Electric Motor Question

TroySD · Nov 29, 2011

Guys,

I making a heater for my cab and I'm going to use a small radiator fan for the air source. Question is, can I make it a two speed with a certain type of switch or am I stuck with it at one speed. I'm thinking its okay to do but thought I'd pose the question any way.

Thanks!

skylarkguy · Nov 29, 2011

a lot of fans in cars use some kind of resistor to change the fan speed. I just replaced one in my honda and it cost nearly $40 (so don't use that one

) but GM's are probably cheap and abundant. It might take some experimenting but you may end up with 4 speeds.

hunterridgefarm · Nov 29, 2011

I know we have taken a two speed switch for a small electric motor and installed a variable speed switch. Works about like a dimmer switch in a light. We have had no problems with it. Not sure if this helps.

Craig Clayton · Nov 29, 2011

I would suggest you find a 12 centrifugal fan from a surplus center that is new. Your rad fan will push enough air to make you feel like you are in a hurricain.
This is how centrifugal fans work ( squirrel cage ) to the layman. The fins point Forward , Reverse, or Straight. Based on the direction of rotation. Forward fins move the largest amount of air but have a lowest static pressure. Straight fins are movers of air but are the cheapest and are between Forward and Reverse in performance. Now for the Reverse fins they move the lowest volume air but have the highest static pressure and should be the quietest.
I would suggest you look at a commerical heater blower and borrow the cfm of the fan and find a surplus fan that is similiar. If you can find either amps of watts or rpm and diameter of the cage and width you will know what it will do.

Craig Clayton

Travelover · Nov 29, 2011

Look at computer cooling fans. They come in all sizes, are compact and take little current to run. You can buy a rotary (multi-position) switch and just solder in different resistors (from Radio Shack) on each leg to get your different speeds. Measure the current draw. A dropping resistor (in ohms) for a second speed would be 12 volts divided by the amperage draw.