Let me run an idea across you guys. Heat Dissipation Towers.

KDOG3

Flashlight Enthusiast
Joined
Aug 4, 2004
Messages
4,240
Location
Sea Isle City, NJ
I use the G&P 1W/3W drop ins for Seoul mods but sometimes I have a problem with heat dissipation, resulting in a blue tint shift from an overheating emitter, or even a module shutdown. I think I may have figured out a way of "wicking" away some heat in a better manner. I think part of the problem is there isn't alot of material for the heat to go to in the heatsink in these modules and the reflector doesn't make "great contact" with the heatsink. I envision stacking 2 or 3 of the .027" copper disc from the shoppe on top of one another - using a VERY thin amount of themal epoxy - and then mounting it to the heatsink in the cavity between the reflector base and the heatsink. You'd have to trim 'em down a bit on 2 sides so they'd fit between the edge of the heatsink and the emitter so the reflector could screw down over top of them. I'm thinking one "stack" on each side of the emitter. Now you'd want to keep the stack shorter than the height of the emiter housing or you might not be able to get the reflector down far enough to focus properly. Then put a dollup of thermal compound on top of the stack so the reflector base contacts the compound (NOT epoxy!) these "heat dissapation towers" will act as better conduits for heat generated by the very nearby emitter. Plus with the stacks, there is now more material for heat to dissipate to also.

I just got off midnight shift so I'm dead on my feet and am going to bed now.

Let me know what you all think!
 

Scattergun

Enlightened
Joined
May 9, 2006
Messages
485
....sounds interesting, but the real effect it has on thermal conduction should be hard to guess...better if you try it out and report back here. Great with new ideas!!
 

65535

Flashlight Enthusiast
Joined
Dec 13, 2006
Messages
3,320
Location
*Out There* (Irvine, CA)
I want to make a 3 cree tower that requires boring out the reflector and Head unit, but it would allow a heatpipe to go from the emitters tot he base.
 

gadget_lover

Flashaholic
Joined
Oct 7, 2003
Messages
7,147
Location
Near Silicon Valley (too near)
The idea will work in open air where the moving air will carry off the heat. More surface area means more heat is transfered to teh air. That's the concept behind grooving a Maglite head.

Inside a flashlight, you have only a few cubic inches of air and it's not moving, so the "tower" idea won't do much.

I've seen copper braid used to connect movable heat generating devices to the chasis of electronic components. Maybe that would help your situation? Dropin-> copper braid -> insert that fits against the light body.

Daniel
 

KDOG3

Flashlight Enthusiast
Joined
Aug 4, 2004
Messages
4,240
Location
Sea Isle City, NJ
Well my point is to move heat from the heatsink to the much larger surface area of the reflector, not to the air.
 

gadget_lover

Flashaholic
Joined
Oct 7, 2003
Messages
7,147
Location
Near Silicon Valley (too near)
I misread the first post. Sorry. I thought the "stacks with thin epoxy layers were supposed to be used as if they were finned radiators.

Moving heat to the reflector does not change much unless the reflector can radiate or conduct that heat to somewhere else. If the reflector has a large contact surface with the head, then it might improve the situation.

It just occured to me that a heat sink is like a kitchen sink, and heat is like water. If the sink gets full, then no more water will go into it. If the drain is too small, the water will not flow out as fast as it goes in. When a heat sink gets as hot as the LED it will no longer be cooling the LED (I.E. it fills up). When the contact area of the heatsink to a radiating surface is too small, it lets the heatsink "fill up".

The thermal compund lets heat transfer better between poor fitting flat surfaces, but it's not designed to bridge gaps. It's supposed to be as thin as possible.

Daniel
 

Effulgence

Newly Enlightened
Joined
Jan 4, 2007
Messages
96
Location
California, USA
I've seen plenty of Zalman CPU heatsinks and the like, that have extra fine fins. They're really thin and do a great job. Most of the fins I've seen on some flashlight mods seem quite thick. Perhaps there is a way to make fine fins on a flashlight head?
 

Thujone

Flashlight Enthusiast
Joined
Oct 18, 2006
Messages
1,688
Location
Nebraska
Effulgence said:
I've seen plenty of Zalman CPU heatsinks and the like, that have extra fine fins. They're really thin and do a great job. Most of the fins I've seen on some flashlight mods seem quite thick. Perhaps there is a way to make fine fins on a flashlight head?

You dont want super fine 'fins' on the outside of your light as they would bend or break easily.
 

soffiler

Enlightened
Joined
Feb 15, 2006
Messages
522
Location
Cranston, RI
There's a mathematical relationship between the thickness of the fins, the height of the fins, and the distance between them. Strictly from a heat-transfer standpoint (aside from bending or breaking) fins can definitely be too "fine". When they are thin, they do not conduct heat as well, so the heat isn't being efficiently transported to make use of the surface area of the fin. Also, they can be too close together. Again there's a mathematical relationship. Air doesn't flow as well in thin gaps. The people who know this stuff the best are chip-cooler heatsink companies. Take a look at some commercial off-the-shelf heat sinks and base your fin proportions on them and you'll be a long way ahead of the game without needing to do the math yourself.
 

wquiles

Flashaholic
Joined
Jan 10, 2005
Messages
8,459
Location
Texas, USA, Earth
The key is not only the HS design/style, but where and how is the heat being transfered or being moved to? How are you getting the heat out of the light?

Like others have posted above, the best comparison is CPU's in PC's. The heatsink removes the heat from the hot CPU to the copper material, and then via fans, this heat is removed into the air surrounding the inside of the computer case, and then the case fans push this hotter air out of the case and bring cooler air from the room. Depending on the room's temperature, and how big it is (its heat capacity), there will be some equilibrium point reached, but for most houses/offices this equilibrium point does allow for the CPU to be cool enough to work reliably and without frying itself.

Of course, in the PC example we are actually using power/energy to actively help this transfer of energy to take place. In a light, most of us want longer runtimes from the sealed, built-in energy storage (batteries), so an active approach with fans is not as attractive since this fan would "steal" or "divert" some of this "useful" energy into something it is not "light" ;)

In a flashlight, the only two ways to move heat are fairly pasive (unless you also use fans):
- You have heat transfered from the body/light to your hand (assuming you are normal human being, you will "absorb" heat as you should be cooler than the light) and then
- Passive heat transfer to the air surrounding the body/light. Assuming the light is moving with you as you walk, exposed fins would help to some degree just like they do in the CPU heat sinks. If you are however not moving at all or the air around the light is not moving relative to the light, then the fins are not nearly as effective :(

Note that in both cases the heat needs to arrive to the outside surface of the body/light so that either the hand and/or the air around the light can take some of this heat away. So at least to me, once you find a good/effective way of getting the heat from the LED/light to the outside surfaces of the body/light, you are doing as good as you can do with a passive system :)

I am not an expert - just sharing my 2 cents worth ;)
Will
 

Anglepoise

Flashlight Enthusiast
Joined
Nov 4, 2004
Messages
1,554
Location
Pacific Northwest
Will....That was a great , simple explanation.

I still strongly believe that the LED has to be firmly attached to part of the flashlight body. This gives the heat a fighting chance to get out to my hand.

Its seems to me that many recent designs do not address this heat situation and stories of P4s turning a nasty blue color in use, seem to back this up.

Any type of drop in LED module is going to be at a distinct disadvantage when compared to a well thought out bulkhead design, where the LED is attached directly to the body of the light or has a large surface area that is 'touching' the
body of the light.
 
Last edited:

rivethead147

Newly Enlightened
Joined
Apr 9, 2007
Messages
25
about the only way to change/force the direction of heat from a flashlight body is rifling (incase not familiar: the circular lapse grooves you seen in a barrell of a long distance rifle, as well as used in modern hand guns). you would have to take the fins (math/proportion correct), drop a lead to the rifling and rifle out to the head/reflector. it will create a range of problems, heat and presuure from batteries as well as reflector to consider and rifling will diminish water resistance.

basically, reconsider a larger tube instead. also, the tube material will make a differance in heat dissipation as well, the idea is good, just has to be refined.
 
Top