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limadelta(at)gmail.com
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Posted: Wed Jan 19, 2011 8:40 pm Post subject: Off topic -- Slowing an electric motor

I built a wind tunnel for my son’s physics project.  Works great!  The issue is that I would like to slow the fan down to generate airspeed below the Reynolds number of a dimpled golf ball.  Current airspeed is about 58 mph.  I need to slow the fan to generate airspeed below 30 mph.  The motor is a permanent split capacitor type: http://www.grainger.com/Grainger/DAYTON-Direct-Drive-Blower-Motor-7E658.  Any thoughts on how to slow it down?  I've read that slowing it with a dimmer might damage the motor.   

   

Thanks,  Dan O’Brien  [quote][b]

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nuckolls.bob(at)aeroelect
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Posted: Wed Jan 19, 2011 8:50 pm Post subject: Off topic -- Slowing an electric motor

At 11:35 PM 1/19/2011, you wrote:



  	  Quote: 	
		  I built a wind tunnel for my son’s physics project..  Works great!  The issue is that I would like to slow the fan down to generate airspeed below the Reynolds number of a dimpled golf ball.  Current airspeed is about 58 mph.  I need to slow the fan to generate airspeed below 30 mph.  The motor is a permanent split capacitor type:  http://www.grainger.com/Grainger/DAYTON-Direct-Drive-Blower-Motor-7E658 .  Any thoughts on how to slow it down?  I've read that slowing it with a dimmer might damage the motor. 	


   It is difficult to slow these critters. May I suggest

   another motor?  Ebay has a bunch of DC motors and

   controllers intended for treadmill service . . .

   but easily adaptable to other tasks. These controllers

   usually have some form of tach feedback for very

   stable speed control.



   Alternatively, how about putting a damper across

   the inlet to throttle air flow?



 

 

   Bob . . .    [quote][b]

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raymondj(at)frontiernet.n
Guest

Posted: Wed Jan 19, 2011 11:18 pm Post subject: Off topic -- Slowing an electric motor

do not archive



You can't talk about a wind tunnel and not include at least a photo!! 

Better yet a parts list and a blueprint 



Raymond Julian

Kettle River, MN



On 01/19/2011 09:46 PM, Robert L. Nuckolls, III wrote:

 	  Quote: 	
		   At 11:35 PM 1/19/2011, you wrote:



> I built a wind tunnel for my son’s physics project.. Works great! The

> issue is that I would like to slow the fan down to generate airspeed

> below the Reynolds number of a dimpled golf ball. Current airspeed is

> about 58 mph. I need to slow the fan to generate airspeed below 30

> mph. The motor is a permanent split capacitor type:

> http://www.grainger.com/Grainger/DAYTON-Direct-Drive-Blower-Motor-7E658 .

> Any thoughts on how to slow it down? I've read that slowing it with a

> dimmer might damage the motor.



 It is difficult to slow these critters. May I suggest

 another motor? Ebay has a bunch of DC motors and

 controllers intended for treadmill service . . .

 but easily adaptable to other tasks. These controllers

 usually have some form of tach feedback for very

 stable speed control.



 Alternatively, how about putting a damper across

 the inlet to throttle air flow?

 Bob . . .



 *

 *

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limadelta(at)gmail.com
Guest

Posted: Mon Jan 24, 2011 7:41 pm Post subject: Off topic -- Slowing an electric motor

Just following up on my question last week about slowing a permanent split capacitor motor for a wind tunnel I built for my son's science project.  A poster indicated that one can slow such motors with a dimmer switch, which is what I did.  Worked great.   We were able to measure the drag coefficients of golf balls with different dimple patterns at different Reynolds numbers.  Cool project.  I've attached a compressed picture of the wind tunnel as one poster requested. 



Thanks for the help guys!

Dan O'Brien

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