陀螺 is an inexpensive wood toy that we grew up with and there're similar spinning tops all over the world. I can't buy one here, so I want to build one for my kids to learn. My initial build was too big/fragile, so I redesigned a smaller one(https://youtu.be/BSIfdugXvtA) and with no sound holes. Since this is a 3D printed object and the high impact to the ground will likely to break it easily, I found the duct tape is a perfect remedy for that and recommend to cover it before your first shot. Total print time is about 10+ hours with 0.24 layer height.
Even though the original screw holes are designed with M6 0.8, but it fits M5 0.8 nicely due to the print tolerance. I made another one(filename with a M6 at the end) with M7 1, so that it can fit with M6 1 bolts. If you use a drill bit to clean up the holes or you have a perfect print machine, you can fit M6 0.8 or M7 1 bolts. The M6/7 bolts are better/stronger and provide more weight. The M5 spinning tip is weaker and can actually bent from the drop.
To increase the spin time(more angular momentum), I use the pennies/nuts to build up the weight. It is important to make the bottom heavier, so that it will always spin on the tip.
M5/6 0.8 or M6/7 1, 5x 30mm+ bolts and many nuts(I use M8 nuts for the weight)
Some small screws
Coins w/ diameter <= US penny 1982+ ( optional, I used 42 pennies, 30 in top cap and 12 in the base)
Twist rope (~2m, cotton is probably better)
Heat shrink tube(optional for the rope end)
Introduction (in English)
Basic steps (in Chinese)
https://youtu.be/B02usJQlxuo (in English w/ English subtitle)
https://youtu.be/NkbZWYAtvQI (in Chinese)
https://youtu.be/Db4lH3BZE0Q (in Chinese)
Use the coins with the same composition, i.e. after 1982
Randomize your layer starting point, use random in the "Z Seam Placement" with the cura.
It might be better if the body is annealed with an oven.
Just need few screws for the top cap and don't need to put screws to all holes.
The hot glue is used to glue down the nuts to the side wall, so that they don't move around. You don't have to use the same size of nuts inside, as long as they fit in symmetrically.
You can use just the nuts/bolts without the pennies if you don't have them and no need for the both caps in this case. The pennies are useless and this is one way to dispose them. Also you do not need to fill all the holes with pennies in the top, but they do have to be symmetrically filled. In other words, you can fill them either all 6 holes or every other one(total 3 holes). You might want to print a thicker top cap by enlarge z axis from the slicer, because the weight of coins might break it if you have lots of coins in the top cover. Alternatively, use hot glue to glue them first before closing the cap. You could also skip the weight in the top, because just the bottom weight should still be good enough.
The nylon twist rope from the dollar store isn't ideal, but works fine. The problem with that is the fibers are easily pulled and break up from the strands.
The spinning tip is made of a bolt and nuts. It is important to use heavy duty tape to tape around them. Otherwise, the rope might get caught on to the nuts and tangle together with the spinning top. Once you feel comfortable with the tip, it is important to glue it permanent, so that it does not come loose. (Optional) You can also sand(with sand paper or metal filer) the tip from the drill press(or the drill), so that it is rounded on the edge of the bolt head.
To play is not difficult, but requires some practices. Steps are listed below(assume right hand person):
- used the left thumb to hold one end of the rope on to the gyro
- Wrap the rope clockwise like showing in the video on the plastic body, the first couple loops are important and need to be tight.
- After wrapping it, hold the end of the rope with the pinky finger and wrap around couple loops, hold it tight.
- Finish wrapping all the rope, hold it tight and position the spinning tip to the left
- Throw it out and pull back right before the rope fully extended