Once we decided to use the foam square gyroscope, we proceeded to experiment with different ways of attaching helium balloons onto the rigid frame.
Firstly, we bunched three balloons together and attached each bunch onto the sides of the gyroscope. Unfortunately, it turned out to be an unsuitable method of attaching balloons as strings and tape were not taut enough to stop the balloons from moving around the gyroscope. In fact, the structure was so flimsy that thrust from the drone causes it to rotate upon takeoff, which is undesirable.
A side view illustrates the problem more clearly:
To increase rigidity, we attached two foam crossbars onto the gyroscope. The crossbars pushed the balloons apart and stopped them from moving around the frame. However, due to the added weight, we added four more balloons to the structure to provide sufficient lift.
Yet, it turns out that the structure was now too heavy to manoeuvre efficiently. Thrust from the drone had difficulty propelling the structure in the desired direction due to the significant increase in drag caused by the addition of more large balloons.
Finally, after some trial and error, we found the most suitable way to attach balloons onto the gyroscope frame while maximising manoeuvrability. Using nylon string, we tied the balloons individually onto the frame, with three balloons on each side. This arrangement ensures that thrust from the drone does not blow onto the balloons so strongly that they move about too much and affect flight stability.
To increase lift so as to maximise power-saving capabilities of our prototype, we added two more balloons. However, with thrust from the drone, the entire structure now has positive buoyancy, which means there is a net upward force causing it to move higher and higher. This makes it difficult to control the drone, as opposed to the prototype with six balloons. For the six balloon prototype, it has slightly negative buoyancy in flight, hence there is a net downward force on the system. This causes the structure to stay within line-of-sight when flying, which enhances manoeuvrability and stability.
Overall, after repeated testing, we figured out a way to attach the balloons that strikes a good balance between manoeuvrability and power conservation.
