DIY BLDC motor

[hhoka]

Hey everyone, I'm thinking about building a brushless motor and I have a few questions.

I know the stator is made of steel plates, but what purpose does it serve and how can I replicate something like this? Also, how are the plates held together?

Do more windings improve the speed/torque of the motor?

Is the positive side of the coil the south or north pole?

Thanks 

[max_torque]

Despite being a fundamentally simple device, the modern high performance brushless motor is actually a subtle and somewhat complex device, where compromise is the aim of the game!

Factors such as lamination thickness, insulation, mechanical retention and material all make large differences to the performance of the eMachine. As do many other factors such as the winding scheme and the magnet geometry.

My suggestion other than doing a lot of Googling (plenty of people have built their own brushless motors on a DIY basis) would be to buy a small off-the-shelf motor from one of the usual suppliers, and take it apart and perhaps modify it to help you learn what factors matter the most.  It's a big topic, and potentially a lifes work, and these days, things like 3d magnetic simulation increasingly are used to optimise the performance of the eMachine.  And of course, once you have the eMachine itself, you need to drive it, so rapidly you'll find inverters and brushless motor drivers become an interesting topic!

one source for really cheap brushless "motors" is to use motorbike generators, cheaply available on ebay:



You'll need to sort out a basic bearing arrangement because the rotor is normally carried directly on the crankshaft, but that's not too difficult, and then you have a cheap motor to play with

(they are not very efficient, but great for messing around with!)

[amyk]

A lot of good information here: http://www.flyelectric.org.uk/motors.htm

[excitedbox]

To answer your question on the metal plates. Those metal plates are used to shape the magnetic field in the motor. Normally a magnetic field builds two circles around the magnet and going through North and South poles. This way most of the magnetic field gets pushed to one side of the magnet to increase the efficiency of the motor. Look into Hallbach arrays for a better understanding of what I am talking about.

 There are many videos on YouTube of people building pretty good bldc motors and even some plans for quite powerful ones. I think for a diy motor it is not necessary to worry about those metal plates and focusing the magnetic field. You will squeeze maybe 5-10% more power out of a given design. One 3d printed design on YouTube uses a plastic stator and produces a good amount of power.

Good luck and keep us updated. I love DC motors and would love to see your results.

[james_s]

A good place to start is modifying brushless spindle motors from old CD/DVD ROM drives, that's what the RC airplane guys were doing in the beginning before China started making millions of brushless motors and prices fell way down to where it's not really worth building anymore except for fun.