....as you can see at :
https://youtu.be/UVB_Utm3dFk
https://en.m.wikipedia.org/wiki/Pen_spinning#/media/File%3APen_spinning_-_Fingerpass_Normal.gif (https://en.m.wikipedia.org/wiki/Pen_spinning#/media/File%APen_spinning_-_Fingerpass_Norma.gif)
....from a manner to manipulate a simple object into a self-spinning one ?!
We will replace the pen with a tube , attached to a pivot. Inside the tube we have a free sliding mass/bar and two springs.
Now , the challenge : to obtain a self-accelerated spinning motion of this simplej arrangement (rotating tube/"pen" ) due to a continuous unbalance of gravity and rotational inertia...
Al_ex
.....is related to a well known desk toy :
https://theswingingsticks.com/how-the-swinging-sticks-works (https://theswingingsticks.com/how-the-swinging-sticks-works)
The first proposal ( https://overunity.com/18541/developing-a-successful-game (https://overunity.com/18541/developing-a-successful-game) ) was to take out the electromagnetic "assistance".
This time the challenge implies to play a possible single "self" rotating tube/"stick" with an oscillatory mass inside ( a free sliding "to and fro" mass/rod and two springs ) , due a continuous gravity unbalance and centrifugal switch every half-turn.
Take a look at :
https://overunity.com/18407/higher-and-speeding-up/ (https://overunity.com/18407/higher-and-speeding-up/)
Al_ex.
I just checked out the video and GIF you shared, and I have to say, pen spinning looks pretty cool. Your idea to replace the pen with a tube and experiment with self-accelerated spinning motion is intriguing. I'm not sure how successful it will be, but it sounds like a fun experiment.
The difficulty is choosing a spring with the exact coefficient you need.
It needs to be strong enough to move the mass
But also weak enough for gravity + momentum to compress it
Then the timing must also be exact