Making power with old hard drives

Discussion in 'The Projects Forum' started by vortmax, Nov 2, 2012.

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  1. vortmax

    Thread Starter Member

    Oct 10, 2012
    This is a continuation of a thread I started in a different forum, but I think it belongs here now. The old thread is here:

    Basically what I am attempting to do is transform a hard drive into a cheap Tesla turbine generator that can put out enough power to drive a mcu and some other components. I have about 24 hours of research invested in this so far, so I decided to just take apart my drive and go for it.

    A Tesla turbine is a fin-less rotor design. It makes use of a stack of thin plates stacked closely to one another. When high speed air is blown tangentially across the edge, the air interacts with the rotors via viscosity and skin friction to accelerate them. As the air loses momentum, it travels towards the center of the rotor where it is exhausted out of drilled ports. This design is very simple and very stable at high RPMs.

    I am using a hard drive because the platters are already closely spaced (not ideally spaced, but good enough) and are already attached to a high speed bearing. The drive motor should be able to be coaxed into working like a generator as well, which eliminates adding additional hardware to the build.

    To try it out, I found an old SCSII server drive that has been kicking around my house for a few years. I completely gutted it, then re-installed the platter assembly. You can see the backside in the first picture where I have attached some hook up wires.

    I am running two of the contacts through a 1 Ohm resistor to place a load on the motor. The other two clips in the picture are running to my O-scope so I can take a look at the waveform and get a voltage measurement out of it.

    To spin the plates up to speed, I'm using a 20 psi air source and just holding the tip of the tube near the plates. This is not optimal and I am losing quite a bit of power doing this. The plates are also not vented yet, so the turbine is running at a small fraction of its potential output...but for a proof of concept, it gets the job done.

    Picture #2 is the Oscilloscope screen. You can see here the motor is producing a nice sine wave at 1.65V. With a 1 Ohm load, this is 1.65A or about 2.7W of power. I didn't have a helper to take this picture, so I had to set the air supply down. This let the drive spin down for a few seconds before I could snap the shot. Before setting the air down, the drive was up to just north of 3V (9W).

    In the next few weeks I'm going to vent the rotor, smooth out the pocket for the platters, make a real nozzle and try running higher pressures. I'm hoping these modifications will let me hit between 15 and 20W of power which should be plenty to run a small project.
  2. Papabravo


    Feb 24, 2006
    Aren't you wasting a boatload of power running the compressor to get the air to turn the platter? Why would you do such a thing?
  3. vortmax

    Thread Starter Member

    Oct 10, 2012
    simple answer....because I can.

    This is part of a competition project / demonstration piece to show off something cool. The electronics this controls are going to play midi files on a small pipe organ which requires compressed air we decided to up the geek factor and run the entire thing on compressed air.

    ...and these turbines are very robust when it comes to mixed phase and dirty inputs. They can run off of air, steam, combustion byproducts, long as the materials will handle the conditions. So if you wanted to go full blown steam punk, you could hook this up to a boiler.
  4. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    You might want to re-do that sine power calc... ;)

    And personally I think you will get MUCH better power output for the same amount of air using a more conventional turbine like a rotary vane type where the vanes are perpendicular to the air outlet nozzle.
  5. vortmax

    Thread Starter Member

    Oct 10, 2012
    yea you're right. Fell kind of stupid now. I still think once I bring everything into spec and hook it up to some big caps, I will get enough power to do something with it (I'm maxing out around 5000 RPM, when I need to up near 20k RPM under load). I'm also going to look into gearing it down and hooking it up to a better generator.

    And yes, I would get better power out of a conventional bladed turbine. I would also get better power out of a battery, or by rectifying line voltage....but where is the challenge in that?
  6. takao21203

    Distinguished Member

    Apr 28, 2012
    Tesla Turbine.
    1 Ohm resistor.
    20K RPM.

    If you connect the 1 Ohms resistor, do you get some negative velocity?
  7. vortmax

    Thread Starter Member

    Oct 10, 2012
    negative velocity? I'm not sure I understand what you mean. If I spin it up with no load, then attach the 1 Ohm resistor (or attach any load), then yes, it spins down (negative acceleration).
  8. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    OK, I get it, it's a cool project and I was not trying to stomp on your enthusiasm, just to help you make it work better.

    I made something similar, using a flat motor from a VCR "capstan motor" which like yours is a 3phase flat motor with permanent magnet rotor and 3 coil stator;


    It's a human powered lantern that is quite efficient at lighting a 1W LED from turning the crank.

    If you use 6 schottky diodes you can make a "3-phase bridge rectifier" (google that). The schottky diodes have a smaller voltage drop so they waste less power than normal diodes.

    Your motor coils will not be very efficient at 20k RPM, I would aim for only a few thousand RPM.

    The rotor type will be critical, if you can make something flat with little blades around the edge (and blow the air onto the little blades from a very close distance) you will get a HEAP more power out.

    You can get a small rotor like that out of a little $3 desktop vac cleaner they sell in the junk shops.
  9. don'tknow


    Feb 5, 2015
    very good job. I obviously need help. i have to make a generator out of vcr brushless motor... but everything has to be on its place.. the motor will be rotaded with another set of magnets V rail etc.. but thats not important. I need help with the inside of the motor .. how to rewind it ,what to connect on what.. damn.. i don't know. and yes. magnets have to spin , not the other way around. is that possible? if you manage to help me with this.. there is a god. i need this because thats all I need.. jk. this motor has all I need for this project but it does not generate power.. main problem . how to make it generate power? thank you if you're there.
  10. ronv

    AAC Fanatic!

    Nov 12, 2008
    Go back to the main page and click start a new thread, then fill in what you want.
    You will get better results over tacking on to an old thread.
  11. MrChips


    Oct 2, 2009
    Please do not revive an old thread. Start a new thread of your own.
    This thread is now locked.
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