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Brushless motor from computer parts

video Brushless motor from computer parts

My aim is a completely DIY brushless hubmotor for electric assist on bicycles based on recycled parts.
This is prototype 2. Prototype 1 was just a quick lashup and 3 will be full scale testing.

28 comments

Mar 26, 2011. 4:30 AMploomus says:

Im thinking of doing similar thing for my bicycle to generate the power. I dont have the HDD magnets yet but ill try to find these. What do you think how does the size of coil matters much? I mean is the bigger coil better then smaller?

Mar 31, 2011. 4:23 AMomnibot (author) says:

Couldn't really say about the coils but I suggest matching their size as close as possible to the magnets.

Aug 18, 2010. 4:54 PMabadfart says:

very nice here in the us we have a festival called tour de fat which is a celebration of alternative vehicles and im building a very heavy bike so thank you for this

Aug 18, 2010. 7:39 PMabadfart says:

you could use the mount on a disk break hub to mount the magnets

May 18, 2010. 6:54 AMxxameht says:

those magnets that are used in hdd's are usually (when they are the size he is using) actually two magnets butted up to each other, insofar as they have more than 2 poles
each one has (im not sure) a NS-NS arrangment could make a bit of a difference if that were taken into consideration

May 16, 2010. 2:42 PMaeronut01 says:

Are you going to make an instructable on how to make one? Would be cool if you did.

May 18, 2010. 3:46 AMomnibot (author) says:

I might do that, actually. Hadn't planned on it but with one thing and another it's been growing in my mind. Can't promise anything but keep a lookout.

May 16, 2010. 4:08 PMkclo42112 says:

that would make a cool generator ,but would not be strong enough to power a bicycle. I once used a starter motor and a 12volt SLA battery from one of those kids power wagons,and that barely crept along,,I do plan on trying again with a ten speed ,so maybe the gears will help.

I think on your Idea it may work if the magnets were placed along the hub ,and a series of coils were placed on a hemicircle outside the rear tire,as stated ,it would not self start but in theory would sustain the momentum you are going for some time.Thats the only way i see any amount of torque coming from such a motor ,the thing would need to be almost the same diameter of the wheel itself

Apr 12, 2010. 2:47 PMkillersquirel11 says:

Those magnets look like they're from a hard drive.

Apr 21, 2010. 11:35 AMomnibot (author) says:

They are. The aim of this project is to recycle computerparts.

Apr 21, 2010. 6:53 PMkillersquirel11 says:

random fact: that type of motor is called an axial flux hub motor

Apr 23, 2010. 3:20 AMomnibot (author) says:

Tnx .. I've been trying to figure that out.

Jan 21, 2010. 8:54 AMprofpat says:

can you post your wiring schematic?

Oct 31, 2009. 8:35 PMsimonkoenig911 says:

how bout that 'ible?

Nov 6, 2009. 1:12 AMomnibot (author) says:

Wokring on it but can't promise anything yet, I'm short on magnets.

Nov 8, 2009. 4:40 AMsimonkoenig911 says:

Sep 11, 2009. 4:00 PMaaronanalog says:

Here is an idea : Could you use this as a generator instead of a motor ? If you have it on the wheel as you described then when you pedal it should be able to output power to a battery bank. If used this way with another motor you could probably charge the batteries while they push the bike for a range extender. I am learning about this stuff, so I could be wrong.

Sep 18, 2009. 5:36 AMomnibot (author) says:

Yes, it does work like a generator if you bypass the electronics and add a rectifier (diode-bridge) and that could indeed charge a battery. Doing this while using another motor for powering the bike however runs into the laws of thermodynamics .. basically you can't get more out than you put in. Powering a generator which powers the motor powering the generator sounds like a good idea until you try it ;) I'm still experimenting with this motor to learn more about timing, switching and practical uses while I look for more magnets for the final project. I regret every harddrive I ever threw away.

Mar 24, 2009. 6:12 PMparanoidelephant says:

Could you use the sensor as your accelerator? mount it on a rail and slide it back and forth over the coil, to change speed and possibly direction of your bike.

Mar 25, 2009. 4:06 PMomnibot (author) says:

That sounds like a logical non-programming approach. Much like an internal combustion motor this motor need it's point of "ignition" at the right place. The right place is often a compromise. One position could give more torque while another gives higher speed. It's possible that this is less effective though. As a reverse I think it is the only possible solution except for using a microprocessor. However .. this would only alter the point of activation of the coils and not change the amount of power used for the motor.

Mar 25, 2009. 5:51 PMparanoidelephant says:

even though it may be not as effective for constant speed, you probably would want higher torque for slow starts and uphill travel. just a thought

Mar 26, 2009. 3:37 AMomnibot (author) says:

True, I expect I'll find this out in the fullsize experiments.

Mar 16, 2009. 1:25 PMGMer56 says:

A double pole, double throw relay, right? How much force does this thing have?

Mar 16, 2009. 2:22 PMomnibot (author) says:

How much force does what have? The relay needs 12-30 Volts DC to switch and switches 250 Volts AC at 5 Amp. I'm still trying to work out how to measure the output from the motor but at 5 Volt it uses about 2.5 Amp making it 12.5 Watts if I'm not mistaken. Originally I tried it with just the halleffect-sensor but it almost burned out, got plenty of spares though :)

Mar 13, 2009. 7:09 PMdpsilver says:

u said that this one gets too hot at 12 v so may be installing a fan on one end of ur motor will help keep things cool

Mar 15, 2009. 7:55 AMomnibot (author) says:

Oh yes, that would probably help. It doesn't get so hot that it fails though and I expect that the final version will work better with more even coils, more coils and a current-limiting PWM. Using it outdoors will probably help heatdissapation a bit to. I'm just surprised it was this easy. This version pulls about 2,5 Amp at 5 volts so it has a bit of power. If I'm not mistaken that's around 12,5 Watts. Currently I'm looking at what configuration to use on the next one. 1,2, 3 or more phases. Also the relay is turning out to have trouble with higher speeds so depending on the RPM a MOSFET may be needed, I'm looking for that by taking stock of the parts in old CRT's.

Mar 2, 2009. 1:14 PMtieguy says:

Things you should do, 1. post this in instructable form. 2. boost the power, get it running at 30 MPH. 3. slap it on a skateboard and hope for the best. all this would be much appreciated, mainly the first.

Mar 2, 2009. 1:52 PMomnibot (author) says:

I thought about it but this just a prototype I've experimented and finished with. There will be an 'Ible on the next one whether it works well or not for improvements and such. There will be no slapping anything to anything, it will be built on a bike for that purpose.