Ceiling fans starting full speed - Why?

[jpanhalt]

A little OT, but my log home has high ceilings ( pitch = 12:12) and lots of ceiling fans. The problem is that two of them are on a single beam in a large room (26' x 26' with 26' ceiling) and it is impossible to keep them synchronized so they don't "beat". In the olden days, multi-engine aircraft had "synchrophasers" (e.g., B-29). I have been keeping an eye open for something that will do the same. Needless to say, they are hard to reach.

 

[ronsimpson]

synchrophaser

Fan motors synchrophaser using chain gears. Some assembly needed.

synchrophaser

 

[jpanhalt]

That would be very neat, but hard to install.

John

 

[MaxHeadRoom78]

Looks like a Tellurion.
Max.

 

[JimB]

Fan motors synchrophaser using chain gears. Some assembly needed.

That picture reminds me of a splash screen in some piece of software which I used during my "day job".
The picture in the screen was a 3D CAD drawing of 3 or 4 gears which could never ever mesh together, the pitch of the teeth was all wrong. That felt quite appropriate, in several ways.!

JimB

 

[Ramussons]

The title should have been

Ceiling fans starting at full speed setting- Why?

 

[MaxHeadRoom78]

Looked into this further and came up with this.
Before the DIAC triggering device fires, the capacitor must charge to 28 or so volts. However, if the voltage at the end of the cycle is insufficient to trigger the DIAC, the next half-cycle starts with C1 charged in the incorrect polarity so that it takes all the longer for C1 to discharge through zero and then charge to the opposite threshold.
After the DIAC initially fires, this condition changes substantially so that the phase delay angle is reduced and the motor snaps on at a minimum rpm –sometimes higher than desired .
Circuit can be modified to prevent this if needed.
Max.

 

[Triode]

That picture reminds me of a splash screen in some piece of software which I used during my "day job".
The picture in the screen was a 3D CAD drawing of 3 or 4 gears which could never ever mesh together, the pitch of the teeth was all wrong. That felt quite appropriate, in several ways.!

JimB

My schools chapter of the ASME had a logo with three gears meshed together in a triangular formation. The teeth would fit, but due to the rotation direction of gears 1 and 3 this arrangement could never move. I always found that kind of funny.