Heli Tail Rotor Problem

[adriantan]

Hi... I have a constant problem with my ZAP 400. My tail blades fly off now and then. The reason being the small ball bearing holding the blade at the tail always seem to fail. The question is... is this normal failure on stock tail setups? I just don't want it to give way when I am high up in the air. When you lose the tail... you lose the chopper. And even though the bearing isn't that expensive... the rest of the replacement parts are! most of the times I have been lucky in that the tail blade flies off even before take-off but what happens if it's already flying in the air? Scary thought.

How can I ensure the tail blade doesn't fail?
1) The blades are balanced so failure can't be due to excessive vibration.
2) The tail blades could be pulling too much centrifugal force because my headspeed is pretty high. Would that be a problem? Surely the bearings can handle high rotor speeds.

Has anyone experienced this problem on their Zaps? Does the TREX have such problems? Perhaps its time for an upgrade...

[Trex SE]

Try using thread lock to lock down the allan bolt holding the tail rotor grip. Be very care full that the thread lock not applied to the bearings.

The step is simple.
1 - hold the tail rotor blade grip with bearing already sitting in.
2 - push the allen bolt in till the threaded portion extended from the blade grip.
3 - apply the thread lock to the threaded portion. A little will do.
4 - with the allen driver ( 1.5mm ) hold down the allen bold in the blade grip and screw it down onto the hub.

I hope this helps.   

[adriantan]

hi Trex....

Thanks for the tip but I doubt it would work. The problem I have is not with the bolt working loose. It's with the problem of the bearing (which the bolt holds the tail blade onto) failing. When the bearing fails (i.e. breaks apart) then the whole tail blade flies out even though the bolt is still retaining the inner part of the bearing and still holding onto the shaft strongly.  The guy at the shop tells me that this is a part that fails all the time so could this be a design flaw 

[Trex SE]

It is quite normal for the taper screw to loosen out and eventually the tail blade fly off. The plastic blade grip is a wear and tear part especially if the tail blade hit the ground too often. You needed to change it.

[adriantan]

Well unfortunately that's not the problem. It's not the taper screw working loose. It's the BALL BEARING which is breaking apart! I must be the first and only person experiencing this bad sh*tty luck.

Basically when the blade flies off, it will consist of TAIL BLADE, PLASTIC GRIP, TAPER SCREW, all still nicely fixed together. The other part remaining on the rotor hub would be the allen screw and the inner wall of the bearing, still tightly securred.

I do wonder why the ball bearing sleeve can fail and break apart. Even the small ball bearings come off (naturally) when the bearing fails. The failure part is actually the "thin plastic" sleeve which holds the inner and outer walls of the bearing in place. :'(