XtrmBol: Exercise Gyro Toy

I have always been fascinated by these exercise gyroscopes and wanted to understand how they work, so I set to make one. After many prototypes it seems the important points are: add enough mass, distribute the mass as far from the rotation axis as possible, ensure there is enough friction so that adding torque transfers energy to the gyro.

Another important point is to ensure there are no sharp edges or bits on the gyro core. RPMs can go well over 9000, so make sure the fast rotating thing is super smooth before firing it up.

The parts to print are: 2 gyro half-cores, 1 case bottom, 1 case top, 1 holding ring and 2 washers. I found the ring and washers noisier if printed in PLA so I recommend PETG for those. And then to assemble it you need 14 M5-20mm bolt screws and 2 M4-20mm bolt screws. This image shows the whole lot:

First screw the M4 bolts. These will serve as axle for the gyro to rotate around:

Then assemble the gyro core using the M5 bolt screws. Make sure they go in through a large hole and exit through a small hole on the other half, as shown below:

Then set the washers and holding ring:

This is probably the trickiest step; here is a video on how it's done:

Set the gyro core on the bottom part of the case:

And finally put the top part of the case:

The XtrmBol is ready!

Here is a video showing its operation: 

At the beginning it might be tricky to add speed, which is probably because the axle is not experiencing enough friction with the case. After a few tries it should start to feel better. If you are in a hurry you can sand the areas where the axle rolls; this is something I had to do when using thinner M3 axles on earlier prototypes but with the M4 axle that shouldn't be an issue.

Enjoy!