Improvised fan

[DBSP]

I'm not completely shure it's called a fan in english so please correct me. But it's the kind of thing you have in your kitchen and turn on when your steaking bacon.

I came up with the idea about two months when I paid a visit to the recycling station.
I bought a cooling fan used in computers and a battery eliminator to power it.
I then took a paper tube that fitted the fan and cut it in half, and then put the fan in the middel and taped it securely.

When it is run it is powerful enaugh to remove allmost all fumes from a boiling pan of water. I fix it over the stove or werever I'm using it with strings. To lead the fumes outside i took a large plastic bag and cut it in strips wide enaugh to reach around the pipe and then tape it so that it forms a tunnel, this tunnel i just put out a window.

I use it when consentrating H2SO4 and things like that wich give off dangerous fumes such as when boiling off water/HCl from explosives as hexamethylenetetraminedinitrate and MMAN.
It would allso be useful when making picric acid and such. It's very good and simple to make, anyone who want to be inside when synthesising explosives should have something similar to make it more safe.

Any comments, thoughts?

[Lagen]

The only problem I can see is resistance to corrosion. These things usually have metal axles and teflon, sometimes ball bearings. Even if they're brushless there's still a lot of copper wiring, ICs and other components that will get corroded by NOx, H2SO4, HCl...

This problem could be solved by making your own impeller out of PE or PTFE, complete with a plastic axle and teflon bearings. Magnets would be placed around the circumference and sealed with silicone rubber. The impeller could be driven by coils outside the pipe, this would require a driver circuit. All this could be improvised with parts taken from a magnetic stirrer...

[vulture]

Why would one give up a magnetic stirrer to make a fan??!! I wish i had a magnetic stirrer!

[Lagen]

It was just an idea. Personally I would build the circuits from scratch - the magnetic stirrer circuits would surely have to be tweaked to a higher frequency... You could at least get suitable coils, and PTFE coated magnets. A yet easier approach could be trying to acidproof the PC fan by sealing the circuits with some silicone potting compound and replacing the axle. But sooner or later you will have a reaction product that will ruin common PC fan materials. I think teflon is the only sure way to go.

[DBSP]

The best thing about this fan is that it is dead simple and cheap. If the fan gets destroyed by corrosion or something like that i doesn't matter since there are more fans availible than you could cont in a day.
If you want another fan just take it from an old computer most people will give you their old ones. Or buy it at a recycling station the fan i bought costed about one and a half $ wich is nothing. And the fan seem to last quite long too I've used my one quite alot and it still functions properly.

[mrloud]

What you are talking about is called a fume cabinet. Its just a box with a window and a narrow gap under the window for your hands to fit in. You could easily make one from stuff found at the hardware store or if you are strapped for cash, at a construction / demolition site.
Why not get a big cardboard box and mount the extractor fan in the top of that. Use some heater ducting to carry the fumes out the window. Seal it all up with duct tape. Cut a hole in the side of the box so you can reach in and do your stuff.

The important thing is that air keeps flowing *into* the access hole and *out* the extractor pipe. I would use at least two bathroom type extracor fans to make sure that that the volume of air being moved is enough to prevent any nasty fumes from comming out the hand slot. It all depends on how much toxic gas you are producing.
http://www.clydeapac.com.au/v3/images/lfc60.jpg
http://www.louisville.edu/admin/dehs/lsfume.htm

[PYRO500]

what I use is called a spot fume hood, my lab has open walls and a tin roof so I don't have to worry about fumes alot, but I don't want the cieling turning pink again :rolleyes: or my lungs or other stuff to get corroded so I have a funnel that is chemically resistant, and I have it hooked to some PE water line tubing and one side is connected to my water aspirator, the other is connected to the funnel witch hangs over the pegboard and draws up most of the fumes. Now my vacuume sorce uses a spa pump that recirculates water through a tank, on it's way it either goes through the water aspirator or through a bypass so the motor dosen't get overworked. it is a great system and draws near the max vacuum al the time and is very stable, I will get pics when I find my digital camera.

[Ctrl_C]

take you pics with a tripod or with the camera still please...the ccd on your camera takes forever to capture and they get blurry.

[PYRO500]

I'll try not to use that one again, I think I'll use plain film and scan the pics, the camera I used never wanted to download right either, it had a plastic serial port connector and I had to download the pics several times so I wouldn't get artifacts. another thing those cheap ccd camera's do is smear pixels, when ther eisn't enough light they are designed to compensate by not clipping the voltage going in and out of the ccd but soem don't do that well beyond a certain point thus not taking good pictures in wierd light, I think that may have been the culprit for why the picture of my finished HNO3 looks wierd, I have a few pictures of my still that are blured beacuse of motion but the picture of my HNO3 in ice bath looks kinda awry, anyways I may upload a video of a runaway reaction that involves boiling HNO3 and tons of red fumes, it looks like nitro gone very wrong but it isn't, I think it was some organic reactant, anyway's, when I dump that tape I will see about upping it.

[AfroFukinPyro]

Im currently constructing a fume hood out of polycarbonate plastic. The fan will be a dust collecter fan (which my dad and I will hook up to the rest of the work shop as well, and it will be positioned right inside or outside of where the vent will exit through the wall. Since my lad area is fairly small (about a 5-6' long table) the fume hood will be built around the entire bench. To avoid interference with everyday lab work, the front shield of the hood will be able to lift up, making full frontal :rolleyes: (hmmmm,that wasn't intended) access when the hood is not in use.

However, I will be using a fume hood almost all the time for what I'm doing, so why not make my howl lab bench one? The reason I have to use It for most everything is that I can't let harmfull acid vapour damage my dads tools (It's happened before), and there is a fire alarm right bye my lab table which sends the fire dept the second it goes off (The men in yellow don't like false alarms).

Please tell me what you think of my design.

[nbk2000]

If you use an ordinary fan while working with flammable gases or solvents, you're going to get flash-fried.

[Anthony]

PC fans would be ok because they're brushless. The larger (120mm) ones will move 100+CFM.

[nbk2000]

Brushless isn't the same as sparkless...I've seen my CPU fan spark in the dark. Presumably static buildup from the dust bunnies in the heatsink fins. (Not much for maintainence)

My computer is a miracle...miracle it still working. :D I heard a loud "POP" come off of it earlier. Didn't see where, but it was pretty damn loud. Many is the times somethings gone POP, BUZZ, or ZZZZAAATTT with the damn thing, yet it keeps on ticking away. :p

[CommonScientist]

NBK - that is hilarious, have you ever had a small fire in it? With all the dust and the sparking, it could happen. It could turn into that microwave from hell like your website :)

PTFE coated stirrer magnets can be bought at lab supply places such as Ace Glass inc.

Could you get a turbo charger form a car and coat the inside it? It would be hard to melt the teflon , but it would be a great fan. You could hook it up to a vacum celaner motor, which should be contained in a box or some place so that fumes cannot get to it.

[Dave Angel]

Lagen mentioned earlier that one might use an impeller. Wouldn't I be correct in thinking that impellers only work when completely submerged in a liquid, and thus would not be suitable for the intended purpose here?

Perhaps one could create the necessary rotational energy in isolation to the duct and its flammable / corrosive gases, and transfer it to the fan in the duct by means of a car fan belt? Slots in the side of the duct wouldn't have to be large to let the belt travel in and out so losses of gases would be minimised.

[Edit]

Ah yes I've remembered what it was that confused me about those impellers I think. That is that to use one for propulsion on water the entire unit must be completely submerged, where as a propeller can come out of the water slightly and still provide propulsion.

CommonScientist I like your logic that, indeed, I wouldn't be correct if the statement which you make contradicts mine and isn't incorrect.

[CommonScientist]

No you wouldnt be correct, unless im wrong, a car turbocharger uses an impeller to move AIR, not nessisarily water. Have you ever visited one of those home-made jet engine forums? They use them for that too. Some can produce up to 45+ psi. You just take the exaust side off of the turbo and use the spindel to mount a pulley so you could use a belt. The only problem would be the angle - a turbo sucks air in the side of the impeller casing and ejects it out the bottom, so thus you would have to angle it on its side so it could suck in through a duct with maximum air flow.

______
/ turbo )-------
\______)------- discharge
| |
| duct|
| |

^|^|^
^| ^
fumes

I tried to diagram it as best as possible.

[Chemical_burn]

Why not use a belt or chain driven squirrel cage fan with the motor outside of the fume hood. Then just have the axel runing inside the hood to drive the blower on the fan. Then just seal the opening the axel is running though with a silicon gasket and grease it with silicon based grease.

You could probably use a silicon belt to drive it . To protect the gears or pully I would coat them with spray on teftlon or use alluminium and allow the outside layers to oxidise this would provide some protection to chemical fumes.