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Spring question

  1. Jan 31, 2011 #1
    Hi all!

    I tried searching the answer over the internet but with no luck - how does a child spring toy car works? the ones that you draw backwards and then release. I know that it works with a spring but im interested in more exact details like how to spring draw back turns to circular motion.
    Also while im at it, what would be a good way to release energy stored in a spring through a determined amount of time? meaning, i can draw back the spring and release just like that but all the energy will be released right away in a short period of time. How can i extend that period of time using only mechanical components?

    thanks !

    This is NOT a homework question. Its for a little project of my own that im thinking of doing.
  2. jcsd
  3. Jan 31, 2011 #2
    Im not sure what kind of toy you are talking about, so the response will be slightly vague, but typically, if it is something like a dart gun, or something of the sort, it is essentially just controlled by a simple mechanism (typically just the thing you pull it back with) that compresses the spring, and locks it into place, then when you pull the release mechanism, the spring is decompressed.

    As far as your project goes, what is it that youre trying to build? The ammount of time you want to spread out the energy can affect your method. Do you want to operate it manually or does it need to be automated? Im a mechanical engineering student, so solving these little problems has become somewhat of a hobby.
  4. Jan 31, 2011 #3
    im also a mechanical engineering student :) too bad that now days these kind of problem are mostly taking place as a hobby because my university consider these kind of stuff as low-tek ..

    i need to make a metal rod vibrate up and down in a linear motion (no circular movement, atlist not one that is noticeable) and instead of using an elecric motor and creating somewhat of a offset and convert it to a linear motion i rather stay with mechanics for reliability reasons and use some sort of a spring to store energy (that you manually put into) and then release it. I need the metal rod to vibrate for about 5 seconds each time in about the same amplitude

    any ideas how you can control the spread of energy release for a certain amount of time?
  5. Jan 31, 2011 #4
    im trying to think if maybe the spring constant would have an effect on the ability to oscillate at a particular rate. is there a limit to the length you want to use? because common sense dictates, the longer the spring, the longer the wave to take to travel along it. I think the rigidity would also effect the speed of the wave. it is a perplexing problem haha.
  6. Jan 31, 2011 #5
    well the length has its limitation, the max length is about 5cm and a radius of maybe 0.5cm tops. anyway, the smaller the better.
    I figrued maybe i should try and study how spring-drawn clocks work like the old ones, it has some sort of a spiral spring (no constant radius) and it is combined with gears
  7. Jan 31, 2011 #6
    the thing about clocks is that I dont think they oscillate in a linear path, ive pulled apart some mechanically driven alarm clocks and such to have a look, and the best ive come up with it that their compression is applied about a circular path or something like that
  8. Feb 1, 2011 #7
    you can convert circulat to linear motion using the Da Vinci's slider device for example, there are some other options too. If you can create a circular motion with a high and somewhat constant angular speed using the principals of the clock mechanism its a good solution for me :)
  9. Feb 1, 2011 #8
    Makes sense. Im not great at reading and imagining it haha, I am very tactile when it comes to this kind of stuff.
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