Blimp - Matthew Warren

I bought the following pieces: (I had links to all the components I used but the products change constantly)

3 press fit propellers
3 micro servos (around 4 grams)
1 tiny receiver (around 4 grams)

I already had:

small 1s, 100 mAh LiPo batteries
a short thin carbon rod

In total I spent about $25 plus shipping. Not too bad.

Most servos are easy to open. There are either screws in the back, a sticker acting as a piece of tape, or a plastic band. Once the servo is opened, there will be three main types of parts to deal with. The gears, which can be thrown away, the motor, and the circuit boards. Attached to the circuit board is a potentiometer that detects the position of the servo. The pot can either be chopped off and replaced with a resistor, or centered and secured. I went for the easy method of centering the pot and then putting heat shrink over the circuitry to prevent damage. The potentiometer is centered if the "servo" is commanded to a neutral position and the motor doesn't spin. It is easily adjustable by hand. The propellers were simply pushed onto the ends of the motors where the pinion gear used to attach. Due to the shape of the propellers, they work more efficiently in one direction than the other. This means that the blimp goes forward better than it goes backward. Keep this in mind when installing the propellers. The lift motor needs to blow air down more efficiently to keep the balloon flying.

Disassembling the servos is the hardest part of process. Once this has been finished, the three servo motor need to be attached together. I used the thin piece of carbon fiber as support. The three motors and a small receiver were all attached to this carbon stick. Version 1 had one motor facing forward for forward thrust, one facing sideways for yaw control, and one facing up and down to control elevation. This is the easiest to set up. I decided later for version 2 that I was better off with two motors facing forward on each end of the rod and one in the middle for elevation. I then used mixing in my transmitter to vary the thrust of the two forward facing motors for yaw control. This resulted in a slightly faster blimp. With either design it is a good idea to balance the gondola so that the elevation motor is in the middle and roughly lined up with the center of mass.

Once the gondola was completed, it was time to pick out a balloon and attach the gondola. The all up weight of my gondola was 13 grams, about 4 grams heavier than the professional gondola. I walked around the local grocery store with a scale and weight and eventually chose a balloon with 20 grams of lift. I have used football shaped balloons and numerous aquatic animal balloons that look great floating around. Once I got home, I found it was tricky attaching the balloon and the gondola cleanly, a situation not helped by the fact that my balloon kept trying to escape and hit my pointy popcorn ceiling. I ended up attaching the gondola with masking tape and kite string. I ballasted the balloon with coins and small magnets so that it barely sinks with the motors off. This prevents the blimp from getting stuck at the ceiling if the battery dies.

A typical balloon worked for about a week for me. The blimp has proved super entertaining. It is easy to set up, works with any balloon, and can be flown by kids without risk of damaging the walls or furniture. I recently acquired a tiny integrated fpv system that runs on 3.7 V. This enabled my first fpv blimp. It is a lot of fun around the house and the blimp is one of the only aircraft I can fly fpv in my house without risk of damage. (Written before the tiny whoop craze)