Will concrete (cement) blast if i heated around 630 degrees sentigrade?

[Nigel Goodwin]

Certainly a TO39 heatsink isn't anything like I was imagining him wanting to make - and if you can't buy one, then make a simple copper clip-on on with a piece of copper bent round and forming a largish tab - or simply use a different transistor, with better specification and shape.

 

[Joe G]

I've used "play sand" mixed w/ plaster to make my mold sand. The crucible needs to be verified that it won't crack from the heat, especially if its been not used for awhile. the lost foam and lost wax method is a great way to do smaller parts. the sand casting, w/ a pattern, will need a "cope and drag". I've used the lost foam in sand before which did work quit well. for small thin parts it was a bugger....expect to have a long learning curve. also cast parts are not very bendable,

 

[dr pepper]

Might be better to make thin parts from sheet.

Yes casting produces hard parts that dont bend, you can put an agent in that makes that less so, but it only works to an extent.

 

[Willen]

Is this something like what you are intending to make with sand casting:
View attachment 81497

If so, that will be very difficult by any casting method. I suggest making it out of a soft alloy or only half-hard alloy of aluminum.

Can you post a sketch of what you want to make?

John

I am trying to make this (Attached) simple heatsink.

Area of mine is not better for electronics. So I cannot gat required conponents. I need medium powered RF transistor and I found just 2N2219 and another 2N3866. But I never found its heatsink. I need heatsink because it will be hot in my circuit.

If all thing are impossible, I will solder thick copper wire around its can but I guessed it will not be sufficient like real heatsink.

 

[jpanhalt]

First choice is to buy. It is a bit hard to believe that you can get components and can't find heat sinks. Maybe scavenge heat sinks from used equipment.

If you must make the heat sink, take a disk of aluminum*, drill or punch a hole that is slightly smaller than the transistor can. Lay the aluminum against a piece of hard wood with a slightly larger hole, then take a tapered mandrel or punch and push it into the hole. That will slightly stretch and flare the aluminum so you can push it over the transistor can with a friction fit. Two or three radiators like that should work well and will be easier to make than a casting that you have never done before. You can get the same effect by cutting internal tabs around a small hole and bending them to make the friction fit.

Finally, if you can find aluminum tubing about the right size to fit over the transistor, you can make multiple, longitudinal slits, then bend the segments out to make wings. One slit the full length will allow you to adjust the size for a snug fit on the transistor. (edited)

The fine texture of the heat sink you show suggests to me that it is a permanent mold or lost wax casting, if it is a casting. . There may be linear striations on it (not really that clear), which if present, suggest that it is not a casting at all, but rather a disk cut off a longer extrusion. This thread is now up to 25 posts. We could have gotten to this point a lot quicker had you shown what you were trying to make in your first post.

John

*Pure aluminum (i.e., 1000 series alloy) while soft can be difficult to machine and drill, and it may not have enough springiness to make a good friction fit. A harder aluminum, such as a 3003 (3000 series), 5000 series (e.g., 5052) or 6000 series (6063 is often used for extrusions) will be easier to work with. I would not recommend a hardened aluminum, such as 2024 or 7000 series "aircraft" aluminum. Alloy 3003 is sometimes called "half-hard." It is usually easy to find.