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
Is this just to confuse one of your coworkers? 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
Looks like that motor has an internal cooling fan, which now will not be very effective.
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
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.
I suppose I could look that up.
-- John Larkin Highland Technology, Inc trk jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Phase change requires a bunch of energy input/output. One common hotmelt glue is PVA.
NT
There's no internal cooling fan. This is a 40W machine. There's a limit on how hot it can get.
Sylvia.
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
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.
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
doing either would overload the motor, unless you remove blade area elsewhere
NT
It's not the watts so much as watt density that determines temperature rise.
No longer needed. The main fan blade is cooling the motor!
-- Rick C Viewed the eclipse at Wintercrest Farms, on the centerline of totality since 1998
Ah, the scientific method. I hadn't actually tried it, since I knew the efficiency would be reduced and I was starting with a new unassembled fan. Interesting that the difference is significant.
Sylvia.
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.
I made this clock for that.
heat-activiated thermoset formulations seem like a good idea, but wouldn't that clog the gun?
-- This email has not been checked by half-arsed antivirus software
No, it is not!
reversesing the proprellor changes the blade pitch by 180 degrees,
Aircraft make smaller changes to the pitch so that the slope of the blades reverses,
180 degrees gets you approximately back where you started.-- This email has not been checked by half-arsed antivirus software
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** Here we go again .......**FYI:
The term "pitch" = the distance moved by a prop's tips in one turn. The same term also applies to threads and similar.
However, "reversing" a prop means moving the blades through neutral to the the opposite pitch - used by aircraft and boats to achieve movement in the reverse direction.
.... Phil
Yes, I do mean a vertical tip.
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