Tilted Axes, Spirals, and Dynamic Balance

[BenjiHeywood]

I would think the wobble sign would denote a positive or negative rotation axis no? i.e. clockwise as opposed to counter-clockwise precession. In that case the underside / topside of the disc would be exposed from a different side of the disc so to speak as viewed from the front while wobbling. It's still not entirely clear to me how that exactly breaks the flight symmetry however.

I'm not sure i follow, but that might be me.

For a free disc, the wobble has to go around the disc at double the spin rate, i believe. So i don't think it could go the other way?

https://www.quora.com/Why-does-a-free-disk-wobble-twice-as-fast-as-it-rotates

 

[BenjiHeywood]

Hmm, that might be a bad link, Feynman said it was half the spin rate. Anyway, the spin and wobble are tied i think.

 

[BruisedOoze]

I'm not sure i follow, but that might be me.

For a free disc, the wobble has to go around the disc at double the spin rate, i believe. So i don't think it could go the other way?

https://www.quora.com/Why-does-a-free-disk-wobble-twice-as-fast-as-it-rotates

It's largely in regards to sign conventions and a coordinate axis. Angular velocity has a (pseudo) vector direction associated with it (right hand rules and what not).

When we're usually talking about spin we're usually just discussing magnitudes (rpms), and not in a vector sense. A backhand throw from a lefty and righty rotate opposite of each other, and consequently have vectors that point opposite of each other, so they have the opposite sign in a coordinate sense.

Disc wobble is another type of rotation and consequently has its own angular velocity (directionality) associated with it. As such if the precession about the spin axis is in different directions (clockwise vs counter-clock wise as viewed from the top) they will have the opposite sign in a vector sense. Which is what I'm wondering the TechDisc software is doing with the plus and minus shenanigans.

 

[jupiterboy]

It's largely in regards to sign conventions and a coordinate axis. Angular velocity has a (pseudo) vector direction associated with it (right hand rules and what not).

When we're usually talking about spin we're usually just discussing magnitudes (rpms), and not in a vector sense. A backhand throw from a lefty and righty rotate opposite of each other, and consequently have vectors that point opposite of each other, so they have the opposite sign in a coordinate sense.

Disc wobble is another type of rotation and consequently has its own angular velocity (directionality) associated with it. As such if the precession about the spin axis is in different directions (clockwise vs counter-clock wise as viewed from the top) they will have the opposite sign in a vector sense. Which is what I'm wondering the TechDisc software is doing with the plus and minus shenanigans.

Maybe it's that, or they accommodate right and left hand throwers by recording a +/- data point.