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Need ideas for final semester project

  1. Feb 24, 2007 #1
    Its me again.
    I need recommendations for a motor and power supply to make a cordless grass trimer that uses battery..anyone?
  2. jcsd
  3. Feb 24, 2007 #2
    What do you want to do with grass trimer? Are you looking for specific power outputs, effeciency, materials in construction, etc?
  4. Feb 24, 2007 #3


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    Staff: Mentor

    I'd start by reverse-engineering an electric grass trimmer and seeing what kind of motor/how much power it uses. Then I'd look into existing cordless power tools and see if their capabilities come close to what you are looking for.
  5. Feb 27, 2007 #4
    Ok i have problems finding what components and parts...Can anyone give me an exact motor and battery specification for a cordless grass trimmer?
  6. May 26, 2007 #5
    A grass trimmer is a pretty simple device. You just need a battery connected to a fast spinning motor. The motor head has a piece of plastic string (I dont know the official name) that spins very fast and trims the grass. To keep it simple, you might want to use a deep cycle lead acid battery hooked up to a motor which accepts 12 volt input. Charging the lead acid is very simple, you can get a specialty charger, or build your own 13.8 volt power supply
  7. May 26, 2007 #6


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    Gold Member

    It can't just be a fast-spinning motor; you have to have some serious torque behind it as well. Otherwise, it will just stall out. If you have to make it from some other appliance/tool, I'd recommend a router.
  8. May 31, 2007 #7
    I imagine that a cordless drill would work for a motor and battery system. The drill would have to be altered to remove the gearing, but it would probably have a rheostat to allow variable speed and the battery and charger already paired to the motor.

    They are fairly cheap now also, only about $20.00.

    Here is a site showing a reverse engineered corded drill, you can see the gearing:

    http://www.bergen.org/AAST/projects/Engineering_Graphics/Drill/" [Broken]
    Last edited by a moderator: May 2, 2017
  9. May 31, 2007 #8
    Here are the specs for a Black and Decker Cordless grass trimmer:

    And here are the specs for a cordless drill:

    The drill speed is after the gearing, so I imagine much higher rpms could be achieved without the gears, not sure what the ratios are.
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