I'm going to start with the truss bridges as they are the most basic and that's what you start with in the Polydron Bridges kit. I've color coded the pieces in order to make it visually easier to understand, but when you make your own bridges, of course you can use any color combinations you like.
The type of truss bridge I'm going to show in this post is the Howe Truss and in the kit it looks like this:
My Frameworks version looks like this:
If you happen to have solid square pieces, it's nice to use them for the deck as I have in the above picture, but it's not absolutely necessary. However if you have only Frameworks pieces, you might want to add a piece of stiff cardboard on top of the deck in order for the children to drive their toy cars on the bridge.
For this bridge you need:
2 plinths (see previous post here)
20 equilateral triangles
8 squares
Bridge
20 right angle triangles
12 squares or 6 frameworks squares and 6 full squares
Here's the flat layout of the above bridge:
Here's the flat layout using only Frameworks pieces:
In the Polydron Bridges kit they add rectangles at each end of the bridge for stability because without them the bridge will lean.
Because my plinth construction is slightly different, you can't use rectangles, so I've added squares instead:
Of course if you have the pieces available, you can try making longer bridges and explore what kind of requirements you need in order to keep the bridge from buckling (more plinths, etc.)
Pictures of real bridges:
- In Manitoba
- In British Columbia
Links:
Truss bridges on Wikipedia
Howe trusses on Garrett's Bridges
En Francais:
Ponts a treillis sur Wikipedia
Ponts a treillis sur Gramme
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