https://youtu.be/GeyDf4ooPdo
https://youtu.be/tLMpdBjA2SU
Background observation and thoughts
There is obviously something very interesting in this demonstration. The
2nd video in no way is adequate to explain what this video shows. He
held it out early in the video in a way that is impossible with a
non-spinning 40 pound weight. I can easily lift this much compared to
him (it's my workout dumbbell) and there's no way I can hold it out half
way out to arm's length like he did at exactly 1:06 and part of 1:07 (i
just tried it...no way). Also look at 3:30 to 3:34 where his arm is
more extended. That's extremely difficult if it were a static weight.
The way he did the static weight at 1:54 is easier and yet it looked a
lot more difficult. His arm was least tired when he lifted it static.
It should have been getting harder each time, but it was getting easier
as he intuitively learned to take advantage of whatever effect is going
on. I think I know what's happening. They do not explain in the 2nd
video how it can feel so much lighter. The little push at the beginning
seems to store energy to help overcome the increase in potential energy
required to do the lift. But
if that energy was indeed used to help, the lifting energy should have been reduced (somehow) by it and therefore the upward force*distance by his arm must have
been less by that amount. But I am not refreshed on dynamics enough to know if the vertical forces can be made equal and opposite while permitting the downward force on his hand to be less. They only say "it only feels lighter because you give it a little
push at the beginning but it's not lighter". But my thinking is that any excess push at the beginning does not help other than to get it going stably and if there is an excess then the wheel will try to twist upward which might place greater downward force on his hand if it tries to raise it at the same time to keep the bar horizontal. There could be a slight upward twist at the bottom and slight downward at the top which might help something but again I would need to do the dynamics to know. I just suspect it's not helping.. If the downward force*distance is not decreased and the little push at the beginning is not really helping anything other than to get it going, I think the solution to the enigma is this:
Solution
The
angular momentum is changed in one direction by pushing on the bar
sideways and this increases the downward force against the locked
"upward" muscles, like the push at the beginning. I've confirm this
part by experiment and have a video. The center of gravity of
the wheel rises as it twists slightly upward. Then the applied
side-torque by the hand is released which allows the hand to rise to the center of
gravity of the wheel with less force than the weight of the wheel as the angular momentum change is
reversed, so the wheel is vertical again. Then the 2 steps repeat, as
fast as muscles can twitch, following the path of least resistance. It
is a lot easier to lock a muscle against a weight than it is to contract
the position more. So briefly increasing weight in the first step will
not overcome the locked position. They show the extent of the downward
force changes in the 2nd video which shows what I've describe could be a
large effect. The push at the beginning could be the other half of the
effect, and by not letting it twist upward as in my first step, the
energy is stored for extraction throughout the lift, if the lift is done
smoothly.
