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Home experiments - How to build a fan, part 1
The way it's done at iceteks!
By Red Squirrel



(My latest model (at the time this was written), still under construction, click here to listen to the beast!)

In this how-to, you will learn how to make a fan, from my own experience, that is.  Computer fans are cheap and easy to install, why build your own?  Just for the fun, and danger! 

For this, you will need the following:

A 12V+ motor (you can get one at Radio Shack for about 5$)  
The one I used is 18 000 rpm at 18 VDC.  I'm testing it on a 10 volt power adapter.  It's been tested in a computer power supply and will probably be used at a lower voltage, to decrease the noise (this beast is noisy, if you like a quiet computer, don't even think about this!).

Some old thin can lid, or if you want to go ever more cheesy (and safer), get a 2x4, a jig saw and cut away!
I tried both, you are better off with the thin can, easier to cut (if you have thin-metal cutters) and better air flow.  Currently, I'm using thin can.

A source of DC power (for best results: same voltage as motor or lower) ex: a AA battery holder with batteries.  If you have a power supply that is open, you can solder yourself wires to the board and use that, don't touch the capacitors whatever you do (I did, it hurts).   I use a Nintendo(TM) Power adapter which is rated 10 volts.  If you do, MAKE SURE IT'S RATED DC, not AC, or you will be building a vibrator, seriously!

wires or crocodile clips, or you can solder it, your choice.

Glue gun, or some other sticky way to have the blades hold to the shaft, note, G-force is extreme, Elmer's school glue is not a choice, if you do get that to work, let me know how much you used!

old propeller, you don't need this, but it makes it easier to hook up the blades, since there's the end where the shaft goes in, for the blades, just cut them off, if you just used that, you did not really build the fan yourself. :)
Or you can do what I did with the wood one, take a small piece of wood, drill a hole and there you go, the shaft can go in.  Glue the blades on it.  Again, measure with a lot of precision to equal it.

Ok, let's start!
Now you must have some material to build the blades, the motor, DC power source, something to stick in the shaft (old propeller for example), glue gun, any method to wire it with you.  If not, go trough the list of materials to make sure, it's better to know that you have access to everything, we won't need it right away.


Wiring the motor
This is probably the simplest task, take 2 wires, put one in the - of the power source, one (not the same one!) in the + and then put the other ends to the two poles of the motor, the motor will spin.  If it does not spin, check your connection.   If it still does not spin, check to make sure you have the right voltage, or if you have voltage at all (is the Dc adapter plugged in?).

Building the blades
Now disconnect any wire, it will go better if the motor is not turning. :)  If you already have an old propeller, you are done the hardest part, skip to the next paragraph.   If not, find yourself a block of wood and cut out something like this:

Note, the dimension of this is rather small, the hole should be a bit smaller then the shaft of the motor, the rest can be the size you want, but remember the less load, the faster it will turn, but leave room for the blades, this picture hardly has room for them, but is just to show an example.

Ok, the challenging part, the blades.  If you don't understand the way air is moved in a fan, this can be hard, I'll try to explain it my best.  When I made my first fan, I already knew this (who knows from where!) so it was not hard.  So let me explain how this works, with pictures.


On the left, it shows a picture of the motor, this is just to show you what angle we are looking at the blade on the right. 
The blade line is the blade from side view, the blue is the air and the green arrow is the direction the blade is going.
Noticed that because of the angle of the blade, the air on the bottom is pulled by it and it is directed on top. This is how an air plane's wings direct the plane.  But with a fan, the blade turns, but sideways, it is moving straight, and that's how it picks up the air, in a circular manner. 
But one blade would be enough and do the job, but because this is turning, balance comes in, that's why there's always more then one, in these home made fans, it's best to just put 2.  2 big ones that is.

So to make blades with a thin can cover,  Hammer it down against cement (or if you have access to an anvil, even better!) to make it as flat as possible.  Once done, bend it in half.  If you notice that you did not bend it exactly in the center, which is most likely since it's not evident to bend aluminum perfectly, simply cut the excess portion.  Now, you have a half pie.  Notice where were coming to?  If not, just continue and you will catch on.  Now, from the center of the straight section, cut a pie about 1/3 of the half pie, or your choice, this will be the size of the blade, note that if it's too big, it will move more air, but will also improve the chance of it flying from the G-force caused by it spinning at roughly around 10000 rpm.  Just to compare, a car's engine runs at 1000 rpm or lower when not moving, if it reaches 8000 rpm, it's usually dangerous for the engine!

Ok, now that you cut the pie, it's time to decide if you want to cut off the sharp edges, I did on mine, which is on the top.  Now we have a small pie, now is the time to bend it the way you want.  Bend it at the tip to make it vertical so that it can do proper air flow.  You can design this how you want.  Think of what part of it will be glued, and what part will be moving the air.

 Now, this part gets tricky, remember how we bent it?  Now we have to unbend it, the center bend line should be the exact center, so we will be able to cut there, to have 2 blades.  When I made mine, the problem I had is that when I bent it, it did not bend right in the center, there was still some left to bend.  The hammer did the job.

Now cut as straight as possible in the bent line, now you have 2 blades!  Congratulations!  Notice how I saved you from working on each one individually?   That was the whole plan of the bending part.

Now, fire up your glue gun and wait until it is ready, while waiting, decide how you want your blades to be placed on the wooden piece or the old propeller (which you took off the blades right?).  If you didn't, put it in the motor, to ensure it fits, and that it is well balanced, by turning it on and feeling for vibration, you will get some, unless it is perfectly balanced, but no one is perfect, if you got this part right, wait until you put the blades to break the champagne. :)

Now, your glue gun should be ready.  Put glue on the shaft section (your wooden block, or the old propeller piece) and glue the blade on it.   Do the same for the other blade, make sure it is very centered, both blades' point should be facing each other.   Now, just go nuts and put glue everywhere the blade and anything else is close by, you need a very solid connection, depending on your motor.  Even though you will never run your motor at it's peak, you still want it to be able to, in case you ever decide to hook up a air conditioner thermostat to make it go faster.  Or you might want to put a switch and switch to a higher voltage when you leave the room (more like, leave the house!).

Ok, after playing around with it, you probably thought of something, how will we hook it up the the computer?
I did not do that part yet, the next tutorial will show this, you can experiment if you like.  I'm thinking of using a bottle neck, elastics and bring the Venturi effect the the next level.


I hope you enjoyed this and that it was interesting to you! 

- Ryan
Forum Moderator 









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