Step 3: Mass and Lift Capacity
So I ended up with a control and video feedback system just under a 100 g.
Then I weighed the other RC components: servo’s, batteries and extension cords and everything together. Note that at that time I was still thinking to use a fourth servo (the white one) to tilt the camera, which I later dropped to keep it simple. I was at 172g
I pre-inflated the balloon with air to its desired size, which was determined by the maximum diameter still passing a common door. I tested a plastic clamp holding it closed and not being very impressed with it decided afterwards to use some string.
I left the air out and put in a good blob of “Hi-Float”, rubbing it out al over the inner surface. Then I inflated the balloon with helium to the same size again.
I checked the lift capacity by subtracting the weight from the ballast with the balloon pulling upwards from the weight when holding the balloon down by hand: 260g. So there was still plenty of room for the iris, a frame, small parts like the propellers and margin for loss of helium over time.