Intro: Magnetic Flywheel Spinner
This heavy flywheel spinner suspended with magnetic bearing can spin for a ridiculously long time..
Step 1: The Flywheel
The flywheel is from an exercise bike. It weighs 14 kg and has a diameter of 46 cm
I made the wheel more aerodynamic by cutting 2 round pieces from plywood and glueing one on top and the other at the bottom of the wheel.
I increased a 3kg of mass to the flywheel by adding four ferrite ring magnets on it. In the middle of the ring magnets there is wooden piece with hole going through the center of it. I made it with a lathe. Its purpose is just to secure and center the ferrite magnets to the wheel.
I added a threaded rod (Ø1 cm, length 46 cm) and secured it to the flywheel with couple of nuts and washers. In the center of the flywheel there is a hole (Ø 1 cm) The threaded rod fit tightly to this hole making the setup nice and balanced.
This threaded rod made a huge difference by making the spin more stable. Inertia wasn't wasted on wobbling. Thanks to the threaded rod the wheel stayed more horizontally levelled.
The total weight of the wheel with added parts is 18 kg
Step 2: The Bearing
At the upper end of the threaded rod that is secured to the flywheel, there are a neodymium magnet ( N35, 100 kg pull force, Ø60mm x 15mm) and a nut that is welded to a 1 1/16 inch ball bearing
Through the uppermost neodymium magnet ( N42, 130 kg pull force, Ø60mm x 15mm) goes a bolt with round tip. This bolt is secured to the board with a nut and a washer.
So the contact points are the 1 1/16 inch ball bearing and the bolt with the round tip. Between these contact points I added some olive oil before the launch.
Key for a long spin is fine tuning the magnetic pull so that it is only just sufficient to carry the weight of the flywheel, hence generating extremely low friction between the contact points. In this case the magnetic pull provided by these two huge neodymium magnets was too strong so I reduced the magnetic pull by adding smaller repelling magnets on top of the uppermost magnet. Without the steel casing of the uppermost magnet this wouldn't be possible.
Step 3: The Launch
I simply made the wheel spinning by launching it by hand. Hand with the glove is pushing upwards while the other hand pumping the speed. The initial speed was only less than 200 rpms but the wheel spun for 8 hours and 34 minutes!