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Groups > sci.electronics.design > #489320 > unrolled thread
| Started by | Sylvia Else <sylvia@not.at.this.address> |
|---|---|
| First post | 2017-12-26 17:54 +1100 |
| Last post | 2017-12-27 18:40 -0500 |
| Articles | 20 on this page of 65 — 24 participants |
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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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| From | FMurtz <haggisz@hotmail.com> |
|---|---|
| Date | 2017-12-27 15:57 +1100 |
| Message-ID | <xLF0C.152308$Cr5.114083@fx36.iad> |
| In reply to | #489346 |
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. > If you reversed the motor, you would also reverse the blades because although the blades would pass air either way ,they work more efficiently
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| From | Sylvia Else <sylvia@not.at.this.address> |
|---|---|
| Date | 2017-12-27 09:50 +1100 |
| Message-ID | <fag21nF8dvaU1@mid.individual.net> |
| In reply to | #489339 |
On 27/12/2017 5:21 AM, 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? > > No. Imagine you have a piece of right-hand threaded rod. Whichever end you look at it from, it's still right-hand threaded. Sylvia.
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| From | whit3rd <whit3rd@gmail.com> |
|---|---|
| Date | 2017-12-26 18:55 -0800 |
| Message-ID | <2ead0efc-09f6-4a45-b947-b5c15a2a9866@googlegroups.com> |
| In reply to | #489339 |
On Tuesday, December 26, 2017 at 10:22:11 AM UTC-8, 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? No. The fan blades are a right-hand screw whether pointed forward or backward. You'd have to scan 'em and invert the Z coordinate axis and 3D print a new set, or reach into a mirror and pull out the image.
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| From | Steve Wilson <no@spam.com> |
|---|---|
| Date | 2017-12-27 05:40 +0000 |
| Message-ID | <XnsA8586DD37A7Bidtokenpost@69.16.179.22> |
| In reply to | #489339 |
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? Many turbine propeller aircraft can reduce their landing roll by placing the propellers in reverse pitch. The blades are still turning in the same direction, but the thrust vector is reversed. They are not very efficient in this mode, but are still able to slow the aircraft. To visualize what would happen in a pedestal fan, imagine turning it around 180 degrees. The motor is still spinning the propeller in the same direction, but the thrust vector is reversed in relation to the floor. In order to reverse the thrust vector, either the propeller pitch has to be reversed, or the motor has to be reversed. John is right. Doing both would cancel.
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| From | FMurtz <haggisz@hotmail.com> |
|---|---|
| Date | 2017-12-27 17:24 +1100 |
| Message-ID | <61H0C.24094$uY5.14366@fx21.iad> |
| In reply to | #489377 |
Steve Wilson wrote: > 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? > > Many turbine propeller aircraft can reduce their landing roll by placing the > propellers in reverse pitch. The blades are still turning in the same > direction, but the thrust vector is reversed. They are not very efficient in > this mode, but are still able to slow the aircraft. > > To visualize what would happen in a pedestal fan, imagine turning it around > 180 degrees. The motor is still spinning the propeller in the same direction, > but the thrust vector is reversed in relation to the floor. > > In order to reverse the thrust vector, either the propeller pitch has to be > reversed, or the motor has to be reversed. > > John is right. Doing both would cancel. > Wrong,reversing motor would reverse air flow, reversing the propeller would be same air direction but would put the leading edge in the right position for efficiency.
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| From | Steve Wilson <no@spam.com> |
|---|---|
| Date | 2017-12-27 07:12 +0000 |
| Message-ID | <XnsA8581666945CAidtokenpost@69.16.179.22> |
| In reply to | #489378 |
FMurtz <haggisz@hotmail.com> wrote: > Steve Wilson wrote: >> 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? >> Many turbine propeller aircraft can reduce their landing roll by >> placing the propellers in reverse pitch. The blades are still turning >> in the same direction, but the thrust vector is reversed. They are not >> very efficient in this mode, but are still able to slow the aircraft. >> To visualize what would happen in a pedestal fan, imagine turning it >> around 180 degrees. The motor is still spinning the propeller in the >> same direction, but the thrust vector is reversed in relation to the >> floor. >> In order to reverse the thrust vector, either the propeller pitch has >> to be reversed, or the motor has to be reversed. >> John is right. Doing both would cancel. > Wrong,reversing motor would reverse air flow, reversing the propeller > would be same air direction but would put the leading edge in the right > position for efficiency. Wrong. Think about it. Reversing the propeller pitch reverses the thrust vector. This is how turbine aircraft shorten their landing roll.
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| From | FMurtz <haggisz@hotmail.com> |
|---|---|
| Date | 2017-12-27 18:40 +1100 |
| Message-ID | <L7I0C.55485$qV5.23752@fx37.iad> |
| In reply to | #489381 |
Steve Wilson wrote: > FMurtz <haggisz@hotmail.com> wrote: > >> Steve Wilson wrote: >>> 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? > >>> Many turbine propeller aircraft can reduce their landing roll by >>> placing the propellers in reverse pitch. The blades are still turning >>> in the same direction, but the thrust vector is reversed. They are not >>> very efficient in this mode, but are still able to slow the aircraft. > >>> To visualize what would happen in a pedestal fan, imagine turning it >>> around 180 degrees. The motor is still spinning the propeller in the >>> same direction, but the thrust vector is reversed in relation to the >>> floor. > >>> In order to reverse the thrust vector, either the propeller pitch has >>> to be reversed, or the motor has to be reversed. > >>> John is right. Doing both would cancel. > >> Wrong,reversing motor would reverse air flow, reversing the propeller >> would be same air direction but would put the leading edge in the right >> position for efficiency. > > Wrong. Think about it. Reversing the propeller pitch reverses the thrust > vector. This is how turbine aircraft shorten their landing roll. > > The original discussion was about reversing the propeller don't know where the pitch comes in (missed that) you would not be likely to reverse the pitch on a simple fan.
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| From | Steve Wilson <no@spam.com> |
|---|---|
| Date | 2017-12-27 12:34 +0000 |
| Message-ID | <XnsA8584CFAC9278idtokenpost@69.16.179.22> |
| In reply to | #489382 |
FMurtz <haggisz@hotmail.com> wrote: > The original discussion was about reversing the propeller don't know > where the pitch comes in (missed that) > you would not be likely to reverse the pitch on a simple fan. Requires new fan blades with reversed pitch.
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| From | FMurtz <haggisz@hotmail.com> |
|---|---|
| Date | 2017-12-28 00:36 +1100 |
| Message-ID | <olN0C.22128$P14.8141@fx01.iad> |
| In reply to | #489389 |
Steve Wilson wrote: > FMurtz <haggisz@hotmail.com> wrote: > >> The original discussion was about reversing the propeller don't know >> where the pitch comes in (missed that) >> you would not be likely to reverse the pitch on a simple fan. > > Requires new fan blades with reversed pitch. > ???? If you reversed the motor the air would blow the other way with the same blade except that the leading edge would be on the wrong side, so you would reverse the blade without altering pitch to rectify that,IE take it off shaft reverse it and pit it back.
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| From | rickman <gnuarm@gmail.com> |
|---|---|
| Date | 2017-12-27 17:59 -0500 |
| Message-ID | <p218lc$k8v$1@dont-email.me> |
| In reply to | #489389 |
Steve Wilson wrote on 12/27/2017 7:34 AM: > FMurtz <haggisz@hotmail.com> wrote: > >> The original discussion was about reversing the propeller don't know >> where the pitch comes in (missed that) >> you would not be likely to reverse the pitch on a simple fan. > > Requires new fan blades with reversed pitch. That's not the topic of conversation. The OP wishes to reverse the entire propeller on the shaft. That rotates the pitch by 180 degrees which is only a change at all if the blades are not symmetrical which they likely aren't. It does not actually change the pitch, it changes the shape of the blades compared to the rotation. -- Rick C Viewed the eclipse at Wintercrest Farms, on the centerline of totality since 1998
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| From | krw@notreal.com |
|---|---|
| Date | 2017-12-27 09:39 -0500 |
| Message-ID | <91c74dta5hvi3hce4hhbbpilir3bjo63j3@4ax.com> |
| In reply to | #489381 |
On Wed, 27 Dec 2017 07:12:07 GMT, Steve Wilson <no@spam.com> wrote: >FMurtz <haggisz@hotmail.com> wrote: > >> Steve Wilson wrote: >>> 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? > >>> Many turbine propeller aircraft can reduce their landing roll by >>> placing the propellers in reverse pitch. The blades are still turning >>> in the same direction, but the thrust vector is reversed. They are not >>> very efficient in this mode, but are still able to slow the aircraft. > >>> To visualize what would happen in a pedestal fan, imagine turning it >>> around 180 degrees. The motor is still spinning the propeller in the >>> same direction, but the thrust vector is reversed in relation to the >>> floor. > >>> In order to reverse the thrust vector, either the propeller pitch has >>> to be reversed, or the motor has to be reversed. > >>> John is right. Doing both would cancel. > >> Wrong,reversing motor would reverse air flow, reversing the propeller >> would be same air direction but would put the leading edge in the right >> position for efficiency. > >Wrong. Think about it. Reversing the propeller pitch reverses the thrust >vector. This is how turbine aircraft shorten their landing roll. No, as others have pointed out, a right-hand screw is still a right-hand screw if you insert it the other end of a nut. Reversing the pitch of a propeller changes it from a right-hand screw to a left-hand screw.
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| From | amdx <nojunk@knology.net> |
|---|---|
| Date | 2017-12-27 10:45 -0600 |
| Message-ID | <p20io8$bsp$1@dont-email.me> |
| In reply to | #489381 |
On 12/27/2017 1:12 AM, Steve Wilson wrote:
> FMurtz <haggisz@hotmail.com> wrote:
>
>> Steve Wilson wrote:
>>> 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?
>
>>> Many turbine propeller aircraft can reduce their landing roll by
>>> placing the propellers in reverse pitch. The blades are still turning
>>> in the same direction, but the thrust vector is reversed. They are not
>>> very efficient in this mode, but are still able to slow the aircraft.
>
>>> To visualize what would happen in a pedestal fan, imagine turning it
>>> around 180 degrees. The motor is still spinning the propeller in the
>>> same direction, but the thrust vector is reversed in relation to the
>>> floor.
>
>>> In order to reverse the thrust vector, either the propeller pitch has
>>> to be reversed, or the motor has to be reversed.
>
>>> John is right. Doing both would cancel.
>
>> Wrong,reversing motor would reverse air flow, reversing the propeller
>> would be same air direction but would put the leading edge in the right
>> position for efficiency.
>
> Wrong. Think about it. Reversing the propeller pitch reverses the thrust
> vector. This is how turbine aircraft shorten their landing roll.
>
>
OK I took the cover off a 3 blade fan that turns clockwise. I removed
the blade put it on backwards. The fan still blows air in the same
direction. It doesn't blow very much air though.
Certainly is some design consideration in the way the blade is curved.
Mikek
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| From | tabbypurr@gmail.com |
|---|---|
| Date | 2017-12-27 09:01 -0800 |
| Message-ID | <5fdda9b3-30ff-42e4-ab86-cd9f9bea8501@googlegroups.com> |
| In reply to | #489403 |
On Wednesday, 27 December 2017 16:46:09 UTC, amdx wrote: > On 12/27/2017 1:12 AM, Steve Wilson wrote: > > FMurtz <haggisz@hotmail.com> wrote: > >> Steve Wilson wrote: > >>> 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? > > > >>> Many turbine propeller aircraft can reduce their landing roll by > >>> placing the propellers in reverse pitch. The blades are still turning > >>> in the same direction, but the thrust vector is reversed. They are not > >>> very efficient in this mode, but are still able to slow the aircraft. > > > >>> To visualize what would happen in a pedestal fan, imagine turning it > >>> around 180 degrees. The motor is still spinning the propeller in the > >>> same direction, but the thrust vector is reversed in relation to the > >>> floor. > > > >>> In order to reverse the thrust vector, either the propeller pitch has > >>> to be reversed, or the motor has to be reversed. > > > >>> John is right. Doing both would cancel. > > > >> Wrong,reversing motor would reverse air flow, reversing the propeller > >> would be same air direction but would put the leading edge in the right > >> position for efficiency. > > > > Wrong. Think about it. Reversing the propeller pitch reverses the thrust > > vector. This is how turbine aircraft shorten their landing roll. > > > > > OK I took the cover off a 3 blade fan that turns clockwise. I removed > the blade put it on backwards. The fan still blows air in the same > direction. It doesn't blow very much air though. > Certainly is some design consideration in the way the blade is curved. > Mikek so if you then also change the motor direction, you get reverse flow with good efficiency. It's ain't rocket science, it's fan science. NT
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| From | amdx <nojunk@knology.net> |
|---|---|
| Date | 2017-12-27 12:34 -0600 |
| Message-ID | <p20p2r$48g$1@dont-email.me> |
| In reply to | #489407 |
On 12/27/2017 11:01 AM, tabbypurr@gmail.com wrote:
> On Wednesday, 27 December 2017 16:46:09 UTC, amdx wrote:
>> On 12/27/2017 1:12 AM, Steve Wilson wrote:
>>> FMurtz <haggisz@hotmail.com> wrote:
>>>> Steve Wilson wrote:
>>>>> 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?
>>>
>>>>> Many turbine propeller aircraft can reduce their landing roll by
>>>>> placing the propellers in reverse pitch. The blades are still turning
>>>>> in the same direction, but the thrust vector is reversed. They are not
>>>>> very efficient in this mode, but are still able to slow the aircraft.
>>>
>>>>> To visualize what would happen in a pedestal fan, imagine turning it
>>>>> around 180 degrees. The motor is still spinning the propeller in the
>>>>> same direction, but the thrust vector is reversed in relation to the
>>>>> floor.
>>>
>>>>> In order to reverse the thrust vector, either the propeller pitch has
>>>>> to be reversed, or the motor has to be reversed.
>>>
>>>>> John is right. Doing both would cancel.
>>>
>>>> Wrong,reversing motor would reverse air flow, reversing the propeller
>>>> would be same air direction but would put the leading edge in the right
>>>> position for efficiency.
>>>
>>> Wrong. Think about it. Reversing the propeller pitch reverses the thrust
>>> vector. This is how turbine aircraft shorten their landing roll.
>>>
>>>
>> OK I took the cover off a 3 blade fan that turns clockwise. I removed
>> the blade put it on backwards. The fan still blows air in the same
>> direction. It doesn't blow very much air though.
>> Certainly is some design consideration in the way the blade is curved.
>> Mikek
>
> so if you then also change the motor direction, you get reverse flow with good efficiency. It's ain't rocket science, it's fan science.
>
>
> NT
>
Obviously we have a bunch of Rocket Scientists here because the fan
science was under dispute. I didn't know so I got the fan out and
checked it. Sylia knew, it's not intuitive or it would not have been
disputed.
After a failure of a ceiling fan, I replaced it with a new one.
It has just a tad less air where our bed is, I'd like to increase the
angle just a few degrees or put a horizontal tip on the the end of each
blade to push air away from the center.
A 3D printer would be very handy.
Mikek
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| From | rickman <gnuarm@gmail.com> |
|---|---|
| Date | 2017-12-27 18:03 -0500 |
| Message-ID | <p218u6$k8v$2@dont-email.me> |
| In reply to | #489410 |
amdx wrote on 12/27/2017 1:34 PM: > On 12/27/2017 11:01 AM, tabbypurr@gmail.com wrote: >> On Wednesday, 27 December 2017 16:46:09 UTC, amdx wrote: >>> On 12/27/2017 1:12 AM, Steve Wilson wrote: >>>> FMurtz <haggisz@hotmail.com> wrote: >>>>> Steve Wilson wrote: >>>>>> 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? >>>> >>>>>> Many turbine propeller aircraft can reduce their landing roll by >>>>>> placing the propellers in reverse pitch. The blades are still turning >>>>>> in the same direction, but the thrust vector is reversed. They are not >>>>>> very efficient in this mode, but are still able to slow the aircraft. >>>> >>>>>> To visualize what would happen in a pedestal fan, imagine turning it >>>>>> around 180 degrees. The motor is still spinning the propeller in the >>>>>> same direction, but the thrust vector is reversed in relation to the >>>>>> floor. >>>> >>>>>> In order to reverse the thrust vector, either the propeller pitch has >>>>>> to be reversed, or the motor has to be reversed. >>>> >>>>>> John is right. Doing both would cancel. >>>> >>>>> Wrong,reversing motor would reverse air flow, reversing the propeller >>>>> would be same air direction but would put the leading edge in the right >>>>> position for efficiency. >>>> >>>> Wrong. Think about it. Reversing the propeller pitch reverses the thrust >>>> vector. This is how turbine aircraft shorten their landing roll. >>>> >>>> >>> OK I took the cover off a 3 blade fan that turns clockwise. I removed >>> the blade put it on backwards. The fan still blows air in the same >>> direction. It doesn't blow very much air though. >>> Certainly is some design consideration in the way the blade is curved. >>> Mikek >> >> so if you then also change the motor direction, you get reverse flow with >> good efficiency. It's ain't rocket science, it's fan science. >> >> >> NT >> > Obviously we have a bunch of Rocket Scientists here because the fan science > was under dispute. I didn't know so I got the fan out and checked it. Sylia > knew, it's not intuitive or it would not have been disputed. It is hardly non-intuitive. They just weren't paying attention to the problem. Anyone can muck up even an intuitive issue if they just plain don't consider the problem and instead drag in irrelevancies like what aircraft do. They just needed to actually look at the type of fan in question. From then on the problem *is* very intuitive. > After a failure of a ceiling fan, I replaced it with a new one. > It has just a tad less air where our bed is, I'd like to increase the > angle just a few degrees or put a horizontal tip on the the end of each > blade to push air away from the center. You mean a vertical tip? The blades should already be horizontal and push the air downward (or upward if you reverse the direction of rotation). -- Rick C Viewed the eclipse at Wintercrest Farms, on the centerline of totality since 1998
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| From | tabbypurr@gmail.com |
|---|---|
| Date | 2017-12-27 15:18 -0800 |
| Message-ID | <778a36a5-1a97-4db2-88d6-e95d1dfa66a6@googlegroups.com> |
| In reply to | #489418 |
On Wednesday, 27 December 2017 23:04:42 UTC, rickman wrote: > amdx wrote on 12/27/2017 1:34 PM: > > After a failure of a ceiling fan, I replaced it with a new one. > > It has just a tad less air where our bed is, I'd like to increase the > > angle just a few degrees or put a horizontal tip on the the end of each > > blade to push air away from the center. > > You mean a vertical tip? The blades should already be horizontal and push > the air downward (or upward if you reverse the direction of rotation). doing either would overload the motor, unless you remove blade area elsewhere NT
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| From | amdx <nojunk@knology.net> |
|---|---|
| Date | 2017-12-28 09:18 -0600 |
| Message-ID | <p23204$36t$1@dont-email.me> |
| In reply to | #489418 |
On 12/27/2017 5:03 PM, rickman wrote: > amdx wrote on 12/27/2017 1:34 PM: >> On 12/27/2017 11:01 AM, tabbypurr@gmail.com wrote: >>> On Wednesday, 27 December 2017 16:46:09 UTC, amdx wrote: >>>> On 12/27/2017 1:12 AM, Steve Wilson wrote: >>>>> FMurtz <haggisz@hotmail.com> wrote: >>>>>> Steve Wilson wrote: >>>>>>> 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? >>>>> >>>>>>> Many turbine propeller aircraft can reduce their landing roll by >>>>>>> placing the propellers in reverse pitch. The blades are still >>>>>>> turning >>>>>>> in the same direction, but the thrust vector is reversed. They >>>>>>> are not >>>>>>> very efficient in this mode, but are still able to slow the >>>>>>> aircraft. >>>>> >>>>>>> To visualize what would happen in a pedestal fan, imagine turning it >>>>>>> around 180 degrees. The motor is still spinning the propeller in the >>>>>>> same direction, but the thrust vector is reversed in relation to the >>>>>>> floor. >>>>> >>>>>>> In order to reverse the thrust vector, either the propeller pitch >>>>>>> has >>>>>>> to be reversed, or the motor has to be reversed. >>>>> >>>>>>> John is right. Doing both would cancel. >>>>> >>>>>> Wrong,reversing motor would reverse air flow, reversing the propeller >>>>>> would be same air direction but would put the leading edge in the >>>>>> right >>>>>> position for efficiency. >>>>> >>>>> Wrong. Think about it. Reversing the propeller pitch reverses the >>>>> thrust >>>>> vector. This is how turbine aircraft shorten their landing roll. >>>>> >>>>> >>>> OK I took the cover off a 3 blade fan that turns clockwise. I >>>> removed >>>> the blade put it on backwards. The fan still blows air in the same >>>> direction. It doesn't blow very much air though. >>>> Certainly is some design consideration in the way the blade is >>>> curved. >>>> Mikek >>> >>> so if you then also change the motor direction, you get reverse flow >>> with >>> good efficiency. It's ain't rocket science, it's fan science. >>> >>> >>> NT >>> >> Obviously we have a bunch of Rocket Scientists here because the fan >> science >> was under dispute. I didn't know so I got the fan out and checked it. >> Sylia >> knew, it's not intuitive or it would not have been disputed. > > It is hardly non-intuitive. They just weren't paying attention to the > problem. Anyone can muck up even an intuitive issue if they just plain > don't consider the problem and instead drag in irrelevancies like what > aircraft do. They just needed to actually look at the type of fan in > question. From then on the problem *is* very intuitive. > > >> After a failure of a ceiling fan, I replaced it with a new one. >> It has just a tad less air where our bed is, I'd like to increase the >> angle just a few degrees or put a horizontal tip on the the end of each >> blade to push air away from the center. > > You mean a vertical tip? The blades should already be horizontal and > push the air downward (or upward if you reverse the direction of rotation). > Yes, I do mean a vertical tip.
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| From | Sylvia Else <sylvia@not.at.this.address> |
|---|---|
| Date | 2017-12-28 12:38 +1100 |
| Message-ID | <faj09fFsqq6U2@mid.individual.net> |
| In reply to | #489410 |
On 28/12/2017 5:34 AM, amdx wrote: > On 12/27/2017 11:01 AM, tabbypurr@gmail.com wrote: >> On Wednesday, 27 December 2017 16:46:09 UTC, amdx wrote: >>> On 12/27/2017 1:12 AM, Steve Wilson wrote: >>>> FMurtz <haggisz@hotmail.com> wrote: >>>>> Steve Wilson wrote: >>>>>> 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? >>>>>> Many turbine propeller aircraft can reduce their landing roll by >>>>>> placing the propellers in reverse pitch. The blades are still turning >>>>>> in the same direction, but the thrust vector is reversed. They are >>>>>> not >>>>>> very efficient in this mode, but are still able to slow the aircraft. >>>>>> To visualize what would happen in a pedestal fan, imagine turning it >>>>>> around 180 degrees. The motor is still spinning the propeller in the >>>>>> same direction, but the thrust vector is reversed in relation to the >>>>>> floor. >>>>>> In order to reverse the thrust vector, either the propeller pitch has >>>>>> to be reversed, or the motor has to be reversed. >>>>>> John is right. Doing both would cancel. >>>>> Wrong,reversing motor would reverse air flow, reversing the propeller >>>>> would be same air direction but would put the leading edge in the >>>>> right >>>>> position for efficiency. >>>> >>>> Wrong. Think about it. Reversing the propeller pitch reverses the >>>> thrust >>>> vector. This is how turbine aircraft shorten their landing roll. >>>> >>>> >>> OK I took the cover off a 3 blade fan that turns clockwise. I removed >>> the blade put it on backwards. The fan still blows air in the same >>> direction. It doesn't blow very much air though. >>> Certainly is some design consideration in the way the blade is >>> curved. >>> Mikek >> >> so if you then also change the motor direction, you get reverse flow >> with good efficiency. It's ain't rocket science, it's fan science. >> >> >> NT >> > Obviously we have a bunch of Rocket Scientists here because the fan > science was under dispute. I didn't know so I got the fan out and > checked it. Sylia knew, it's not intuitive or it would not have been > disputed. > > After a failure of a ceiling fan, I replaced it with a new one. > It has just a tad less air where our bed is, I'd like to increase the > angle just a few degrees or put a horizontal tip on the the end of each > blade to push air away from the center. Ceiling fan blades tend not to be anything like the right shape. The ones I have are just flat with a bent edge. Properly aerodynamic ones are available but are expensive, and, in truth, look a bit odd. Sylvia.
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| From | M Philbrook <jamie_ka1lpa@charter.net> |
|---|---|
| Date | 2017-12-30 09:41 -0500 |
| Message-ID | <MPG.34b16facaac4ada898a086@news.eternal-september.org> |
| In reply to | #489410 |
In article <p20p2r$48g$1@dont-email.me>, nojunk@knology.net says... > > On 12/27/2017 11:01 AM, tabbypurr@gmail.com wrote: > > On Wednesday, 27 December 2017 16:46:09 UTC, amdx wrote: > >> On 12/27/2017 1:12 AM, Steve Wilson wrote: > >>> FMurtz <haggisz@hotmail.com> wrote: > >>>> Steve Wilson wrote: > >>>>> 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? > >>> > >>>>> Many turbine propeller aircraft can reduce their landing roll by > >>>>> placing the propellers in reverse pitch. The blades are still turning > >>>>> in the same direction, but the thrust vector is reversed. They are not > >>>>> very efficient in this mode, but are still able to slow the aircraft. > >>> > >>>>> To visualize what would happen in a pedestal fan, imagine turning it > >>>>> around 180 degrees. The motor is still spinning the propeller in the > >>>>> same direction, but the thrust vector is reversed in relation to the > >>>>> floor. > >>> > >>>>> In order to reverse the thrust vector, either the propeller pitch has > >>>>> to be reversed, or the motor has to be reversed. > >>> > >>>>> John is right. Doing both would cancel. > >>> > >>>> Wrong,reversing motor would reverse air flow, reversing the propeller > >>>> would be same air direction but would put the leading edge in the right > >>>> position for efficiency. > >>> > >>> Wrong. Think about it. Reversing the propeller pitch reverses the thrust > >>> vector. This is how turbine aircraft shorten their landing roll. > >>> > >>> > >> OK I took the cover off a 3 blade fan that turns clockwise. I removed > >> the blade put it on backwards. The fan still blows air in the same > >> direction. It doesn't blow very much air though. > >> Certainly is some design consideration in the way the blade is curved. > >> Mikek > > > > so if you then also change the motor direction, you get reverse flow with good efficiency. It's ain't rocket science, it's fan science. > > > > > > NT > > I am glad you Rocket experts aren't talking about centrifugal impellers.. ;)
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| From | makolber@yahoo.com |
|---|---|
| Date | 2018-01-03 13:48 -0800 |
| Message-ID | <a60e337d-2638-4083-ada8-ed4fae5845f6@googlegroups.com> |
| In reply to | #489732 |
On Saturday, December 30, 2017 at 9:41:08 AM UTC-5, M Philbrook wrote: > In article <p20p2r$48g$1@dont-email.me>, nojunk@knology.net says... > > > > On 12/27/2017 11:01 AM, tabbypurr@gmail.com wrote: > > > On Wednesday, 27 December 2017 16:46:09 UTC, amdx wrote: > > >> On 12/27/2017 1:12 AM, Steve Wilson wrote: > > >>> FMurtz <haggisz@hotmail.com> wrote: > > >>>> Steve Wilson wrote: > > >>>>> 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? > > >>> > > >>>>> Many turbine propeller aircraft can reduce their landing roll by > > >>>>> placing the propellers in reverse pitch. The blades are still turning > > >>>>> in the same direction, but the thrust vector is reversed. They are not > > >>>>> very efficient in this mode, but are still able to slow the aircraft. > > >>> > > >>>>> To visualize what would happen in a pedestal fan, imagine turning it > > >>>>> around 180 degrees. The motor is still spinning the propeller in the > > >>>>> same direction, but the thrust vector is reversed in relation to the > > >>>>> floor. > > >>> > > >>>>> In order to reverse the thrust vector, either the propeller pitch has > > >>>>> to be reversed, or the motor has to be reversed. > > >>> > > >>>>> John is right. Doing both would cancel. > > >>> > > >>>> Wrong,reversing motor would reverse air flow, reversing the propeller > > >>>> would be same air direction but would put the leading edge in the right > > >>>> position for efficiency. > > >>> > > >>> Wrong. Think about it. Reversing the propeller pitch reverses the thrust > > >>> vector. This is how turbine aircraft shorten their landing roll. > > >>> > > >>> > > >> OK I took the cover off a 3 blade fan that turns clockwise. I removed > > >> the blade put it on backwards. The fan still blows air in the same > > >> direction. It doesn't blow very much air though. > > >> Certainly is some design consideration in the way the blade is curved. > > >> Mikek > > > > > > so if you then also change the motor direction, you get reverse flow with good efficiency. It's ain't rocket science, it's fan science. > > > > > > > > > NT > > > > > I am glad you Rocket experts aren't talking about centrifugal > impellers.. > > ;) next topic, why does swapping I and Q cause a spectral inversion? :-) mark
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