Making a cable stayed bridge
By the end of the three days the children will:
…be familiar with all the types of bridges that we have designed
…have made a chosen bridge design
…have tested and modified their bridges
…have built a second bridge that improves the strength and design quality of their bridge
…have made a landscape to place their bridge in.
After a presentation and explanation about the different types of bridges stresses and loads etc. we then began to decide on a bridge that we wanted to make. The group decided to build a joint project that incorporated the strength of a beam bridge with a cable stayed bridge and a truss bridge. The first bridge was drawn out on individual white boards and it was decided to use lolly pop sticks as the road on two long square rods of wood. One would also make the truss with lolly pop sticks. As is usual during the design/making process, changes were made due to moments of inspiration. One was that the coloured lolly pop sticks would be better to use than the plain ones. They thought of arranging them in a rainbow pattern. The other was not to use the lolly pop trusses. The cable tied stays were drilled (first picture) at five centimetre intervals. The stays were placed near the end of the bridge removing part of a lolly pop stick to get them to sit against the wooden rods. The string cables were then tied every five lolly pop sticks apart. The children had time to test the bridge. Two litres of water was placed in the centre which was supported easily by the bridges sturdy construction. They also had time to play with their new bridge. I brought them some cars and also LED coloured lights to brighten up the bridge even more.








Making of a Truss bridge
The Truss bridge that started out as a part of the rainbow cable stayed bridge, now needed finishing. Although probably the strongest bridge with triangular truss structures was not the most interesting to the boys. However, on the second day we finished the truss sections. On the third day we joined the two truss sections together and added a road made of cereal box card. The strength of a truss bridge is incredible with it easily holding three litres of water. I think we could have put more on it but there were no more jugs.




Making a tied arch bridge
This was the final bridge the boys made. We didn’t have any flexible arch material so we created a triangular leaning arch with string cables onto a cereal box card road. The stays and arch construction were difficult to make and the drill holes for the ties were also tricky. However, we got there in the end. The centre was joined across with rods drilled into the arch and wired together. We decided we liked the red of the Golden Gate Bridge so it was painted red. This also was surprisingly strong with a two litre jug placed on it with no visible tearing of the card or cracking of the structure.
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