Exoskeleton strength: Scaling setbacks
Why did Tube 3 crumple?
When the tube and cube size is multiplied by 2, tube strength multiplies by 4, and weight multiplies by 8. So, as size continues to increase, tube strength increases at a faster rate, and weight increases at an even faster rate. When the tube and cube get to be a certain size, weight will have outpaced tube strength to such a degree that the tube crumples.
The same principles apply to arthropods. As you saw in the first experiment, if you scaled up an ant proportionally (keeping its exoskeleton thickness the same in relation to its body), the ant's legs would crumple under the strain of holding up its body.