Step 6: Adding the Servo Axis

Start with a long, thin beam of balsa - the longer the better, up until it starts bending with the motors. Mine is about a foot long. Next, cut two struts of balsa, about 2", and glue little cylinders of plastic to the end of each. Slide the long beam through the cylinders and keep it there. Now, build little cradles out of balsa to hold the motors on the end of the beam -- you can see these in the overhead shot . They should be a tiny bit less wide than the motors, so that the motors are gripped firmly once in place. Glue one strut to each side of the frame, at the back -- see the picture. Once those are secure, glue little knobs of balsa onto the beam, on the inside of the plastic cylinders, so that the beam can't move side-to-side from its centered, stable position.

Once the glue has dried, it's time to add the shaft mechanism. Get a 2" beam of balsa and glue a tiny piece ( 1 cm ) of coffee-stirring straw to the end. Whittle down a bit of balsa until it fits through, then slip it through the straw and cut it down so there's a little bit sticking out each side. Glue each end to a 1cm piece of balsa, oriented perpendicular to the straw and the shaft, and glue each piece to the long beam below. Let it dry. If you did this right, you should have a shaft fixed to a joint on the beam; when you push and pull the shaft, the beam should rotate one way and then the other. This is really important: make sure that the shaft is fixed to the top part of the beam when the motors are correctly oriented, facing away from the main blimp frame.

Finally, the servo. Create a 'cradle' that fits around the servo like the one seen in the picture, and make sure the bits above and below the servo are made of plywood or another hard wood; I glued them to a third balsa piece. Drill one hole into each of these strong sections, then thread a thin wire through each hole and though the mounting holes on the servo. Twist the wires tight so that the servo doesn't move during operation. Glue or otherwise affix a little piece of wire to the end of the shaft mechanism that's nearest to the blimp frame, then fit the wire into one of the small holes that come pre-drilled in the servo arm. It should fit snugly but be free to rotate. Finally, glue the wooden servo mount to the main frame, and you've finished the servo assembly.

Here are a couple videos of the servo mechanism in action:


Be aware that you may have to fine-tune the length of the push-rod to get the range of motion you need. Anything above 45 degrees of rotation will probably be enough, because putting the motors in reverse will effectively double that range.
You blimp looks awesome, only the code is without any doubt the most incomprehensible code I have ever seen! I can't make heads or tails from it. Could you explain the how te code works? I really like the 433 MHz set I got, but I haven't found a clear code that I can adapt to my homemade rover. <br> <br>Thom
Darn, I have been trying to figure out your code for quite some time, IT-IS-SO-SIMPLE, I have tried to use virtualwire but then I can't use the servo library (they hate each other). Thanks for sharing it!
when I first read the title I accidently read &quot;Hydrogen bomb.&quot;
Nice work on this project! I had the same 433 Rx Tx units and could never get them to communicate properly! Definitely one of the best troubleshooting sections I've read!
this soo reminds me of the hindenburg. tho to be fair, hydrogen had nothing to do with the explosion. zinc paint(?!) was the problem. <br>very cool project. <br>tho 433mhz might not be legal in USA, but even a toy car with arduino could work
You are my hero. I have tried filling a smaller blimp with hydrogen in the same way, but using only very small amounts of lye (five attempts with no success). I would love to build a setup like this some day, especially one using a hydrogen fuel cell for power. One question: does the water buffer remove any steam or water vapor from the hydrogen entering the envelope? I always worried about getting water in it. Thanks for a very informative 'ible.
You're right to be worried about water vapor. It will only be a problem if you let the reaction get too hot, which will make it start steaming or even boil if it gets out of hand. If you make sure it doesn't get more than a little warm ( I dunno, 75 deg F), the water vapor will be negligible. If you're really worried about it, you could try running the gas through a percolator to cool it down before it enters the envelope (meaning some of the vapor would condense out). The buffer I have is mainly to prevent any water in liquid form that bubbles up from getting close to the envelope. Don't give up on lye!
Awesome. Love the chemistry lab details and the troubleshooting section.

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