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
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
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,
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
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
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!