An Upper Rotor Fix for the Robocopter GST T-Series
My girlfriend recently bought me an Extreme Flier Robocopter GST T-Series R/C mini helicopter in a groupon deal. It's amazing fun, essentially a very small radio controlled helicopter that you fly inside your house. It's rechargeable from a computer, very agile and controllable (once you get the hang of it and don't panic) and has what appears to be a reasonable construction. It's body is a metal shell, and most of the parts screw together, all in all, very repairable. Which is why it's strange that a) the upper rotor assembly hangs off two plastic pins less than a millimetre wide and b) the spares seem very hard to come by.
When mine broke, the initial symptom was that the helicopter started swinging round in circles. Then the upper rotors hit the lower ones and it fell out of the sky. There are two items that control the upper rotor assembly, the plastic cross pin that holds the rotor hub onto the metal shaft and the two loop-clips that connect the balance bar to the rotor hub. The loop-clips just pop off however, the cross pin had actually snapped. Super glue didn't work.
My Quick Fix for the Rotor Assembly
You'll need a pin of some description, I used a sewing pin (needles are too brittle), a pair of pliers, preferably long-nose with a reasonable cutting section, a fine needle or second pin (finer than the sewing pin), a small cross point screwdriver, some small pieces of rubber or plastic (I used some insulation off an old pair of headphones), a gas flame (on the stove top) or soldering iron and a steady hand. PLEASE NOTE, sharp hot objects will be used, don't stick yourself, burn yourself or otherwise injure you or anybody else. Try to make sure an adult is at least supervising the repair work...
1. Disassemble the upper rotor assembly.by first loosening the two screws just under the balance bar. Take the whole assembly off the main metal shaft.
2. Take the rotor hub off the plastic shaft section (if it hasn't already fallen off).
3. Take apart the hub by undoing the two screws at opposite corners of the square (not the ones that hold the actual blades onto the hub).
4. Take the plastic rod with the balance bar attached to it, look for the cross pin. On an unbroken assembly, the cross pin sticks out another one or two millimetres on either side and these fit into the holes on the inside of the square rotor hub. When these pins break, the hub is no longer attached to the shaft, apart from at the loop-clips.
5. Using the pliers, cut the point and the head off the sewing pin to leave about 6mm of the pin shaft. Cut the plastic or rubber so it is about 1-2mm long and will fit both over the shaft of the pin and into the holes on the inside of the rotor hub.
6. This is the very delicate part, Heat the needle in the gas flame, (holding it with the pliers) and while it is hot, carefully poke a hole through the remains of the cross pin, as level and as cleanly as possible. (If you have a dremel tool and some skill you may be able to use a very fine (1/4mm ish) bit to drill the hole instead). As the pin is hot, it should go through quite easily. To pull it out, gently twist the pin with the pliers until it frees and you can pull it out.
7. Poke the 6mm pin shaft through the hole. You will not be able to use it like this as the main shaft has to go up through the plastic bar all the way to the balance bar at the top where it is held on by the two screws just under the balance bar. You will however, be able to see whether the pin actually fits.
8. Fit the balance bar back onto the helicopter and tighten the two small screws that hold it in place. The main rotor shaft now runs up the middle, across the hole you have just made.
9. Cut the 6mm pin shaft into two equal parts with the pliers. Try to make sure they are equal. Check they fit into the holes in the cross pin and don't stick out too far (otherwise the rotor hub will not fit back on).
Spares and Repairs for Other Makes
10. Carefully heat the small pins and quickly set them in the cross pin. The heat will slightly melt the plastic, helping to keep them firmly seated. Alternatively super glue could be used, though be careful you get the pins seated correctly before the glue sets.
11. Put the small pieces of rubber or plastic over the pins to firmly hold the rotor hub onto the pins.
12. Re-assemble the rotor hub and make sure all screws are tight (careful not to strip the plastic by over-tightening the screws). Clip up the loop-clips and you're ready to get flying again!
I've flown my copter for about an hour (~10 flights) with this fix and so far its holding and she flies steady. I am going to get a replacement if its available but am anticipating this might take some time. Meanwhile I hope this keeps you flying too! Please note, this is a temporary fix to keep me in the air until I can get a spare part ordered.