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Building a triple stator axial flux motor

Awesome low tech mfg! very nice end product, congrats mate!

I have one question: Why did you put the coils in the plastic and the magnets in the aluminium? Shouldn't it be in reverse for heat dissipation of the coils?

Keep up the good work and best of luck!
 
at lebowski: in theory how many motors could you have running axially to each other, is there any limiting factor,
just a thought: have different windings running on separate controllers, a bit of a failsafe incase a controller blows,
you could still get back home.
 
Miles said:
h0tr0d said:
I have one question: Why did you put the coils in the plastic and the magnets in the aluminium? Shouldn't it be in reverse for heat dissipation of the coils?
Click to expand...
That would just create more heat...
Click to expand...
Care to elaborate?
 
H0tr0d.

Anything that conducts electricity will cause eddy currents. So having the coils in anything conductive while the magnet moves past it will create an eddy break.
 
Arlo1 said:
H0tr0d.

Anything that conducts electricity will cause eddy currents. So having the coils in anything conductive while the magnet moves past it will create an eddy break.
Click to expand...
Ok, that's a fair statement. But there is no problem on the aluminium rotor?
Even so, some calcs would be fun. Normally eddy losses are very low but the cooling effect could be interesting.
Thanks Arlin
 
h0tr0d said:
Arlo1 said:
H0tr0d.

Anything that conducts electricity will cause eddy currents. So having the coils in anything conductive while the magnet moves past it will create an eddy break.
Click to expand...
Ok, that's a fair statement. But there is no problem on the aluminium rotor?
Even so, some calcs would be fun. Normally eddy losses are very low but the cooling effect could be interesting.
Thanks Arlin
Click to expand...
Uhm try sliding a magnet down a peice of aluminum.

This is why the shape and side of the magnets vs the coils is crucial to get right in a AF motor if you have a magnet following the same arc of a winding it will cause eddy currents. SO you will usually see magnets smaller then the radial measurement of the coils.
 
Way cool project, makes me want to build such a motor!
 
Arlo1 said:
Uhm try sliding a magnet down a peice of aluminum.

This is why the shape and side of the magnets vs the coils is crucial to get right in a AF motor if you have a magnet following the same arc of a winding it will cause eddy currents. SO you will usually see magnets smaller then the radial measurement of the coils.
Click to expand...

My question, in other words, was why not a plastic rotor also. No problem with eddy currents on the rotor? Sorry if this really is a very basic question...
Abraço
 
h0tr0d said:
Arlo1 said:
Uhm try sliding a magnet down a peice of aluminum.

This is why the shape and side of the magnets vs the coils is crucial to get right in a AF motor if you have a magnet following the same arc of a winding it will cause eddy currents. SO you will usually see magnets smaller then the radial measurement of the coils.
Click to expand...

My question, in other words, was why not a plastic rotor also. No problem with eddy currents on the rotor? Sorry if this really is a very basic question...
Abraço
Click to expand...
Why not read a book on the subject and get a broader understanding of how forces are applied?

The one I've been using covers a good deal of info: Axial Flux Permanent Magnet Brushless Machines
Authors: Jacek F. Gieras, Rong-Jie Wang, Maarten J. Kamper
Publication Date: June 6, 2008 | ISBN-10: 1402069936 | ISBN-13: 978-1402069932 | Edition: 2nd
A good reference, more comprehensive than any other so far, though I found that it is missing some continuity if reading from end-to-end. All equation examples in the book are available in a CD inserted on the back cover and expressed in Mathcad - however I found that is an expensive application for an individual to own.

Personally I would suggest reading across many sources to develop a broader perspective on application. Some authors use different formulas to arrive at the same conclusions; by reading many sources a common thread, a baseline of essential equations and understanding will become apparent. I also use tools like FEMM to model concepts and advance theoretical design. Though having basic knowledge of physics and materials is crucial to answering your question. And I could tell you that answer... like giving you a fish so you can feed yourself today, or I can teach you how to fish for yourself. We all fish differently. :)

Here's your pole. KF :wink:
 
h0tr0d said:
Arlo1 said:
Uhm try sliding a magnet down a peice of aluminum.

This is why the shape and side of the magnets vs the coils is crucial to get right in a AF motor if you have a magnet following the same arc of a winding it will cause eddy currents. SO you will usually see magnets smaller then the radial measurement of the coils.
Click to expand...

My question, in other words, was why not a plastic rotor also. No problem with eddy currents on the rotor? Sorry if this really is a very basic question...
Abraço
Click to expand...

The way I see it (didn't read any books...) you get eddy currents when you have a piece of metal in a changing magnetic field.

The stator sees a varying magnetic field, so there should be no metal there or, if you really want metal, it should be laminated (as is done with radial flux motors)

The rotor does not see a varying magnetic field, only a constant field. Therefore you can use metal here.
The rotor is exposed to the varying magnetic field of the stator, but this makes the rotor turn in such a way that
RELATIVE to the rotor there's no varying magnetic field.
 
KingFish: Thanks for the reference, I'll save that "pole" for future use (It's wasn't a "hunger" question, it was more like a "craving") :D
Seriously, ever thought about writing a book? You have some very good writing capabilities...

Lebowski: That was the answer I was looking for, thanks.
Edit: Question answered on page 1... :p
 
I have thought before about rolling or coiling Metglas to make inductors for axial flux motors.
http://www.metglas.com/products/magnetic_materials/2605sa1.asp
Geometrically speaking, coiling is really good, right?

Looking at the Launchpoint coreless motor, we, apparently, don't need a core for awesome power density, just a well thought geometry like Luke said...
 
these are a few pictures of the typical chain tensioner that I use
the ball bearings are from a sports shop. 16 roller blade wheel bearings for very cheap :mrgreen:
the little chain wheel is from a rear mech.
DSC01313.jpg
DSC01314.jpg
DSC01315.jpg
 
Hey with all this talk about Iron cores, Have you considered a powdered Iron mix and play with the ratios.

You can even make a sort of paint or putty. Would this increase induction? And would an Iron resin mix be easier to works shapes with?
 
Hi Lebowski

Thanks for sharing this build. Dig reading your posts and now I am ruined as to which motor design to try as my first motor build. Can not stop thinking about this simple design and came across a post that miles referenced on a circuit board ironless stator design AF motor. This has certainly killed any efforts I had toward chasing iron stampings, at least for the moment. Is there No coging on your motor. Lots still to learn on all the tradeoffs.

cheers
 
yep, there's no cogging. It runs a smooth and easy as a bicycle wheel.

I've made some testruns with the motor of this thread and it runs extremely good.
It's used in a mid-drive and the power is just amazing, more than 2kW mechanical output
run through gears really works :D climbs the 13% hill up to my street without me even
putting it in the lowest gear :D

If you're thinking about building a motor like this, I think the design is ideal for having
the parts made with laser or water cutting. All the rotor plates, back iron and attachment
pieces for the Deore axle are made from flat steel or aluminium, perfect for automated cutting.
This really takes the main work out of the build, it should then be easy to build in about
40 or so hours. The main job remaining will be the glueing of the coils, all the rest is just
assembly work (maybe some thread cutting)

I posted an update after one year of commuting to work with my v1 AF motor
http://endless-sphere.com/forums/viewtopic.php?f=6&t=39338&p=810005#p810005
 
Like it. Back iron can be Swiss cheesed :lol: (sorry, could not resist) and lightened where not needed easily with a water jet. Thinking that coils could be encapsulated in the stator structure possibly in expanding foam type insulation while between two well waxed fixture plates or wound on plastic bobbins to aid bonding them down quickly. Not sure how all these factors would effect the flux. Lots more to learn before heading out onto something like this.

cheers
 
interesting tidbit of information:

http://physics.stackexchange.com/questions/17200/can-magnetic-fields-be-redirected-and-focused-at-one-point

apparently it is possible to use a cone-shaped piece of iron on top of your magnets to focus a magnetic field. :D

This opens the possibility to have iron cones on top of all the rotor magnets. With the fields thus focussed
to a smaller area, the center hole in the coils can be made smaller than the magnet size -> the total length
of wire for a certain amount of turns is reduced -> less resistance -> more efficiency and/or for the same losses
more power.

would be interesting to see a FEMM simulation.... now I have to figure this tool out.
 
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