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

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

Sylvia.

I decided I was unwilling to be defeated, and a fair amount of soldering, heatshrinking and hot gluing later, I got it to work.

Sylvia.

If you reversed the motor, you would also reverse the blades because although the blades would pass air either way ,they work more efficiently

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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** Ouchhh !! He fell at the last fence !!!

Reversing a moulded fan blade on its drive shaft does NOT reverse the pitch - as pointed out by others here, it simply swaps leading edges for trailing ones.

FYI:

The DHC-4 Caribou and the Douglas DC6 series ( piston engine planes )have fully reversing props.

.... Phil

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.

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.

Thread seal or drill and tap propeller boss for a grub screw.

I don't think hot glue will be strong enough. It might be possible to cut right-hand threads over the left hand threads, but that would probably result in severe loss of strength. It might work for a very coarse thread with high helix angle, like the level wind mechanism on a fishing reel:

If there is enough length of thread on the shaft, you might be able to put a second nut on it and lock it in position once it's tight. Loc-tite on the threads might also work. Another method is to use a lock-nut, or create the equivalent by deforming the threads in the nut or on the shaft.

Paul

threadlock or superglue. I suspect it won't be needed though, it's not as if a pedestal fan applies much torque.

NT

Yes, I'll just wait and see. No point in fixing it if it's not broken.

Sylvia.

You might have old sticky nail polish around. Some drops in the thread at the joint of screw and nut will do.

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-TV

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.

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.

"Don't try this when airborne"

Loc-Tite. If you never want to restore the fan, Epoxe.