Slingshot physics

Discussion in 'General Slingshot Discussions' started by Mycophage, Jan 22, 2014.

  1. BoyntonStu

    BoyntonStu Member

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    One thing to consider about slingbows, they usually are fired many seconds after the draw. Therefore it does not make sense to draw a slingbow with the same force as a slingshot.

    Slingbows like mine can be drawn using left and right rubber,

    If each draw is 50 pounds, it will be much more powerful than any slingshot.
     
  2. JoergS

    JoergS Administrator

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    Crossbows should use a lot more draw weight than conventional slingshots, especially when shot in cold weather.

    Rubber stores energy thermally, means, the bands warm up when you draw them out and cool down when they snap back. When you let them cool down in drawn condition, they loose draw force as they cool. This stops when they reach the temperature of the environment.

    When you let them snap back after they have cooled down completely, they will STILL cool down again, getting much COLDER than the environment. You can build a refrigerator with rubber.

    So what do you do to solve the problem? You simply use A LOT more rubber. When you want a total of 10 kg draw weight, you use 30 kg. OK, it goes down to 10 kg after it has cooled down to the German winter temps after ten minutes. But that still is enough.

    For a normal slingshot, no such need. It will still work better in the summer - but it will also have a higher draw weight, with the same bands.

    To come back to the question, multiply the calculator output by two for TB Black. That is close enough.

    I recommend doubling those values for crossbows.
     

  3. JoergS

    JoergS Administrator

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    Please no German outside of the German sub forum. That isn't very polite to the majority of our members, kiitos. If you don't want to write in English, please shut up. Thanks.
     
  4. studer1972

    studer1972 scooter trash

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    Will a cutting disk work attached to a drill?
     
  5. ruthiexxxx

    ruthiexxxx ruthiexxxx

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    Not very well, I wouldn't think. Too slow
     
  6. JoergS

    JoergS Administrator

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    +1. It would work, but it would be faster to do it with a manual hack saw.

    Please make sure to wear ar least a paper mask when do a lot of angle grinder work. Breathing in that dust can't be healthy.
     
  7. Mycophage

    Mycophage New Member

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    Thanks, Joerg, I was just thinking about that cooling off problem, and just adding another band to compensate for it, I'm glad the master confirmed that as a good idea. Also, I simply cannot believe how quickly, and thoroughly helpful the people of this forum are! I've been really sick all week, and actually feel bad because I couldn't keep up following all the posts! Thanks guys!
     
  8. studer1972

    studer1972 scooter trash

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    Yep, good info. I wear a mask even for sanding and drilling. My lungs and sinuses are really sensitive to dust.