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  1. #1
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    Newton's Cradle

    On many a post here on the Zone, I have read where someone had made an "Impulse Buy" on eBay or other stores.

    Well, while surfing through eBay I noticed a seller that had large chrome steel precision balls. 2.5000 +-.0002" to be exact! Now most people would just keep surfing, but I bought FIVE of them (chair) So for the next few evenings I stepped away from my current projects and started designing a HUGH "Newton's Cradle" using these large balls! It took me a little while to make everything proportionate, and I have to say that I must be totally NUTZ

    The base plate is 1" thick aluminum, 11.375 wide, 15.125 long! The over all height of this widgit is 13.938" Not sure what the total weight is, but each ball weighs 2.7 Lbs! The material has been ordered, and the balls arrived today! The swing arms are aluminum, and have steel double sealed bearings pressed in. The pivot point at the center of the ball is to be a 1/4" hardened dowel pin, so each ball will need to have a hole drilled & reamed through the center. The balls will spin freely on the dowel pins, and the ends of the pins will be pressed into the swing arm fork!

    The last FUN project I've done was the large Turner's Cubes, I hope this project is as rewarding!

    Here is a picture of the 5-balls, and a full scale sketch on graph paper!
    Attached Thumbnails Attached Thumbnails 100_4602.JPG   100_4602b.JPG  

  2. #2
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    Neat project

    Not to spread rain on a great plan, but......

    The action will continue longer (if that is important) if you get rid of the sealed bearings and use a line contact pivot. (like a beam balance might show in example)

    Soo.....Soo much less friction.

    Waiting to see the video!

    CalG

  3. #3
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    Actually, I'm too worried about the level of friction, or the actual run times! The idea of making one so big is the selling point for me

    I will make the prints available to anyone with an equal level of eccentricity and skills!

    Eric

  4. #4
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    Anyone know a source for cannon balls?

    This man is on a mission.

    "Go big, or go home!" ;-)

    CalG

  5. #5
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    May 2005
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    Heh, heh, I knew you had big balls, but so round too!

    Cheers,

    BW

  6. #6
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    I am not interested in prints, if you make something that works and keeps going for a long time I will buy one provided the price is not astronomical.

    I have always dreamed of making one of these using balls about two feet in diameter hung from about twenty feet high. The period would be several seconds and if it was built correctly would run for a longggggg time.

    P.S. The Turner's Cube sits in a 'Tunneller's' beer mug above my desk at home.

    And if anyone tells me exactly what a Tunneller's beer mug is, and PMs their address, I will send them a money order to buy themselves a few beers or donate to their favorite charity, their choice.
    An open mind is a virtue...so long as all the common sense has not leaked out.

  7. #7
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    The Tunneller's Beer Mug is a double walled mug that will refill itself from the chamber between the walls. They're seen as a piece of magician's apparatus more often than not.

    Or not.

    Hey, I made this stuff up as I go!

    Cheers,

    BW

  8. #8
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    After a lot of research this weekend, looking at the commercial grade Newton's Cradles. It was obvious that a string or nylon tether is insufficient support for even the smallest balls. The process of getting all the balls aligned so the centers are perfect is either nonexistent or nearly impossible on most models. From what I've read, the balls loose 90% of the energy in misalignment! Its like shooting pool, a hit to the side makes the ball deflect (English)

    The poor alignment made the balls separate, in such a manner that the returning ball made a double collision, and all the balls would twist, and rattle on the end of their tethers. Some people stated the balls should have a slight gap between them, and most were against it! Personally, if there is to be a transfer of energy, they should be in contact!

    So on my machine, the balls will be supported by a triangular pendulum, which is precision made. This will ensure the alignment of the balls to be within .001 at worst case! Because each ball will weigh 2.7 lbs, the need for precision steel bearings is essential! I think the actual run time will be surprisingly long for this unit!
    Attached Thumbnails Attached Thumbnails End_View2.JPG   End_View.JPG   Pivot_Arm_with_ball2.JPG   Pivot_Arm_with_ball.JPG   Side_View2.JPG  

    Side_View.JPG  

  9. #9
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    The precise alignment, lack of gap and the rigidity of the support frame, as well as friction of course, all influence the running time.

    I was just re-reading your first post mentioning putting a reamed hole through the balls. Needless to say this will be difficult and I wonder if it is really necessary? Grip the balls between little spherical caps held by setscrews in the forks; the balls do not need to rotate.
    An open mind is a virtue...so long as all the common sense has not leaked out.

  10. #10
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    Sorry Geof, but I do not think setscrews will contribute anything but faster, cheaper manufacturing! The setscrews will never stay put, as a point on the end will be nothing more than an angle for the weight of balls to slide down and fall off spreading the fork. The loss in precision from locating on a screw thread is also a big issue. I have no problem drilling and reaming a .2505" dia. hole through the balls, as I have a solid carbide drill bit and reamer! The dowel pins are .2502" dia. which gives me .0003" clearance. After the balls are drilled, I will put a full radius on the dowel pins, and make the hole in the fork .0002" smaller so the pins can press into the fork! This ensures the maximum precision & strength for securing the 2.7 lbs balls!

    Eric
    www.widgitmaster.com
    It's not what you take away, it's what you are left with that counts!

  11. #11
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    The material for the base, top, and the four posts has arrived!
    Attached Thumbnails Attached Thumbnails 100_4665.JPG  

  12. #12
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    This is just sooo coooool!
    Bill
    billyjack
    Helicopter def. = Bunch of spare parts flying in close formation! USAF 1974 ;>)

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