1J20.80 - Arches
Demonstrate the stability of various arch designs from hemispherical to parabolic.
Pull out the two different arch sets. There is the arch with all blocks of equal size, centering ring, and base with wood stops. The second arch is the large parabolic arch with 19 blocks, plastic base plate, blue anti-slip pads, two centering rings and two sets of wooden wedges.
Obtain the wooden blocks for each arch demo you want to build. The small parabolic uses nine blocks and two feet labeled F-J. The large parabolic uses nineteen blocks and two feet labeled A-J. Each block has a designated handedness. Some blocks are designated "L" for left-hand side, and others "R" for right-hand side. The tops of the letters on the blocks should point towards you, and the bottoms of "L" or "R" should point towards your audience. Each arch big and small come with a stacking device. Place the thin piece of polycarbonated on the table or bench, followed by standing the stacking device center on the plastic rectangle. Place the two blue anti slip pads directly next to the stacking device. If using the large arch, take the two feet labeled A-J, and have them pointed inward towards the stacking device ontop of the blue antislip pads. Use blocks A (L) and A (R) and place them so the tops of their letters face you, while the bottom of their letters face the audience. The L and R designate which side of YOU to place them on. Next, add blocks B(L) and B(R) and orient them the same way but now sharing a face with blocks A (L) and A (R). Repeat this for blocks C-I (L) and (R). Once all blocks are added and aligned correctly, we can now add in our keystone block J. J is symmetric and does not have a handedness. Place J in the middle between the two towers of blocks and gently force it into place. The blocks should all compress and repel lifting the arch off of the stacking device. Pull the stacking device out from underneath the blocks which are now self stable. The small arch uses only nine blocks, and two feet. This arch uses the blocks labeled F-J (L) and (R), and the small stacking device. Assembly is the same process but starts with F blocks instead of A blocks.
Simple Arch - Each block is cut to the same angle and assembled. This is a crude arch that works, but needs friction to hold the arch together.
Parabolic Arch - Each block is cut to a specific angle that allows all of the vertical forces to cancel only leaving compression between the blocks. Every block is different.