Converting a Box Fan to 12vdc with Treadmill Motor

[wooferhound]

I have taken a standard 120vac box fan and converted it to run on 12vdc using a treadmill motor. I had been thinking about this since I got some more solar panels for Christmas 2010 and I have seen the dump load controller dumping continuously every afternoon after about 12:30 noon. I hated to see this power being wasted so I needed something that would pull a higher current that would benefit me in the afternoons. My solar power system works without an inverter and I use the 12 volt power straight off of the battery.



In all simplicity all I did was unscrew the factory motor and replace it with a Treadmill Motor, I changed the power switch too. This took me a fairly long 6 hours to do because I didn't buy any parts and used stuff that was collected in my shop, and I am really picky about stuff that I build and it always takes me longer than it should when I build stuff for myself



An L bracket was added to the back to keep the fan from falling over from the weight of the motor. I used some corner brackets and bent them to fit the existing brackets on the treadmill motor. Drilled and bolted everything together, and discovered that the motor was spinning the wrong direction for the blades. So the motor was wired in reverse polarity to get the proper rotation direction, I hope this is OK for a treadmill motor?

The motor that I used is rated
2.5 Horse Power
120 volts DC
18 amps
7100 RPM
CW rotation
Class 8



I used 5 minute epoxy glue to attach the blades to the motor. I had to cut out some plastic in the center of the blades to get a good flush fit. The hub of the blades was exactly the same size as the flywheel on the motor so I glued the outside edge of the blade hub to the flywheel.

I took it inside and hooked it up to my solar power. While it was running the voltage was measuring 12.3 volts and it was pulling 1.5 amps which comes out to 18.5 watts. It runs about as fast as a factory fan set to Low speed and I did not need a speed control. Nice pleasant whoosh sound that is not offensive at all. The motor stays cool to the touch even after hours of operation.

After testing I replaced the factory plastic blade guards which required a little cutting to accommodate the treadmill motor sticking out the back. It weighs about 5 times more than the factory fan and pulls about 1/5 of the power. I just run it during the day when the system is dumping power. I ran it late one night and when I turned it off I was reading a 10v battery voltage which went up to 11.7 volts when I turned the fan off. I'm real happy with the results of this project and I am enjoying it right now as I am writing this..

I got the idea from other members that had done the same thing and were claiming amazing efficiency running from 12dc.
An Efficient 12V Ceiling Fan - by SamoaPower
http://www.fieldlines.com/board/index.php/topic,128905.0.html
Solar 20'' Box Fan - By Ghurd
http://www.fieldlines.com/board/index.php/topic,143414.0.html

[ghurd]

"Cool!"

Maybe this is the link you intended?
http://fieldlines.com/board/index.php/topic,129725.0.html
G-

[wooferhound]

Maybe this is the link you intended?

You are so correct . . . there must be something wrong with my mouse clicking finger ?

[jaysicle]

I'll bet it moves a great deal of air for 18.5W !. Very cool.

That concept (or entire device) might work well to vent an attic. Solar loaded - mine is 55°C/131°F up there on a day like today, even with tons of soffit vents, - 32°C/90°F ambient.
 
How much are you thinking it will retail for ?, - And how much to ship to Canada?

Nice build,... inspiring actually - Thanks woof.

[ruddycrazy]

Eh Woof looking good mate  eh here's an idea for a dual purpose fan to suit all seasons. Grab some nichrome wire install that for a heating fan in the winter months.....

Cheers Bryan

[Bruce S]

Hey Woof, that's pretty neat!!
Go charge up those NiCds and use them to run this, that way if they drop in voltage they'll come right back 
Have fun!

[Rover]

Really cool, I have a left over 2 hp Baldor treadmill motor, hmmm. .weighs about 30 lbs.. pretty sure it would squash the cage... but does give me ideas for other purposes. Retired treadmill motor, retired Wind turbine re-purpose, used now as turbine testing platform... could be retired again

[ghurd]

"it was pulling 1.5 amps"
Was the 1.5A measured when the blade was first installed?
If the motor was sitting for a year or few, the amps will get lower after a day or 2 of running.

Have any stray 10 ohm 25W power resistors laying around?
Might be worth trying one in series as a 'Low Speed'.  Amps will go down with less percentage of windspeed reduction.
I can pop one in the mail for a test, if you'd like to try it.

Love the anti-tip-over L bracket. 
So simple, so obvious, yet one I know of is still C-clamped to the lip of a dresser!
G-

[12AX7]

Hey woofer!   you had better keep your eyes open..     OSHA will be knocking at your door!

Last time I played with a fan like that it lost it's balance and would rock across the floor like it was dancing to disco. 

I like it!

ax7

[wooferhound]

"it was pulling 1.5 amps"
Was the 1.5A measured when the blade was first installed?
If the motor was sitting for a year or few, the amps will get lower after a day or 2 of running.

Have any stray 10 ohm 25W power resistors laying around?
Might be worth trying one in series as a 'Low Speed'.  Amps will go down with less percentage of windspeed reduction.
I can pop one in the mail for a test, if you'd like to try it.

This treadmill motor had not been run (except for testing) in 4 years or maybe more. I may check it again soon and see if there is any change in current.

This is my larger fan, I have a smaller fan that is made from a 4 inch muffin fan. It's attached to my computer desk and serves as my low speed low current fan, so I really don't need a low speed on the bigger one. Plus I have a can full of power resisters. Thanks for the offer and information.

[wooferhound]

Last time I played with a fan like that it lost it's balance and would rock across the floor like it was dancing to disco. 
ax7

Actually this seems to be balanced very well. I wire-brushed everything really well before I glued the blades to the motor. Plus my bracket on the back seems to be working fine. Now my cloths washer is a different story . . .

[wooferhound]

Go charge up those NiCds and use them to run this, that way if they drop in voltage they'll come right back 
Have fun!

Hmmmm ,  a cordless Box Fan, I feel another project coming on . . .