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Catapult trigger

  1. Nov 20, 2013 #1
    Does anyone have any cool ideas for a catapult trigger. I plan to have a hook attached to bottom of cup that holds the ball and 2 hooks on the base that when you pull the catapult all the way down and put a nail through all three hooks. There will be a string attached to the nail but I need something that would pull the string and the nail along with it.
  2. jcsd
  3. Nov 20, 2013 #2
    Step 1 (optional) Get a dog
    Step 2: Train your dog to do fetch command
    Step 3: Attach the string to the dog's tail and do the fetch command
    And... that's how you do remote controller.
  4. Nov 21, 2013 #3


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    Staff: Mentor

    A slot-car motor could wind the string around a pulley or shaft.
  5. Nov 21, 2013 #4
    A trigger complicates thing a bit too much as far as a catapult is concerned...
    But even so, here is something I had thought of doing:
    (With a trebuchet - 5th grade sci. project...never completed the trigger part)
    A Large spur gear fixed to the 'projecting shaft' synced to another gear (a spur gear cut to get 120 deg section) attached to a (4.5V I think) DC motor controlled by a switch.
    The motor gets the shaft down- switch off- Lock and load- Switch on again- as the gears lose contact the projectile launches-gears regain contact- cycle continues.
    But I never tried it out...no spur gears of the required sizes and cutting up beyblade rip-cords wasn't exactly working out...project was due soon too...
  6. Nov 21, 2013 #5
    The trigger must be small in size can't be too big, and must be made with materials from home( easy to get and doesn't cost much)
  7. Nov 21, 2013 #6
    For example anything I could do with magnets?
  8. Nov 21, 2013 #7
    Permanent magnets won't help but electromagnets might but a mechanical solution is the best IMO.
    How much automation do you want? If you are okay with manually dragging down the shaft and just are looking for a trigger you could just use things like board clips/clothespin and a piece of string for a simple solution. Or if you are looking for something more elegant you could use a string and pulley (a bobbin or a reel would do nicely) attached to a handle which can spun to bring the shaft down and released to fire.
  9. Nov 21, 2013 #8


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    Staff: Mentor

    Since this is likely a schoolwork project, I will move the thread to the Homework Help forums, and only give a visual hint...

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