Bridge that Gap challenge
If you look around your neighbourhood, you will probably see lots of different bridges - road bridges, footbridges, rail bridges, and sometimes even canal bridges! There are many different types of bridge.
Your challenge is a build a simple truss bridge, test it, and improve the design so that it can carry a greater weight.
Levels of difficulty:
Level 1 - Build a truss bridge which is about 45cm (18 inches) long. See photo below for an example. Test its strength by putting a single book in the middle of the bridge.
Level 2 - Make the bridge longer, so that it can span a 59cm (23 inch) gap between two tables.
Level 3 - Test your bridge by adding books one at a time to the middle of the bridge. Eventually it will start to deform, and then break. Now think of ways to make your bridge stronger, and re-test it.
Equipment: Large K’NEX set.
Approach: K’NEX is superb for building bridges, provided you get the design right. Think about how you can make your bridge really strong.
1. Watch carefully watch happens when you add each book. Sooner or later you may see that one part of the bridge starts to bend, or maybe a connector starts to come apart, and then eventually the whole bridge collapses.
2. Think about how you might improve the design to stop this happening - maybe by adding some extra K'NEX rod or connectors?
3. Then test the bridge again, to see if your improvements have helped, and to observe how the bridge deforms and fails again when you add even more books. Then back to step 2!
Handy Hints (please click to view):
A2 - 3 ways to connect K'NEX rods and connectors
A5 - Strong 3-D structures
Teachers' Notes
Helps pupils learn how to make structures more stable and withstand greater loads; how structures can fail when loaded; and techniques for reinforcing and strengthening them.
Possible solution: See photo.
Before starting: Look at bridges in your neighbourhood, and pictures of different types of bridge around the world.
Conclusion: Firstly, ask the children what they have learnt in the process of completing the challenge. Then ask them to compare the different bridges built by the class, and assess the strengths and weaknesses of each.
Copyright © Andy Shercliff 1996 and K'NEX User Group 2004
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