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OpenMotor

by bitswype, published

OpenMotor by bitswype Feb 2, 2013

Description

I've always loved motors. I had the nutty idea to design an "open source" motor that could be printed and built using nothing more than magnet wire, some patience and a few off the shelf components like skate bearings and the like. I developed a parametric openscad script for designing the coil forms and structure of the motor, printed a few pieces then got pulled away. This is what I was able to complete. The idea was this was to be a simple 3 phase induction motor. The electronics required to drive it would be complicated, but the motor itself is dirt simple, 3 coils and a core. The SCAD script generates all the pieces.

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I recently had the idea to use iron waste tin cans with flat walls to make custom magnetic circuits. With plate shears one can cut many identical shapes and stack them - this is way faster than sawing and filing. When the plate-iron of the used cans is lacquered with advertisement you even get eddy current suppression for free.

All you'd need here (to BOOST this motors performance SEVERAL ORDERS OF MAGNITUDE) is a template from the cross-section of the coil holder part and a cross section of the rotor (a circle) to mark where to cut the sheet-iron. (The outer part of the coil holder needs to be made quite a bit thicker to sufficiently close the magnetic circuit). For minimizing cutting effort you could use printed parts for the inner side coil wire retention and furthermore printed geometry for sheet-iron alignment and sheet iron compression (to remove air-gaps from bent dents in the sheet). The latter two could be done by boring holes through the stack and clamping with screws instead (M3?). To keep the air-gaps as small as possible cut the iron-sheets slightly over-sized on the sides where the magnetic circuit is supposed to close and file them to the correct common size when the stacks are assembled.

I'd suggest to add three plate-iron-stack wedges between the coil holder segments. This way the rotor-stator-air-gap can be adjusted while the air-gap between the three coil-holder segments can be kept zero.
It might add a lot of "webars" to each wound segment if they can be filled with nails. There is iron in motors because just a coil produces a poorly performing magnetic field. Iron has the ability to soak up the magnetism from the coil which adds to the field of the coil.
Brushless DC motors are commonly used in electric RC airplanes and 'copters. Controllers for them are fairly cheap and readily available from many hobby stores and online sources.

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License

OpenMotor by bitswype is licensed under the Creative Commons - Attribution license.

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Instructions

print 2 endplates and the forms. Wind the forms with magnet wire and place a solid electrically conductive (does not have to be magnetic) core within the forms, preferably with small shafts to support it on either side. If you dont want a working motor, you can also print the armature (add support for the bottom shaft) and you have all the pieces of the "open motor". There are also some blank winding forms under "motor.stl" for fun.

My hope is that someone will be inspired by this, and take it one more step : )

BTW, there was some gnarly math to get the endplates to look like that, intersecting circles at specific points and all that ... :D
It might add a lot of "webars" to each wound segment if they can be filled with nails. There is iron in motors because just a coil produces a poorly performing magnetic field. Iron has the ability to soak up the magnetism from the coil which adds to the field of the coil.
Sep 13, 2014 - Modified Sep 13, 2014
mechadense - in reply to gddeen
I recently had the idea to use iron waste tin cans with flat walls to make custom magnetic circuits. With plate shears one can cut many identical shapes and stack them - this is way faster than sawing and filing. When the plate-iron of the used cans is lacquered with advertisement you even get eddy current suppression for free.

All you'd need here (to BOOST this motors performance SEVERAL ORDERS OF MAGNITUDE) is a template from the cross-section of the coil holder part and a cross section of the rotor (a circle) to mark where to cut the sheet-iron. (The outer part of the coil holder needs to be made quite a bit thicker to sufficiently close the magnetic circuit). For minimizing cutting effort you could use printed parts for the inner side coil wire retention and furthermore printed geometry for sheet-iron alignment and sheet iron compression (to remove air-gaps from bent dents in the sheet). The latter two could be done by boring holes through the stack and clamping with screws instead (M3?). To keep the air-gaps as small as possible cut the iron-sheets slightly over-sized on the sides where the magnetic circuit is supposed to close and file them to the correct common size when the stacks are assembled.

I'd suggest to add three plate-iron-stack wedges between the coil holder segments. This way the rotor-stator-air-gap can be adjusted while the air-gap between the three coil-holder segments can be kept zero.
Nice! Any link to a driver able to power such motor?
bitswype - in reply to fma
Sorry, no. I was going to build one since I don't know if there is anything easily available to drive this motor. A stepper driver might work. Maybe : )
Brushless DC motors are commonly used in electric RC airplanes and 'copters. Controllers for them are fairly cheap and readily available from many hobby stores and online sources.
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