Armed with this knowledge, we set out for a fan that is as quiet and small as possible. Orbit Computers in Nijmegen has turned into my favourite hardware store: they were the only ones who understood why I would want a slot-in DVD-ROM. (They didn't have it, though -- my second choice, Computerland, did. Still, it's nice to talk to people who at least understand what kinds of problems you try to solve.)
Anyway, we walked in and asked for the smallest and quietest and smallest casefan he had. This confused the sales-guy a lot. So we explained the problem of the overheating HDD to him, and he came with all sorts of harddisk-cooling stuff (most of them involving lots of fans) -- which we didn't have room for. So I carefully explained the situation to him (having a desktop case is really rare these days, it seems), but I don't know whether he understood it or not.
On a display rack, I found a Coolermaster Blue Ice chipset cooler and showed him that. The back said that it produced 25 dbA -- exactly within the specified parameters!
The guy looked at me, and said: "Yeah, but that's for cooling chipsets!" "Not if I unscrew this heatsink and glue it in my case next to the harddisk," said I. It took him five whole seconds to get it, but then he agreed with me. I also picked up a connection cable and an amusing miniature keyboard. There are PIC routines for interfacing with a keyboard, might be fun to do that for scrolling texts or something like that....
Anyway, we got home and got to work and of course, we made pictures.
The heatsink/fan from the top.
The heatsink/fan from the side. The heatsink looks like copper, but it's so light that I suspect it's painted aluminium. Funny enough, this assembly looks suspiciously like the heatsink/fan on the C3 CPU itself!
The fan glued in place.
klik demonstrating how well the glue works by lifting the whole case by the fan!
With the splitter cable, the fan gets its juice. It's too far from the motherboard to be powered by the case fan header, so we just split off the power-line to the DVD-ROM.
Yes, the fan has blue LEDs in it... I didn't know this at the time I bought it, honest! It was only until I searched for a good webpage to link to when I saw the blue lights!
The fan blows into the 'tunnel' where the harddisk is. So the airflow is (when seen from the front of the case) from left to right.
Checking the airflow with tiny strips of paper. We had to tape some vents shut, to maximise the airflow along the harddisk.
Checking that the air indeed comes out on the other side.
We ran some tests, and, without the DVD-ROM assembly on top of it, harddisk temperatures seem to stabilise around 36 degrees. Still comfortably warm, but not the overheating temperatures we got before. With the DVD-ROM in place and even playing a DVD, the temperatures do not increase -- but this is with the case still open.
breyten suggested I get a notebook harddisk, which I might consider if this fan-scheme doesn't work...