way to transfer as much heat as possible away from the LED die and any driver electronic circuitry to the skin of the flashlight housing out to the air and the operator's hand to keep the light as cool as possible for as long as possible. 

If people want to spend $1000 for an ultra cool flashlight, and its not based on practical design, not my problem. If it actually has exotic materials that provide for great thermal transfer at exorbitant prices and doesn't really work any better than my Malkoff Wildcat at 4 times the price, also not my problem. More power to them. 

For all those little lights that have Ti shells but don't really use high power, this discussion doesn't really apply and I am not trying to say it does.

Only time will tell if those people who are buying the latest higher power LED lights in Titanium hosts find out that there lights don't last as long, if they burn out there LEDs. Most probably howeverr they simply wind up "babying" them by not ever running them for more than a minute or so at a time and these lights are really shelf queens. 

What I am saying is for myself. If I were to be a SST-50 type light that was being driven to or near full power capability, I wouldn't even consider it unless it was in an Aluminum Host or something with better than thermal transfer, not Ti which is 11 times less effective. No swimming pools required. 

The original poster showed some excellent data that the Titanium of a certain flashlight design wasn't doing as good a job as much lower cost aluminum using an SST-50 LED as the light source. From a _thermal_ standpoint, there is no justification to have made that flashlight host from Titanium and the data shows it. 

I concur with that data and say that the current marketing trend of using expensive Titanium in conjunction with high power LED lights which need more and more cooling than the 1 to 3 watt lights of "yesteryear" will eventually lead to performance failure.


----------



## RocketTomato

Mac, what material is the heatsink made of? Brass? Did you use any thermal compound between the housing and the heatsink?

For a control experiment, I would swap the LEs between the two lights to make sure the results are reproducible and not due to some difference in the light engines.


It would also be interesting to remove the front window of each light and then directly image each emitter and monitor the temperature change of the LED directly. (I know the absolute emissivities are not known and therefore we cannot get an accurate temperature, but the relative differences will be constant and thus informative.)


----------



## precisionworks

Peter Atwood makes an item called a Big Shot, used to hold 3 oz of distilled spirits. They are works of art & functional as well, made from a bar of stainless steel. I would imagine that he chose SS instead of titanium because the thermal conductivity of SS (.036) is even lower than that of Ti (.043).

Which is probably why you see very few SS flash lights.


----------



## easilyled

MrGman, I'm not disputing that Aluminium is a much better thermal conductor than Ti.

What I am questioning, and it is only a question, because I don't know the answer, is whether if the Ti light is big enough and the Aluminium heatsink inside it is also big enough to distribute the immediate heat from the heatsink further away, whether the junction temperature in the SST-50 in this light will be at an acceptable temperature when the SST-50 is driven at 2.8A to run the light at an extended period of time.

If this was the case, it wouldn't matter to me one iota, whether Aluminium is a better thermal conductor, because there are many other reasons why I prefer Titanium. 

Without carrying out sophisticated tests on this light, we don't really know, unfortunately.

I know you could do your output test over time which would give some indication of whether the led was overheating but someone would have to send you a Ti light of these proportions for testing and I myself am not willing to send you one from the UK!!

If Mac still has any of his Ti Mag-sized lights for testing, I'd love to see one of those on an FLIR diagram.

I would not be expecting the heat distribution to be any different from the FLIR diagrams already shown, because the heat is still going to be concentrated around the head.

The bottom line, however would be the temperature itself.

If the temperature in the area immediately surrounding the led was not excessive, this would be the most relevant and revealing fact.


----------



## strinq

easilyled said:


> What I am questioning, and it is only a question, because I don't know the answer, is whether if the Ti light is big enough and the Aluminium heatsink inside it is also big enough to distribute the immediate heat from the heatsink further away, whether the junction temperature in the SST-50 in this light will be at an acceptable temperature when the SST-50 is driven at 2.8A to run the light at an extended period of time.



Actually this is my question phrased a little differently. Will Ti overheat the LED when driving an LED to max? Assuming both Al and Ti lights are the same size. 

Also based on the fact that Al is a better conductor, lights with LEDs driven to max can be *smaller *than Ti lights. They can also be held longer.
The question of all the thousands of people using Ti lights have not been burned sounds statistically sound but from my personal experience i've had a light that got very uncomfortable to hold after some time (Al) and i was holding it all the while. If it was made of Ti, it probably would be uncomfortable to hold very fast and maybe even reach temps where it's dangerous to touch especially if coupled with the fact that it might be left standing without my hand to help conductivity. No arguments about the difference between leaving a light unattended and holding it, many have said that leaving some lights unattended for an X period of time makes a light not touchable compared to holding the same light for the same X period of time. 
Note that i use the words _maybe _and _might_. Same question as urs again, will Ti lights breach the temp safety limit?


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## easilyled

strinq said:


> ..........Also based on the fact that Al is a better conductor, lights with LEDs driven to max can be *smaller *than Ti lights. They can also be held longer......
> The question of all the thousands of people using Ti lights have not been burned sounds statistically sound but from my personal experience i've had a light that got very uncomfortable to hold after some time (Al) and i was holding it all the while. If it was made of Ti, it probably would be uncomfortable to hold very fast and maybe even reach temps where it's dangerous to touch especially if coupled with



I think that you are reasoning that because the heat stays localized around the head in a Ti light that it would feel more intense.

However, I think this would be outweighed by the fact that the heat would take much longer in a Ti light to reach the outside of the casing where your hand will feel it because of the much higher thermal resistance of Titanium.

So I would expect your hand to feel the heat from an Al light much more quickly.


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## easilyled

Just to give a sense of scale, this is Mac's Al. heatsink for the big Titanium light pictured below that I have been referring to in my previous posts.


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## octaf

easilyled said:


> Just to give a sense of scale, this is Mac's Al. heatsink for the big Titanium light pictured below that I have been referring to in my previous posts.


 

Wow, that's one big beautiful Titanium light you have there, easilyled !!!


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## octaf

Would anodizing on the surface of aluminum make difference in heat transfer or heat resistance ?


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## easilyled

octaf said:


> Wow, that's one big beautiful Titanium light you have there, easilyled !!!



Thanks octaf.

Yes its a beauty, made by Mac and its your favourite Grade 5, 6Al 4V, as far as I know. 

I would have thought that anodizing the Al heatsink would slightly impede the conduction compared to leaving the heatsink bare.


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## precisionworks

> If it was made of Ti, it probably would be uncomfortable to hold very fast


As easyled said, a Ti light could be hand held for a longer time before becoming uncomfortable. Even when the emitter area became too warm for comfort, the battery tube portion would remain at a lower temperature.


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## octaf

easilyled said:


> I would have thought that anodizing the Al heatsink would slightly impede the conduction compared to leaving the heatsink bare.


 

I meant anodizing the Aluminum light body, not the Al heat sink...


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## easilyled

octaf said:


> I meant anodizing the Aluminum light body, not the Al heat sink...



I think I recall reading somewhere that anodized Aluminium is slightly less conductive than bare Aluminium.

I don't think it would make a large difference though.


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## Th232

Dunno about conductivity, but since anodising is on the surface I'd be more interested in the emissivity. FWIW:

Highly polished Al: 0.039 - 0.057
Heavily oxidised Al: 0.2 - 0.31
Anodised Al: 0.77

Polished Ti: 0.19

And...
Polished Ag: 0.02 - 0.03
Highly polished, pure Au: 0.018 - 0.035

Sourced from:
http://www.engineeringtoolbox.com/emissivity-coefficients-d_447.html

That said, my thermodynamics knowledge is limited to one 2nd year eng course, so I don't think I'm particularly qualified to say how much of a difference any of the above will make.


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## strinq

easilyled said:


> I think that you are reasoning that because the heat stays localized around the head in a Ti light that it would feel more intense.
> 
> However, I think this would be outweighed by the fact that the heat would take much longer in a Ti light to reach the outside of the casing where your hand will feel it because of the much higher thermal resistance of Titanium.
> 
> So I would expect your hand to feel the heat from an Al light much more quickly.



ah yeah, didn't consider that. 


So it would take a longer time before being uncomfortable to hold.
But still, will it go beyond the threshold of being safe to hold is another question of course. Just an example. Eg:max 150C at emitter, Al will reach just say max 60C at the head. Will Ti made lights reach dangerous levels such as 80-100C (don't take time into consideration, just whether it will or will not reach those temps)? 

The tube might be safe, but it's actually dangerous as it doesn't give any indication (or at least a very bad indication) on how hot the head is. = OUCH, injury when the head is suddenly touched.


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## easilyled

strinq said:


> ah yeah, didn't consider that.
> 
> 
> So it would take a longer time before being uncomfortable to hold.
> But still, will it go beyond the threshold of being safe to hold is another question of course. Just an example. Eg:max 150C at emitter, Al will reach just say max 60C at the head. Will Ti made lights reach dangerous levels such as 80-100C (don't take time into consideration, just whether it will or will not reach those temps)?
> 
> The tube might be safe, but it's actually dangerous as it doesn't give any indication (or at least a very bad indication) on how hot the head is. = OUCH, injury when the head is suddenly touched.



Well I suppose its possible. More likely if the light is left on unattended in high-level mode and then picked up after a long time.

Not something that I would put high up in my list as the most dangerous thing that can happen though.


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## TranquillityBase

easilyled said:


> Well I suppose its possible. More likely if the light is left on unattended in high-level mode and then picked up after a long time.
> 
> 
> 
> 
> *Bingo! Well put Daniel.* And yes, it is possible, consider it more of a guarantee when the drive level is 1 amp or higher (with a smaller light, such as a 1.000" diameter based light).
> 
> Aluminum lights can get wicked smoking hot if the drive level is high enough, and Ti lights WILL get much hotter with the heat concentrated in the area if the electronics.
> 
> 
> 
> 
> Not something that I would put high up in my list as the most dangerous thing that can happen though.
> 
> Click to expand...
> 
> 
> You should put this high on your list, *please* consider those that are unaware of the danger, such as a small child.
Click to expand...


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## easilyled

TranquillityBase said:


> .... You should put this high on your list, *please* consider those that are unaware of the danger, such as a small child.



I stand corrected Scott. (and string) 

I don't have any children, just a girlfriend who finds my hobby perplexing, to say the least, and isn't tempted to handle any of my torches.

I would not leave a high power torch on unattended either, but I certainly take your point that its something that people should be aware of. :thumbsup:


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## Nanomiser

Mac,

Beautiful illustration of thermal loading and heat transfer, thank you :thumbsup:


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## strinq

easilyled said:


> Well I suppose its possible. More likely if the light is left on unattended in high-level mode and then picked up after a long time.



Meaning it can get reach a point where it becomes impossible to use compared to Al (even while being held) but as u said, should be a rare occurrence unless someone insist on using the light on max for long extended periods of time. 

Some food for thought here actually. So if someone actually wants to use a small light with the LED driven hard, they should opt for Al instead of Ti (again only if Ti is proven to cross that safety barrier). 

Good thread this.


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## precisionworks

> So if someone actually wants to use a small light with the LED driven hard, they should opt for Al instead of Ti



My son has a small, single cell Ti light that runs a direct drive MC-E on a Li-Ion battery. Seems like 20 minutes is the max run time, and I'd imagine the output is well over 500 lumens. He's never mentioned a heat issue, and he runs it dies. Until batteries are developed with a higher energy density, or until emitters are made that have far greater output than those available today, the battery would seem to provide the safety factor that prevents overheating.


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## kwkarth

precisionworks said:


> My son has a small, single cell Ti light that runs a direct drive MC-E on a Li-Ion battery. Seems like 20 minutes is the max run time, and I'd imagine the output is well over 500 lumens. He's never mentioned a heat issue, and he runs it dies. Until batteries are developed with a higher energy density, or until emitters are made that have far greater output than those available today, the battery would seem to provide the safety factor that prevents overheating.



I'm fairly sure there's a current limiting resistor there too.


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## bkkd

gadget_lover said:


> What's your interpretation of those results?
> 
> Which did better at getting rid of heat?
> 
> 
> Daniel



you have got to be an electrical engineer .......


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## precisionworks

> I'm fairly sure there's a current limiting resistor there too.


Milky would be the one to ask, as he installed the LE in a Mirage Man Ti head. I thought that direct drive meant just that, with nothing between battery & emitter.


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## kwkarth

precisionworks said:


> Milky would be the one to ask, as he installed the LE in a Mirage Man Ti head. I thought that direct drive meant just that, with nothing between battery & emitter.



Nothing between emitter and battery =  city  unless you want to intentionally use an unsuitably underpowered battery.


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## cmacclel

kwkarth said:


> Nothing between emitter and battery =  city  unless you want to intentionally use an unsuitably underpowered battery.




That all depends on the Forward Voltage of the Emitter. 


Mac


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## precisionworks

According to Cree, the Vf of the MC-E is 3.9 volts maximum. An 18650 is rated at 3.7 volts, so it should be able to be directly connected to the die package.

http://www.cree.com/products/pdf/XLampMC-E.pdf


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## Th232

precisionworks said:


> According to Cree, the Vf of the MC-E is 3.9 volts maximum. An 18650 is rated at 3.7 volts, so it should be able to be directly connected to the die package.
> 
> http://www.cree.com/products/pdf/XLampMC-E.pdf



Shouldn't the max voltage of an 18650 should be the same as any other Li-Ion, 4.2V, resulting in ? Assuming we're connecting the MC-E dice in parallel, that is.


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## tino_ale

cmacclel said:


> That all depends on the Forward Voltage of the Emitter.
> 
> Mac


Ditto to that!


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## PlayboyJoeShmoe

If the wet finger trick (neg of battery to ground on light) makes the LED(s) glow it's DD.

My Ultrafire MC-E does not, but my Xtar and MTE P7 lights do! These two use a resistor in the tail for 'low'.

The UF MC-E uses a driver.


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## mknewman

So nobody has asked the pertanent question: "Mac, will you build me a P60 host that will take a 18650 made out of Sterling Silver?".


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## Aircraft800

Wow! Very cool thread Mac! I didn't know you had thermal imaging equipment. 

I was in a machine shop recently, and the engineer was making Titanium brake pucks for racing Vettes. The original steel pucks get so hot that the brake fluid could boil, but the new Titanium ones he makes block the heat transfer. He claimed almost a 50% decrease in heat!


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## tino_ale

cmacclel said:


> Tino your exactly right. The problem is when a light is assembled it is difficult to measure to measure the heatsink temp. as close as possible to the die unless you drill holes into the light  This was a quick and dirty simple test. I hope to set another test up tonight with a thermal coupling into the heatsink as close as possible to the LED. I will then re-run the same test with the same heatsink / LED in both bodies.


Hey Mac, did you get to set-up your test? Measuring temp as close to the LED with both bodies.


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## cmacclel

tino_ale said:


> Hey Mac, did you get to set-up your test? Measuring temp as close to the LED with both bodies.




Nope and doubt I will have time in the near future to do so 

Mac


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## don.gwapo

Hmmm... this proves that Ti lights is more of a form than function lights compared to Al coz it has a better heat transfer than Ti.


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## cmacclel

don.gwapo said:


> Hmmm... this proves that Ti lights is more of a form than function lights compared to Al coz it has a better heat transfer than Ti.



That is not entirely true. It all depends on how much heat-sinking your application requires. 
Mac


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