modded mag bike light question

[bryguy17]

so, I think I finally found somewhere that will let me use some machines, and I wanna get a bar light going for my bike

I have a bunch of D-cell mag lites lying around, so I figured I'd cut one of them up to brush up on my machining skills, and make myself a bar light.

I'm going to be machining new fins into the head, but I'm stuck on which kind. I can just use a part-off tool and cut some slots on the lathe (like many do with these), or I can do something like this:

I'd like to do the latter, since it's fairly simple with a rotary table on a mill, it's easier to make a mount for, and it looks way cooler. only thing is that it's about 7 sq. in. less heatsinking area than the turned slots. trying to decide whether it's going to be worth having that extra surface area on this light.

FWIW, It'll be a 4X cree XRE R2, cutter 17mm stars, carclo 20mm optics, maxflex driven 4S with an 11.1V lithium pack. only 15.8W of dissipated power, including the heat from the maxflex. It'll be setup in duo mode, 1000mA on high beam and 300mA on low.

also, there's going to be a fat heatsink sitting inside of everything, so that may change things.

thanks in advance

 

[BillyNoMates]

In my experience, the air moving over the unit will provide more than enough cooling, even with a smooth surface.

If you are looking for adequate cooling when stationary (ie relying on natural convection) then a (very) large suface area will be needed, but bear in mind that heatsinks that rely on natural convection usually need a DeltaT of 50C to generate sufficient air-flow via natural convection (so the case still ends up being hot).

From an asthetic view, those drilled slots are extremely cool - I used a similar approach on my home-brew bike light when attempting to remove material.

 

[bryguy17]

yeah, I definitely like the look of the milled slots better, and they aren't too terribly hard to make (3 passes with a .250" ball end mill should do), it should easily mount to a rotary chuck.

I do want it to not overheat though. I live in a warmer climate (california), so I don't have the benefit of cold air all the time. As that picture sits, its got 17 sq. in. of dissipating area, not including the bezel, body, or tail cap, so I've got >1 sq. in. per watt.

mags are cheap, I just guess I'll try it and see what happens.

BTW, what mount did you use? trying to find with with a simple single bolt to connect it to the light.

 

[BillyNoMates]

The mount is an Electron EHP300/305/310.... I got mine from ChainReactionCycles at £2.99. Take the top adpator of the mount and you are left with an M4 bolt.

I think you will be fine with the milled slots....but it will get hot if you are not moving 15W of dissipated heat is a lot to get rid of via natural convection alone.

Good luck with the project.

 

[bryguy17]

yeah, I know it'll get hot, I'm just trying to avoid it getting TOO hot. it'll only be pushing about 5W of power on low mode, which is where it will be most of the time.

thanks for the tip on the mount too. hope I can get it cheap here in the states...