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Old 31st July 2001, 02:26 AM   #1
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Well, as you must already know i'm building a 2x15w based on the JLH'96. Now, i'm still battling with the heatsinks. Each channel dissipates a maximum of 90W, so that's atleast 0.3C/W per channel, or 0.15C/W total. I found some small 0.6C/W sinks, but at 25$ each, 100$ IS painful

So, my dad runs a metal shop. I've been doing some calculations, and if i stack 20 15x15cm plates (bolted together with a separator in between, say three 5mm thick bars), i'd be in the vecinity of 0.1C/W. Nice so far; and i really don't mind the metalworking. My issue is this: my dad works mainly with stainless steel; hence, i can have enough 2mm thick steel sheet to build the damned thing. Alumminium is not as readily available unfortunately. Am i mistaken, or should the steel work better dissipating heat than the Al? I thought the only reason aluminium was used for heatsinking was that it can be easily anodized. Any takers? It would be a bit more heavier, yes, but i can live with that if there's a thermal benefit.

Ah, and i plan to have them black painted (with black automotive paint); it's nowhere as thin as an anodizing, but's not thick either, so radiation should improve a lot. Is this ok?
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Old 31st July 2001, 04:13 AM   #2
blmn is offline blmn  Brazil
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Lisandro,

Try http://www.brasele.ind.br, they have a lot of big heatsinks not so expensives, as far as I know. I have a catalog of them, and they have good products. I bought many of them and the costs are good.

I suppose you're living near Brasil, so, the shipping costs would be acceptable.

regards
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Old 31st July 2001, 05:07 AM   #3
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Thank you, i'm checking that. Through i'll probably go with the homemade one; free (or almost) is the best price!
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Old 31st July 2001, 05:09 AM   #4
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First of all, steel might be better at disipating heat than aluminum (I don't know), but it's nowhere near as good at conducting heat (a completely different issue). For a heatsink to function properly, it must be able to conduct the heat away from the sources (transistors, MOSFETs, resistors, etc.), to the fins, where it is disipated to air. Steel can't conduct heat well enough for this task.

Where there are only a few heat sources, I've heard of copper bars being used (perpendicular to the fins) to spread the heat (attach heat sources to the copper, and the copper to the aluminum heatsink). This creates a 'line source', instead of a 'point source' of heat, and will often allow the heatsink to function better. This might be useful for you.

Also, the general design you describe can be quite effective (in aluminum). A good example of this type of heatsink can be found at 'http://home.earthlink.net/~lotusblossom/index.html'.

Finally, most automotive paint has a gloss finish. This is not good for a heatsink. A heatsink works better if it's got a flat finish.

For best results, use black anodized aluminum.

Good luck
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Old 31st July 2001, 05:37 AM   #5
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Quote:
Originally posted by Thoth
First of all, steel might be better at disipating heat than aluminum (I don't know), but it's nowhere near as good at conducting heat (a completely different issue). For a heatsink to function properly, it must be able to conduct the heat away from the sources (transistors, MOSFETs, resistors, etc.), to the fins, where it is disipated to air. Steel can't conduct heat well enough for this task.
Really? That's funny, i was almost convinced it was the other way arround... i'll have to stick to Al then; it's available for me, just not as easy. But again, buying sheets of Al will STILL be cheaper than paying for those 4 heatsinks.

Quote:

Finally, most automotive paint has a gloss finish. This is not good for a heatsink. A heatsink works better if it's got a flat finish.
No no no, this is a matte black finish; it's a thin coat of paint, like those used in industrial equipment. Again, nothing as good as black anodizing, but i think worth the try.

Thanks!
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Old 31st July 2001, 06:25 AM   #6
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Lisandro,
Have a read of the heatsink artical at, http://www.sound.au.com/index.html
very good information.
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Old 31st July 2001, 12:10 PM   #7
peted is offline peted  United Kingdom
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Lisandro, if you are up to a bit of metal bashing, check the stuff on my site re handmade sinks. Mail me direct if you want more.

http://users.computerweekly.net/peted/sink.htm

Pics of the beast are in the parent page.

Cheers

Pete


[Edited by peted on 07-31-2001 at 02:14 PM]
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Old 31st July 2001, 08:51 PM   #8
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Quote:
Originally posted by phil
Lisandro,
Have a read of the heatsink artical at, http://www.sound.au.com/index.html
very good information.
That's where i took all the info i needed, plus the heatsink calculation sheet. Thanks!
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Old 31st July 2001, 08:53 PM   #9
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Quote:
Originally posted by peted
Lisandro, if you are up to a bit of metal bashing, check the stuff on my site re handmade sinks. Mail me direct if you want more.
[Edited by peted on 07-31-2001 at 02:14 PM]
Saw your pics the other day; great work btw! Basically, my idea is to do almost the same, only a tad smaller and box-shaped. BTW, could you brief me on how you painted yours and how it performs? Thanks.
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Old 31st July 2001, 09:25 PM   #10
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L-

I have made them from aluminum. Check out my site. There is also a link to where the instructions are. If you have access to metal cutting tools, it's not a problem.

Vince
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