Planning Task: To build the tallest tower possible using only wooden blocks and rubber bands that will allow access for a small toy deer. Potential Issues:
Possible Solutions: A door way can be built up by gradually bringing the layers of bricks on top of two pillars, forming a pyramid shape. This sollution is quite fragile and may not be able to support the tension forces created at the top of the gap by the compression forces from above. A pole could be created by connecting three blocks with rubber bands that would be able to carry the forces around the doorway and down to the ground.
Another option we considered was creating square shaped blocks and connecting them with rubber bands, as we found this structure much stronger than thin pillars.
Compression forces acting downwards create outward tension forces on the bottom surface. Therefore reinforcment needs to be used in areas of high tension such as above doorways to carry this force around the gap and down into the ground.
Materials: We determined that the blocks were all a constitent, flat shape and were relatively light, meaning they are easy to stack without needing to be attached and will not create too much compression force. However, we found that using rubber bands to attach multiple bricks together decreased this ability to stack the blocks, therefore we looked into ways of avoiding the use of rubber bands in the construction.
To create the rest of the tower we decided to stack the blocks and offset the joints so there were no week sections where all the gaps were alligned. We decided a square shape with rounded corners would be easier to create and stronger as there are no edges. We also decided to curve inwards each of the sides to counteract any external forces that may have been present.
Constructing the tower
We began by gradually building up the walls, leaving a gap at the front that would just allow the deer to move in and out. We decided to make the base quite large, as this would allow for more height as we were planning on reducing the size of the tower the higher we got and we realised we had enough blocks to do this. In hindsight, it was unnecesary for it to be this large.
We had some difficulty creating the doorway over the entrance and a small portion did collapse. However, we learnt from this and maganged to gradually build across the top by ensuring each piece that we insterted was counterbalacnced.
We deciided not to conitinue buiding up the tower the whole way round, as this would reduce the amount of compression force on the doorway and would allow us to gain height more quickly. This did however make the exposed sides vulnerable to tipping in or out and so we had to be careful to build directly up.
As shown above, the compression forces travel down the tower in a zig-zag path though the overlaps in bricks. At the opening, forces are diverted outwards and carried down to the ground.
Testing the towers stabilty One of the other groups used the same building technique, but had fully enclosed the tower. We found that the tower was able to hold a significant amount of weight when placed carefully on top, as the weight spread down the tower. As seen in the picture on the right, the tower was not built up perfectly straight, meaning the weight was not distributed evenly, putting more pressure on one side. Had this not happened, the tower would have been able to hold an even larger weight. The tower collapsed when more bricks were poured on top, rather than gently placed. This is because the falling blocks created unbalanced forces on parts of the tower.
Deconstructing the tower
After completing the tower, we began to take out pieces to test its stabilty and identify the collapsing point. We found that quite large sections of blocks could be removed without the tower collapsing, however it did greatly reduce its structural stabilty. The tower collapsed once we removed all of the blocks on one half as the remaining side had nothing to support it and evidently wasn’t built perfectly straight.