同时动画两个div onload，jquery帮助

I am trying to make a sort of "scales" look, where two divs will slowly animate up and down like being weighed on a scale. I could use some help with the functions though please, I can not get two to animate simultaneously on page load, and I need them to go up, then back down, then up, etc... Make sense? Here is what I have so far, I am kinda new to jquery obviously, :) Thanks for any help!I am trying to make a sort of "scales" look, wh