Window insert for 12VDC fan ventilation

rayra

Expedition Leader
eta MkII design start further down the topic, here.


Something I've been doodling for a while. Seen things like it on police K-9 vehicles. And I want it for a similar purpose and also as something useful for vehicle camping etc. Essentially it's a window insert, trapped in place by the window, with 12v fans fitted to circulate air into / out of the vehicle.
Computer fans are just the thing for this, native 12VDC, very low amp draw, many sizes, many options for near-silent operation. And being DC you can add a rheostat and dial their speed up / down.
I just happened to have a tower PC I was gutting out and it had a large 10" / 240mm? fan in its side panel. So I set that aside with this in mind. The pressboard is 1/4" thick, also some leftover scrap.

Here's a couple pics of fitting a panel. The bottom edge is cut / curved to fit the top of the window glass (which I'd also traced onto the pressboard to get a snug fit at the top of the insert). That's then sandwiched with a couple 1-1/2" wide strips. The idea is to just socket the insert on top of the window edge, then raise the window and guide the top edge of the insert into the groove for the glass.

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I added a simple $3 cigarette lighter plug from walmart, and added a 6' lead that will let me plug it into the power port on the back of the center console. I think I might have a rheostat laying around, too.


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It's 'reversible' in that the insert will fit in either side. It's set up to pull air into the vehicle, but setting it in the other side would turn it into an exhaust setup.


Ultimately I'll probably re-execute the thing, newegg.com has nice quiet fans available in bundles, (4) x 120mm for $13. A row of smaller fans would work better, move air at the highest / hottest layer, and have the window reach higher / closed more. And be less noticeable. I can put some screen mesh between the fans and the pressboard

The whole thing could be built for <$30 starting with nothing. as this stands now, the only thing I didn't have laying around already was the cig plug.

Cmputer fans come in a massive variety of size, color, CFM ratings etc etc. You can be as plain for fancy with this as you wish. The average 120mm fan is 30-50cfm. The Suburban is 140cu' of cargo, call it just about 200cu' of interior volume. So with four fans running at max, that would be the full volume of air replaced every minute. Which pretty much means you could keep the vehicle interior at ambient.

120mm fans typically use 1/3-1/2A, so even running four wouldnt be a severe burden overnight.
 
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pugslyyy

Expedition Vehicle Engineer Guy
Nice. If you are trying to keep the interior cool probably better to use it as an exhaust fan and try to pull air in from someplace lower. Heat rising and all that.

I used these 120mm fans - they weren't the cheapest (I bought 4 for $20) but had good ratings and have held up.

https://www.amazon.com/gp/product/B00066ISFC
 

rayra

Expedition Leader
Very similar to the set of four I'm eyeballing at newegg -

http://www.newegg.com/Product/Product.aspx?Item=N82E16835103052


Mostly to keep air moving. As mentioned earlier it won't get cooler than ambient, but being in the SoCal deserts and in combination with my awning projects, it shoul ddo well enough. Definitely want to hook up a rheostat for both noise and power consumption control.

I'm also thinking about the other recent topic about 'security'. Especially out alone in the southwest. I was considering making some 'socks' out of tent screen fabric -
https://ripstopbytheroll.com/products/0-5-oz-ns50-noseeum-mesh
which will slide over the door window frames, lower the window, close the door, and you've got bug-free insulation. But I'm now thinking that with the fan insert I can push more air thru while keeping the windows more closed.

/ruminations & speculations
 

pugslyyy

Expedition Vehicle Engineer Guy
Very similar to the set of four I'm eyeballing at newegg -

http://www.newegg.com/Product/Product.aspx?Item=N82E16835103052


Mostly to keep air moving. As mentioned earlier it won't get cooler than ambient, but being in the SoCal deserts and in combination with my awning projects, it shoul ddo well enough. Definitely want to hook up a rheostat for both noise and power consumption control.

I'm also thinking about the other recent topic about 'security'. Especially out alone in the southwest. I was considering making some 'socks' out of tent screen fabric -
https://ripstopbytheroll.com/products/0-5-oz-ns50-noseeum-mesh
which will slide over the door window frames, lower the window, close the door, and you've got bug-free insulation. But I'm now thinking that with the fan insert I can push more air thru while keeping the windows more closed.

/ruminations & speculations

Those look like nice fans, and I like the v.1 so I'm sure the next one will be even better. You may have to play a bit with the size of the openings (whether it be inlet or outlet) to get the air movement right. The velocity of the air is important, and the smaller the opening the higher the velocity - but unless you have a college degree in that stuff it is better to just experiment until you figure out what works best for you.
 

Martinjmpr

Wiffleball Batter
Clever idea, you just need to put a screen extension or something to cover that gap at the back of the window to keep the bugs out.
 

paranoid56

Adventurer
the only other thing i would maybe try (as this is exactly something i have been thinking of doing also) is to maybe power them from a solar panel. that way your main battery wont drain and being that they dont draw much power a small panel should work.
 

PGW

Observer
Cool idea! What about using a PCI slot fan/squirrel cage fan? With the smaller profile it would work with the window just barely cracked. If you had window vents you could also use it in the rain. Not sure if the motor would be reversable and it may have to be exhaust only unless you want the fan to hang outside the window.
 

wagex

Adventurer
Very similar to the set of four I'm eyeballing at newegg -

http://www.newegg.com/Product/Product.aspx?Item=N82E16835103052



I'm also thinking about the other recent topic about 'security'. Especially out alone in the southwest. I was considering making some 'socks' out of tent screen fabric -
https://ripstopbytheroll.com/products/0-5-oz-ns50-noseeum-mesh
which will slide over the door window frames, lower the window, close the door, and you've got bug-free insulation. But I'm now thinking that with the fan insert I can push more air thru while keeping the windows more closed.

/ruminations & speculations
they sell those already made they are usually called sun shades, but its mesh that slides down over the top of the door then you just close the door
 

rayra

Expedition Leader
all very interesting.

My design impetus for this is something that can run in the overnight, when I'm sleeping in the vehicle. I can open all the other windows a few inches, and have a sunroof. So plenty of ways to have heat escape.

I've seen a variety of 6" oscillating fans in the Trucking and RV markets, but they all seem noisy and have a higher amp draw.

In my own case, I'm adding a second group78 battery as segmented / isolated 'house' power and also a portion of my cargo platform / drawer setup is going to have a bunch of power flavors and connections and if I can fit them in, a couple smaller sealed 12VDC batteries. And I'm looking to add solar support as well. So there'll be plenty of power for such fans going forward.



Another idea could be an insert for the sunroof opening, set up as an exhaust. That would certainly vent the most heat, but it wouldn't put any air on me as I sleep. When camp is set up, just plunk it down on the sunroof opening.
 

PGW

Observer
You could also have an exhaust/intake fan to move fresh air in/out of the truck and then a separate fan(s) pointed right at you for when you sleep. That is probably the route I will take.
 

rayra

Expedition Leader
I did some stuff like that, back in my computer modding days. 4" ABS pipe fittings line up well with 90mm fans. There's a 45deg ABS elbow, chrome painted, in that tangled blue mess. Directed exterior air right to the CPU cooler and the vidcard. Primitive by today's designs. This was at least 15yrs ago, wasn't really anythign even then. Farting around.

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pugslyyy

Expedition Vehicle Engineer Guy
I think the biggest potential issue with cracking the windows open along with the sunroof is that you are just moving the air at the top of the vehicle. You really need the outlet at roof height and the inlet at floor height to move the heat out. I have the same problem in my camper, all the openings are up high except for the door.
 

rayra

Expedition Leader
I think the biggest potential issue with cracking the windows open along with the sunroof is that you are just moving the air at the top of the vehicle. You really need the outlet at roof height and the inlet at floor height to move the heat out. I have the same problem in my camper, all the openings are up high except for the door.

true except for one major thing, hopefully the outside air is cooler. So that's sinking in the vehicle and the hotter air inside is rising up and out the top / other windows, sunroof.
And either way, I'm pumping in the total volume of air every minute or so, so the 'old' air has to go out. Granted it's at nowhere near 100% efficiency, but it's still a vast improvement over stale / stagnant air. Providing it's cooler outside. Given my haunts, that's not often the case on the Summer until very late at night / early morning.

awnings105.jpg


Too, the angle of the window gives the fans a bit of down angle, maybe 5 degrees. So their airflow is is hitting the other side instead of going straight across the top. So convection can sort the rest out. Or it would be easy enough to add a diverter panel to steer the air downward or rearward or both. The aformentioned elobow joints could easily be fashioned into a 'header' / side pipe arrangement, diverting the incoming air right at the sleeping arrangement / cargo deck. Even better if the elbows are trapped in a way that makes them turnable, they could be aimed independently without looking totally ghetto. Louvered slats, metal dryer ducting, Cutting the flange off of one end of the elbow as I did in that PC build, to make it look like an exhaust pipe tip. The other flange could be trapped against the fan body by a bracket or even another flat of pressboard, with pipe-sized holes cut thru it. That way the elbows could spin in place and the air aimed wherever you want it.


But a whole other idea is to run some auxiliary wiring and switching to the vehicle's existing ventilation fans, run from an aux battery, and simply make use of the fans and ducting that the vehicle(s) already have. No need to have the key in the ignition or energize all the vehicle's other systems or computers to produce the breeze. And like the window insert, the added benefit of pulling in outside air (on the premise that it's cooler)
 
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