RE: static gap fan speed

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Gregory Hunter by way of Terry Fritz <twftesla-at-qwest-dot-net>" <ghunter31014-at-yahoo-dot-com>

Hi Ted,

Good question.  The so-called "universal" type motor
can be adjusted very nicely with a cheap dimmer
switch.  Universal motors have certain traits that
make them easy to identify:  1)They are brush-type
motors that tend to spark while running.  2)They tend
to be quite powerful for their size.  3)They tend to
run at very high RPM (5000-25000RPM).  Another
interseting bit of trivia--universal motors run
equally well on AC or DC current.

120VAC powered hand tools such as drills, angle
grinders, routers, jigsaws, circular saws, weed
wackers, etc., usually use universal motors.  Also,
most household vacuum cleaners use universal motors.

I've used dimmer switches to vary the speed of most of
the examples I've given, with no harm to the motor or
dimmer. My angle grinder RSG and my two horned sucker
gap (based on a vacuum cleaner motor) are both
controlable via a dimmer switch.

Regards,

Greg
http://hot-streamer-dot-com/greg

--- Tesla list <tesla-at-pupman-dot-com> wrote:
> Original poster: "Ted Rosenberg by way of Terry
> Fritz <twftesla-at-qwest-dot-net>"
> <Ted.Rosenberg-at-radioshack-dot-com>
> 
> John and all:
> That is not the first time I have heard that a
> variac connected to a fan can
> be a benefit to control air speed. My question is,
> must the controller be a
> some what costly variac? How can you determine if
> something as simple as a
> motor control available at your local Ace Hardware
> will work? I am guessing
> that the type of fan motor determins this. If so,
> what types of fan motors
> can be controlled with what types of controllers?
> 
> Thanks
> 
> And
> Safety First
> 
> Ted
> 
> -----Original Message-----
> From: Tesla list [mailto:tesla-at-pupman-dot-com]
> Sent: Wednesday, July 11, 2001 8:35 AM
> To: tesla-at-pupman-dot-com
> Subject: Re: static gap fan speed
> 
> 
> Original poster: "by way of Terry Fritz
> <twftesla-at-qwest-dot-net>"
> <FutureT-at-aol-dot-com>
> 
> In a message dated 7/10/01 8:43:43 PM Eastern
> Daylight Time,
> tesla-at-pupman-dot-com 
> writes:
> 
> > I was looking at a static gap for sale on eBay
> (at:
> > 
>
http://cgi.ebay-dot-com/aw-cgi/eBayISAPI.dll?ViewItem&item=1615460756
> >  ) and was reading the sellers instructions for
> adjusting the fan speed. 
> >  According to these instructions, there is an
> optimal fan speed, above
> >  which spark length decreases.  I've never read
> this before, and am
> >  wondering if anyone can corroborate this.  I
> always figured that I
> >  didn't have to worry about too much air through
> the gap, but just too
> >  little.
> >  
> >   - Bill V.
> 
> Bill,
> 
> It is true that fan speed can matter in some coils. 
> It all depends
> on the CFM of the fan, the "natural" quenching
> ability of the
> coil, etc.  Some coils can use the full fan speed
> with no detriment.
> It's not that too much air "over-quenches", rather
> too much air
> can intermittently stop the gap from firing.
> 
> John Freau
> 
> 
> 
> 


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