Lost the tail today

[Bob O]

Tenth flight on the heli, built the bird with the metal tail unit and have had no real problems with it until today. Third flight of the day, about halfway through the flight, the tail let loose while doing sideways tic-tocs.

My friend figured the heli did at least three piros per second for about one second before I hit TH. The heli stopped piroing after a second or two and I was able to get it upright and level, but not before it lost most of its useable HS.

The heli fluttered to the ground from about 20 feet, landing on its skids fairly hard. Damage was extremely limited thankfully.

Both skids broken.
Small crack in the right frame below the fuel tank. This crack is not all the way through, most likely can be repaired/reinforced if needed.

Everything else appears fine pending a closer inspection. The servos appear to be fine as well.

Cause: the pin that goes through the tail pulley and shaft was gone. This resulted in a lost of power/drive to the tail. I haven't done a full inspection, but there appears to be no damage to the tail unit.

I'll post a full update next week on my next day off work. I consider myself lucky to get away with such light damage.



Sent from my HTC Incredible

[rcflier1]

do you have the belt drive? i thought with the upgrades you went tt.

[Bob O]

No, I wanted the belt model.

Just taking a look at the replacement parts, its appears that the pin for the stock rear pulley is of a different type of metal than the one that came with the upgraded tail assembly. I can't find where the pulley in the upgrade is available by itself, so I'll be trying to replace it with a stock pulley.

I'll do some more searching on this before next week.

[Ah Clem]

Bob,

Is the the same, hardened steel pin that is used on the Raptor 50 to retain the pulleys and the Raptor 90 to retain the gears (retained by a set screw threaded in from the end of the shaft)?

If so, someone posted several fixes for keeping it retained, quite a while back (several years, I think the posts are long gone).

One method was to cut a ring from brass tubing and epoxy it around the portion of the shaft where the pin is, so that it could not possibly back out.

The other was to use heat shrink tubing to retain it.

I used the heat shrink on the Raptor 50 and have never had a problem with it. For the Raptor 90, I went with the brass tubing. Either way, they have never come out or come loose.

Glad you got it down in good shape, sir!

[Bob O]

Thanks for the tip Clem.

Yes, it's a pin held by a set screw, but different from the original design. This pin has threads on it, which I use thread locker on. I also used thread locker on the set screw. During my preflight before the first flight yesterday, everything was intact.

[Bob O]

I just looked at the new pulley, which is a two piece design, and the hole where the threaded portion of the pin goes was distorted/elongated on one end. So obviously the pin backed out and caused some damage to the pulley hole prior to being ejected.

The stock pulley with same tooth count appears to have the same dimensions from side to side, so it should be a drop in fit. I know I lost a tail shaft spacer in this incident, but I'm sure there was a spare or two in the kit when I first assembled it.

I should be back in the air next weekend.

[NitroAl]

I had a similar day losing the tail while rolling out of a big loop! At about 60m high the tail swung around 180deg then took off on a random journey of it's own!
Total damage was Canopy, receiver tray,blades, boom and torque tube. I thought it would be toast since it was already aiming at the ground at speed from altitude before the rudder went AWOL!
The cause was a broken torque tube, I'll be damned if I know how or why. It was about 150mm from the tail!

[carlos]

seen that befor Al.
Ranma had done it, he had fitted to long a screw and it was just touching the torc tube.

In any loss of tail situation it is imprtant to hit throttle hold imediatly, this will stop the heli spinning and an auto will follow if the RC modeler can auto.

[NitroAl]

Yaeh in all honesty Carl I think I may have damaged it myself during the previous rebuild!

I have a tip for anybody building a torque tube X50, When assembling the tail boom bracket (BK2217 L+R) do a dry fit of the tail gear mount (BV2269) you will see that there is excess tab that extends outside of the frames about 5mm or so! This would hold the guide pulleys on the belt version but creates a PITA on the torque tube version should you have to replace the black tail drive gear. In order to remove the boom bracket assembly you will have to remove the elevator servo and loosen most of the bolts in the frames to get the frames far enough apart!
If you shave down the tabs until they are flush with the gear mount it makes it a hell of a lot easier to get the boom bracket assembly out!

[johnbs8]

i too lost the tail on my X50 last week. mine was due to tail linkage rod popping off at the tail. Hit throttle hold instantly and brought her down. just before landing the tail decided to spin 220deg and it came in crooked. skidz and tail fin only damage. replaced tail ball and lonk and all is good now. would have been a perfect auto if not for that quick spin at the last min 2 feet off the ground!!!

[Taxus812]

Geese I'm gonna have to do a full inspection of my tail assembly this week. Sounds like a trend

[Bob O]

Yeah, I don't care to go through that type of inflight failure again.

Sent from my HTC Incredible

[DethWshBkr]

Originally Posted by NitroAl

The cause was a broken torque tube, I'll be damned if I know how or why. It was about 150mm from the tail!

Are you sure the torque tube itself broke? That seems a bit scary if that is the case.

I know with my rebuild, putting the new torque tube in, I noticed the new one seems a bit bent. Not kinked, but not perfectly straight. It does have some wobble in it rotationally.
Figure the head spinning at 2000 rpm, and a 1:5 ratio, means that tail shaft is spinning 10000 rpms. If that torque tube is not PERFECTLY straight, or slightly off balance, I can see it just flinging itself all around and causing some good stress.
I will actually be ordering a pair of the bearings and red grommets, and putting a total of three torque tube bearings (PV1376) on the shaft to help eliminate the possibility of the shaft wobbling, especially at high speeds. Whether this is needed or not, I do not know, but I think it may cause me to be a little more confident. I can see no detriments to this modification either.

[carlos]

Originally Posted by NitroAl

Yaeh in all honesty Carl I think I may have damaged it myself during the previous rebuild! !

deathwish your answer is in a previous post

[carlos]

Originally Posted by Taxus812

Geese I'm gonna have to do a full inspection of my tail assembly this week. Sounds like a trend

Taxus hardly a trend if you damage it.

[Taxus812]

nope I wasnt implying a defect. The trend to me is three people with X50's lost their tail rotor recently and had a hard stop

It doesnt matter to me wether it is self inflicted or not. Im taking a close look at my tail assembly.

[Bob O]

Here are some pics I took this morning while repairing the tail.

First pic shows two different tail shafts. The shorter one came with the kit, and is the one intended for use with the stock plastic tail case. The longer one came with the metal upgrade tail case that I was using from the start.



Second pic shows two tail pulleys. The purple one is the stock one that came with the kit. The silver one came with the metal upgrade tail case.



These last two pics show the silver pulley. The one pic shows how the outer hole was damaged while the pin was coming loose. The other pic shows how the holes in the two part design no longer line up. I was unable to separate the two parts of the pulley. Note that they moved freely when new and during initial assembly.





So, being that a spacer for the metal tail case was lost in the incident, I was unable to simply replace the damaged pulley with the stock one and reassemble. So I reassembled the tail with the stock unit. I can't really say that I'm UNimpressed with the stock tail unit, it went together very easily and seems to be without any slop.

I took this time to replace the tail boom with the factory upgrade CF boom. I have to say that I wasn't impressed at all to find that the CF boom is actually aluminum with a CF appearance to it. Just like the CF boom that came with my T-Rex 600LE. For the price, I thought for certain I was getting an actual CF boom.

I also replaced the tail control rod guides from the stock white pieces to the upgraded black plastic pieces. These black ones don't get glued to the boom, rather they have a clamping design with a screw. I also used the QuickUK tail boom support clamp, which has the side mounting for the boom supports. I'm going to use the CF supports off my Velocity 50.

I'll post some more pics tomorrow after it's all back together. I planned on doing it today but ran short on time.

[DethWshBkr]

Originally Posted by Bob O

I took this time to replace the tail boom with the factory upgrade CF boom. I have to say that I wasn't impressed at all to find that the CF boom is actually aluminum with a CF appearance to it. Just like the CF boom that came with my T-Rex 600LE. For the price, I thought for certain I was getting an actual CF boom.

Your version doesn't come with a the carbon/aluminum boom? It's about 50% carbon, 50% aluminum, yeah. I guess it is still lighter than all aluminum, but does it REALLY make that much of a difference?!

[Bob O]

My kit came with a grey aluminum boom.

I don't know if it makes enough difference for it to really matter. It looks nice though.

What burns me is that the description for the CF boom says it's CF:

**************

FEATURES: Carbon fiber construction ensures light weight

INCLUDES: Carbon Tail Boom

REQUIRES: Removing stock aluminum tail boom

SPECS: Length: 26" (660mm)

[DethWshBkr]

Nice thing, that aluminum boom is what, like 8 bucks?? Thats not too bad!
45-50 for the "carbon" boom is salty. I replaced with the stock carbon boom, just because.