GT 500 tail explodes again

No problem bud.

I have heard the stock shafts are too soft anywho so it may be time to upgrade to an align one there...  best of luck with it tho bud.

Regards,
Demon

just to rule out the obvious Trev, you did use loctite on the tail grip bolts, didn't you? And checked the original bolts when you got the kit? Sticky bearings, especially thrust bearings, can cause the grip bolts to screw out in flight.

Hi Trev, I was pretty sure you had actually loctited the bolts, and that they hadn't simply unscrewed, but I wanted to be certain of that. Somebody needs to load test these cheesey bolts. I don't think there would be a problem using grade 8.8, though, since you'd expect a failure load of approx 200kg for an M2 bolt in 8.8. Even in mild steel, they should take up to 70kg, so I suspect there have been some bad batches in the kits. It's odd that the 500 uses M3 tail blade bolts, and M3 in the main blade grips too. The forces on the feathering spindle bolts must also be significantly higher than those in the tail bolts, but maybe they were from a different supplier, since they're M3, and happily we don't seem to have heard of many failures. I think the sensible course of action is to use known good bolts for the tail and main blade grips, for peace of mind and for safety.

Hi Demon, yes, I know about fatigue, I am a civil engineer by trade - but without wishing to be too much of a nit-picker about it, fatigue failures result from cyclical stresses. With a heli tail rotor running more or less at a constant speed, there isn't a great variation in stresses once it's running. It also seems that users are reporting very early blade grip bolt failure - like on the first flight even.

I wonder if the cheap bolts also have some "necking" at the bolt head - which would reduce the cross-section area and consequently further reduce the load capacity. If the threads are sharply cut, there could be greater stress concentration too, having a similar load-reducing effect.

The fact is it would be illuminating to load test the bolts, and of course it remains a good idea to assume that the HK bolts are not up to it and to substitute known good bolts. The unfortunate thing is that the problem may be limited to just an isolated batch of bolts. Maybe someone who's experienced a bolt failure might keep the other bolt, in which case it could be tested.

It's my intention to get a 500 this year, but probably not until late Summer, at which time I can pull test the bolts myself. I hate to admit it, but it's stuff like this that helps to keep me interested in helis - it might be boring if everything just worked!

I went to the local bolt and bearing suppler.Was able to get grade 12.9 high tensile metric 2mmx8mm bolts.I had to cut them back to 5mm long for the tail rotor grips,this I did with side cutters so not to get them hot.I then dressed the thread ends lightly on the bench grinder,again don't get them hot[this weakens them].