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Old 5th March 2001, 11:21 PM   #11
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Default Please post drawings!

Please post the drawings you showed him!

Can he make a Pass X1000 box?
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Old 6th March 2001, 01:06 AM   #12
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Machining heatsinks (as opposed to extruding them) is going to take a whopping big slab of metal to start with. Sounds like it could get expensive to buy that big a block.
That said...I'm salivating. I imagine that your brother just unwittingly went into machining heatsinks full time. He may rue the day he made you that offer...

Grey
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Old 6th March 2001, 12:39 PM   #13
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Default instead of a solid block

One thing I considered since I have access to a mill is bying 1/2 thick flat stock and milling in 1/8" pockets for fins. Then place the whole thing with fins installed in the oven (cut to appropriate legths of course)at say 450 for half an hour then place on the hot stove to fill any gaps with solder. Assuming the fins and pockets are roughened this should provide a good joint with decent thermal properties. 1/2"X8"X36" $80 from Mcmaster carr and $40-$60 worth of 1/8"X2"X36" flat stock to be cut into fins, $10-15$ worth of solder and access to a mill for hours at a time. I decided to go the surplus route and I will have to add heat sinks as my experiments require. Though I'm sure it would still be cheaper than buying a 2.5"X8"X36 slab of aluminum.

Wade

It may be a simple task but it will also be a tedius one without cnc.
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Old 6th March 2001, 01:57 PM   #14
lmcmaju is offline lmcmaju  Canada
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Hi there,

Check out R-Theta. They have a wide selection of extruded heatsinks and decent prices in Canadian dollars (so even more decent in US$).

You can choose the finish (black anodized or no finish). You can buy small quantity, pay credit card and you get them usually within two weeks. Not bad for catalog items cut to your dimensions.

I just bought a pair and I am extremely satisfy with the product and the service.

http://www.r-theta.com/
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Old 6th March 2001, 04:52 PM   #15
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My brother Lou said he could do just about anything, except extruded heat sinks. He may even be able to get anodizied material. He can get better prices then most people because he works for a machine co. and he know aluminum distributors. He would do it on a milling machine and drill press. 3 hours tops he said.

I will have him make me a set for my amp. I have a web page I'm working on. When it's up, I'll let you guys know.

Vince

[Edited by vdi_nenna on 03-06-2001 at 12:29 PM]
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Old 11th March 2001, 05:49 AM   #16
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Talking big heatsinks

The original Windscale nuclear reactor was air-cooled. This makes me wonder whether we need to resort to water cooling for amps running off the domestic mains supply...

One possibilty, free from potential water leaks, is to use finned heatsinks in conjunction with car radiator fans with a raised supply voltage of 24v or 36v. With *extremely* powerful fans it is possible to get about eight times the effectiveness of free convection cooling. A really big heatsink is around 0.4C/W in free air, so we can realise about 0.05C/W with this method. This is sufficient for about 1000 watts of dissipation per heatsink if running transistors at a reasonable temperature.

Nick Sheldon
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Old 13th March 2001, 03:55 PM   #17
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http://www.surplussales.com/Heatsinks/HeatSinkmain.html

This place has some big ones.
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Old 13th March 2001, 07:56 PM   #18
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Nick,
Well, yes, fans work quite nicely for augmenting the basic convection heatsink, however...
There's this little tiny problem called noise. Fans work well for pro gear (Jan, this is your cue to drop in and back me up) where the dB level is consistently in the 3-digit category, but not so well for home use where the ambient noise level is much, much lower.
I've got a box full of various sorts & sizes of boxer fans. I used to hook two of them in series so they'd run slower (hence quieter), but even that gets annoying if the fans are in the same room.
N.B.: I haven't gotten far enough on the water-cooled idea to see how much incidental noise I pick up. It may not pan out. The pump will be in another room, so the only fear I have at this point is that there will be a throbbing through the lines. Unlikely, but possible. I have a few ideas in mind as to how to handle that, should it become a problem.
Re: Cooling towers. I believe at least some of those designs sprayed water on the heat exchangers so as to have it evaporate and help the cooling along. I'd rather keep the water contained than turn my listening room into a sauna. Of course, maybe there's a benefit there I ought to consider...

Grey
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Old 13th March 2001, 09:47 PM   #19
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Wink Not good at plumbing!

Hi

The main reason I prefer air-cooled heatsinks is because they do not leak embarrassingly all over the floor in front of my students! I am very bad at plumbing, and had a really spectacular flood once with a powerful pump and an imperfect seal.

The fan noise problem is not an issue for me personally, as I now contend with powers of over 10kw even with squalid-state amps (valve bias creeping in here). However, a friend (ex-Marconi) reports that multi-megawatt transmitters which use water cooling are astonishingly quiet.

I think another aspect which appeals is the impressive 8-fold degree of improvement one can get over natural convection with such simple, cheap equipment, albeit powerful, over-run cheap equipment. However, this has to be compared with a 23-fold improvement if you simply *stand* the heatsink in a large tank of water. Of course this relies on the thermal inertia of the water, and is not for continuous use.

Nick Sheldon
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Old 13th March 2001, 10:47 PM   #20
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Nick,
Now you're raining on my parade...I was just starting to get into the idea of a combined sauna/listening room.
Mind you, I may still end up going with air-cooled, but as I think I put above, water-cooled will allow me to direct the heat elsewhere. It will also be much cheaper, considering how much heatsinks would cost in order to dissipate the heat from a decent-sized class A amp. So far, I've got a whopping $6.00 invested in the water-cooled idea, albeit with a fair number of things I'll be pulling from the junkbox. I anticipate spending another $10-20 on pieces-parts to pull it all together, and will report back to you folks when I have results, either positive or negative.
With luck, I'll be able to pull the operating temperature down to something much lower than the 120 degree range. I'm shooting for 90-100 degrees. Obviously, I could make ice crystals form on the output devices if I tried hard enough (and spent enough money), but I can try the water-cooled idea for a comparatively small amount of money. Fallback position is, of course, air-cooled.
...I can't honestly say that I enjoy plumbing, per se, but I've done enough of it that I can generally get good results. Let's just hope that this isn't the time I end up with egg on my face...

Grey
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