I have been working on a new illustration of the Trinity. I am not a believer that the Trinity can be perfectly illustrated by triangles, eggs, H2O, or anything else on earth. That being said, I find the pendulum helpful in this regard (though I know there are some major problems with this illustration).
A pendulum has four working features: A pivot, a rod, the Law of Gravity, and a bob. The pivot is the source. The rod connects the source to the bob. The bob swings back and forth in a constant struggle with gravity to exist at the center. As more weight is added to the bob, gravity dictates that there will be less of a swing. Eventually time (the most common function of a pendulum) will be no more.
Christian theology has four working features: The Father, the Son, the Holy Spirit, and the Church. The Father is the source. The Son connects the Father to the Church. The Church swings back and forth in a constant struggle with the Spirit to exist at the center of God's will. As more people are added to the Church throughout history, the Spirit dictates that there will be less of a swing. When the quality and quantity of the church is maximized, time will be no more.