Follow along with the video below to see how to install our site as a web app on your home screen.
Note: This feature may not be available in some browsers.
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.
The original discussion was about reversing the propeller don't knowFMurtz <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.
On 27/12/2017 3:02 PM, Sylvia Else wrote:
On 26/12/2017 5:54 PM, Sylvia Else wrote:
I decided I was unwilling to be defeated, and a fair amount of
soldering, heatshrinking and hot gluing later, I got it to work.
https://www.youtube.com/watch?v=GWB9I33k-Rs
Sylvia.
One issue I haven't addressed is that the fan is held on by a left-hand
threaded nut, because a right-hand threaded nut will tend to undo itself
in this application. Since I've reverse the direction, I really need the
nut to be right-hand threaded, but there's no way I can change the
threadedness of the shaft.
May need to use some more hot glue - we'll see.
Sylvia.
On 27/12/2017 3:02 PM, Sylvia Else wrote:
On 26/12/2017 5:54 PM, Sylvia Else wrote:
I decided I was unwilling to be defeated, and a fair amount of soldering,
heatshrinking and hot gluing later, I got it to work.
https://www.youtube.com/watch?v=GWB9I33k-Rs
One issue I haven't addressed is that the fan is held on by a left-hand
threaded nut, because a right-hand threaded nut will tend to undo itself
in this application. Since I've reverse the direction, I really need the
nut to be right-hand threaded, but there's no way I can change the
threadedness of the shaft.
May need to use some more hot glue - we'll see.
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.
???? If you reversed the motor the air would blow the other way with theFMurtz <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.
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.
On 27/12/2017 3:02 PM, Sylvia Else wrote:
On 26/12/2017 5:54 PM, Sylvia Else wrote:
I decided I was unwilling to be defeated, and a fair amount of
soldering, heatshrinking and hot gluing later, I got it to work.
https://www.youtube.com/watch?v=GWB9I33k-Rs
Sylvia.
One issue I haven't addressed is that the fan is held on by a left-hand
threaded nut, because a right-hand threaded nut will tend to undo itself
in this application. Since I've reverse the direction, I really need the
nut to be right-hand threaded, but there's no way I can change the
threadedness of the shaft.
May need to use some more hot glue - we'll see.
OK I took the cover off a 3 blade fan that turns clockwise. I removedFMurtz <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.
On 26/12/2017 5:54 PM, Sylvia Else wrote:
I decided I was unwilling to be defeated, and a fair amount of
soldering, heatshrinking and hot gluing later, I got it to work.
https://www.youtube.com/watch?v=GWB9I33k-Rs
Sylvia.
On 27/12/2017 3:02 PM, Sylvia Else wrote:
On 26/12/2017 5:54 PM, Sylvia Else wrote:
I decided I was unwilling to be defeated, and a fair amount of
soldering, heatshrinking and hot gluing later, I got it to work.
https://www.youtube.com/watch?v=GWB9I33k-Rs
Sylvia.
One issue I haven't addressed is that the fan is held on by a left-hand
threaded nut, because a right-hand threaded nut will tend to undo itself
in this application. Since I've reverse the direction, I really need the
nut to be right-hand threaded, but there's no way I can change the
threadedness of the shaft.
May need to use some more hot glue - we'll see.
Sylvia.
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.
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
On 12/26/2017 10:02 PM, Sylvia Else wrote:
On 26/12/2017 5:54 PM, Sylvia Else wrote:
I decided I was unwilling to be defeated, and a fair amount of
soldering, heatshrinking and hot gluing later, I got it to work.
https://www.youtube.com/watch?v=GWB9I33k-Rs
Sylvia.
 Is this just to confuse one of your coworkers?
                       Mikek
One issue I haven't addressed is that the fan is held on by a left-hand
threaded nut, because a right-hand threaded nut will tend to undo itself
in this application. Since I've reverse the direction, I really need the
nut to be right-hand threaded, but there's no way I can change the
threadedness of the shaft.
May need to use some more hot glue - we'll see.
Sylvia.
I used nine of the big glue sticks yesterday to fix a really dumb
bathroom light fixture. Hot-melt is interesting; it seems more like an
epoxy reaction than just melting stuff. If it just melted, you
couldn't get anything positioned before it cooled.
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.
Get one of these,amdx wrote:
On 12/26/2017 10:02 PM, Sylvia Else wrote:
On 26/12/2017 5:54 PM, Sylvia Else wrote:
I decided I was unwilling to be defeated, and a fair amount of
soldering, heatshrinking and hot gluing later, I got it to work.
https://www.youtube.com/watch?v=GWB9I33k-Rs
Sylvia.
  Is this just to confuse one of your coworkers?
                        Mikek
I made this clock for that.
https://imgur.com/a/gwPXM