Thread: Scion xB '06, in-dash Atom 330, Lilliput 889GL; details, pictures, links. Index: pg 1

Originally Posted by rdholtz

Fan Changes

HiJackZX1 and MeeM both questioned the airflow in the chassis, and that got me to reconsider the design. Rather than add other openings in the chassis, I changed from one fan to two. Here's the result of that:

Click images to enlarge.

I'm hoping the two fans won't make a bunch more noise. I'll make sure I have enough slots in the bezel to accommodate the increased airflow.

I can decide after testing which direction I want the fans to operate -- they can suck air out of the case and blow it past the monitor into the cabin, or they can suck cabin air past the monitor and blow it into the case.

I think you should base the flow of air strictly on the processor fan.... If it blows up, have the fans pull the air up also. If it blows down, then have them blow down. With my case, I had really figure out how to do mine because mine is a long case. It draws air in.... passes through the passive GPU heat sink, then through the processor fins, then the processor fan moves that air up, then 2 more fans draw the air out the back. I of course, went over board, and really didn't care about cabin noise. If its silent, your know the PC is on. If music is playing you really don't hear it. Your using really small fans concealed in a dash. I really don't think it will be loud or noticeable. Most of the time you run your A/C don't you? So the noise of the blower will drown out the noise of the fans. i really don't think you need 2 fans though, infact, with the back being open like that, i am with drawing my opinion on the slots as well. Your board isn't anal like mine were it seems to over heat so quickly.

Looks like you're having fun... I'm working on making some sort of button panel for my CarPC and someway to have quick-connect so it takes 2 seconds to remove and replace it. That and the misc. BS in my worklog... All my BS aside, your case is...


...LOOKING GOOD!!!!

Originally Posted by HiJackZX1

I think you should base the flow of air strictly on the processor fan.... If it blows up, have the fans pull the air up also. If it blows down, then have them blow down.

Yep, it seems to me we've discussed something similar. The processor fan blows up, and so I think it's best to have the case fans pull air up and out of the case.

Originally Posted by HiJackZX1

I really don't think you need 2 fans though, in fact, with the back being open like that, i am withdrawing my opinion on the slots as well. Your board isn't anal like mine where it seems to overheat so quickly.

Well, a little overkill is okay with me, and I'm strongly opposed to underkill. I like lots of air motion, and it's pretty hard to run a board too cold.

Originally Posted by HiJackZX1

I, of course, went over board, and really didn't care about cabin noise. If its silent, your know the PC is on. If music is playing you really don't hear it. Your using really small fans concealed in a dash. I really don't think it will be loud or noticeable. Most of the time you run your A/C don't you? So the noise of the blower will drown out the noise of the fans.

Actually, here in Atlanta, I run the A/C a lot less than I did living in Florida, and fuel economy goes over 30 mpg without it. But I still run with the climate control fan -- at least on Low -- and, at lower speeds, I like the windows down. I'm sure I'll hear the fan noise if there's a lot of it, but I'll try and use quiet fans. No matter what I do, the Scion xB isn't the quietest car in the world, so I don't expect noise to be a big problem.

If there is too much noise, I can add resistors to slow the fans, or put in lower-volume fans, or I could put in the 24V fans and run them at 5V.

Originally Posted by freeflashstuff

Looks like you're having fun...

. . . your case is... LOOKING GOOD!!!!

Thanks! Google Sketchup gets some of the credit for quality of presentation. It's an amazing program, and it's free. When the company I work for moved into a new building a few years ago, I used it to do the complete tech center layout -- not just the floorplan, but a genuine 3D model with onscreen walkthrough capability. I also designed all the tech center modular furniture in four sizes and multiple styles. Then Josh and I built over 60 mobile workdesk units from panels produced according to those plans.

Before I started that lab layout, I'd never used Sketchup. There's a learning curve, but it isn't too steep, especially with the new tutorials. If you decide to go into an engineering field, it's an amazingly good tool.

Before I did this chassis design, I'd hardly touched Sketchup for 18 months. It came back to me pretty fast.

You can see a sample of the lab furniture here, and the lab plan here. If you download Sketchup here, you can load the drawings into Sketchup and do the walkthrough.

Baffling Problem

There's one other change that could make a difference in the cooling effect of the chassis fans: the amount of air that comes from -- or goes to -- the cabin, versus the amount that just recirculates inside the dash area. Right now there's nothing to force the air to flow through the bezel slots; I'm just depending on the fans to move air.

But if not enough air gets into or out of the dash, I could place simple baffles -- probably just made of rubber -- around the chassis so air is forced to move through the bezel slots. An old inner tube, even from a bicycle tire -- would be adequate, because we're just directing airflow, not looking for a perfect seal.

Baffles with rubber ends are commonly used to direct airflow around piston engines in aircraft. Even in that hot environment with a good deal of vibration, the rubber lasts many years before it needs replacement. My bet is that the rubber in this installation will be good for as long as the PC is in the car.

Originally Posted by rdholtz

Baffling Problem

There's one other change that could make a difference in the cooling effect of the chassis fans: the amount of air that comes from -- or goes to -- the cabin, versus the amount that just recirculates inside the dash area. Right now there's nothing to force the air to flow through the bezel slots; I'm just depending on the fans to move air.

But if not enough air gets into or out of the dash, I could place simple baffles -- probably just made of rubber -- around the chassis so air is forced to move through the bezel slots. An old inner tube, even from a bicycle tire -- would be adequate, because we're just directing airflow, not looking for a perfect seal.

Baffles with rubber ends are commonly used to direct airflow around piston engines in aircraft. Even in that hot environment with a good deal of vibration, the rubber lasts many years before it needs replacement. My bet is that the rubber in this installation will be good for as long as the PC is in the car.

Up above your radio is a flat area on the dash. Why not have a vent added to the top that leads to the PC?

Originally Posted by HiJackZX1

Up above your radio is a flat area on the dash. Why not have a vent added to the top that leads to the PC?

I'd rather not cut a hole in the dash because I'm trying to keep the vehicle so I can roll it back to stock when I decide to get another car.

Actually, that's a change that would be easily concealed, so it could work. But forcing PC air out through the bezel has the added advantage of pushing air past the monitor and keeping it cooler, too.

Originally Posted by rdholtz

I'd rather not cut a hole in the dash because I'm trying to keep the vehicle so I can roll it back to stock when I decide to get another car.

Actually, that's a change that would be easily concealed, so it could work. But forcing PC air out through the bezel has the added advantage of pushing air past the monitor and keeping it cooler, too.

I was actuallay thinking of that too.... When I meant top, I meant the very top of the dash, the flat part.... Your idea is less destructive, I will never part with my car, so it was OK for me to hack it apart, lol. A small little gap in thetop of the bezel would be cool, because all you have to do is replace the bezel instead of the whole dash.

Originally Posted by HiJackZX1

I was actually thinking of that too.... When I meant top, I meant the very top of the dash, the flat part.... Your idea is less destructive, I will never part with my car, so it was OK for me to hack it apart, lol. A small little gap in the top of the bezel would be cool, because all you have to do is replace the bezel instead of the whole dash.

I set the original bezel aside when I started the carPC project, and bought a replacement from a boneyard. I've already modified it partially for the EeePC installation, and will change it again for the Atom installation.

The slot(s) across the top should let me move air out of the dash pretty well. They'll be relatively subtle additions, since they'll be in the black part of the bezel.

The bezel is polyethylene, so I expect to cut the rounded ends of the slots with my punch, and I'll make the cuts between them with an X-Acto knife.

Revised Monitor Mounting System

I showed the basic chassis plan to Josh, and explained that I was working out a problem: as it was laid out, when the monitor is mounted to the chassis, I can't reach get a screwdriver in to the chassis mounting screws -- the fasteners that hold it to the dash. That means either (1) I can't screw the chassis down or (2) I can't fasten the monitor to the chassis.

He suggested a better system than bolting the monitor directly to the chassis: a simple L bracket with a slot in the top leg and a hole in the bottom leg. It would use the slot to position the bracket vertically, and a screw with a knobbed head would go through the bottom leg and up into the threaded hole in the bottom of the monitor. That sounded pretty good, but I was still concerned about being able to get to the knob when I want to pull the monitor.

I came up with a second approach that built on Josh's L bracket idea. I thought if I made the bottom plate of the L bracket very wide, so it runs under the entire width of the monitor, I might be able to build a hinge system into the bracket. That would provide a way to swing the monitor down so I could get to the chassis mounting screws. The monitor and the PC would be a single assembly that could be moved in and out of the dash as I make changes. But that was going to take a lot of very careful hinge alignment and detail work, and it badly failed the simplicity test.

Now I think the third solution is better and easier. I can make that L bracket as wide as the chassis. The ends of the bracket could wrap around the chassis and be held by the chassis screws; slots would make the bracket height adjustable. Velcro on the bottom of the monitor and two strips up the back would hold onto matching Velcro strips on the bracket. The Velcro would even provide some cushioning.

This mounting system has the advantages of simplicity, adjustability, and ease of manufacture. It eliminates the need for the slot I had in the end panel of the chassis, but it does require that I make slots in the flanges of the bracket.

Here's the preliminary Sketchup version:

Click image to enlarge.

I haven't added the locations for slots and holes to the drawing, yet.

You may also notice that most of the front panel of that bracket is wasted material; I really only need a little along the sides, and some across the bottom. An even simpler version could be made by using 1/2-inch x 1-inch aluminum angle: one piece on each side and a third across the bottom.