Air Swimmers come cheap, but they are quite large compared to modern RC blimp standards, making them not very manoeuvrable in smaller rooms. So with Plantraco creating a new class of nano blimps I wanted to check how difficult it is to build an air swimmer in the nano blimp class, i.e. based on a 9" latex balloon.
Building a working Nano Air Swimmer proved to be quite simple (keeping it simple being the key). It's all in the tail: everything is done with just one servo. The servo combines propulsion and steering, as in commercial air swimmers.
While commercial air swimmers move their center of gravity back and forth to move up and down, I went for an even further simplification: the nano air swimmer is permanently pointing slightly up and moving forwards means moving up, stopping means moving down (a trick used in 2ch toy blimps).
Check out how it performs in this video:
Step 1: Materials and Tools
Used RC gear:
- An ultra micro receiver under 1g. I used my favourite 0.65g DelTang Rx33 DSM2 receiver. This is the most expensive part at around 30 EUR. With a slightly larger 11" balloon you can use the 2.2g OrangeRx R415 which can be found at 22 EUR to 10 USD, depending on the supplier.
- An ultra micro servo under 2g (a regular type, not a linear one). I used a so called 1.7 g servo, which actually weighs 1.9g with wires and connector. Make sure the connector is compatible with your receiver. Such a servo goes 12 EUR to 4 USD, depending on the supplier).
- A 1s LiPo battery around 2g. I used a Zippy 50mAh cell. With a fresh 9" balloon (carrying 8 g) or an 11" balloon I was also able to use a more common 2.5g 80mAh one. Such batteries should cost around 5 EUR or less. Obviously you will need a suitable charger (not shown).
- A 25cm battery extension lead to connect your battery to the receiver. A shorter lead works too, but it allows for less trimming the weight distribution. Specialist suppliers of micro RC gear can make that to order for under 4 EUR.
For the tail:
- Some EPP sheet (Expanded PolyPropylene), 3 mm thick. I used a triangle with two 16 cm long rectangular sides
- About 5cm of 0.8 to 1mm diameter carbon rod.
You can get all of te above at aether-sciences.
For assembly and trimming:
- Some sewing thread.
- Tape (scotch tape or selotape).
- A couple of grams of putty, to be used as trim ballast.
All this is added to a 9" latex balloon, inflated with helium (and treated with Hi-Float). You can get it at the balloon shop (1-2 EUR for one) or bring home a helium bottle (rented or bought, around 50 EUR for a canister + 50 balloons). Depending on temperature and moisture a latex balloon will last longer or shorter. The spare buoyancy needed for the nano air swimmer lasts roughly a day.
- A scale accurate to 0.1g
- A felt tip marker pen