So, as I mentioned in a previous article, my sister bought me a JXD Drift King for my birthday. This was extra cool because I had just received my green Syma S107G the day before. I was a little extra excited about the JXD Drift King because it is a four channel helicopter unlike the Syma, which is just a three channel helicopter.
Sadly, after just a handful of crashes, my Drift King we just spin wildly about a millimeter off of the floor — even at full throttle. I could tell that the lower rotor spinning much faster than the upper rotor. In fact, the upper rotor was barely spinning at all, and this is why the helicopter was spinning wildly.
The Problem: A Slipping Gear
On the Drift King, the upper and lower rotors are powered by two different motors. One motor, which I will call the “front” motor is positioned towards the nose of the helicopter and drives the lower rotor. The other motor, which is positioned more towards the rear of the fuselage, drives the upper rotor. For lack of a better term, I’ll refer to this motor as the “rear” motor. But please don’t confuse it with the completely separate motor that drives the small rear rotor, which has nothing to do with this issue.
What turned out to be the problem, was that the drive gear on the rear motor had slipped so that it was making contact with the circuit board. Below I have an animated diagram which might help clarify everything.
The friction between the drive gear and circuit board was apparently causing the motor’s shaft to slip quite a bit inside the gear. So, even though the drive gear was still making contact with the giant gear that turns the upper rotor, it simply wasn’t spinning very much because the motor’s shaft was just slipping inside of the little drive gear.
What Almost Worked
I found that I could wedge the tip of a really small screwdriver between the drive gear and circuit board and slide the gear back into the proper position. The helicopter would work again, but the gear would just slip back out of place after a crash or two. In fact, after doing this a bunch of times, the gear would slide down the shaft simply by activating the throttle.
Tip: The smallest screw driver I could find still had trouble getting in between the gear and circuit board. So, later I made a little tool by straightening out a paper clip and filing one tip of the wire to a sharp edge.
Did Also Almost Worked
Update: Originally I thought my fix was permanent, but it merely lasted longer than earlier attempts. It stayed fixed for about a week. But the gear finally slipped again. It’s back to just spinning wildly on the ground. >:(
Now, before I show you what I did, let me say here that, if you follow these instructions, you are probably going to make the helicopter where it won’t be returnable. So, make sure you want to do this instead of just returning or exchanging it (if those are options for you).
Basically what I did was take the helicopter completely apart so I could more easily access the drive gear. I then slid the drive gear up the shaft until the shaft began to protrude just a tiny bit on the other side of the gear. I then mixed up some two-part epoxy and, using the tip of another paperclip that I bent out straight, I put a small dab of the epoxy over the end of the shaft so that it completely covered the tip of the shaft and also some (but not all) of the gear. Just reading that sounds confusing to me, so hopefully the images below will make it more clear.
After the expoxy has been applied, I set the helicopter parts aside and let it set for 24 hours. At that point, I put the helicopter back together. And the gear has held just fine even though I’ve crashed it numerous times since then.