I upgraded the tail motor on my 4G3 double brushless to the 2.9g outrunner commonly available. Recently after a hard landing onto the tail, the tail motor shaft snapped right off. It was probably also weakened from the few times I'd straightened it. I thought I was grounded until a new tail motor came... Not so! I took it apart. It's easy: just use a pin (needle, etc) to pop off the c-clip at the back of the shaft. Then the shaft/bell assembly pulls right out.

Use an awl or other small tool and hammer to drive out the old shaft. To be safe, I supported the bell part using an old gear that fit right up into the open side. Then when driving the shaft through, I don't risk bending the probably fragile bell. In any case you need something with a hole in it for the shaft, as you drive it out.

What to use as a new shaft? It's 1.5mm in diam., but reduces to 1mm on the outside where the tail rotor attaches. It turns out the main shaft from a 4#3 heli is 1.5mm! Perfect, and I had several old ones from when I used to fly that piece of junk. I cut from the bottom section a piece of correct lengh. It even has a small hole formerly used for the main gear pin on the 4#3. You can use this instead of the c-clip. Unless you can machine a tiny groove into the end of it that is.

So then I just drove in the new shaft (round off the end of it to make this easier). Reassemble. I glued in a tiny piece of wire in the shaft hole instead of the clip, since I couldn't...Continue Reading