Ah Beav, I am no much better a graphic but I thought I would give it a try. I like this subject, statics and dynamics.
Now, at each end of the horizontal stick is a weight, equal on both ends:
0
|------------|
.........^.......0
So in the picture above,
please ignore all the little "." as these are required to get the graphics to line up,
the "^" is the bubble balancer, the "|-----------|" is the tire on the rim and it is sitting on the bubbler balancer. The "0" is the unbalance location on the tire. The unbalance on the top is equal to theunbalance on the bottom and they are 180 deg apart form the center of rotation. The tire is in static balance. The first of the unbalances is on the top or the outside of the tire when mounted on the SVX and the other is on the bottom or inside of the tire mounted on the SVX. The tire is in static balance.
This is great for slow speeds and narrow width wheels/tires BUT it does not spin. When spinning the unbalance produces a force not accounted for here.
When the tire spins, it produces a couple. The wheel is still statically balanced or even single plane dynamic balanced but not two plane dynamic balanced.
<---0
......|------------|
...............^.......0 --->
The "<---" and the "--->" represent forces due to the spinning of the wheel.
Call the top one "A" and the bottom one "B".
Lets say that A is equal to B and is 1 gram. Lets say you got a 16" rim and the weights go at a radius of 8" from the center of rotation.
Then the unbalanced force at A is 8 gr-in and the force at B is 8 gr-in AND the static unbalance and single plane balance is ZERO because A and B are opposite.
So lets get crazy and say the that A and B are 1000 gm-inches. This is still statically balanced and single plane balanced and I would not even stand next to the balance machine when it was running.
Take care too,
John