Triangle Truss Bridges
Intro: Triangle Truss Bridges
Students design and build truss bridges, then test the strength of the bridge by attaching a scale.
You can find the lesson plan, 1-page project sheet, and more project ideas at STEM-Inventions.com
STEP 1: Materials and Tools
Materials and Tools
The Engineering Creation Kit has everything you need for this project and many more from STEM Inventions.
- Craft sticks (at least 100 per student)
- 4” cable ties (at least 15 per student)
- Glue gun with safety nozzle
- Hot glue sticks
- Alternative: use tacky glue
- Cardboard or newspaper to protect work surface
- Hanging scale
- Strong cord/rope/etc
- Carbine hook or similar device
- Truss bridge patterns (attached PDF or download image)
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STEP 2: Advanced Ideas: Truss Armor / House Frame
Truss armor is made of a simple craft stick and cube construction, but includes a handle near one end. This allows the user to grasp the structure from within and wear it like armor.
Another alternative is the house frame. Although it does not rely heavily upon trusses for its sturdiness, it does show the basic idea of what timber looks like within the frame of real houses.
You can find the wood cubes used in these ideas here.
18 Comments
AbdullahA15 1 year ago
349657296 2 years ago
jprice39 5 years ago
I'm a big fan of your work, and have done many of your projects with my STEM students.
It looks like you had a class set of hot glue guns with, what 9 year olds? How did you manage that safely?
LanceMakes 5 years ago
Hi - glad to hear these resources have been helpful!
Here's how I support safe glue gun use: First, buy glue guns with an insulated tip and use only 10 watts. Introduce how it works. Point out the parts that get hot (the tip and the freshly melted glue). Demo how to use it (always put glue on the bigger of the two objects being glued together, keep hands clear, wait 15-20 seconds to dry). Explain how to handle burns (put burn under cold water immediately for as long as it hurts). When not using glue guns, keep them out in front of you. I like to draw simple houses on cardboard and tell kids to keep the glue guns in their house when resting.
As they start using glue guns, make sure to coach them on proper technique and safety.
Good luck!
jprice39 5 years ago
Thank you again! Keep up the great work!
HalleyRose 7 years ago
its the best thing I have ever made!
burns98 9 years ago
thanks!!! I built this for a socials project as a Canadian Pacific Railway truss bridge!
yapoyo 12 years ago
yapoyo 12 years ago
LanceMakes 12 years ago
kelseymh 12 years ago
Something I'd appreciate (as a physicist) would be some of the mathematics to let students actually calculate the forces, and make a guess as to how much weight their bridge "should" hold (and then test that hypothesis with their butts on the line :-).
Since forces decompose linearly, in principle the students could do the math by hand, with only arithmetic (give them values of sin/cos 30, 60, 45 to use, to avoid the scariness of "trig").
I could imagine an introductory session where they measure
Then, once they have a truss built, take a uniform load and distribute it across the top (or worse, a point load at the center!). Draw force arrows to show how the load (a) pushes on the horizontal top members, and (b) runs down the diagonals to the bottom. The latter is where those sines and cosines come in, which you could "just give" to a younger class.
Don't forget the upward force arrows at the endpoints where the bridge is supported. On some members, you'll have arrows going in both directions, and the students get to learn about tension vs. compression, as well as bending.
Where the arrows meet at the bottom, you've got net forces on the glue joints, and possibly (depending on the design) unbalanced net bending forces on the horizontal members.
Can the joints hold up, based on the earlier measurements? As you add more weight, will the bridge fail at joints, or fail within members?
Then go and test the predictions. I suspect that it might even be possible to get within a factor of two or so between calculation and reality (allowing for measurement error, variations in glue joints, etc.), which is not bad.
LanceMakes 12 years ago
80$man 12 years ago
With regards to kelseymh comment, I would rather have young engineers be exposed to and grasp the concepts of stress, strain, stiffness and strength in addition to the different loading conditions and their interaction/coupling. The development of a students ability to interpret and draw graphs (stress/strain) and diagrams (free body diagrams) to explain and understand property relations and loading conditions are of much greater value than simplified calculations that 'can' predict failure. Doing basic experiments to explain these properties and the governing mathematical relations would be of great value. Whilst the student gains knowledge of these concepts, their ability to intuitively build upon and improve previous designs will grow. Learning from failure, especially during experimentation, is crucial in the development of an engineer's problem solving abilities.
Finally, I have a great appreciation for the efforts taken in education of young people in the fields of mathematics, science and engineering, with commend your initiative and endeavour.
LanceMakes 12 years ago
schumi23 12 years ago
wiredcav 12 years ago
Biodynamic 12 years ago
wilgubeast 12 years ago
Good luck in the Teacher Contest.