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Create a Tennis Ball Launcher

  1. Feb 16, 2009 #1
    Ok, so here I go.


    Objective: It is simply to create a device to accurately toss a projectile.

    -Must fire a tennis ball anywhere between a 5' to 20' operating range.
    -Must fitwithin a 2 by 2 footprint(basically when broken down into parts the device does not exceed 2' by 2').
    -High pressure gases and combustible materials are not allowed(goodbye fun).
    -Must be built mostly from scrap and recycled materials.

    What this launcher has to do is get a tennis ball into a bucket (sitting up) at three points(chosen by my teacher) between 5' to 20'.

    I am allowed three trials for each of the three points. Anything else done, parameters of course, is up to me.

    Problem Attempt: Here are my ideas so far.

    -I am thinking of going for a trebuchet type design. From what I've researched they are plenty accurate but I'm not sure I could break it down small enough parts to fit in a 2' by 2' footprint.

    From there I've considered everything from a pitching machine to a simple catapult(basically I have made little progress). The calculations involved when it comes to getting the angle and velocity right, I have no problem with. All I'm hoping for are a few ideas from which to build momentum.

    Thanks in advance guys and please inform me if anything needs to be clarified.
    Last edited: Feb 17, 2009
  2. jcsd
  3. Feb 17, 2009 #2


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    Beforehand I must add a disclaimer: I didn't do much engineering projects but most of them tended to fail miserably :smile:

    Anyway, maybe you can use a spring to launch the ball. If you can find a rigid spring (high spring constant) you won't need much space, and if you have a metal barrel then you will have relatively low friction so it should be fairly easy to do theoretical calculations (i.e. how much do I have to compress the spring to get the required velocity).

    The biggest problem in predicting the goal will be the friction, both with the launching mechanism and air friction while the ball is in-flight. Luckily you are shooting a tennis ball, which should provide relatively low friction. If your tests show that it is rather small, you can probably predict where the ball will land quite accurately.

    By the way, what is 2 by 2? Inches, meters, yards, Boeing 747 wing spans?
  4. Feb 17, 2009 #3
    2' means two feet.
    2'' means two inches.
  5. Feb 17, 2009 #4


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    If your only constraint is 2'x2', then take complete advantage of no vertical requirement. If you drop a ball inside a vertical shaft that's attached to some sort of lever, then you can precisely calculate the launch velocity. If have a "stop" on the lever so that the ball always leaves at a certain angle, then you could completely predict the distance traveled (assuming the tennis ball's weight is negligible to the dropped mass).

    good luck
  6. Feb 20, 2009 #5
    You want something you can completely control the release speed and angle of.

    I would reccomend a catapult (spring stored energy) design over a trebuchet (gravitational pe). Think about why you could control a spring more than dropping a mass. Also from experience the energy provider in these situations is far less critical than the release mechanism.

    Dont worry about friction or air resistance as its negligable.
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