The moving pivot proved to be much more difficult to design than expected. We did not appreciate the difficulty of keeping the see-saw in place while moving the pivot. Several ideas were tried. The first was a sort of arm that came down and leveled the see-saw. Extensions then would protrude from the arm and rest against the pans at the end of the see-saw, which was supposed to hold it in place. However, the weight of the motor required to move the extensions proved too heavy a burden for the pivot, which was unable to move due to friction forces.
The next idea was a robitic arm that would grab the seesaw and lift it off of the pivot. It would then place the see-saw back on the pivot after the pivot had been moved. We first tried a scheme in which the arm would raise and lower on a hinge. However, since the hand of the arm was not horizontal when it tried to grab the see-saw, it was impossible to get hold of it. We then considered constructing an arm which would move vertically, but this was deemed too costly in terms of Lego blocks, which we were short of already.
The third and only successful idea involved creating two blocking devices which would move in from the sides of the see-saw to hold it in place. The biggest problem here was that if the see-saw was not balanced, the distance the blocking devices would have to move would vary. Also, holding a tilted see-saw in place is very difficult, as the slope of the arm would allow it to "ride up" over the top of the blocking device. To solve this problem, the devices were equipped with sloped Lego blocks at the front. The idea is that the sloped block will push up the sagging end of the seesaw as the blocking device moves in. This proved to work extremely well.
One major concern with the project is the limited number of Lego components. The moving pivot see-saw used virtually all of our standard Lego blocks, and a lot of the custom ones. We had hoped to create two different scale designs. This may not be possible with the limited number of Lego blocks. Also, a few more custom pieces are needed to complete the see-saw. A few more of the "track" type Lego pieces are needed, and a few more standard blocks (with holes in them). Smooth Lego bricks are always welcome as well.