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OT: Running a pedestal fan in reverse - failed - a rant of sorts.

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  OT: Running a pedestal fan in reverse - failed - a rant of sorts. Sylvia Else <sylvia@not.at.this.address> - 2017-12-26 17:54 +1100
    Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. Rheilly Phoull <froggins@iinet.net.au> - 2017-12-26 19:29 +0800
    Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. mpm <mpmillard@aol.com> - 2017-12-26 04:49 -0800
      Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. Sylvia Else <sylvia@not.at.this.address> - 2017-12-27 09:52 +1100
    Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. tabbypurr@gmail.com - 2017-12-26 06:07 -0800
      Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. Sylvia Else <sylvia@not.at.this.address> - 2017-12-27 09:58 +1100
        Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. mpm <mpmillard@aol.com> - 2017-12-26 18:52 -0800
          Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. Sylvia Else <sylvia@not.at.this.address> - 2017-12-27 14:57 +1100
    Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. John Larkin <jjlarkin@highlandtechnology.com> - 2017-12-26 10:21 -0800
      Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-12-26 11:48 -0700
      Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. rickman <gnuarm@gmail.com> - 2017-12-26 14:03 -0500
      Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. John S <Sophi.2@invalid.org> - 2017-12-26 14:31 -0600
        Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2017-12-26 15:44 -0500
          Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. John S <Sophi.2@invalid.org> - 2017-12-26 15:06 -0600
          Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. John S <Sophi.2@invalid.org> - 2017-12-26 16:16 -0600
          Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. John Larkin <jjlarkin@highlandtechnology.com> - 2017-12-26 17:26 -0800
            Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. Sylvia Else <sylvia@not.at.this.address> - 2017-12-27 14:42 +1100
        Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. not@telling.you.invalid (Computer Nerd Kev) - 2017-12-26 21:00 +0000
        Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. rickman <gnuarm@gmail.com> - 2017-12-26 18:37 -0500
        Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. "David Eather" <eather@tpg.com.au> - 2017-12-27 09:48 +1000
        Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. FMurtz <haggisz@hotmail.com> - 2017-12-27 15:57 +1100
      Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. Sylvia Else <sylvia@not.at.this.address> - 2017-12-27 09:50 +1100
      Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. whit3rd <whit3rd@gmail.com> - 2017-12-26 18:55 -0800
      Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. Steve Wilson <no@spam.com> - 2017-12-27 05:40 +0000
        Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. FMurtz <haggisz@hotmail.com> - 2017-12-27 17:24 +1100
          Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. Steve Wilson <no@spam.com> - 2017-12-27 07:12 +0000
            Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. FMurtz <haggisz@hotmail.com> - 2017-12-27 18:40 +1100
              Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. Steve Wilson <no@spam.com> - 2017-12-27 12:34 +0000
                Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. FMurtz <haggisz@hotmail.com> - 2017-12-28 00:36 +1100
                Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. rickman <gnuarm@gmail.com> - 2017-12-27 17:59 -0500
            Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. krw@notreal.com - 2017-12-27 09:39 -0500
            Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. amdx <nojunk@knology.net> - 2017-12-27 10:45 -0600
              Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. tabbypurr@gmail.com - 2017-12-27 09:01 -0800
                Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. amdx <nojunk@knology.net> - 2017-12-27 12:34 -0600
                  Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. rickman <gnuarm@gmail.com> - 2017-12-27 18:03 -0500
                    Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. tabbypurr@gmail.com - 2017-12-27 15:18 -0800
                    Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. amdx <nojunk@knology.net> - 2017-12-28 09:18 -0600
                  Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. Sylvia Else <sylvia@not.at.this.address> - 2017-12-28 12:38 +1100
                  Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. M Philbrook <jamie_ka1lpa@charter.net> - 2017-12-30 09:41 -0500
                    Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. makolber@yahoo.com - 2018-01-03 13:48 -0800
                      Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. DemonicTubes <tlackie@gmail.com> - 2018-01-03 14:08 -0800
                      Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2018-01-04 15:18 +0200
              Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. Sylvia Else <sylvia@not.at.this.address> - 2017-12-28 12:36 +1100
            Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. Jasen Betts <jasen@xnet.co.nz> - 2017-12-28 06:36 +0000
              Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. Phil Allison <pallison49@gmail.com> - 2017-12-28 00:16 -0800
        Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. Phil Allison <pallison49@gmail.com> - 2017-12-26 22:38 -0800
          Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. krw@notreal.com - 2017-12-27 09:40 -0500
    Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. Sylvia Else <sylvia@not.at.this.address> - 2017-12-27 15:02 +1100
      Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. Sylvia Else <sylvia@not.at.this.address> - 2017-12-27 18:11 +1100
        Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. FMurtz <haggisz@hotmail.com> - 2017-12-27 18:42 +1100
        Re: Running a pedestal fan in reverse - failed - a rant of sorts. "P E Schoen" <paul@pstech-inc.com> - 2017-12-27 03:17 -0500
        Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. tabbypurr@gmail.com - 2017-12-27 01:59 -0800
          Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. Sylvia Else <sylvia@not.at.this.address> - 2017-12-27 21:29 +1100
            Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2017-12-27 14:24 +0200
        Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. krw@notreal.com - 2017-12-27 09:43 -0500
        Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. John Larkin <jjlarkin@highlandtechnology.com> - 2017-12-27 11:25 -0800
          Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. tabbypurr@gmail.com - 2017-12-27 11:32 -0800
          Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. Jasen Betts <jasen@xnet.co.nz> - 2017-12-28 06:20 +0000
      Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. amdx <nojunk@knology.net> - 2017-12-27 10:50 -0600
        Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. FMurtz <haggisz@hotmail.com> - 2017-12-28 14:49 +1100
          Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. FMurtz <haggisz@hotmail.com> - 2017-12-29 11:34 +1100
      Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. bloggs.fredbloggs.fred@gmail.com - 2017-12-27 10:22 -0800
        Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. Sylvia Else <sylvia@not.at.this.address> - 2017-12-28 09:41 +1100
          Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. bloggs.fredbloggs.fred@gmail.com - 2017-12-27 15:29 -0800
        Re: OT: Running a pedestal fan in reverse - failed - a rant of sorts. rickman <gnuarm@gmail.com> - 2017-12-27 18:40 -0500

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#489320 — OT: Running a pedestal fan in reverse - failed - a rant of sorts.

For reasons I need not go into, I wanted to make a cheap pedestal fan 
blow backwards, by putting the fan on backwards, and running the motor 
in reverse.

The motor is a typical PSC motor, and reversing it should be just a 
matter of switching a pair of connections to put the capacitor into the 
other phase.

It took me a while to figure out which two wires to swap, but I'm 
confident I identified the correct two. Didn't work. After I'd 
reassembled it the motor didn't run at all, nor make any sound. I may 
have blown the thermal fuse while curing some heat shrink.

Not the failure surprised me - working on this motor is like doing brain 
surgery. The stator windings aren't terminated with insulated wire 
attached to the stator, but are just loose copper wires that are 
soldered to insulated wires, with the junctions covered with glass fiber 
tube, which are then bunched together and then attached to the stator 
with a couple of cable ties. While working on it, any careless movement 
can break a wire (and break one I did, but was able to solder it back).

How on Earth do they make these with any kind of reliability? Or is the 
labour so cheap that they're happy to throw away any that don't work 
after assembly.

The electrical separation of the two stator windings also depends on the 
enamel, and nothing else.

I question its claim to be double insulated - OK, the instructions do 
say not to run it unless it's fully assembled, but the typical punter 
wouldn't realise that the only thing preventing the metal shaft becoming 
live is the copper wire enamel.

Anyway, dead waste of $15.

Sylvia.

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#489325

On 26/12/2017 2:54 PM, Sylvia Else wrote:
> For reasons I need not go into, I wanted to make a cheap pedestal fan 
> blow backwards, by putting the fan on backwards, and running the motor 
> in reverse.
> 
> The motor is a typical PSC motor, and reversing it should be just a 
> matter of switching a pair of connections to put the capacitor into the 
> other phase.
> 
> It took me a while to figure out which two wires to swap, but I'm 
> confident I identified the correct two. Didn't work. After I'd 
> reassembled it the motor didn't run at all, nor make any sound. I may 
> have blown the thermal fuse while curing some heat shrink.
> 
> Not the failure surprised me - working on this motor is like doing brain 
> surgery. The stator windings aren't terminated with insulated wire 
> attached to the stator, but are just loose copper wires that are 
> soldered to insulated wires, with the junctions covered with glass fiber 
> tube, which are then bunched together and then attached to the stator 
> with a couple of cable ties. While working on it, any careless movement 
> can break a wire (and break one I did, but was able to solder it back).
> 
> How on Earth do they make these with any kind of reliability? Or is the 
> labour so cheap that they're happy to throw away any that don't work 
> after assembly.
> 
> The electrical separation of the two stator windings also depends on the 
> enamel, and nothing else.
> 
> I question its claim to be double insulated - OK, the instructions do 
> say not to run it unless it's fully assembled, but the typical punter 
> wouldn't realise that the only thing preventing the metal shaft becoming 
> live is the copper wire enamel.
> 
> Anyway, dead waste of $15.
> 
> Sylvia.
> 
> 

Yeah, you would expect better quality having spent all that money on it.

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#489327

On Tuesday, December 26, 2017 at 1:55:03 AM UTC-5, Sylvia Else wrote:
> For reasons I need not go into, I wanted to make a cheap pedestal fan 
> blow backwards, by putting the fan on backwards, and running the motor 
> in reverse.

Out of respect, I'm not going to ask why you didn't simply turn the pedestal fan around 180-degrees.  :)

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#489353

On 26/12/2017 11:49 PM, mpm wrote:
> On Tuesday, December 26, 2017 at 1:55:03 AM UTC-5, Sylvia Else wrote:
>> For reasons I need not go into, I wanted to make a cheap pedestal fan
>> blow backwards, by putting the fan on backwards, and running the motor
>> in reverse.
> 
> Out of respect, I'm not going to ask why you didn't simply turn the pedestal fan around 180-degrees.  :)
> 

Yes, because you realise that I've obviously thought of that, and have a 
reason why it's not sufficient.

Sylvia.

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#489332

On Tuesday, 26 December 2017 06:55:03 UTC, Sylvia Else  wrote:

> For reasons I need not go into, I wanted to make a cheap pedestal fan 
> blow backwards, by putting the fan on backwards, and running the motor 
> in reverse.
> 
> The motor is a typical PSC motor, and reversing it should be just a 
> matter of switching a pair of connections to put the capacitor into the 
> other phase.

the small mains fan motors I've played with have generally been shaded pole.

> It took me a while to figure out which two wires to swap, but I'm 
> confident I identified the correct two. Didn't work. After I'd 
> reassembled it the motor didn't run at all, nor make any sound. I may 
> have blown the thermal fuse while curing some heat shrink.
> 
> Not the failure surprised me - working on this motor is like doing brain 
> surgery. The stator windings aren't terminated with insulated wire 
> attached to the stator, but are just loose copper wires that are 
> soldered to insulated wires, with the junctions covered with glass fiber 
> tube, which are then bunched together and then attached to the stator 
> with a couple of cable ties. While working on it, any careless movement 
> can break a wire (and break one I did, but was able to solder it back).
> 
> How on Earth do they make these with any kind of reliability?

they don't

> Or is the 
> labour so cheap that they're happy to throw away any that don't work 
> after assembly.
> 
> The electrical separation of the two stator windings also depends on the 
> enamel, and nothing else.
> 
> I question its claim to be double insulated - OK, the instructions do 
> say not to run it unless it's fully assembled, but the typical punter 
> wouldn't realise that the only thing preventing the metal shaft becoming 
> live is the copper wire enamel.
> 
> Anyway, dead waste of $15.
> 
> Sylvia.

Spend twice that on a 1950s fan and it'll probably serve you for life.


NT

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#489354

On 27/12/2017 1:07 AM, tabbypurr@gmail.com wrote:
> On Tuesday, 26 December 2017 06:55:03 UTC, Sylvia Else  wrote:
> 
>> For reasons I need not go into, I wanted to make a cheap pedestal fan
>> blow backwards, by putting the fan on backwards, and running the motor
>> in reverse.
>>
>> The motor is a typical PSC motor, and reversing it should be just a
>> matter of switching a pair of connections to put the capacitor into the
>> other phase.
> 
> the small mains fan motors I've played with have generally been shaded pole.
> 

Yes, the small ones tend to be. None of the 40W pedestal fan motors I've 
had occasion to disassemble over the years (usually because they're 
seizing up) have been shaded-pole. Presumably there's some economic 
driver to this, but I don't know what it might be.

Sylvia.

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#489367

On Tuesday, December 26, 2017 at 5:58:30 PM UTC-5, Sylvia Else wrote:

> Yes, the small ones tend to be. None of the 40W pedestal fan motors I've 
> had occasion to disassemble over the years (usually because they're 
> seizing up) have been shaded-pole. Presumably there's some economic 
> driver to this, but I don't know what it might be.

Oh well, that's an easy one to answer:  GREED!  :)

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#489370

On 27/12/2017 1:52 PM, mpm wrote:
> On Tuesday, December 26, 2017 at 5:58:30 PM UTC-5, Sylvia Else wrote:
> 
>> Yes, the small ones tend to be. None of the 40W pedestal fan motors I've
>> had occasion to disassemble over the years (usually because they're
>> seizing up) have been shaded-pole. Presumably there's some economic
>> driver to this, but I don't know what it might be.
> 
> Oh well, that's an easy one to answer:  GREED!  :)
> 
> 

Well, no doubt, but the question is quite how that translates into using 
shaded pole for smaller motors and PSC for larger ones.

Sylvia.

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#489339

On Tue, 26 Dec 2017 17:54:51 +1100, Sylvia Else
<sylvia@not.at.this.address> wrote:

>For reasons I need not go into, I wanted to make a cheap pedestal fan 
>blow backwards, by putting the fan on backwards, and running the motor 
>in reverse.

Wouldn't those two things cancel?


-- 

John Larkin   Highland Technology, Inc   trk

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

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#489342

On Tue, 26 Dec 2017 10:21:55 -0800, John Larkin
<jjlarkin@highlandtechnology.com> wrote:

>On Tue, 26 Dec 2017 17:54:51 +1100, Sylvia Else
><sylvia@not.at.this.address> wrote:
>
>>For reasons I need not go into, I wanted to make a cheap pedestal fan 
>>blow backwards, by putting the fan on backwards, and running the motor 
>>in reverse.
>
>Wouldn't those two things cancel?

 {>8-} "putting the fan on backwards" ?>:-]
		
                                        ...Jim Thompson
-- 
| James E.Thompson                                 |    mens     |
| Analog Innovations                               |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
| STV, Queen Creek, AZ 85142    Skype: skypeanalog |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |
             
     It's what you learn, after you know it all, that counts.

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#489343

John Larkin wrote on 12/26/2017 1:21 PM:
> On Tue, 26 Dec 2017 17:54:51 +1100, Sylvia Else
> <sylvia@not.at.this.address> wrote:
>
>> For reasons I need not go into, I wanted to make a cheap pedestal fan
>> blow backwards, by putting the fan on backwards, and running the motor
>> in reverse.
>
> Wouldn't those two things cancel?

Turning the blads on backwards only makes them work less efficiently. 
Turning the motor backwards makes the air blow the other way, but also works 
the blades less efficiently.  Doing both makes the air blow the other way, 
but also allows the blades to work with the proper leading edge and so more 
efficiently.

-- 

Rick C

Viewed the eclipse at Wintercrest Farms,
on the centerline of totality since 1998

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#489346

On 12/26/2017 12:21 PM, John Larkin wrote:
> On Tue, 26 Dec 2017 17:54:51 +1100, Sylvia Else
> <sylvia@not.at.this.address> wrote:
> 
>> For reasons I need not go into, I wanted to make a cheap pedestal fan
>> blow backwards, by putting the fan on backwards, and running the motor
>> in reverse.
> 
> Wouldn't those two things cancel?


It seems to me that they would. Reversing the motor makes it blow in the 
opposite direction. Reversing the blades makes it blow in the opposite 
direction.

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#489347

On 12/26/2017 03:31 PM, John S wrote:
> On 12/26/2017 12:21 PM, John Larkin wrote:
>> On Tue, 26 Dec 2017 17:54:51 +1100, Sylvia Else
>> <sylvia@not.at.this.address> wrote:
>>
>>> For reasons I need not go into, I wanted to make a cheap pedestal fan
>>> blow backwards, by putting the fan on backwards, and running the motor
>>> in reverse.
>>
>> Wouldn't those two things cancel?
> 
> 
> It seems to me that they would. Reversing the motor makes it blow in the
> opposite direction. Reversing the blades makes it blow in the opposite
> direction.
> 

You'd need to mirror-image the blades to make them blow the other way
without reversing the motor, ISTM.  Just turning them round wouldn't do it.

Cheers

Phil Hobbs



-- 
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
https://hobbs-eo.com

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#489350

On 12/26/2017 2:44 PM, Phil Hobbs wrote:
> On 12/26/2017 03:31 PM, John S wrote:
>> On 12/26/2017 12:21 PM, John Larkin wrote:
>>> On Tue, 26 Dec 2017 17:54:51 +1100, Sylvia Else
>>> <sylvia@not.at.this.address> wrote:
>>>
>>>> For reasons I need not go into, I wanted to make a cheap pedestal fan
>>>> blow backwards, by putting the fan on backwards, and running the motor
>>>> in reverse.
>>>
>>> Wouldn't those two things cancel?
>>
>>
>> It seems to me that they would. Reversing the motor makes it blow in the
>> opposite direction. Reversing the blades makes it blow in the opposite
>> direction.
>>
> 
> You'd need to mirror-image the blades to make them blow the other way
> without reversing the motor, ISTM.  Just turning them round wouldn't do it.
> 
> Cheers
> 
> Phil Hobbs

 From Wikipedia:

Propeller-driven aircraft generate reverse thrust by changing the angle 
of their controllable-pitch propellers so that the propellers direct 
their thrust forward. This reverse thrust feature became available with 
the development of controllable-pitch propellers, which change the angle 
of the propeller blades to make efficient use of engine power over a 
wide range of conditions. Single-engine aircraft tend not to have 
reverse thrust. However, single-engine turboprop aircraft such as the 
PAC P-750 XSTOL,[6] Cessna 208 Caravan, and Pilatus PC-6 Porter do have 
this feature available.[citation needed]

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#489351

On 12/26/2017 2:44 PM, Phil Hobbs wrote:
> On 12/26/2017 03:31 PM, John S wrote:
>> On 12/26/2017 12:21 PM, John Larkin wrote:
>>> On Tue, 26 Dec 2017 17:54:51 +1100, Sylvia Else
>>> <sylvia@not.at.this.address> wrote:
>>>
>>>> For reasons I need not go into, I wanted to make a cheap pedestal fan
>>>> blow backwards, by putting the fan on backwards, and running the motor
>>>> in reverse.
>>>
>>> Wouldn't those two things cancel?
>>
>>
>> It seems to me that they would. Reversing the motor makes it blow in the
>> opposite direction. Reversing the blades makes it blow in the opposite
>> direction.
>>
> 
> You'd need to mirror-image the blades to make them blow the other way
> without reversing the motor, ISTM.  Just turning them round wouldn't do it.
> 
> Cheers
> 
> Phil Hobbs

I studied the situation a bit more. You are correct, Phil.

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#489361

On Tue, 26 Dec 2017 15:44:21 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

>On 12/26/2017 03:31 PM, John S wrote:
>> On 12/26/2017 12:21 PM, John Larkin wrote:
>>> On Tue, 26 Dec 2017 17:54:51 +1100, Sylvia Else
>>> <sylvia@not.at.this.address> wrote:
>>>
>>>> For reasons I need not go into, I wanted to make a cheap pedestal fan
>>>> blow backwards, by putting the fan on backwards, and running the motor
>>>> in reverse.
>>>
>>> Wouldn't those two things cancel?
>> 
>> 
>> It seems to me that they would. Reversing the motor makes it blow in the
>> opposite direction. Reversing the blades makes it blow in the opposite
>> direction.
>> 
>
>You'd need to mirror-image the blades to make them blow the other way
>without reversing the motor, ISTM.  Just turning them round wouldn't do it.
>
>Cheers
>
>Phil Hobbs

I guess it's like screw threads, same sense from either end. If it's a
shaded-pole motor, the only thing to do is heat-gun the blades.


-- 

John Larkin   Highland Technology, Inc   trk

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

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#489369

On 27/12/2017 12:26 PM, John Larkin wrote:
> On Tue, 26 Dec 2017 15:44:21 -0500, Phil Hobbs
> <pcdhSpamMeSenseless@electrooptical.net> wrote:
> 
>> On 12/26/2017 03:31 PM, John S wrote:
>>> On 12/26/2017 12:21 PM, John Larkin wrote:
>>>> On Tue, 26 Dec 2017 17:54:51 +1100, Sylvia Else
>>>> <sylvia@not.at.this.address> wrote:
>>>>
>>>>> For reasons I need not go into, I wanted to make a cheap pedestal fan
>>>>> blow backwards, by putting the fan on backwards, and running the motor
>>>>> in reverse.
>>>>
>>>> Wouldn't those two things cancel?
>>>
>>>
>>> It seems to me that they would. Reversing the motor makes it blow in the
>>> opposite direction. Reversing the blades makes it blow in the opposite
>>> direction.
>>>
>>
>> You'd need to mirror-image the blades to make them blow the other way
>> without reversing the motor, ISTM.  Just turning them round wouldn't do it.
>>
>> Cheers
>>
>> Phil Hobbs
> 
> I guess it's like screw threads, same sense from either end. If it's a
> shaded-pole motor, the only thing to do is heat-gun the blades.
> 
> 

One option whether it's a PSC motor or a shaded pole motor is to reverse 
the stator, and deal with any wire routing issues that arise. However, 
in the case of the motor I had, it's been designed to make reversing it 
impossible - perhaps so that the people used to assemble it can't get it 
wrong.

Mind you, I'd have thought connecting the multiple stator wires to their 
leads would be the biggest source of error.

Sylvia.

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#489349

In aus.electronics John S <Sophi.2@invalid.org> wrote:
> On 12/26/2017 12:21 PM, John Larkin wrote:
>> On Tue, 26 Dec 2017 17:54:51 +1100, Sylvia Else
>> <sylvia@not.at.this.address> wrote:
>> 
>>> For reasons I need not go into, I wanted to make a cheap pedestal fan
>>> blow backwards, by putting the fan on backwards, and running the motor
>>> in reverse.
>> 
>> Wouldn't those two things cancel?
> 
> It seems to me that they would. Reversing the motor makes it blow in the 
> opposite direction. Reversing the blades makes it blow in the opposite 
> direction.

I'm useless at this sort of thing, so I figured I'd get some practice
working it out:

A working solution to having a fan blow the other way is to turn it
around. The effect of this relative to an observer in a fixed position
is that the blades are rotated and the direction of spin is reversed.
So to have the fan blow the other way without rotating it requires
that the blades be rotated and spun in the opposite direction.

-- 
__          __
#_ < |\| |< _#

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#489356

John S wrote on 12/26/2017 3:31 PM:
> On 12/26/2017 12:21 PM, John Larkin wrote:
>> On Tue, 26 Dec 2017 17:54:51 +1100, Sylvia Else
>> <sylvia@not.at.this.address> wrote:
>>
>>> For reasons I need not go into, I wanted to make a cheap pedestal fan
>>> blow backwards, by putting the fan on backwards, and running the motor
>>> in reverse.
>>
>> Wouldn't those two things cancel?
>
>
> It seems to me that they would. Reversing the motor makes it blow in the
> opposite direction. Reversing the blades makes it blow in the opposite
> direction.

Reversing the blade does *not* make the fan blow in the opposite direction. 
Look at a fan blade and you will see this immediately.

-- 

Rick C

Viewed the eclipse at Wintercrest Farms,
on the centerline of totality since 1998

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#489359

On Wed, 27 Dec 2017 06:31:28 +1000, John S <Sophi.2@invalid.org> wrote:

> On 12/26/2017 12:21 PM, John Larkin wrote:
>> On Tue, 26 Dec 2017 17:54:51 +1100, Sylvia Else
>> <sylvia@not.at.this.address> wrote:
>>
>>> For reasons I need not go into, I wanted to make a cheap pedestal fan
>>> blow backwards, by putting the fan on backwards, and running the motor
>>> in reverse.
>>  Wouldn't those two things cancel?
>
>
> It seems to me that they would. Reversing the motor makes it blow in the  
> opposite direction. Reversing the blades makes it blow in the opposite  
> direction.
>

Turning the blade around just changes the relative position of what you  
would normally call the leading edge. If the fan still runs in the same  
direction it will still blow in the same direction but the once was  
leading edge is now the trailing edge. Sylvia has the process right. Trust  
an ex-aircraft model flyer on it.

-- 
The latest set of Shadow Broker tools shows the UK, USA, Canada,  
Australian and New Zealand spy agencies were hacking into domestic home  
routers. Who gave them permission to spy on our kids?

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