Lost the tail today

[Elgyn]

I'd stick with the aluminum boom. I have carbon on my JR's and they flex too much for my liking. Although they are nice and light

[Bob O]

Originally Posted by 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.

Does the torque tube model come with the CF boom?

One things for sure, when this one gets replaced, it WILL be with a stock boom. Too bad the aluminum boom doesn't come in black.

[DethWshBkr]

Originally Posted by Bob O

Does the torque tube model come with the CF boom?

Mine did!

[KouDy]

If you mean CF as entirely CF then no. Torque tube kit has that alu-CF hybrid.
I should probably change it to alu one since when i crash it will be better to destroy just the alu one

[Taxus812]

I have the torque tube kit and I'm I'm using the aluminum tail boom instead of the cf one that came with the kit.

[rcflier1]

mine had a composit boom in the fbl kit

[YBNORMAL]

Originally Posted by Bob O

Does the torque tube model come with the CF boom?

One things for sure, when this one gets replaced, it WILL be with a stock boom. Too bad the aluminum boom doesn't come in black.

My TT came with the CF/AL hybrid. I have an order in with Tower for a few of the aluminum booms but they are currently backordered due in late April.

YB

[Bob O]

Guys,

Here are pics from after the last tail failure. I replaced the upgraded metal tail with the stock unit.

I have to run errands right now, but I'll be back later with the story of what happened yesterday as well as new pics.

[Bob O]

Okay, here's the incident. Yesterday I met a fellow club member at the field to help him out with his new built-up Cub, 4-stroke Saito, etc. He is new to nitro, wanted some help setting the mixture, etc. I brought the heli even though my time was limited on this day. I had enough time for two flights.

The stock tail has been performing flawlessly for the past 8 flights or so. There was no indication of any problems until the end of the first flight. While coming out of an inverted forward loop at the end of the flight, there was an extreme tail wag. When I landed it, the heli spooled down to a stop on it's own whereas previously I have always had to slow it to a stop with my hand on the head button.

Helped my friend out with his plane for a bit and then returned to the heli. Not giving the warning signs the proper attention, I reduced the tail gain and went back up. This second flight the tail wag was gone, but the tail blew out on me twice in some very basic 3D. I cut the flight short and upon landing, the heli was done spooling down before I could walk up to it. There was also a clicking sound during the final revolutions of the spool down.

Upon checking the heli on the bench, I found the head very hard to turn by hand. My club mate came over and noticed that the belt appeared to be sticking to the auto-rotation gear. Belt tension was good but I couldn't figure out what was going on at the time. Being that I didn't have time for another flight, I just packed up the heli and went home.

This morning I proceeded to do some work on the heli. During my initial build, there was some main gear slop (vertical play), so I used another OWB shim to take up the slop. I removed that shim thinking that the belt was being squeezed between the flanges of both gears. Upon reassembly and setting boom tension, I noticed that the head was still tight and would barely turn by hand. It was now that I proceeded to look at the actual tail for a problem.

So upon looking at the tail case, I could see a melted area around the bearing on the left half of the tail case. I didn't know if the bearing had seized up or what, so I proceeded to disassemble the tail case. Upon removing all the bolts, the case would not separate. I was able to get the tail case off the belt and inspect it even closer. I had to pry the old left half off the shaft and what I found was that the pin had come out.

Here are some pics that show exactly what happened. I read the fixes posted earlier in this thread about heat shrink or brass collar, but I didn't do either one. Instead I just cranked down harder on the grub screw and trusted that it would keep the pin in place. When I removed the screw, it was still tight, but somehow the pin managed to back out. At least with the design of the stock tail case, the pin is somewhat prevented from backing out completely, at least enough that it creates some symptons prior to complete failure of the tail case.

There was no damage to the pin or the pulley, and the pin was able to be pressed right back into place. Before I put the tail back together, I'm going to remove the pin and file a small flat spot on it right in the center where the grub screw makes contact. That should keep the pin from slipping out again, provided the grub screw does not come loose.

Anyway, I consider myself extremely lucky to have been able to land before the tail case suffered a complete failure. I'm convinced that another minute or two would have been all it would have taken for the pin to wear all the way through the case. You can't tell from the pic, but the tail case is actually worn all the way through in a couple of spots. Looking at it from the inside while holding it up to the light I could see right through it.

I have a different idea of a permanent fix for this problem that I'm going to submit to Thunder Tiger.

So, my heli will be down for the weekend. But just as well being that I have to start a new work week tomorrow, and the weather is taking a turn for the worse. I'll have her back in the air next weekend.

[rcflier1]

why not just convert to the tt? so far i have no issues..[knock wood]

[Bob O]

Originally Posted by rcflier1

why not just convert to the tt? so far i have no issues..[knock wood]

Torque tube isn't without issues. Although I never had a problem with my previous torque tube.

This heli has the best tail out of the three nitro birds I've had. If I can keep the pin from coming out in less than 10 flights everything will be fine.

I'm convinced my upcoming mod to the pin will do the trick. I'm also anxious to hear what Thunder Tiger has to say about my "fix". I'll probably send a message to Nick Maxwell about it rather than try to reach the right person at TTA. Nick has been easy to communicate with on fb.

[Ah Clem]

Bob,

Sorry to see the pin back out in the last set of photographs.

That is exactly what used to happen to the old Raptors (.50 and .90 sized).

The pin would back out and either melt, cut the tail case, or jam the tail shaft.

Please keep us posted on your fix for the problem.

You can always still try the brass ring epoxied about the pulley, if all else fails, sir.

[johnbs8]

in a month ill be attending flight school with nick and a few other pros. if ya have any questions or concerns i can deff relay them. i cant wait to sit down with nick and go over both my helis and fine tune them. then its bang bang in the air i go. cant wait!!

[Bob O]

I envy you, john. I wanted to sign up for that course but it would have used the money I have set aside for the Spartan FBL unit. Hopefully next year I can go if they do it again.

Sent from my phone

[Bob O]

Just about to put the bird back together. Took a couple of pics of the new pin. I used a dremel and cutoff wheel to carefully put a flat spot in the center of the pin. It's not exactly "flat" as you can see in the pic, but it's enough that the grub screw goes into the relieved area and tightens up nicely.

We'll find out this weekend how long it holds.

[johnbs8]

bobo, that coupled with the shrink wrap on the end and it should never come off unintentional. ive been shrink wraping mine for three years and have never had a problem.

[Bob O]

Okay guys, I did five flights yesterday with no issues. I intended on using this modded pin until something could be done by Thunder Tiger, but I ended up finding my own different fix. It was very quick and hopefully permanent.

I pulled the tail case apart today and found the modded pin still in position with the grub screw still tightened against it. I should have just left well enough alone, but I want to test my "new and improved" idea, so I pulled the modded pin and replaced it.

I'm hesitant to say what mod I'm currently using, as I have yet to put a single flight on it. I'd hate for someone to use it, crash their bird, and blame it on the mod. Once it's proven itself over a bit of time, I'll make a post on it. If it's going to fail, it should do so on the first flight, IMO. If it lasts for a gallon, it should last indefinitely.



With any luck, I'll get out later today and during this week.

[Bob O]

Flew three tanks today, first one just hovered in case the tail let go. Second and third were my usual flying. No hint of a problem other than my belt binding in the autorotation gear. It's been doing this the last several flights, you can hear and see it during spool up and during spool down.

I inspected every tooth on the belt and they were all fine. I ran the belt tension from loose to tight and can't get rid of it. I'm going to replace the belt and see if that helps. If that doesn't do the trick, the autorotation gear will have to be looked at closely. It didn't start this clicking/binding until about 10 to 15 flights in.

Sent from my phone

[johnbs8]

the belt stretched. replace it. i had the same problem. no matter what i did tighten or loosen it would click when you spun the rotor blades. the teethe on the belt are not aligned properly now and it will do it no matter what ya do. does it look like the belt is snugging the auto gear instead of coming of straight?

[Bob O]

Originally Posted by johnbs8

SNIP
does it look like the belt is snugging the auto gear instead of coming of straight?

That's exactly what it's doing. Instead of coming off nicely, it wants to hug/stick to the gear before popping off.

I'll replace it before I fly again. My replacement belt is the standard goldish color, not the red.