I have two helicopters. A Syma S109G and an S108G. They are –by far– the most-fun thing I can imagine at this price point. What is more, they absorb ridiculous amounts of crashing without apparent damage. But they will take damage and wear down eventually. The S109G was not able to lift itself, even after I straightened out the shafts and cleaned and lubricated the gearing. I thought the battery might be going downhill. The S108G was flying okay, but it wanted to turn left more than it used to do, and it sounded like it had a little gas motor inside, after it hit the refrigerator. Today I had some slack time* and decided to take a peek inside both planes.
The S109G was flying again, maybe a minute per charge. A kind soul at work donated a full set of replacement blades from his dog-eaten helicopter. The first set of blades was thoroughly chewed-up from repeated crashes. The lower main rotors lost lots of chunks (about 1/4 total length x 2mm) and it would still fly, but the upper rotors losing chunks was the end of the fun. New blades let it fly again, which was not entirely unexpected. But it wasn’t flying amazingly well, or for long. I opened it up and measured the power going to the motors. These aircraft have two little motors and two little transistor switching circuits to drive the motors. I thought in all my tinkering I might have killed one of the FET switches. 4.2V DC at the motor terminals looked about right. But one motor wasn’t turning strongly, if it turned at all which it did about 1/3 the time when I hit the collective. Dead motor. Boo. I left it in pieces and moved on to the S108G.
The S108G had lost a tooth on the gears when the rotors suddenly stopped under the fridge. That was the noise. I went to swap in a gear from the S109G and found the gears in the S108G are captive, held on by a pressed-in pin. Bummer. But the motors are the same, and it looks like each bird has the same two motors, a black top and a white top. They have the same motor output gears, spaced the same on the same-colored motors. I pulled the defunct white top motor from the S109G and traded it into the S108G. This involved fine-wire soldering and a delicate touch but it was done.
Sharky rides again!** I had forgotten how high-performing the S109G is. That fresh motor made it a whole new airplane, thank God. And now that I’m a better pilot I think this set of blades should last a bit longer. Now I just need to scratch together a couple of dollars for a set of gears, rob a motor from that other dog-eaten helo, and I should be back in the fun times-two!
Thanks God for making me clever enough to figure this stuff out.
*nap time for the babies. #4 ended up n0t-sleeping and I had #1 and #2 entertain him. This worked only marginally well but at least no 3mm long screws ended up in the carpet.
**The S109G has shark teeth on the front, and the children dubbed it “Sharky” as it chased them around the living room. The S108G Laser Mouth, with a very bright white LED under the nose.