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Hey, may be a long shot, but is it nessecary to use a voice coil? Analog is not really needed in this application. Why Couldn't I use a digital signal routed through a stepper motor? The stepper would likely
be a bit jittery, but this might not be important as we are creating pressure, not sound. I suppose that there
would be a need for a modified Analog to digital converter, but there are a lot of digital abilities out there and only one Analog rotary subwoofer. Lastly, any interest in a treadmill motor? They are usually brushless and work well :scratch:with speed control.
 

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Don't believe this was ever built, the primary hangup being the linear motor. I believe Steve Callas was working with Fi at one point a long time ago for a custom motor to drive it but that's where it stalled. I believe a modified sub motor is probably the cheapest way to go but not the easiet in terms of integration to linkage to the fan. There are some off the self linear voice coil motors available (BEI kimco, moticont) but they're pricey $800-1300 and still require mods and mounts. Moticont now offer hollow models since I was interested in this, but one with an ID large enough to accomodate commonly available linear bearings and similar BL to high powered sub are around $1300. A sub motor could be used but you'd have to bore a hole through the back plate and pole piece and then theres the attachment of linkage from the coil/former to the blades. Not sure how machining friendly the alloys used for magnetics are since they're mostly iron.

your RC copter swashplate has a lot in common and really only needs a linear VC motor axially mounted but stationary to the shaft riding on a linear bearing.

I've looked into the bits and pieces and don't really think one of these could be constructed for less than $2500 or there abouts, as you'd spend $1000 or so on the VC motor, 500-1000 in machining to modify,mounts, framework, a few hundred in linkage, small rod end bearings, shafts, and linear bearings, you'd also have a few hundred in a VFD and fan motor. then there's the machining of the fan hub, bushings,bearings for blade shafts, etc. you'd also need some flat stock for fans blades.

This would make for an awesome project but is not cheap or trivial that's for sure.
 

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What if the solution is to think inside-out, so to speak? The complication of the idea is connecting the voice coil to the blades, correct? So what if you didn't have to? Move the coil from the center to the circumference of the fan. Then use small magnets in the tip of each blade. The suspension could be in the hub of the fan. Or the fan could have a ring around the circumference to house the suspension. It would probably be most effective with two coils- one in front of and one behind the fan in a push/pull configuration. You could also use two magnets in each blade- one on the leading edge and one on the trailing edge with their polarities opposite each other.

With the coils and magnets arranged in this way you could use much smaller, more affordable magnets. And there would be no complicated machining. I'd recommend carbon fiber for the blades since it is light and stiff.

The design in my head is best explained as being like a spoke wheel from a horse-drawn carriage. The rim would have a "C" cross section to shroud the tips of the blades and hold the suspension. Each "spoke" of the wheel would provide the necessary structure and act as the axis for one of the blades. This fan "wheel" would then spin as a unit inside the housing just like any other fan.

Now that I think about it, the voice coil could stay at the center if that's best from an electromagnetic perspective. The only thing different about my plan is removing the mechanical link between the voice coil and the fan blades by simply putting the magnets in the blades. I realize using multiple small magnets may not produce as much power as one large magnet. But they may be sufficient for this application given the apparent efficiency of the rotary design.
 

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This has been done.
I have no posts on here so it wont let me post a link, but check out Chris Hudlin on youtube. He has videos with the sub he made..
It is very cool,
Im in the process of ordering all the stuff to make my own with carbon fiber blades!
 

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Bueller.......

Any more info on this as far as someone else building one as Chris Hudlin's DIY setup is what I was going to try if not?
He has full instructions via a "How To" PDF and his YouTube are also excellent!
 
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