"Heat Sink Putty" ?

I've never heard of putty. Silicone grease is common, of course.

Aluminium powder mixed with epoxy might work.

Graham

**Do you need heat sinking? 4 Watts is not much power. You could use a 6 Amp bridge, which can dissipate quite a bit of power, before requiring any heat sink. If you do need it, then use silicon glue (the stuff used for guttering, kitchens, bathrooms, etc). It remains flexible and will transfer reasonable heat to the frame. I seriously doubt that you need it though.

Trevor Wilson

Thermal epoxy is better than regular epoxy but the conductivity is very poor compared to copper, and copper is poor compared to diamond. Might try the suggestion of adding metal filings to regular epoxy putty. Thermal epoxy is not really putty.

greg

The thermal epoxy I am currently using on a project is a lot thicker than regular epoxy. Its Omega Bond 101.

greg

Then use zinc oxide with epoxy, that should not be conductive... But regardless, nothing will work very well, IMHO...

Seems like there are atachments to the frame for accesories, and if they are aluminum, it will make a great way to do it. Curved surface aluminum block.

greg

snipped-for-privacy@zekfrivolous.com (GregS) wrote in news:fqgvvv$r1s$ snipped-for-privacy@usenet01.srv.cis.pitt.edu:

whatcha need is diamond-filled epoxy..... 8-)

you can buy very finely powdered copper at craft stores. by the time you get enough copper or other filler mixed in the epoxy,it IS the consistency of putty..... ;-)

better to machine an aluminum mount to mate closely with the bike tubing and coat it with thermal paste,mount the circuit to the Al. plate. with thermal paste.

Or use a switcher-type regulator for lower heat dissipation.

--
Jim Yanik
jyanik
at
kua.net

snipped-for-privacy@zekfrivolous.com (GregS) wrote in news:fqgvvv$r1s$ snipped-for-privacy@usenet01.srv.cis.pitt.edu:

there's a silver-filled thermal epoxy,Arctic Silver.

--
Jim Yanik
jyanik
at
kua.net

If there's a brazed boss in some convenient spot, you can screw a block of aluminum to that (or even a 1" square plate). The rectifier won't need conduction cooling at these power levels, so it's just the (three terminal TO-220?) regulator or pass transistor that gets warm.

Generator mount bracket or headlamp bracket are good candidates. If they get warm, it sinks to the frame quick enough.

Loctite makes a number of thermally conductive paste adhesives, and even a thermally conductive RTV. I've used 383 to fill small holes, its consistency is similar to acrylic latex caulk.

TM

Bridge tectifiers usually have isolated cases anyway.

Trevor's idea is good though. Use a larger bridge than actually needed (they're not expensive) and it'll happilly dissipate the heat without additional cooling.

Graham

That's a particularly good idea.

Graham

Per Trevor Wilson:

I just checked the specs on the one I ordered. 25 amps/50v.

Sounds like my dinky little hub alternator will barely warm it up. So much for the heat sink requirement....

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PeteCresswell

Heat sink putty is old hat.It's been around for many years. cuhulin

There is an epoxy but it doesnt work like you want.It must be applied thinly and used to conduct heat to a heatsink. Just get a really big rectifier. I have a 5 amp power supply that uses a 20 amp bridge and its bolted to a piece of wood.

Jimmie

Per Jimmie D:

That's what I (inadvertently) did. 25 amp/50 volt to handle about 1 amp/20 volts max.

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PeteCresswell