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-   -   Lost my tail today :( (http://www.helifreak.com/showthread.php?t=359098)

FR4-Pilot 11-23-2011 05:11 PM

Lost my tail today :(
 
9 Attachment(s)
As a last minute call I decided to take my helis to work today and get a few flights in during lunch. The weather was sunny, no wind, around 45F. I head out at lunchtime with a few spectators, only today I didn't go behind the trucking terminal where I've been flying. The sun is much lower this time of year and I would have to face right into it at that field. Instead I stayed in our parking lot and decided to fly over the little lake that borders the forest preserve. First flight, Blade 400, flips, loops, rolls, circuits, all over the lake - no problems. Second flight, Mini-Titan - same - no problems. Third flight, Blade 400, (actual flight 182). I'm hovering inverted over the lake about a minute into the flight. Suddenly I hear a strange "flutter" but can't tell if it's the heli or one of the cars in the parking lot (it's lunchtime, people are heading out). I flip the heli over, bring her closer and can hear an abnormal hum that is coming from the heli's general direction. Still not sure. She's handling just fine, but I land her anyway. The strange noises continue as the main rotor spools down. Then the entire tail rotor shaft starts wobbling all over the place. Soon the tail rotor comes to a complete stop, but the mains are still spinning - that's not good! Now there's lots of clicking too - glad she's on the ground!

Later before leaving work I decide to disassemble the tail and see what happened. Well, it turns out one of the tail shaft bearings failed (seized?) got very hot and melted the plastic that was holding it in place. At some point during it's failure the tail shaft got bent as well - not sure what caused that, but given that it was spinning at around 14,000 RPM it probably didn't take much.

I'm very thankful that the heli survived yet another mechanical failure that should have resulted in a crash. The fact that I didn't loose tail control while inverted over water remains a mystery to me ...

-John

MiataJohn 11-23-2011 06:45 PM

I have had two bearing fail in the tail case on different occasions. No damage either time.

desertblade400 11-23-2011 07:12 PM

Lost my tail today also. I'm thinking the current crop of tail shafts just aren't any good. When I got to half throttle today, the tail made some noises. I leaned over it and watched as the tail shaft bent before my eyes. I've had my Blade for a year now and I've never seen that happen before. I just put in new bearings and such the other day and all was fine. So I put in a new shaft and all is well, again.

FR4-Pilot 11-23-2011 07:30 PM

I wonder if the bearing heating up had anything to do with the shaft bending? I would think there would be some pretty serious heat necessary to weaken the shaft (like to the point of flames). I didn't expect to find that shaft bent that's for sure. These were newer bearings too - probably replaced them last summer. Time for a Boca Bearing order ... :)

-John

Gloryhair 11-23-2011 08:13 PM

I've had that happen as well. Except my tail shat bent a lot worse, and took out my tail fin.
I try to apply a drop of oil to all the bearings every once and a while. Seems to be working out ok. So far. Hope you get back in the air soon. It was an awesome day here too. I bet the shaft bent at the sheer force of the vibrations from the bearing crapping out. Those blades spin sooo fast! Just a little off balance causes some nasty vibes.

FR4-Pilot 11-23-2011 09:13 PM

This has me thinking ... definitely some high quality Boca bearings then for the new tail case, but also for the tail drive shaft as well. The latter will require splitting the frame open to get to the top bearing ... which is a major tear-down of the heli .... so also some high quality bearings for the main shaft while we're in there ... and my one-way is kinda loose too ...

-John

Andrew73 11-24-2011 04:08 AM

Sorry to hear about the failure, but anyhow a lucky escape as you were hovering over water. Nice inverted pics too.

Harbormaster 11-26-2011 10:51 AM

I kept waiting for the part where the heli went into the lake. ;) Cool that you got her landed and were able to do your NTSB inspection on the whole bird and not a collection of parts.

I have had the same thing happen--a tail bearing completely failed and come apart in pieces. My working theory is that a) the stock bearings are not that great and b) that I was running my belt too tight.

When I started practicing autos with my B400, I loosened the belt up a LOT per the "How to learn to auto without a sim" video on YouTube, and I have been surprised just how loose it can be and still work just fine. I'm sure that takes a lot of load off those little bearings.

Still, as a rule, it might be a good idea to replace those bearings yearly and make sure the bearings get a careful treatment from The Greaser at installation.

dscobell 11-26-2011 02:26 PM

Been there done that. My bearing burned right through the side of the tail case just as I brought it closer to figure out what the screeching was all about. In a full piro, the little monster tried to take my head off. I hit TH and made a run for it. It fell at my feet..

Glad to hear yours went a little better..

FR4-Pilot 11-26-2011 02:53 PM

Well, good news is since the shaft was bent I'll be replacing that as well as installing the new metal tail grips/hub I have sitting here waiting ... :)

It's starting to sound like we've only got about 10-15 seconds of control remaining once the tail bites it - then it's every man for himself :wow2:

-John

Harbormaster 11-26-2011 02:53 PM

Quote:

Originally Posted by dscobell (Post 3425013)
I brought it closer to figure out what the screeching was all about.

LOL. And lived to tell the tale. :wow2: (I know it feels to have a heli come after you.)

Something that I have learned the hard (and expensive) way is that as soon as anything the least bit "funny" happens, get it on the ground!

FR4-Pilot 12-10-2011 03:15 PM

3 Attachment(s)
Okay, new tail parts installed. Went with the metal E-Flite tail grips - two bearings per grip - no more wobble :)

The metal grips are almost twice as heavy as the stock plastic ones.

A quick test flight today went well - it was around 20F.

-John

Harbormaster 12-10-2011 06:54 PM

Looking good! :thumbup:

MiataJohn 12-13-2011 12:54 PM

Quote:

Originally Posted by FR4-Pilot (Post 3459903)
Okay, new tail parts installed. Went with the metal E-Flite tail grips - two bearings per grip - no more wobble :)

The metal grips are almost twice as heavy as the stock plastic ones.

A quick test flight today went well - it was around 20F.

-John

John

I am preparing to install the same grip setup, but have a couple of questions.

1. My package has 4 washers 8mm dia. x .24mm thick. Do you know where they should be placed? It looks like they might go on each side of the grip between the bolt head and grip and nut to grip, but I don't see them on your installation.

2. Did you put the second bearing on the blade end of the grip? Mine seems pretty tight stock.

John

FR4-Pilot 12-13-2011 04:41 PM

Hey John,

The washers are tail blade spacers - the metal grips accept a tail blade with a wider root. If you re-use the stock white tail blades you'll need them (or if you've filed down KBDDs to fit the stock plastic grips you'll also need them).

Each of the metal grips has two bearings - one near the hub and one closer to the blade - I didn't have to install them, they come that way. The stock plastic grips only have a single bearing closer to the blade - no bearing near the hub.

-John

MiataJohn 12-13-2011 06:44 PM

John

Thanks for the quick reply:thumbup:. Things are coming into focus. I know it's wishful thinking, but hope it warms up for you soon.

Have a great New Year - John

FR4-Pilot 12-17-2011 08:37 PM

2 Attachment(s)
Thanks John - Happy Holidays to you too - and everyone else as well !

Got to fly the B400 today for the first time in the snow. The heli did great - especially the new metal tail. My fingers were done after about 1/2 hour ...


http://www.helifreak.com/attachment....1&d=1324175810


Also flew the 100th flight on the Mini-Titan!

http://www.helifreak.com/attachment....1&d=1324176477
-John :YeaBaby:

Luvmyhelis 12-19-2011 03:52 PM

Darnit, lost my tail yesterday also. My cf tail servo control rod snapped at a junction. I had been flying it all over, and had just brought it down to within about 6 ft in front of me in a blast of the rotor wash. I throttled it up and the tail of coarse snapped slightly into attention. With these arctic temps I think it affected my glue joint and the heli took off into an uncontrollable spin. Right into a soft landing in a bush inches away from a concrete bird bath. That would have been quite ugly. Lost all the normal parts, fs, Microheli gear, bearings, new tail grip hub, and oddly even my new Kbdd blades which snapped due to the cold. All in all I am happy with this wreck. I had been buzzing all over the neighborhood I live in just to get off a flight since it had been too cold for too long. Just thinking of what would have happened with it up hundreds of feet away if this part had given out any earlier? Wow! This time, I consider myself pretty lucky!

MiataJohn 12-19-2011 06:47 PM

Major bummer. Sounds like one of my typical flights except I hardly wreck the blades anymore. Ya gotta move down south. About 75 this afternoon.:)

John

FR4-Pilot 12-19-2011 07:15 PM

Well, they say misery loves company ...

I lost my tail, again, today. This was the 4th flight with the new tail case, tail shaft, bearings, metal hub and grips. Luckily it happened on the launch pad at the beginning of the second flight. First flight went fantastic. Either the boom slid in, or one of the pulleys bit the dust. Bent another tail shaft :( Don't know the condition of the bearings or the tail case back there yet - I'll have to tear it down, again ...


-John

UPDATE: Both front and rear pulleys were fine (rear shaft bent though). Belt is fine (no missing teeth, no cuts, etc.). Bearings are fine as far as I can tell - no notchiness and all balls accounted for ;). It appears that the boom slid in (belt too tight?) - and the screws that hold the horizontal stabilizer to its mount were loose (holes stripped out). Excessive vibration back there? Maybe putting the metal grips on made the vibes worse ... ?


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