dvs1

I need a little help identifying a problem that occurred today.

First and foremost this isn't my first heli that I have built and I use loctite on all metal screw components.

Second the heli is a TREX 450 sport that has never been crashed and has about 20 hovers and mild flight on it. I check everything after every flight especially the head assembly for any looseness, especially the feathering shaft.

So down to the problem: I was practicing my hovering down to about half my flight time. Landed the heli let the blades spool down about half way then let them spool up to beginning another hover when right as the heli was lifting I head a loud pop and exactly as I heard it both blade grips and blades parted company from the heli landing over 100 ft apart. Problem is after disassembly and inspection neither bolt on the feathering shaft that holds the grips on were broken. In fact the only damage was to one blade from bouncing off the concrete.

I have never had this happen before and would like for it to not happen again. Can anyone tell me the cause for this and what I can do to prevent it in the future. Its not too bad with 325 blades but I dont really want to be anywhere close if it were to happen to my 690 blades on another heli I have.

Thanks in advance

ehernan3

You said the grips came off. The only thing holding them in are the feathering shaft screws. So either at least one broke, or are least one backed out of the feathering shaft. Can you please describe what allowed the grips to come off the head?

dvs1

That is the problem, The feathering shaft screws did not break, they did not pull the threads from the shaft either. So they came loose in the duration of a 3 minute mild flight. They were loctited with blue and there was absolutely no play or loseness before the flight. So I'm wondering should I be using red loctite for the feathering shaft screws or was this just a freak occurance?

ehernan3

I have a T-Rex450. I have had problems with these screws coming loose in the past, and I find them before flight not by rocking the blades up and down, but by trying to pull the grips out of the feathering shaft. Push in the grips and pull them out. That's the only sure means of checking if the screws are backing out before each flight. I've never had them come apart during flight.

Since it seems your's backed out, it's likely that the threads were not clean before applying blue loctite. Remember, these screws pass through a few sets of bearings on the way to the feathering shaft. Two of these are sealed, but the first set they encounter are open bearings. if the grease on these open bearings contacts the screw threads, the loctite is obviously not very effective.

Disassemble the grips, check the bearings for excess grease. Clean the threads, reapply loctite(blue), and reassemble. Let sit for a day before attaching the blades and then try to remove the screws with light finger pressure on the tool(allen key, drivers, etc), one on each end of the feathering shaft. If they come out easily, the loctite is not holding and you need to do a better job cleaning the threads, perhaps even inside the feathering shaft.

Good luck!

dvs1

Now that I think about it I would almost guarantee you are right. I just had the shaft out 3 flights ago to grease the bearings in the blade grips. Now that you say that I bet the bolt got some grease on it and the loctite didn't hold or even set up. I will have to be extra careful about that in the future. Thanks!

ehernan3

If I read your post correctly, you've only flown this heli 21 times. It's not necessary to grease the bearings in the grips after only 21 flights. If you do this less often, you'll reduce risk of problems with loctite

Also, the bearings take very little grease. Most don't realize that the grease performs only on the points of contact between the balls and the races. The rest is wasted. Moreover, it flies out of the races and makes a mess.

Finally, when you tighten the grips, rotate them at the same time. When you feel them start to bind, you've tightened them too far. You may be surprised that this occurs while the screw still feels loose. The loctite will keep them from coming out, not bolt tension, and your preflight checks(glad you're doing them!) will give you confidence. If you use bolt tension until it feels 'about right' like a normal bolted joint, you'll ruin bearings. Ask me how I know [:@]

dvs1

Thanks for the tips, since I wasn't sure about the maintenence scedule for the bearings I figured I would just check them to be safe.

As far as the sealed bearings do you just feel for roughness or binding of the bearings to determine replacing them or do you just replace them at a scheduled interval?

ehernan3

As far as the grip bearings are concerned, I never replaced them. About one year after I purchase my 450, I went to a flybarless head . Ask me after another year.

But at the same time, I decided to give the heli a detailed inspection(over 370 flights by then), and found the main shaft bearings were grinding, so I ordered new ones. When I received the replacements, I was amazed how different they felt compared to the worn ones. I've since kept a closer eye on these.

dvs1

How do you like the flybarless? I see that is what most TREX helis are going now. I'm thinking if I ever do more than $400 damage to my Raptor 60 that I will go with a TREX 550 or 600 as low as the prices are. I love the electrics so much more than nitro, and while my Raptor is awesome as far as size it is a little unpractical for me and replacement parts add up too fast. I think a 600 class would be perfect for me but have no experience with flybarless. Less moving parts is awesome and less to replace for repairs. What kind of damage would you expect from a flybarless with a blade strike, do they hold up better than a flybar head or worse?

I only ask because while I haven't done any severe damage to my helis for some time. I fear it is inevitable that my time is coming soon and once you reach the repair price of a crash that is around $400 I might as well buy a new heli for a couple hundred more and have a newer model with newer technology.

ehernan3

I love flybarless. I went with BeastX, using the RJX head for the 450. About one month later, Align came out with their DFC head, but since I've not damaged the RJX head, I'm using the money on repairs[:@]. Blades still break, main gears strip, main shafts bend, etc.

I'd love to fly bigger helis, but as you say, the cost for damage is much higher. I think my whole heli cost $400 as a Super Combo, so I can't imagine having crash damage that cost $400 alone. Wow.

Flybarless is amazing in the wind, and made it easier(for me, anyway) to learn inverted hovering. When I freak out, I can level the heli upright or inverted and take my thumbs off the sticks for a few seconds until I stop shaking. With a flybar, I couldn't do that. So the workload is a little bit less, and I'm enjoying my flying more.

I got about one more minute of battery life, which I attribute to less drag(no flybar or paddles), and the heli also flies faster and more quietly(again, no drag from flybar or paddles). Finally, yes, the parts count is lower, and therefore not only costs less when you crash, it takes less time to repair.

You won't regret going flybarless. There are plenty other flybarless threads online to get good feedback from people using them. The BeastX has it's own thread for people posting their setups on HeliFreak.

dvs1

Thanks again for all your info, I appreciate it!