Update: 10-22-17. KRONOS K70 GB. $50. 243 on list!

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Saigon
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interested in one

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Hello,
Please add one for me.
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@Fritz15

+1

I was thinking that is exactly what the C8 makes such a good light, fins on the right place, good construction, good heat transfer especially the new type with integrated shelf, so this might be a good guideline for manufacturers, instead of trying to re-invent the Wheel.

Edited by: sb56637

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I’m in for one also. Thanks.

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fritz15 wrote:
JasonWW wrote:
DB Custom wrote:
I’ve seen thermal imaging tests taken as a light was turned on and in the first seconds as the heat made it’s way through the heat sink. They said the pattern was almost exactly an inversion of the light coming out the front, so if you consider the light out the top as the top half of an X and the heat out from under the emitter as the bottom half of this X, you see where the heat needs to go for fast and immediate dispersal.



I have to disagree with you on this one, buddy. Heat does not flow directionally like in your picture. When the emitter heats up that copper MCPCB, the heat gets spread across it very evenly. Not perfectly, but decently. This is why larger diameter MCPCB’s do a better job at transferring heat.

Once that copper disc gets hot, the heat transfers into the aluminum below it and starts spreading out evenly like a drop of water on a sponge. Areas that are thick will take longer to heat up than thin areas. This means the thin areas will get hotter first.

Did you see a thermal image of a flashlight cut in half? I’m guessing it was a whole light. What you probably saw was the battery tube and other thin areas down low start to “heat soak” so to speak, while the thicker areas around the head was still soaking up the energy (heat).

The photo you show pretty much proves that. Thermal imaging shows actual temperatures. The fact that the temps were lower around the thick sections all around the emitter shows this design is doing it’s job and keeping things cooler.

Does that make sense?

While I don’t completely agree with either of you I support DB Custom’s point that the cooling fins aren’t in the best place. The way heat spreads out is comparable to how a liquid without gravity would flow (imagine the liquid has it’s source right under the LED). It goes into the direction of the smallest resistance. So the first few cooling fins are pretty deep and I am sure you would see a better thermal performance if they’d not be as deep. When designing the BLF GT we also did extensive thermal analysis and the results were pretty clear – having the fins distributed around the shelf yields a significantly better thermal performance compared to having them above the shelf (here we even disregarded any transitional resistances). See the following thermal analysis of a BLF GT design with fins around the shelf and fins above the shelf:

Edit: Also, the thicker the walls, the more evenly the heat gets distributed and more heat can flow away from the source. Again, think of the liquid, the thicker the walls the more space there is for the liquid to flow away.


I agree that you want more surface area (fins) near the heat source as this will increase heat transfer through radiation. This slows down and hopefully limits the max temperature of the flashlight.

To sum it up, lots of mass around the heat source helps transfer the heat through conduction (from LED into the metal), then lots of surface area around the heat source helps transfer that heat through radiation (from metal to surrounding air).

Please don’t use an analogy of liquid spreading in zero gravity. This is way off. Liquids, like water, in zero G don’t really spread, the surface tension keeps it together as I’m sure we’ve all seen videos of astronauts playing with water. It’s a bad analogy and may confuse others. It certainly confuses me, at least.

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fritz15 wrote:


In order to really understand what we are seeing here, we need a cross section view. (I could flip flop the thermal images from these same exterior designs just by manipulating the internal shapes)

Also, where these images taken after the same time frame? I assume so, but want to make sure.

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I think one thing to take into consideration is that the above does not solely compare thermal properties of fins between led and reflector vs fins between led and batteries. The two lights are of a slightly different design as well. For example, the fins on the cooler running light are deeper.

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hIKARInoob wrote:
I think one thing to take into consideration is that the above does not solely compare thermal properties of fins between led and reflector vs fins between led and batteries. The two lights are of a slightly different design as well. For example, the fins on the cooler running light are deeper.

I think you’re misunderstanding the picture. The “cooler running” of the light on the left is a BAD thing! For the best performance, the heat should be pouring out of the light, like the one on the right.

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DavidEF wrote:

I think you’re misunderstanding the picture. The “cooler running” of the light on the left is a BAD thing! For the best performance, the heat should be pouring out of the light, like the one on the right.

This actually depends on the cross section views and how much time has elapsed in these images.

If these shots are after 30 seconds and the light on the left has more mass around the heat source, then it is clearly the better thermal design.

If these shots are after 15 minutes and both lights have the same thermal mass, then the light on the right has the better thermal design.

Thermal imaging shots like this are not the best way to judge a design. They are helpful, but not the best. The LED temperature is the crucial factor and that is not shown here. Whichever light has the cooler running LED of these two images is the better thermal design.

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JasonWW wrote:
I agree that you want more surface area (fins) near the heat source as this will increase heat transfer through radiation. This slows down and hopefully limits the max temperature of the flashlight.

To sum it up, lots of mass around the heat source helps transfer the heat through conduction (from LED into the metal), then lots of surface area around the heat source helps transfer that heat through radiation (from metal to surrounding air).

Please don’t use an analogy of liquid spreading in zero gravity. This is way off. Liquids, like water, in zero G don’t really spread, the surface tension keeps it together as I’m sure we’ve all seen videos of astronauts playing with water. It’s a bad analogy and may confuse others. It certainly confuses me, at least.

Yes, good summary, ideally a large, high powered light has both, a lot of mass around the heat source and also a lot of surface area.

The analogy is good enough to illustrate where and how fast the heat will flow in the host. I think you might have misunderstood me. You are right that it does not make sense to talk about the distribution of a constant amount of water. But if you place your water source right under the MCPCB and fill up the host (where there would be usually aluminium) then the way the water spreads is similar to the way the heat spreads.

JasonWW wrote:
In order to really understand what we are seeing here, we need a cross section view. (I could flip flop the thermal images from these same exterior designs just by manipulating the internal shapes)

Also, where these images taken after the same time frame? I assume so, but want to make sure.

The shelf temperature would be enough (which was also quite a bit lower for the better design). Not without restricting the self thickness or some other awkward design changes. The point of this comparison was to see the performance of two designs with different fin location and the same internal designs. Yes, since it is one thermal analysis. The image displays the equilibrium state of the heat distribution.

hIKARInoob wrote:
I think one thing to take into consideration is that the above does not solely compare thermal properties of fins between led and reflector vs fins between led and batteries. The two lights are of a slightly different design as well. For example, the fins on the cooler running light are deeper.

The slight changes in design are not relevant for the point, which is that cooling fins right around the shelf improve thermal performance.

DavidEF wrote:
hIKARInoob wrote:
I think one thing to take into consideration is that the above does not solely compare thermal properties of fins between led and reflector vs fins between led and batteries. The two lights are of a slightly different design as well. For example, the fins on the cooler running light are deeper.
I think you’re misunderstanding the picture. The “cooler running” of the light on the left is a BAD thing! For the best performance, the heat should be pouring out of the light, like the one on the right.

No, it is a good thing. The left design is better since the fins are located where there is the biggest amount of heat. That means the temperature at the fins is as high as possible which allows for an as good as possible heat exchange between air and host. The higher the temperature difference between host and air the better the heat exchange works.

I am sorry I caused quite some confusion with the picture. Long story short, there should be fins around the shelf for an optimal thermal performance.

I’ll see if I have a comparison with the two shelf temperatures somewhere floating around, then it should be more clear.

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fritz15 wrote:
No, it is a good thing. The left design is better since the fins are located where there is the biggest amount of heat. That means the temperature at the fins is as high as possible which allows for an as good as possible heat exchange between air and host. The higher the temperature difference between host and air the better the heat exchange works. .

That is something which i have learned different, it is all about area, so more fins (leaving in the middle if they have to be thick or thin) create a larger surface area, so the device can get rid (dissipate) the heat faster.

Edited by: sb56637

fritz15
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This should make things more clear.

Left is BAD fin location, right is GOOD fin location:

Left is overall hotter and has a 5 degrees higher shelf temperature:

Same settings and loads and coefficients and time and same everything (well apart from fin location).
Also this comparison only considers the location of the fins.

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Yokiamy wrote:
fritz15 wrote:
No, it is a good thing. The left design is better since the fins are located where there is the biggest amount of heat. That means the temperature at the fins is as high as possible which allows for an as good as possible heat exchange between air and host. The higher the temperature difference between host and air the better the heat exchange works. .

That is something which i have learned different, it is all about area, so more fins (leaving in the middle if they have to be thick or thin) create a larger surface area, so the device can get rid (dissipate) the heat faster.

Yes, more fins the better, but my post above illustrates how the fin location also matters a lot. The best would be fins all over the place.

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DavidEF wrote:
hIKARInoob wrote:
I think one thing to take into consideration is that the above does not solely compare thermal properties of fins between led and reflector vs fins between led and batteries. The two lights are of a slightly different design as well. For example, the fins on the cooler running light are deeper.
I think you’re misunderstanding the picture. The “cooler running” of the light on the left is a BAD thing! For the best performance, the heat should be pouring out of the light, like the one on the right.

This would be true if the area very close to the led would be of very high temperature (white in colour); then you would have poor heat sinking, as with a thin screw-on led board.

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Yokiamy wrote:
fritz15 wrote:
No, it is a good thing. The left design is better since the fins are located where there is the biggest amount of heat. That means the temperature at the fins is as high as possible which allows for an as good as possible heat exchange between air and host. The higher the temperature difference between host and air the better the heat exchange works. .

That is something which i have learned different, it is all about area, so more fins (leaving in the middle if they have to be thick or thin) create a larger surface area, so the device can get rid (dissipate) the heat faster.


I don’t see the contridiction here. You are both saying the same thing. Lol
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fritz15 wrote:
hIKARInoob wrote:
I think one thing to take into consideration is that the above does not solely compare thermal properties of fins between led and reflector vs fins between led and batteries. The two lights are of a slightly different design as well. For example, the fins on the cooler running light are deeper.

The slight changes in design are not relevant for the point, which is that cooling fins right around the shelf improve thermal performance.

I certainly believe you. Nevertheless, from an outsider not knowing any details, including the cross section this is something that came to my mind.

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I was really interested until I realised that this is basically an over driven S70S with a pretty body and a bigger board.
If that’s it then I don’t see why it is worth it.

It looks like it’d just going to get silly hot, have a temperature drop down after 3 minutes which even Thorfire fixed and then its the case of crappy replies.

If I was asking questions to a seller and they started getting shirty with me I’d move along and buy something else. The pre-sale is the chance to show off how amazing you are, how much you care about your customers, how much you know about your product and the time to get to really sell it. If you’re just skipping over questions and saying “wait” whats the point in posting it to begin with.

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chrisc wrote:
I was really interested until I realised that this is basically an over driven S70S with a pretty body and a bigger board.
If that’s it then I don’t see why it is worth it.

It looks like it’d just going to get silly hot, have a temperature drop down after 3 minutes which even Thorfire fixed and then its the case of crappy replies.

If I was asking questions to a seller and they started getting shirty with me I’d move along and buy something else. The pre-sale is the chance to show off how amazing you are, how much you care about your customers, how much you know about your product and the time to get to really sell it. If you’re just skipping over questions and saying “wait” whats the point in posting it to begin with.

+1

Edited by: sb56637

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fritz15 wrote:
DavidEF wrote:
hIKARInoob wrote:
I think one thing to take into consideration is that the above does not solely compare thermal properties of fins between led and reflector vs fins between led and batteries. The two lights are of a slightly different design as well. For example, the fins on the cooler running light are deeper.
I think you’re misunderstanding the picture. The “cooler running” of the light on the left is a BAD thing! For the best performance, the heat should be pouring out of the light, like the one on the right.

No, it is a good thing. The left design is better since the fins are located where there is the biggest amount of heat. That means the temperature at the fins is as high as possible which allows for an as good as possible heat exchange between air and host. The higher the temperature difference between host and air the better the heat exchange works.

I am sorry I caused quite some confusion with the picture. Long story short, there should be fins around the shelf for an optimal thermal performance.

I’ll see if I have a comparison with the two shelf temperatures somewhere floating around, then it should be more clear.


OK. Sorry, hIKARInoob. I was the one who misunderstood. Facepalm

Thanks for explaining, Fritz.

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DavidEF wrote:
OK. Sorry, hIKARInoob. I was the one who misunderstood. Facepalm

Don’t worry about it; I truly appreciate the sharing of thoughts. Wink

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In for at least one piece

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Rusty Joe wrote:
Get rid of the 3-min step-down and I’m in.

With up to 9 amps, it will most likely stay at 3 minutes.

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FlashPilot wrote:
Great job Kronos! Your light looks great! But the thicker floor plate isnt going to help a whole lot in transferring heat through the head because its not the thermal bottleneck. What are the chances of making the head a solid 1 piece unit for a few dollars more, and keeping the aluminum walls thick to follow the contours of the reflector to better transfer heat through the head? All that dead air between the reflector and the head should be solid aluminum, as thick as possible, without any right angles, using only radius cuts, and of a 1 pc design to assist in maximum cooling. Any compromise here limits heat transfer, which heats the base of the floor plate assembly… which in turn heats up the battery tube and the cells. Then we wind up with another powerful light, where the battery tube is almost as hot as the head after a full power run. This has been the limitation in almost every high powered light sold up to this point. Now you have a chance to address that problem directly before its too late. As it is now, the light has the same thermal bottleneck as the S70 (and most others), which survives at 5 amps. Since you’re almost doubling the amps, I think you’d do much better in asking ThorFire if they can accommodate us. Every little bit is going to count at those power levels, and cells shouldn’t be used as heat sinks for such an awesome light that you’ve created!

Thoughts?


It is an idea we can certainly look into. To make it happen would require a redesign of the head/reflector and possibly a new round of samples/prototypes (potentially more delays)…but we’ll see what we can come up with! Smile

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So let’s add a fan then for longer high output runtimes?

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Team KRONOS wrote:
FlashPilot wrote:
Great job Kronos! Your light looks great! But the thicker floor plate isnt going to help a whole lot in transferring heat through the head because its not the thermal bottleneck. What are the chances of making the head a solid 1 piece unit for a few dollars more, and keeping the aluminum walls thick to follow the contours of the reflector to better transfer heat through the head? All that dead air between the reflector and the head should be solid aluminum, as thick as possible, without any right angles, using only radius cuts, and of a 1 pc design to assist in maximum cooling. Any compromise here limits heat transfer, which heats the base of the floor plate assembly… which in turn heats up the battery tube and the cells. Then we wind up with another powerful light, where the battery tube is almost as hot as the head after a full power run. This has been the limitation in almost every high powered light sold up to this point. Now you have a chance to address that problem directly before its too late. As it is now, the light has the same thermal bottleneck as the S70 (and most others), which survives at 5 amps. Since you’re almost doubling the amps, I think you’d do much better in asking ThorFire if they can accommodate us. Every little bit is going to count at those power levels, and cells shouldn’t be used as heat sinks for such an awesome light that you’ve created!

Thoughts?


It is an idea we can certainly look into. To make it happen would require a redesign of the head/reflector and possibly a new round of samples/prototypes (potentially more delays)…but we’ll see what we can come up with! Smile

Here are some simpler to employ ideas. Just leave some extra mass where avaliable (the red areas) assuming the driver cavity is not filled up by a big coil.

Then more surface area below the fins on the bottom part of the head. These are small changes, but could really help with cooling.

Check this out.

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Is the side switch going to be able to turn the light on and off or will it only switch modes?

If only switch modes, that means you have to make the light feel good with a reverse grip on the end so your thumb can hit the end switch to turn on and off. You have kind of a bulky end cap. Maybe it’s size feels good, maybe awkward? I would just make sure it feels good.

Personally I like turning my L6 on and off with the side switch with the rear being a lock out.

Have you guys came up with a firmware yet? Something like the ramping UI in Narsil would really make this light stand out from the rest. There are very few factory lights that have ramping. Having it would help justify the higher price. It would make it a more premium light to match it’s upscale looks.

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JasonWW wrote:
Team KRONOS wrote:
FlashPilot wrote:
Great job Kronos! Your light looks great! But the thicker floor plate isnt going to help a whole lot in transferring heat through the head because its not the thermal bottleneck. What are the chances of making the head a solid 1 piece unit for a few dollars more, and keeping the aluminum walls thick to follow the contours of the reflector to better transfer heat through the head? All that dead air between the reflector and the head should be solid aluminum, as thick as possible, without any right angles, using only radius cuts, and of a 1 pc design to assist in maximum cooling. Any compromise here limits heat transfer, which heats the base of the floor plate assembly… which in turn heats up the battery tube and the cells. Then we wind up with another powerful light, where the battery tube is almost as hot as the head after a full power run. This has been the limitation in almost every high powered light sold up to this point. Now you have a chance to address that problem directly before its too late. As it is now, the light has the same thermal bottleneck as the S70 (and most others), which survives at 5 amps. Since you’re almost doubling the amps, I think you’d do much better in asking ThorFire if they can accommodate us. Every little bit is going to count at those power levels, and cells shouldn’t be used as heat sinks for such an awesome light that you’ve created!

Thoughts?


It is an idea we can certainly look into. To make it happen would require a redesign of the head/reflector and possibly a new round of samples/prototypes (potentially more delays)…but we’ll see what we can come up with! Smile

Here are some simpler to employ ideas. Just leave some extra mass where avaliable (the red areas) assuming the driver cavity is not filled up by a big coil.

Then more surface area below the fins on the bottom part of the head. These are small changes, but could really help with cooling.

Check this out.

!{width:95%}http://img.photobucket.com/albums/v335/JasonWW/Flashlights/KRONOS%20K70%...!

And also make the head in one piece, as most of the fins are just cosmetic…justbuyanL6 Big Smile

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