Stepper Motor specs for big project.

Discussion in 'The Projects Forum' started by AceScottie, Jul 17, 2017.

  1. AceScottie

    Thread Starter New Member

    Jul 17, 2017
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    I am wanting to start a project later this year.
    I am looking for a stepper motor that can spin anywhere between 300-600Kg at about 30-60RPM.

    I know there is a lot of math involved and its something im not good at.
    I asked a friend who worked it out at 10,000Nm but i can only find a motor for 50Nm so doesnt sound right to me.
    preferably the motor needs to accellarate quite quickly, but if it takes 2-3 seconds to reach 30-60RPM that should be fine.

    Can anyone help me selecting a motor if it even exists.

    it will be spinning a hollow sphere made from steel with the motor on one side and a bearing on the other.
    Thanks for any help you can provide.
     
  2. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    Distance of sphere to bearing ? Or is the shaft thru center of sphere ?
    Connection method, flexible or ridged ?
    Diameter & skin thickness of sphere ?
     
  3. strantor

    AAC Fanatic!

    Oct 3, 2010
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    Would it work to have a wheel riding on the sphere to turn it?
     
  4. AceScottie

    Thread Starter New Member

    Jul 17, 2017
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    Was thinking of using a traction wheel instead but then there would be no way of getting any cables inside the sphere. I was intending on using slip ring connectors to connect power through.
    The sphere would be roughly 1.5m in diameter and have a fixed point where i connects to the motor and another fixed point on the other side running on a bearing.

    to be honest it would be 3 rings rather than 1 whole sphere, each ring would have a motor and step down in size.
    http://prntscr.com/fwtk9v its not perfect but thats a basic example.
     
  5. MaxHeadRoom

    Expert

    Jul 18, 2013
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    600kg is well over half a ton.
    Where does 300Kg-600Kg enter the picture.
    Is the weight of the item you are spinning Or?
    Much more info needed.
    It is amazing the amount of posters here that want a solution for a mechanism with virtually no details of the mechanism etc at ALL!
    Max.
     
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  6. Alec_t

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    Sep 17, 2013
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    Can't you make the structure a lot lighter? Use steel where strength is absolutely necessary, but use light-weight material in between?
    Follow the principle of aircraft designers: "Simplicate and add lightness".
     
    Last edited: Jul 17, 2017
  7. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Start by actually measuring the torque required to turn it empirically.
    Max.
     
  8. AceScottie

    Thread Starter New Member

    Jul 17, 2017
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    Its a gyroscope type device.
    it will mainly be spinning me :) in a hopefully very controlled manner.

    and well the steel for the rings (150cm should drop down to about 100cm for the inner rings) 150cm diamiter with 3cm thickness (maybe a bit less depending on answers from a metal worker), and 15cm deep gives a total weight of about 83Kg per ring. rounding a bit gives a total of 252Kg for all 3 rings.
    so:
    252Kg steel Rings
    63kg for me
    4kg for a seat
    10kg~ for misc stuff (plastic shell, computer, brackets, mounts, wires, connectors, computer components etc.)

    all in all about 319kg. then there is the weight of the motors to add on.of which i have no clue the weight.
    (i might be able to make the rings 150cmx7.5cmx1cm which will drastically reduce the weight but not sure about the stability of that till i get an email back from the metal workers)
    this will all be spinning across all 3 axis at a relatively nice speed

    I dont have a lot of information as the project is not due to start till September, but i want to do the initial material cost and planning so i can get a budget together on how much this is going to cost.
     
  9. strantor

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    Oct 3, 2010
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    I don't think steppers are the right answer for this. You're going to strap yourself inside a gyroscope and start moving it around, that is going to be an unpredictable and uneven load on the motors. I imagine sometimes they will be working against your inertia and sometimes your inertia will be working in the same direction, and try to over-spin the motors. It is challenging for steppers to do this. For this I would expect to see some torque-control motors. Regular DC motors with a speed limiting regen drive.
     
  10. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Definitely NOT steppers.:eek:
    Max.
     
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  11. Alec_t

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    Sep 17, 2013
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    Using only one motor and one bearing :confused:.
    I worry over the safety aspects of this project. You will be turning yourself into a massive flywheel. Any imbalance will impose large lateral forces on both motor(s) and bearing(s). The energy stored in 300kg of flywheel at 60rpm is considerable and capable of doing serious damage (if not to you, then to anyone/anything around you).
     
    Last edited: Jul 17, 2017
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  12. strantor

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    It's like a very exciting 3-part rotational guillotine that you get inside of. What could go wrong?! :p

    If I were to get inside it (not sure why I would), I would strap my head and all my limbs down so they don't fly into the blender.
     
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  13. shortbus

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  14. AceScottie

    Thread Starter New Member

    Jul 17, 2017
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    i do intend to have a plastic shell on the inside and one over the outside to prevent that, although might record throwing in a watermelon before i add that to see what happens XD

    And the seat will be fixed with a racing harness. i dont want it to spin fast enough to rag you around but enough to get some Gforce's happening the main point is going upside down. its meant for a space sim or flight sim.

    the entire think will be bolted to the ground and in a large warehouse. if anything does go wrong then it will hit the barriers (i wont be inside it while testing. i might be insane but i dont have a death wish)

    anyway i dont think i will get far without any motors, so any idea of the power i would need ? DC or otherwise ? my main requirement to solve this is is how much torque and possible an example of the motor needed.
     
  15. MaxHeadRoom

    Expert

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    Generally a project such as this is the mechanics are completed and then tests are done to establish the motor requirements.
    Max.
     
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  16. AceScottie

    Thread Starter New Member

    Jul 17, 2017
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    yea but an idea of where to start is what im looking for. i dont want to spend £300 each on motors just to realize they cant even spin a grape. or spend £35 each for them to just snap in half the second load is put on them. bit of an exaggeration but you get where im going.
     
  17. MaxHeadRoom

    Expert

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    Which is exactly what I said, The motors will be dependant on the final mechanical demands?
    You don't start with them!
    Max.
     
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  18. dendad

    Member

    Feb 20, 2016
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    Maybe you can use a couple of Fisher and Paykel washing machine BLDC motors, at least for a scale model test. They can spin a fairly large drum of water and clothes. There is a lot of info on them on line, but mostly for wind/hydro generators.
    Still, your project sounds quite crazy.
    I get motion sick on merry go rounds!
     
  19. strantor

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    Same family of motor control as stepped. I see it as being more challenging that need be.
     
  20. Bernard

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    Aug 7, 2008
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    Call me crazy but I just opened another can of worms. Space for the motors is very limited, less than 5 in.
    but a hydraulic motor can be fairly short like for example- 5.4 cu. in. White, torque 1430 in.
    lb. & 1985 intrmit. 4.53 in long. There are inline live swivels available. I don't relish sitting with my chin on my knees with 2000 lb. hot oil flowing around me.
     
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