Linear Actuators

Discussion in 'Hobby Engineering' started by Cynide, Nov 6, 2017.

  1. Cynide

    Cynide Member

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    Hi Guys!
    Hoping someone can help here and recommend a suitable product.

    I have an object that is 180mm tall, in a 200mm deep cavity, that i want to lift up by 180-200mm to be able to access it.
    Looking at linear actuators, any with a 180-200mm throw are all far far longer than 200mm in length and won't fit in the cavity (note the cavity has a lid over it when it's not in use).
    Is there an actuator that will allow me to do this, or do i need to use some form of belt drive and place the motor out of the way?
    The object will weigh about ~8kg, and I can always use 2 actuators (one at each end of it) if necessary.
    Speed of raising/lowering the object is not a major concern.
    I will have 12v power available to power it.

    Cheers!
     
  2. Gonadman2

    Gonadman2 Member

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    Threaded rod and a nut, with a drive on the end?
     
  3. mtma

    mtma Member

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    Until you reach the category of actuators known as telescopic actuators, the collapsed length is usually no less than the stroking length. There are also some neat actuators that push a strip of material out of them that can extend well beyond their collapsed lengths.

    A common method to approaching this problem is to use a scissor mechanism or reversed block and tackle type arrangement.
     
  4. RobRoySyd

    RobRoySyd Member

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    The scissor lift type of mechanism would be the best solution I can think of. Linear actuators don't like off axis loads so the "deck" would need to run in guides. With a scissor lift the electric/hydraulic actuators can be affixed via clevis pins avoiding problem of off axis loads entirely.
     
  5. mtma

    mtma Member

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    Actually I just thought of something relatively straightforward:

    Buy a chain window opener, like one of these

    Put your thing onto some rails, nice filing cabinet rails with ball races either side would work fairly well, actuator inside the cavity and wind up and down as needed. The one linked for example claims to push circa 25kg so it should be fine with an 8kg item. Wireless models available out of the box if you wanted that too.
     
  6. OP
    OP
    Cynide

    Cynide Member

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    Thanks for the suggestions guys.
    I need to put a bit more thought into the design and i'll get back to you how it goes.
     
  7. cvidler

    cvidler Member

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    e.g. car electric aerial.
     
  8. ShadowBurger

    ShadowBurger Member

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    check out:
    • Nema 17 stepper motors
    • threaded rod (ie bunnings) or actual lead screws with the right guide nut to suit (smoother)
    • shaft coupler to join the stepper to the lead screw or threaded rod
    • DRV8825 stepper drivers and an Arduino Nano to control it - hit me up if you need a hand coding this, happy to help
    These guys stock all that stuff http://www.aurarum.com.au

    Once you have those, assembling it is actually pretty easy. the problem you'll have with any solution is the height of the mechanism - 20mm probably won't cut it or at the very least won't allow you to fully extend the object from the enclosure. the stepper motor / lead screw is probably the lowest profile installation and will offer the longest lift

    EDIT: to add to this - you'll probably want to have smooth rod coupled with linear bearings on each corner of your object to keep it level and centred (or some other kind of low-friction slider mechanism). ie. don't use the leadscrew to keep your object centred and level
     
    Last edited: Nov 17, 2017 at 10:39 AM

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