I’ve been thinking about Zebralights recently.
One of the things that they do right is unibody design which improves heat transfer to parts farther apart from the head.
This make cooling with hands much more effective, but radiation and convections improve slightly as well.
I’ve been thinking about ways to emulate it.
Soldering / glueing the head.
Pretty permanent, not for me
Liquid metal TIM
Not for alu. But otherwise seems good.
Regular thermal paste
These tend to have high solid content. And often the solid is some ceramic.
They will eat the threads quickly. Silver-based paste would be gentler to the threads but that’s $$$.
But…if during regular operation I always unscrew the tail cap, I can use thermal paste near the head with few ill effects.
It won’t make the light much better, but should make it somewhat better.
As long as it’s not electrically isolating the tube from the head, or you don’t need those to be electrically connected, you can use some thin thermal paste like MX-4 for threads.
Tried it and, as sp5it says, pretty pointless. Over time the paste gets stuck within the threads and despite it doesn't really hampers threading performance, it looks quite ugly. The whole threaded surface transmits heat well enough for this to be of any significance.
I’m not sure I agree. No touchable part of the light should be too hot to handle. But there’s some space between “too hot to handle” and “comfortable to hold” though.
Good food for thought! I personally wouldn’t do it.
The surface quality (machined) of the threads is generally pretty good, resulting in decent heat transfer, at least for a two discrete solid interface.
Regular grease on the thread - although not a dedicated thermal grease - is a solid, resulting in much better thermal conductivity compared to air.
Thermal grease could actually be a bit abrasive; although I’m not too sure about this, but I believe it consists very small metallic particles. These abrasive particles could roughen the surface of the threads, resulting in decrease of thermal conductivity of the threads.
I think the effect of using thermal grease on the threads is mostly interesting on theory level, but will have little effect in reality.
Only some thermal pastes like IC-D are abrasive.
The rest are just fluid, no particles.
You can usually tell by the consistency.
IC-D and arctic silver are very thick, while stuff like MX-4 and NT-H1 are far less viscous and also clean off much better.
OK How about some nice” NO-OX-ID A-Special Electrical Grade Conductive Grease ”
NO-OX-ID “A-SPECIAL” is the electrical contact grease of choice for new electrical installations and maintenance. NO-OX-ID is an electrically conductive grease that keeps metals free from rust and corrosion. This electrically conductive grease which has been used in the power industry for over 65 years to prevent corrosion in electrical connectors from low micro-power electronics to high voltage switchgear. NO-OX-ID electrical grease prevents the formation of oxides, sulfides and other corrosion deposits on copper, aluminum, and steel surfaces and conductors. The purpose of a electrical contact lubricant is to prevent corrosion and lubricate the connection for easier maintenance. NO-OX-ID “A-Special” electrical grease prevents corrosion attack on all metal surfaces. Attack can come from battery acid, salt, moisture and various industrial chemical vapors in the environment. When this conductive paste is used on aluminum connectors in joints, NO-OX-ID “A-Special” prevents the reformation of oxide films, which cause high resistance and subsequent failures. NO-OX-ID A-Special conductive grease is recommended by connector manufacturers for trouble-free joint connections. When nuts, mounting bolts, and cotter keys are coated with NO-OX-ID “A-Special”, they will never rust or freeze assuring you easy, trouble-free removal. NO-OX-ID “A-Special” should be used wherever the formation of a corrosive product will effect the proper functioning of the metal surface. This electrical contact grease is easily applied, easily removed, and gives long lasting reliable performance even on dissimilar metals. No-ox-id A-special comes in convenient 2oz jars. Illumination Supply note: This is an excellent flashlight grease that is non-toxic. It is even certified as being usable in meat & poultry plants! We have found it excellent in all the lights we’ve tested it on, from twisties to clickies, and it is one of the few greases available that is electrically conductive. A jar will last a very long time.
I actually just bought some NO-OX-ID earlier today but for better electrical conductivity instead of thermal conductivity. Not sure how this performs thermal wise.
- The contact in the upper thread (close to the head) doesn’t necessarily needs to be electrically conductive. Most of the driver boardss (used in many products) use the tube’s end face to make contact, not via the threads. Unless there are special design out there.
- The thread grease brands normally used in flashlight are dielectric, they are not electrically conductive
- If you put any grease or thin viscosity or very soft TIM in the thread, most of them will likely to be squeezed out the thread cavity. Even those with very loose thread tolerance. Thus the metal to metal contact will always presents.
- Any grease will replace the air gaps and improve thermal performance. And they’re already much better than air. In super hot flashlights, dry thread vs greased thread makes a difference that can be felt just by holding the flashlight. (properly greased thread felt hotter in the tube).
A well used lubricated thread (in non anodized thread) will develop aluminum dust mixed in the grease (those ugly grey smelly stuff). This alone is a better TIM than the grease alone.
In my opinion TIM in the thread will improve thermal performance but the difference would be miniscule. Unless you’re using a poorly made flashlight with extremely loose thread tolerance. I use moly-graphite bearing grease in flashlight threads (non petroleum based/O-ring safe).
In gritty thread (poor thread finish), I mix very fine SiC powder with mineral engine oil. Threading it back and forth until the the grittiness gone. Clean them well and then add micronized graphite powder (normally used for cylinder bore and valve stem) mixed in Nyogel. The powder is very fine and it will fill all the pores. They work very well to a point they make the thread felt catchy - good for non permanent thread-locking.
I used Artic silver in 2D maglite builds all the time, seemed to help. The maglite head is not electrically connected anywhere though and you used the tail cap to insert the batteries.
Thank You Boaz, I just remembered i used GB Ox-Gard on a house that had aluminum wiring. I had to install copper pigtails on all end point connections. With continued use aluminum expands, contracts and oxidizes enough to cause wire to heat up trying to conduct. Ive seen outlets melted from the heat, common in this type of scenario. Point is I still had a couple of tubes of this stuff in my electrical bag. Works good.
