Tail Rotor Mischief.

[Granpappy]

I took my Trex 500L Dom out for a spin this morning, and BANG, she went into a spin and then recovered. I brought her back and the tail rotor was behaving very oddly with waggling and bouncing back. Anyway I checked the drive chain because there seemed to be a lot of backlash and noticed some of the teeth on the bevel gear stripped out. (Photo below).

I've no idea what caused this, no previous impacts or anything. I took wed, thurs, fri off work to do a bit of flying. Yesterday my 450 crashed because of either TR Servo or Gyro failure (I haven't determined which yet). This morning this on my 500L. So it is Thursday lunchtime and I have no helicopters left. Marvelous.....

[Delarado]

Thats a shame Youve had a tail strike at some point it would seem, if you look at the blades you can see where theyve been forced round and hit the grips

[Granpappy]

Thats a shame Youve had a tail strike at some point it would seem, if you look at the blades you can see where theyve been forced round and hit the grips

I see what you mean. It's interesting because this is pretty much a virgin heli. Only the second flight today. I did run it up and take off from a grassy area which I had to land in when a dog walker wandered by unexpectedly. I wouldn't have thought it would strip the gears though. That sort of impact would have destroyed the TR blades. Oh well......

[bigpops]

If the tail did catch on the ground, you got away with it very lightly.

The last time I caught the tail on a Trex 500, it instantly folded itself in half and cost about £100 to fix it.

[bill rob]

I glued a small bit off an old tail to mine to lift it up further from the grass,,seems to work.

[Granpappy]

I glued a small bit off an old tail to mine to lift it up further from the grass,,seems to work.

Sounds good. I was just wondering whether to strip it down in preparation for the new gears arriving tomorrow................or just go to the pub.

I think I will go to the pub.

[Delarado]

pub every time

Those gears are quite sensitive. Even a little damage on one tooth can cause several more to strip over time, as each tooth is taking more stress to make up for the damaged one, eventually they all start to fail like dominos!

[Mike Sanders]

You must have caught the tail blades in the grass as you landed. It is a common occurrence.

I have made a small disc of clear plastic and bolted it to the bottom of the fin so it raises the tail another 10mm or so. It has saved me quite a few tail drive gear sets.

[dillwhacker]

The gears always strip if the tail blades hit something strong (like a blade of grass or an ant)...
I always fit 550 tail-fins to 500s and 700 fins to 550s just for that extra inch.

[Granpappy]

I found a real oddity when I replaced the gears today. The 4 M2.5 6mm bolts that hold the side plates on (2 on each side) bottomed out before the side plates were tight. This is how it was assembled from the factory. I'm guessing that under load, the side plates would have spread a bit reducing the meshing of the gears and causing slippage. I rung the Align dealer who told me the plates should be tight. Anyway, I shortened the 4 bolts with a dremel and refitted the side plates.