DIY wooden-frame motor

[spinningmagnets]

Lock posted a link with a DIY motor that used strong neo magnets and copper wire coils, plus off-the shelf-bearings, but most of everything else was made of wood.

http://endless-sphere.com/forums/viewtopic.php?f=1&t=10697&start=30#p210297

I have been familiar for some time with the axial-flux, dual rotor, air-core Permanent Magnet Alternator (PMA) encouraged at www.otherpower.com. For less than $1,000 a builder can use a car spindle and brake disc, along with home-made wooden blades to make a wind-gen that performs about as well as commercial units that often cost over $9,000. There are similarities between some types of motors and generators.

What caught my eye the most was that this wooden motor had air-core coils. Actually filled with solid resin, but the point being there is no iron/steel in the centers. In the wind-gen PMA, air-core leads to low cogging and easy start-up in light winds. Wood can be fun to use in those places where it is possible to use it, but the real question is about building a DIY direct drive motor with very low cogging, in the size and shape you want.

For an application, I'm thinking along the lines of a Stoke-Monkey. I am not familiar with the design rules of permanent-magnets motors, could someone enlighten me as to the drawbacks?

 

[johnrobholmes]

When you don't have a steel stator, there aren't many drawbacks. You would need more copper to get the same flux, so copper losses will increase for a given power level. Lack of cogging is very nice though. It has me thinking about the "perfect" ebike motor for sure. Axial flux lends itself very well.

 

[spinningmagnets]

Here's a thread from an RC forum about making a DIY axial-flux motor. Its quite small, but the principles are the same, and it should scale up.

http://www.rcgroups.com/forums/showthread.php?t=227057

 

[amberwolf]

Another way to minimize cogging is to use parallelogram shaped magnets, so that each "pole" of the magnets overlap, so that there is no "locked" position for any pole to any magnet. I don't know how that affects efficiency, but it is how many induction AC motors are made (like cieling fans) in the flux ring iron, and I have seen BLDC motors and some generator designs that used this (in pictures, not IRL).

 

[karma]

i wana start one if i ever get off my lazzy ass. i have the magnets :wink: most of them pulls from hardrives.