Heatsinks for your poweramp

[joecool85]

Has anyone tried sand casting aluminum heatsinks? DIY aluminum sandcasting is supposed to be pretty easy.

Nope.  Do you mean actually smelting aluminum and pouring it into a cast?  Also, not sure you'd be able to get a flat enough surface when done.  The side the chip mounts on needs to be like glass ideally.

[rowdy_riemer]

You could flatten the mounting surface afterwards. Or better yet, build a mold template and use lost wax casting.

[J M Fahey]

Well, in fact I *did* something like that, back in the Stone Age.
There were extruded heatsinks available, but fins run along the extrusion axis, and I needed transversal ones, to make my own vwersion of "big" US/Japan rack power amps, where they were used as the sides of the rack cabinets.
*Huge* heatsinks !!!
I made a wooden model, sandcast them, cleaned the very rough surface by airsanding (casting sand adheres to the surface) and last but not least, had to find a guy with a machine that mills aluminum engine blocks, I needed *one* surface quite flat to mount transistors.
Truth is: a lot of work, and the engine block guy charged more for his work than al, the other costs put together. Not worth it.
What I still do, is cut, bend and rivet 1/16" aluminum sheet, to build quite fancy heatsinks.
That *is* cost effective.
PC 12V fans have made the problem much smaller; any heatsink is 300/400% more efficient if blown cold air, and PC fans are very cheap and reliable.
Sometimes I buy surplus CPU fans and heatsinks and bolt them to existing amps (think Bandits, Fender M80, etc.) which use the chassis as heatsink.

[phatt]

Sand Casting,, jeezz mate long gone

If you ever see how fast Ally comes out of an extrusion machine you will instanly see the folly of the idea.

Casting Only used now for specialised applications.

Trust JMF to try it,,,   Somehow that does not suprise me as he has been known to try the impossible.  

Re Fans,
= Cheap crap in my opinion,,, If one cares to look at almost any industry a proper heat sink is not cheap and in this day Fans are proly 10 times cheaper that a heat sink.

A fan might look trick but WILL ONE DAY STOP!!! Whereas a correctly designed heat sink will NEVER FAIL.
Phil.

[joecool85]

Sand Casting,, jeezz mate long gone

If you ever see how fast Ally comes out of an extrusion machine you will instanly see the folly of the idea.

Casting Only used now for specialised applications.

Trust JMF to try it,,,   Somehow that does not suprise me as he has been known to try the impossible.  

Re Fans,
= Cheap crap in my opinion,,, If one cares to look at almost any industry a proper heat sink is not cheap and in this day Fans are proly 10 times cheaper that a heat sink.

A fan might look trick but WILL ONE DAY STOP!!! Whereas a correctly designed heat sink will NEVER FAIL.
Phil.

I agree I'd rather have a nice (read: large) heatsink than a fan, but if cost/time/space is the issue, fans can work.

[rowdy_riemer]

Well, in fact I *did* something like that, back in the Stone Age.
There were extruded heatsinks available, but fins run along the extrusion axis, and I needed transversal ones, to make my own vwersion of "big" US/Japan rack power amps, where they were used as the sides of the rack cabinets.
*Huge* heatsinks !!!
I made a wooden model, sandcast them, cleaned the very rough surface by airsanding (casting sand adheres to the surface) and last but not least, had to find a guy with a machine that mills aluminum engine blocks, I needed *one* surface quite flat to mount transistors.
Truth is: a lot of work, and the engine block guy charged more for his work than al, the other costs put together. Not worth it.
What I still do, is cut, bend and rivet 1/16" aluminum sheet, to build quite fancy heatsinks.
That *is* cost effective.
PC 12V fans have made the problem much smaller; any heatsink is 300/400% more efficient if blown cold air, and PC fans are very cheap and reliable.
Sometimes I buy surplus CPU fans and heatsinks and bolt them to existing amps (think Bandits, Fender M80, etc.) which use the chassis as heatsink.

You rock, JM, you've done everything!!!

[rowdy_riemer]

Sand Casting,, jeezz mate long gone

If you ever see how fast Ally comes out of an extrusion machine you will instanly see the folly of the idea.

Casting Only used now for specialised applications.

Trust JMF to try it,,,   Somehow that does not suprise me as he has been known to try the impossible.  

Re Fans,
= Cheap crap in my opinion,,, If one cares to look at almost any industry a proper heat sink is not cheap and in this day Fans are proly 10 times cheaper that a heat sink.

A fan might look trick but WILL ONE DAY STOP!!! Whereas a correctly designed heat sink will NEVER FAIL.
Phil.

If only we all had extrusion machines.

As silly as it might be, I might give sand casting a go. I've been looking for an excuse to sand cast something anyway.

Well, I might only dream about it. School is eating up all my free time. Next week, I have to take a calc II final exam that is big enough that I have to show up on two different days to take it. Then, it'll be time for two more classes, including Calc III.

If I ever do give it a go, I'll set up a power transistor whose only job is to get hot, and I'll try to measure it's effectiveness. If I can't get a flat enough surface for mounting, it'll no doubt get warmer than it should.

[joecool85]

If only we all had extrusion machines.

As silly as it might be, I might give sand casting a go. I've been looking for an excuse to sand cast something anyway.

Well, I might only dream about it. School is eating up all my free time. Next week, I have to take a calc II final exam that is big enough that I have to show up on two different days to take it. Then, it'll be time for two more classes, including Calc III.

If I ever do give it a go, I'll set up a power transistor whose only job is to get hot, and I'll try to measure it's effectiveness. If I can't get a flat enough surface for mounting, it'll no doubt get warmer than it should.

Keep us posted if you do, could be interesting at least.

[J M Fahey]

A *large* thick toothed file will work wonders, and be it's own reference as to what "flat" means.
That said, "home" sandcasting doesn't strike me as particularly easy.
I had them made at a casting shop, which already had the melting pots, ovens, "sand boxes", sandblasting equipment, grinders, etc.
As to why I made a lot of things, Argentina was a Tariff protected market until 1976, where we "opened" our Economy, under bayonet pressure, paying 30000 "dissapeared" to make it possible.
We also went from 4% to 35% (real) unemployment and increased our External Debt to 50x the original one.
In 1965 *we* sold electronics to Korea, made everything (including Mallory capacitors, CTS pots, Jensen speakers, FAPESA tubes, Texas semiconductors) except color picture tubes.
*Anything* which had a market could be made locally at a profit.
There was a short "Spring" in the 80's where we even made submarines, Saddam's missiles, AMX tanks, sold nuclear reactors to Canada and Australia, etc.
Then our Industry got clubbed to death in the 90's, until now.
Oh well.

[rowdy_riemer]

There's actually A LOT of guys who do their own sand casting. There's a lot of stuff on instructables.com about it.  Check out this example: http://www.instructables.com/id/Ultimate-Guide-to-Making-a-Cheap-but-Effective-Alu/ I've got a large and small coffee can and some quickcrete saved up. I still need to get the stuff for the mold.

[phatt]

Hi Rowdy R,
Just remember your sand has to be DRY and I mean Really DRY.
Any mosture and boom it will explode in the cast and destroy itself.

Remember this is molten metal you are playing with,,,
YES I've Worked in both a Steel foundry and also a small Bronze Art foundry.

Lost Wax (done correctly) will yeild extremly accuate results,,, far better than sand.

If you just can't help yourself ( and it sounds like that might be the case LOL )
Then consider taking on pedal cases!
These can be made from *Monks metal* which melts at fairly low temp.
(about 400 deg C from memory,,, been a long time)
 A soft "Zinc based Alloy" used to make door handles and automotive parts,,,and Yes the Boss pedals also.

You would then have something Totally Original and likely worth selling
just look at the Mayer Octavia pedal as example,,, very unique and oh so cool.
Cheers Phil.

[rowdy_riemer]

Nothing like steam explosions. Heheh 

I've considered doing pedal cases, too. I've read on one site about using zinc with aluminum as a strong alloy. Actually, I may have read this from one of the Gingery books. Making a wooden model would be fairly easy. Whatever I do, I'll try to remember to post the results however good or bad they may be. (hopefully no hospital trips from shrapnel)

[J M Fahey]

Making pedal cases would be *great:
Just 2 points to consider:
1) since the metal will fill the mold only by gravity (not aided by high air pressure or centrifugal force) and
2) sand mold walls are cold, prematurely cooling and "freezing" the metal,
you will have to make box walls somewhat thicker (say 3 or 4 mm vs, 1.5 mm as in Hammond boxes) and preferably use a zinc alloy instead of pure aluminum.
You can buy zinc parts to melt for cents a pound at car graveyards (old carburetors, windshield motor cases, handles, water and gasoline pump bodies, etc.)
Just go there and fill your trunk for peanuts.
Check: http://en.wikipedia.org/wiki/Zamak

[rowdy_riemer]

I can also use American pennies. It would not be as cheap, but they are easy to find. I'm, of course, not going to do that, though, because that would be illegal. 

[J M Fahey]

Don't think so.
If anything, making pennies out of Zamak, or even better  silver Dollars (Zamak takes *any* metal plating beautifully, including silver and gold) would.
Of course, it might be more profitable too.