GenericOTC Newton's Cradle 7.25" Desk Top Pendulum Toy with 5 Metal Balls

I love having my Newton's Cradle available for students to explore, especially when studying the Laws of Motion, but the frame comes out of the base easily and if a ball gets tangled it is very difficult to restore.

For the money this product is pretty good. The balls are steel, quite heavy with shiny plating and securely mounted, and the (plastic) base is quite sturdy. It doesn't move when the balls are in motion. However, there are two things to be prepared for.First issue: The upright supports I received just would not fit into the holes in the base. The support spacing was wider than the hole spacing. Using a file I was able to widen the holes a little, and then was able to jam the supports in. They lean a little because the holes are larger, but it doesn't affect the motion.Second issue: Be prepared to hassle with the unpackaging and possibly untwisting the balls. The balls and strings are already attached together and are well held during shipping by a piece of syrafoam inserted between the strings. The only way I could see to get the syrafoam out was to slowly break it up and remove it piece by piece. When I got it out the balls were not tangled, but after hassling with supports I ended up with tangled balls. Untangling the heavy balls with their thin transparent strings is a challenge, but in about 5 min the job was done.

I think that this toy is really cool, I think it's fun to see the way it works and how it moves... But I have one major complaint...The metal pieces don't fit into the board correctly.It makes me kinda mad.Those little metal pieces are just a millimeter or two too long to fit in the holes they're supposed to. Even then, it's still pretty sturdy, but you shouldn't just get away with having a mis-fitted product.I mean... It's cool... And I REALLY wanted to like it... But I plan on asking for a refund on it. To me, it's just not acceptable to make your toy mis-fitted like that.UPDATE: After more than 20 minutes of playing with it, I have many more complaints:1) It only goes 12 seconds (on average) before dying out2) When the strings get entangled, it's just hell to mess with3) The middle balls swing around instead of staying still (like they should).4) It just looks unprofessional. (Particularly where the strings go through the top of the balls, and where the strings are attatched to the metal part)

As another customer experienced, I received it with one of the the fish lines broken. I fixed it with 5 min epoxy and dental floss, which was kind of tricky. The 4th ball was a little out of alignment and I managed to stretch the fish line without breaking it to get it closer in line.The vertical distance from the supports to the balls is 5.5 inches. The balls are good quality (not chrome plated, probably nickel plated) and weight 45 grams, 2.2 cm diameter. It has 30 to 40 swings back and forth, 0.39 seconds between strikes, before becoming small and nonexistent at about 80. Reviewers complain that the balls move too much, even after the first strike, but this is normal if the balls are touching before the first strike. The 4th ball moves noticeably forward and the first 3 move back ever so slightly in accordance with a detailed physics explanation (see wikipedia). The silver support bar is cheap plastic.As another reviewer said, I seem to remember cleaner and more distinct action as a child, but heavier balls would not improve it. A video on youtube shows what appears to be the exact same balls with a different support working much better, so the alignment must be crucial. An improvement would be if the balls were slightly separated, but this would require reworking the wire connections and being very careful about the alignment. With a separation, the first strike is a sequence of independent collisions which prevents the intermediate balls from moving. Contrary to intuition, touching balls decreases the effect, making the 4th ball move more and the 5th ball move less, at least on the 1st strike. You can confirm this by sliding quarters on a table under the two conditions of almost-touching and not touching. The almost touching condition should send the 5th quarter further.If I manage to re-string the device with a slight separation between balls, I'll post a video to show the difference.As others have said, I wanted a more professional very, but was not able to find it anywhere.

We've had this for about 10 years and it is still clicking away. Very sturdy and excellently made. Aside from the few times a child or two has tangled it up (my fault--maybe keep it away from small children), there hasn't been a single problem.It is such a soothing desk toy to have during a stressful workday. Great to interact with on a long phone call when you just need something to do that doesn't require your brain.

It's a little wobbly when you set it up and I don't like the fact that about 50% of the times that you knock the balls to try and use the cradle the middle ones move too. The design is made so that you move a ball from the outside and it transfers the energy neatly to the ball on the other side by hitting the balls in the middle, however, in this cradle the middle ones don't transfer the energy neatly because they wobble back and forth too much and as a consequence kinetic energy is lost in the process. This means that the cradle doesn't last as long in movement and that the movement doesn't look as beautiful. We do have to take into account that it performs fine for the cheap price, that's why I'm giving it 4 stars. Perfectly performing cradles start at around the $70 mark.