In Mexico its very hot so I need a super powerful portable battery fan. I made one from a computer fan but it was not powerful enough.
For this build I am building my own super powerful ducted fan. I am using a 18V drill motor, an RC plane propeller and laptop batteries to run the fan. It is nice and windy at 4 volts and not too loud. At 12V it super powerful and loud and slides across the table.
I was thinking of mounting it to my bike and running it at 16V to see if it will push me a little but now I am building a larger one for that.
Step 1: Parts Required
The motor and batteries are the most expensive parts. You can find used drills with broken batteries for very cheap and just used the motor. I got a used 18V drill for $6. Used laptop batteries usually have 6 cells and don't work well if one cell is dead. You can buy these batteries for next to nothing and take out the good cells to make a powerful battery pack.
DC drill motor (or another motor)
Laptop batteries (or others)
Fan blades (I used a plastic propeller)
1/8" plywood for duct wall
Plywood and 2x1 for motor mount arms
Switch (I used a 2P2T switch for 2 speed)
Step 2: Testing Motor and Batteries
Mount the motor with fan to something solid.
The the motor with different voltage and test the current and wind power you would like.
In my test 4V was about 1.5A which is a good low power setting. 8V used about 3A which was a perfect high power setting.
I will used 4 batteries, 4 in parallel for 4V and 2 sets of 2 parallel batteries in series for 8V. So on low power it will last around 5 hour and on high power for about 1.5 hours.
I wired up a 2P2T switch to change between series and parallel. Please find the wire at the instructable below.
Step 3: Building Duct and Motor Mount
First I made a T by gluing 2x1s together. I measured the pieces so that the propellor had about half an inch of clearance to the end of each end of the T.
After gluing to pieces together I carve the edges to make them more aerodynamic.
I glued two triangle of wood to old the motor.
I soaked a piece of 1/8" plywood in water and then bent it and let it dry. I cut 3 strips that were 3.5" with the wood grain perpendicular to the strip so its easier to bend. I used the T as a guide and glued the 3 pieces together with overlap joints and leaving one joint open. I glued the 3 T ends to the plywood duct. It is important to mount the motor and rotate the prop to make sure the clearance is enough all the way around.
I then cut two pieces 1/4" plywood about 4.5 by 1.5 to form the top duct support. I used two pieces to go around and hold the motor. I glued these supports to the duct and to the T.
I glued a piece of wood to the T to stop the motor from sliding backwards. The motor pushes the air forwards so the motor is then pushed back.
I also used 2 zip ties to hold the motor down.
Step 4: Battery Pack
I started by using a 6 cell laptop battery to power the fan. I did some tests with the bike and running the fan at 12V.
As a cooling fan 4V or 8V is more than enough power.
Step 5: Wires to the Motor
I soldered two 14 gauge wires to the motor. I rapped them in electrical tape so the wouldn't short out.
I taped the wires to the support arm so it would not move and get sucked into the prop.
Step 6: Testing
I hooked the motor to 2 parallel sets of 3 cells in series. The voltage was about 11.8V. Even with the multi meter the current was 3.38A. The multimeter has some resistance so the current is closer to 4A.
At over 47 Watts this is one crazy powerful little fan.
I think at 16V this fan could push my bike some decent thrust and it would sound really cool.
Step 7: Adding Protection
The prop spins so fast in this fan you need some protection.
I used some wire cutters and cut a circle out of protective grate from a larger fan that was about half an inch larger then the duct. I bent the wire around the duct. I then used hot glue to glue protection on the front and back.
Step 8: Adding a Switch
I added a switch so that the fan can be easily switched on and off.
This is just temporary as I want to use the 2T2P switch so I can have two speeds.