Need advice

[DarrellS]

I just received some Cree Q5 LED Drop-in Modules from DX. I test ran them @ 12v and within 3 minutes or so they were so hot I could not touch them. I dropped the voltage to 6v and the same thing. I am planning on building something similar to the double barrel light by pe2er. When installed in the copper tubing will this dissipate enough heat? Or am I doing something wrong? Thanks for any and all help.

 

[znomit]

Yes you've got 4-5W of heat in a tiny bit of aluminium so it will get hot. You need to ensure good thermal contact between the dropin and the copper and you'll be ok when riding in the breeze, will likely still get hot on the bench with no airflow.

 

[DarrellS]

Thank You for the info.

 

[pe2er]

I am planning on building something similar to the double barrel light by pe2er.

:)
You are doing nothing wrong. I Have exactly the same experience. I Use some auminium tape to make the brass slug the same diameter as the aluminium reflector, and then inserted it into a 22mm brass coupling with heatsink compound in between.

After doing some test on my desk, I found that the housing would still run hot. So I added a 22mm endcap to the housing, making it longer and increasing surface area.

On the desk, the light housing still gets fairly warm. On the bicycle, the light hardly gets warm, but outside temperatures have been around freezing the past few months. So znomit is dead on with his comment:

Yes you've got 4-5W of heat in a tiny bit of aluminium so it will get hot. You need to ensure good thermal contact between the dropin and the copper and you'll be ok when riding in the breeze, will likely still get hot on the bench with no airflow.

I Still use this light and like it very much :)
This is the latest light I built for my other errand bike: Dyna powered Amoeba clone :D

Erwin

 

[DarrellS]

I had some time to work on my light this evening. I decided to build the entire light out of copper to try and transfer more heat away from the modules. All of the joints are coated with GC type 44 heat sink compound. It seems to have brought the operating temp down quite bit. This is my first try at LED lighting but so far I am happy with the progress and results. Going to work on a mounting system tomorrow as I am still waiting on the glass lenses from DX.

 

[DarrellS]

I hope the Moderators do not mind, but this light is not actually going on a bicycle, although it could be adapted for that use. I build wooden kayaks and am going to use it for night paddling on this boat.

 

[BrianMc]

To Mods: A kayak is human powered, so I for one, vote the thread stays here!

To DarrellS: Beautiful Kayak!

You can't depend on a slip stream helping the cooling, so getting the temps down to "won't burn you" in a static test I would think is good from a safety point alone.

Having gone a bit overboard (had to pun) with a copper spreader heatsink in an anodized aluminum shell for a bike light, I can vouch for its ability to move heat and be cost effective. It isn't as good as anodized aluminum for transfer to air, but lots of area like you have, counters that, then some. Copper/brass has a nice nautical look.

I recommend silver solder for the joints. Thermal compounds and glues are an order or two of magnitude poorer than metal, but much better than air for heat transfer. Though with that much surface area it may be a non-issue. The silver line showing at the joints is a good look, too.

 

[pe2er]

decided to build the entire light out of copper to try and transfer more heat away from the modules. All of the joints are coated with GC type 44 heat sink compound.

Yes, adding a lot of copper will lower the temperature significantly. Just make sure that there is sufficient thermal contact between the P60 module and the copper pipe. Obviously, I would not have done it like this (as I did not... I made two separate housings and used plumbers solder to join the parts of the housing... :naughty:), but as BrianMc remarked adding this extra piping may be a good idea considering you will have less airflow on your kayak.

Talking about kayaks... This is a beautifully built one. My compliments :) Wish I had your woodworking skills.

How/ where are you going to mount your light?

Would be awesome to make an underwater-light illuminating the waves around your kayak from underneath :cool:

EDIT: Oops, I see I am not the first one to have this idea: