What do you think of this heatsink?

It's for a single 3W white star and to be used as a mountain bike handlebar light. It will be constructed out of a 1" hex bar of aluminum. I don't have a lathe so I needed a design that was easy to fabricate with my drill press. Flat sides make fabrication much easier and also allow mounting to standard handlebar mounts with little difficulty.

The star and reflector will get mounted inside the large hole. It will be sealed against the elements by epoxy around the rim holding a lens in place. The depth of the large hole is such that a 17mm reflector will be held properly in position. The diameter of this hole will mean that a star must be trimmed. Alternatively I could use an emitter or add in a bushing to position the reflector; I haven't decided which the best option is yet. Wiring will be through the hidden side of the sink and go to a remote regulator/battery pack.

The total length is approximately 3" and the total exposed surface area is approximately 20 square inches. It should be very light, in the range of 75g for the completed light, (not including the battery)



Any comments, thoughts or suggestions?

I think figuring out to make a small lights without the need for a lathe is a great idea. Though I can't offer any suggestions, I look forward to what you create.

That will be more than enough surface area...

but how are you going to make the inset LED surface interface flat? an end mill bit in the drill press?

If the bored hole matches standard round stock diameter.
Hacksaw off a piece of round to suit & AA epoxy it in place.

Theepdinker

[ QUOTE ]
SKYWLKR said:
how are you going to make the inset LED surface interface flat? an end mill bit in the drill press?

[/ QUOTE ]

Good point, I didn't think about that. Originally the design didn't have an inset, just a flat face to mount to but I worried about the protection of the star and reflector so I made the mount inset without thinking it through.

Because I don't have an end mill bit I'll have to rethink a bit. I could make it two pieces, the sink with a flat face and then a second piece, (drilled all the way through) to act as a collar to provide the protection. But I'm not sure how well this would hold up. The surface area to allow bonding is only about a tenth of a square inch. I'm not sure how strong that will be, maybe it's enough.

Also maybe this is a good reason to go with the emitter and not a star. Due to the smaller footprint I could possibly make a flat surface in the center of the countersunk hole to mate the emitter to and leave the rest of the countersunk surface as is.

For this I guess I need an end mill bit suitable to the size of an emitter, much better than the size of a whole star I would assume.

[Edit:] Well a quick search of Ebay shows me that end mills are priced very reasonably, (easily under $10 and many near $5 and in a wide variety from fractions of millimeters to over an inch in diameter). I don't mind getting one to make my project one piece and remove the doubt of a bonded joint.

Snowman,

That's a great idea. I don't know if you can order hex tubing with a particular diameter hole in it, but if you can, get some with a 3/4" diameter hole in it.

If you are able to do this, you could just use a tap to thread the tube 13/16-20, and use an Aleph light engine to house the emitter and circuit. With the light engine, using a 20mm McR reflector should be a snap, and all without a lathe.

some endmills (Ok most) will leave a post at the dead center is they are not moved a long a track.

try and find one that has blades across the face.