heli_headcase
Veteran
Location: Hovering around Atlanta
| Before you fly...There are a few weak spots in the tail rotor design; easy to fix but has to be done.
#1) Grind a pair of SHALLOW flats on the tail drive wire where the pair of M3 set screws contact the wire just forward of the tail gearbox.
#2) Disassemble the tail blade grips. Remove the long M3 setscrews used as axles for the grips. The tips of those screws must fit inside the hole cross drilled through the end of the tail rotor shaft. The hole is almost exactly the same diameter as the tip of the screws. You must put more of a point on the tips of the screws and be sure the tips fit into the hole, not hit the steel next to the hole. Follow?
#3) Use red Loctite to install the M3 screws back into the tail hub. Mind the screw tips and the hole in the shaft.
#4) Back to #2 for a moment - When the tail grips were disassembled, did you look carefully at the thrust bearings? I'll bet they weren't assembled correctly. The washers (races) are two pairs of specific sizes. Two are larger and two are smaller. The ID and OD (inside and outside) diameters follow in one race. The smaller races go outboard, next to the locknut and the larger races sit next to the tail hub. Unless someone already fixed this, it was assembled wrong from Kyosho. Note this upon reassembly and don't forget to use thick grease on the balls in the bearings.
#5) When the bearings are reinstalled on the screws, place a little red Loctite INSIDE the nylock nut prior to screwing it down on the setscrew. You don't want thread lock being pushed toward the bearings and the nylon in the nut isn't to be trusted to hold the nut from rotating in operation. Stop turning the nuts when they just touch the bearing assembly and then back off 1/4 turn.
#6) Open the gearbox and make sure the input shaft bearings are completely greased. These are "open" bearings and have no shields. I always saw dry bearings in these cases. Any light grease will do.
#7) Make sure the brass sleeve and aluminum nut in the pitch slider are correctly thread locked and that there is NO binding or roughness in the slider's bearings. It's common to find the nut tightened and crushing the bearings. It's far better to see a tiny bit of play in the slider than no play at all.
#8) See that black washer under the screw head for the white tail pitch bellcrank pivot? Remove it from under the screw head and place it last at the tip of the screw before it threads into the mount on the gearbox. Left in the factory position, the bellcrank will bind with the slightest of tightening effort of that screw. With the washer directly against the mount, the steel sleeve in the bellcrank can't be pressed into the plastic of the mount allowing the screw head to get too close to the bellcrank pivot center, pinching it.
#9) Lastly (bet you thought I'd never stop  ), make sure all of the drive wire guides in the tail boom are spaced evenly apart and not all run together or all at one end of the boom. Two wire guides were provided in the earliest DX heli's, three were in later models. Frankly, I used two and drilled them to accept a brass tube of 1/8" outside diameter, approximately 4" shorter than the tail boom. Glue the brass tube into the guides and then grease the drive wire before installation. Much better than stock. Don't forget to tighten the tail drive coupler set screws onto the flats you made in Step #1.
Happy Concepting!
HHC
So many heli's - too little time... |
