Wednesday, May 18, 2016

Bridge Building Series - Truss Bridge 1

Truss bridge building instructions 1

We’ll make different truss bridges using two different materials - foam cubes and cut drinking straw pieces.

Design Rules for both bridges:

1.      Bridge must span 10 inches (25 cm)
2.      Bridge must have a place to attach a small cup in the center of the span (preferred).
3.      The ends of the bridge are not taped onto the support structure.

Bridge 1 – Marshmallow/foam cubes/cheese balls & toothpicks

NOTE: The best material for this project is foam cubes. However, a container of foam cubes can get very expensive (I've paid $27.49 for a container of 105 foam cubes), so if you can find more affordable ones, please let me know.

I've done this project with marshmallows, and it's doable (for intermediate grades). And cheese balls get messy, but doable as well.

·         A bag of marshmallows, foam cubes, or cheese balls
·         A box of toothpicks
·         Tape
·         Small cups
·         Paper clips
·         Weights – pennies, paper clips, etc. Anything is OK as long as they weigh the same. You want to compare how much different bridge designs can support
1.   Create a square with four foam cube pieces and toothpicks. Create 3 more. Put them together to create a cube. 

2.   Create several more cubes and put them together until you reach 10 inches in length. Remember, your bridge must be longer than the span it needs to bridge (add an inch or two to the total length of your bridge).

3.   Place the bridge between two desks, tables, chairs, etc.
4.   Hang a small cup in the middle of the bridge (use hole puncher and paper clips) and load it with pennies, paper clips, etc. to weigh it down and test its strength.

~same number of coins in the cup as the beam bridge project

added another cup of coins

added more coins to each cup

Again, this project works best with these foam cubes. I purchased from Amazon, but they are pricey. I did find some smaller foam cubes from the Dollar Tree store, and they worked well. But it's very difficult to find them consistently. You can see them on their online store, and the store managers don't seem to know when or if they'll ever get another shipment. So, if you find another source of reasonably priced foam cubes, please let me know.