Make your own... heatsink! · 1547 days ago by Max
Hi again; sorry for the delay in writing this. I had a lovely article ready on building an amplifier, unfortunately, I wrongly adjusted the gain (or perhaps a component shorted out - I'll never know) and, long story short, a 1/4W resistor ended up having about 50W put through it, thus exploding the resistor, and the shrapnel somehow shorting out a couple of nearby transistors as well, (also managing to put 30V DC through a test speaker, shorting that out as well, and - worst of all - shorting out a channel of my iPod which I was using for testing it and which I hadn't bothered connecting in series with a resistor; so now my iPod only plays through one channel). Anyhow, enough ranting...
When building my 800W amplifier, I obviously needed a rather large heatsink (or, rather, four of them). I thought you might want a little (and I mean little!) tutorial on how to build your own while I try to fix the amp. A heatsink is, basically, dissipating the heat efficiently from a component (such as an IC or a single transistor in my case). It should have as high a surface area as possible (you can actually mill grooves out of the fins themselves if you want to increase it that much); however, a little like electricity, larger blocks of metal conduct heat much better than smaller ones; thus, if you have the component joined to the rest of the heatsink by only a piece of thin wire, the heat dissipation will (understandably) be fairly low.
Basically, there are two main methods, the former producing a better quality heatsink but taking a little more time and money (£60 for my 4 175x75x60mm heatsinks if I were to have made them that way), and the latter producing a slightly worse heatsink but taking up less time, being cheaper, and wasting basically no metal. I'll cover both ways in this article.
Method 1: Subtraction
I call this method 'subtraction' because it involves starting out with a solid block of aluminium and milling grooves out. This does give better results, but is much more expensive.
Firstly, you must start out with a block of aluminium of the overall dimensions you want your heatsink to be (Figure 1). You could either order it in or cast it yourself (though you'll need to make your own mould if you choose the latter even though it may be marginally less expensive).
Figure 1: A solid block of cast aluminium.
After having obtained your block of aluminium (with the conductive surface [the one facing the component] as flat as you can make it) you should mill grooves down either horizontally (Figure 2)...
Figure 2: The block with holes milled in 'horizontally'.
...vertically... (Figure 3)
Figure 3: The block with holes milled in 'vertically'.
...or even both, one of the advantages of this method (Figure 4)
Figure 4: The block with holes milled in both ways.
...and, hey presto, you've got your heatsink! (N.B. if you've never milled aluminium before, the trick is to do it in small 'layers' of about a millimeter at a time, and go back and forth. This method is very time-consuming, especially for thick heatsinks.
Method 2: Addition
I've called this 'addition' simply to be the opposite of subtraction. The method sort of is addition; it involves milling smaller grooves into a base block and sticking fins into the grooves.
There's nothing really more to say about this. Take a block of aluminium (Figure 5). This should be fairly thin (much thinner than the block you used for the first method, anyway).
Figure 5: A base block of aluminium (no, really, it is aluminium =D).
Then, mill grooves (horizontally or vertically) into the block - these should go through roughly half the depth of it (Figure 6)
Figure 6: The base block with grooves milled in.
Finally, stick fins inside it. These should also be made of aluminium and should be of the thickness of the hole you milled (in my case 5mm). They *should* fit nicely in (friction fit). If they don't, you'll have to weld the aluminium together (if you have such capabilities, tightly screw it together, or abandon that groove completely.(Figure 7)
"KH" (see comments) has kindly given us this tip: "If you mill the slots for a tight fit you can preheat the base so that it stretches slightly and insert the fins then allow it to cool down for a very tight fit."
Figure 7: The base block with the fins stuck in.
I've actually had a thought. You could perhaps create an (iron?) cast using the second method and cast an aluminium heatsink inside. If anyone tries this method and has any success with it, please leave a comment!
Anyway, that's about it... good luck with your heatsink!
19 inch computer rack · 1639 days ago by Max
Update: New photos (see bottom of page)
It's (nearly) every techie's dream to have their own 19" computer rack. I have now built my own and will show you how to build yours ;D
The simple idea is this. A basic 19 inch rack is simply a box. The internal width is 19 inch, and the height goes up in 1.75" increments. (1U [unit] is 1.75 inches high, therefore if you want to house 2U, you need to make the internal height 1.75×2 = 3.5"). I chose to make my box in wood; it shouldn't overheat as only one computer is going to be stored in it and it has ventilation grills at the sides.
Step 1 - Cutting the Wood
The first step is to cut four pieces of wood. There are two (three?) ways of cutting them so that they glue together. The first is simply to cut the wood at a 45 degree angle and glue it together so that the whole angle is 45×2 = 90* (which is what we want). The second way (which I don't recommend, for reasons of stability) is to cut the wood simply with 90 degree angles and stick it together. The third, and best way, is to cut rebates (more about this in Step 2).
Step 1: Two pieces of wood straight from the saw - please note you need to cut two of each (only one is shown for clarity)
The value of d is the depth of your rack. To find this, take the longest (deepest) appliance you are going to place in your rack, and add 10-20cm onto it.
The value of w is 19 1/8 inches (the 1/8 is added so that the appliance will fit in without any problems (it won't become too big), added to twice the thickness of the wood you are using, which in my case is 18mm MDF. This is due to the nature of the box cuts we're going to do in Step 2. If you are using 18mm wood, w should be 51.9 cm long.
h is the internal height of your rack, added to one times the thickness of the wood you are using. Not twice the thickness, only once. This is, again, due to the nature of the box cuts (they only go through half of the wood). Here's a little table with the number of units (U) you want to make your rack, the internal height in inches, the internal height in mm, and the value of h if you use 18mm wood.
| Units | Internal height (in) | Internal height (mm) | h (mm) |
| 1U | 1.75 | 44.45 | 62.45 |
| 2U | 3.5 | 88.9 | 106.9 |
| 3U | 5.25 | 133.35 | 151.35 |
| 4U | 7 | 177.8 | 195.8 |
| 5U | 8.75 | 222.25 | 240.25 |
| 6U | 10.5 | 266.7 | 284.7 |
| 7U | 12.25 | 311.15 | 329.15 |
| 8U | 14 | 355.6 | 373.6 |
| 9U | 15.75 | 400.05 | 418.05 |
| 10U | 17.5 | 444.5 | 462.5 |
| 11U | 19.25 | 488.95 | 506.95 |
| 12U | 21 | 533.4 | 551.4 |
| 13U | 22.75 | 577.85 | 595.85 |
| 14U | 24.5 | 622.3 | 640.3 |
| 15U | 26.25 | 666.75 | 684.75 |
| 16U | 28 | 711.2 | 729.2 |
| 17U | 29.75 | 755.65 | 773.65 |
| 18U | 31.5 | 800.1 | 818.1 |
| 19U | 33.25 | 844.55 | 862.55 |
| 20U | 35 | 889 | 907 |
Step 2 - Cutting the rebates
The next step is to cut all the so-called "rebates". These are square cuts spanning all the way along one edge of the wood, going halfway down the thickness of it, and as wide as the piece of wood which you want to glue to it (18mm, in my case). This can either be done by lowering a circular saw to the depth desired, then cut in 5-6 "goes", adjusting the saw by 3 or so millimeters each time, to cut a thick groove. Another way is to use a router. This should be done on 2 parallel sides of each of the 19" by 19" pieces of wood.
Step 2: A closeup of one of the rebates
Step 3 - Assembly!
The assembly is fairly painless. Spread glue on the inside of the rebates, then place the two larger pieces into the rebates on one of the smaller pieces. Then, place the remaining smaller piece on top, and clamp the whole thing together. While waiting (at least 4 hours, depending on the wood glue) for the glue to set, you can get on with Step 4.
Step 3: The assembled main framework of the box.
Step 4 - Rackstrip
For this step you will need two equal lengths of rackstrip (or rack mounting rail). One website which stocks rackstrip is Maplin. They are a widely established electronics shop in the UK, but I have never bought that particular item from them so I don't can't comment on construction quality - if anyone does decide to buy from them, feel free to comment on your experiences here and I'll edit the article accordingly.
All you need to do is cut two lengths of rackstrip, both equal to the internal height of your rack which you decided in Step 1. (This is the internal height, not h.)
Be careful, though! You can see from the picture that the holes have a different pitch (small gap, large gap, large gap, small gap, large gap, etc...). You must make sure that the pitch on both of the strips are the same. And since they are going to be mounted opposite to each other, cutting 2 identical pieces rackstrip isn't going to work - you need to make sure the second piece you cut is a mirror image of the first piece.
Step 4: A closeup of the rackstrip.
Step 5 - Mounting the whole thing
The first step is mounting the rackstrip. If there aren't enough holes, you might want to drill some more in the rackstrip and mount them. Depending on what you are planning to mount, you might want to drill more or less holes - 1 hole every 20cm is more than enough for lightweight usage.
You'll then want to actually mount it. As long as the rack is symmetrical, they can be mounted anywhere (I decided to mount mine so that the front of the strip was 1" back from the front of the rack).
The next step is to cut ventilation holes if needed. Drill holes and cut through with a jigsaw to make rectangular (or other-shaped, if you feel rebellious) holes, which can optionally be filled in with wire mesh.
The last step is to place a cover on the back. Cut a cover the right size (i.e. the internal dimension + twice the thickness of the wood). Cut a hole in it for cables if you need to, and glue (or nail it on). If you are going to wall-mount your rack, you will need to cut blocks and screw them in.
Step 5: The "finished" rack.
Final Touches
There are many things you can do to improve your basic rack. One such thing is to cut four thin cuboid "rods" of a good wood such as pine at 45 degree angles, and stick them on the front of the rack, or you could also create a hinged door. But one fairly cheap (yet effective) modification if you are using faced MDF, plywood, or nearly any wood apart from standard MDF, is to get yourself a can of teak oil. This will slightly darken the wood, and add a "professional" look to your rack, as well as protecting it from water spills, etc...
I hope you found this tutorial useful. Please, please, comment on it if you enjoyed it (or didn't!) by clicking the "Comment on this article" link just underneath this paragraph (or filling in the form if it is already there). Happy rack-building!
I've had these photos for some time now but have only just got to uploading them. If you are using Firefox, the better browser ;), you can right-click on any of the images and click "View Image" for a better look (as with any of the illustrations)
Photos of my rack:
Welcome to Max's Projects. · 1724 days ago by Max
Hello everyone!
Welcome to my website. I’ll update this with projects I’m making, things I’m programming, and, just occasionally, things I’m thinking.
First of all, a little bit about my self (just incase you’re really, really bored).
I’m a student at Winchester College, in the UK. I like computers, electronics, anything technical really. I’ve set up this website / blog in order to share my knowledge with other people, and mainly in the hope that people will comment on my articles and help me, and others, by sharing their knowledge.
That’s about it for the moment…
Max
Tell me what I can do to make this better... [3]