Slight detour from that dry bouncing ball stuff...
Famous animation director John Kricfalusi is leading an online tutorial in which he is endeavoring to teach classic 2D animation by copying examples from Golden Age animation of the 1930's and 40's. It sounds unlikely, but consider that great composers like Bach and Handel learned their stuff by copying note-for-note the works of older masters.
So maybe he's on to something.
Anyway, the first assignment was to do the bounce cycle in a clip from an old Bosko cartoon
Here's my semi cleaned-up effort; I haven't removed all the overlapping lines. This is all hand drawn (and damn, it took a long time to do), no computer "tweening" involved.
(Music created with Voyetra "Dance eJay 2")
The original clip is so foggy that I had to guess at several details. I get the sense that the feet are turning up to expose the sole of the shoe, so I drew it that way but it's just a theory. The sliding of the heels as he lifts his foot... it's in the original, whether they meant it or not, so I did that too rather than try to "correct" it. The major adjustment I made was to make the hips do more of a slow in/slow out at the top of their motion. I think it gives it a bit more weight to swing faster through the bottom of the arc. He still looks like he's hitting a rock at the top, though. I also exaggerated the lagging of the feet as the lift up and down.
I did this in layers so I could study and tweak the motion of each body part separately without having to erase over something that was already working:
By keeping things on layers I could also experiment with offsetting the timing of the body parts. Here the hips have been advanced one frame. I think it gives the head a more bouncy look:
John K says he's waiting for 20 people to do this lesson before he goes on to post lesson #2. I think I'm only the 10th, so there may be some delay. Back to bouncing balls...
update... Bosko in glorious nuanced shades of gray: