Shit you're right my bad, too many Marc(o)s here lol. Glad to hear you got it going!
> Marc, I am still sort of confused about the magnet magic as well... but
> from what I understand, the magnet spins; it's magnetic field makes a
> disk connected to the needle start to spin as well. The disc has a
> spring/coil attached though. That spring fights back against the
> rotation so the disk doesn't just spin in circles... It only spins as
> far as the balance between the force of the spinning magnet and the
> spring pushing the other direction.
Almost, the rotation of the magnet doesn't necessarily cause the disk to spin per se. It causes a magnetic field to be created that exerts a force in a certain direction. It uses the same electromagnetic principles as a stator/flywheel but instead of current you set it up for the tiny force generated to act upon that disk and rotate/hold it. The faster you go, the faster you spin the magnet, the greater the amplitude that force is and the further the needle moves.
So that electromagnetic force is applying a torque to the disk that the speedometer needle is attached to, and that electromagnetic force is balanced against the spring tension to create a pretty decent estimate for how fast you're going. Pretty cool shit.