Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Foam balls

  1. Mar 14, 2012 #1
    Part of a project I'm doing requires obtaining a foam ball from a cup. The foam ball is spherically shaped and is 4" diameter. You cannot damage the ball. There are a lot of restrictions, but most designs will not violate them so I will not list them. One requirement however is that our device weigh no more than 1lb. Obtaining the ball will only be part of this device so the actual weight of whatever we use to get the ball must be much less than 1lb.

    I'm a bit stuck on how to accomplish this task. I'm trying to avoid a grabbing mechanism which would involve more weight and some programming to grab the ball.
    Instead I'm leaning more to some attraction device such as a vacuum, velcro, or static electricity. The vacuum does not seem practical though. Velcro doesn't seem to stick to the foam ball. Static electricity would be hard to generate in this project and it doesn't seem to work very well.

    The whole project is just you must build a device that starts at one end of a ping pong table and you must get the ball that is located on the opposite side of the ping pong table and bring it back and hit a button. In the middle where the net used to be, there is fixture that we have to climb over.

    Does anyone have any ideas on what I can use to obtain the foam ball?
     
  2. jcsd
  3. Mar 14, 2012 #2
    Sitting here stuck on this, only one idea:

    It's foam, maybe pinching would work. Rig up a light spring and release it to pinch the ball to pick it up. Think plastic chip bag clip. I'm not sure if you have to raise the ball too, but if the ball is light enough, you could have the spring help with that too in some way.
     
  4. Mar 14, 2012 #3

    NascentOxygen

    User Avatar

    Staff: Mentor

    Is the ball rattling around in the cup with plenty of space all around it, or is it a tight fit?
     
  5. Mar 14, 2012 #4
    The ball is very light. We just have to grab it and return to the starting place. I attached a picture of the ping pong table.
    I'm trying to avoid using a grabbing mechanism, but that is probably the best way to go. This would involve programming which could get annoying.
    I don't know the exact details, but the ball is sitting on top of a cup. My friend said about 2/3 of the ball is sticking out of the cup.
     

    Attached Files:

  6. Mar 14, 2012 #5

    NascentOxygen

    User Avatar

    Staff: Mentor

    So upending the cup will not be a feasible method if the ball is stuck, even slightly. Clasping below its midriff sounds a possibility then?

    It is difficult to solve a puzzle if you don't know the specifics.
     
  7. Mar 14, 2012 #6

    DaveC426913

    User Avatar
    Gold Member

    When you mentioned the ball is 2/3rds exposed, this is what I thought too.

    You don't need to grab it. What would be wrong with a forklift-like appendage?
     
  8. Mar 14, 2012 #7


    I forgot to mention this is a competition, so speed is very important. Sorry for leaving that out. Reaching the ends of the ping pong table will be cake for my group's device. We're using a motor that generates 1100rpm. We had to use gear reduction to make it slower. At this present rate it could reach one end of the table in probably about 1/3 of a second.
    I haven't seen the ping pong table they built and the information they gave did not say anything about the cup. I think the container holding the foam ball is fixed to the table.
     
  9. Mar 14, 2012 #8
    I would really like to use some very sticky adhesive like tape. But it must not damage the ball and it must be strong enough so the ball does not fall. Does anyone have any clue what could be used?
     
  10. Mar 15, 2012 #9

    NascentOxygen

    User Avatar

    Staff: Mentor

    Flypaper? Unless there is a requirement that you must release the ball at some stage. jm82g.gif

    Caution: the organisers could confound the use of sticky stuff my putting a powder coating on the ball.
     
  11. Mar 15, 2012 #10

    DaveC426913

    User Avatar
    Gold Member

    Paper mousetrap. Though that might be so sticky it damages the ball.
     
  12. Mar 15, 2012 #11
    I'm pretty sure they won't change anything about the foam ball.
    I've heard of flypaper, but i've never seen or used it before. I just googled it, but the information was not helpful. Is it very sticky?
    Paper mousetrap? Can you elaborate?

    Also another reason why I wanna avoid a grabbing mechanism is that the chance it could miss the ball.


    Thanks guys.
     
  13. Mar 15, 2012 #12
    Never seen flypaper or glue traps? You must be very sheltered! :P

    Both of these work by being extremely sticky. Glue mouse traps are sticky enough to, well, trap a mouse. You can certainly pick the ball up using it, but as others mentioned, you risk damaging the ball and would need a secondary device to remove the ball from the glue.

    Do you need to drop the ball at the end? Also, do you have the full rules text? I am now intrigued.
     
  14. Mar 15, 2012 #13
    We do not need to drop the ball. Looks like we can't use adhesives as it might damage the ball or leave a stain on it. I'll private message you the project write up.
     
  15. Mar 15, 2012 #14

    DaveC426913

    User Avatar
    Gold Member

    More commonly called a glue trap. And they are extremely sticky.
     
  16. Mar 18, 2012 #15
    (Very interested to know how this went down!)
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Foam balls
  1. Half-life of foams (Replies: 8)

  2. Foam in a cup of soda (Replies: 7)

  3. Foams and gravity (Replies: 5)

Loading...