What causes blade clack? I had a bad case of clack today at about 25 feet up. needless to say it was an ugly crash. lost complete control. there was no wind to speak of and I was doing figure eights when it happened. is there anything that can be done to prevent the blades from hitting each other?

Unless you get the extended shafts from bladecxpro.com, there is really nothing you can do about it.

When the heli is moving in one direction, immediately reversing the stick to the opposite direction in too much of a hurry will cause a blade strike.

Also, sometimes normal flight can cause one also, if the heli catches the air just right. It's just a problem that a Coaxial will have, again, unless you upgrade to longer shafts and shorter flybars.

You may not have actually done anything wrong, it just happens =/.

Once I moved my servo arms out, I have just ben super concious to ease off the right stick when I want the heli to stop, instead of just jamming on it. With a little practice, you can still fly normally, you just have to adjust the movement of your thumbs.

Also, practice panic-flying (OH **** IM ABOUT TO RUN INTO SOMETHING!!!) and coming out by using both sticks in one horizontal direction, aka --

As you are flying at an object, instead of pulling back on the elevator, give left rudder and left aileron, and swing it around hard, this usually prevents the strikes that are common when trying not to hit something.

Other than that, it just comes with the territory. Unfortunately, it will get worse if you adjust your servo arms for more cyclic response.

Bryan

I'm working on a paper addressing a lot of the issues that we see with the Blade CX / CX2. I want it to be complete, but not an encyclopedia. If you like, I'll send a copy of the part that discusses the flybar, how this whole contraption works and what can be done about it.
You can read it over, do what you want with the information and let me know how it all works. Be warned, it is a couple of paragraphs. But the information is correct. Interested?
This forum offers the ability to email any of us directly, so if you want what I have, email me and I'll send it to you right away. Or just post to me on this forum and I'll get it to you. I imagine that the others are tired of me posting the same thing over and over on this forum.
Soloboss

The short answer is, yes it can certainly be controlled. NO MORE BLADE CLACK.
But with my mod, you will spend about a half hour of your time. You will spend about $2. And you will have to tolerate far better performance. Interested?
It's a long post, but I can email it to you and to anyone else having this problem.

There's one way you can definately reduce the blade clack/strikes by 90%... By trimming the lower blades from their original length to 5.5 inches, you can avoid a lot of the blade strikes wihout having to give up hardly any performance or power. A lot of folks have done this because they couldn't get any replacement blades (due to the backorder issues) and were desperate to get back in the air. So, they trimmed down the lower blades that were broken on the tips to 5.5 inches, and Wa-La! Flies pretty darn good and with 90% less blade strikes!

I can see real potential in that plan. Especially when I'm out of town and run outa blades! So, if you trim the upper blades also, what happens? I expect you get more RPM and the performance might come back.
I don't see a darned thing wrong with what you are doing. The big deal with my flybar mod is that I don't get blade clack and my performance most certainly INCREASES!. No compromise.

Good tip and Thank You

I am very interested in your flybar mod. Please let me know what you did.

OK, you asked for it. Note that I'm not a helicopter engineer and there is no guarantee that this will give you the results that you want. If you don't mind that the heli is more responsive and climbs better, you'll be happy. If you don't mind that the heli will move with less stick, you'll be happy. The lightweight flybar may require that you reset the trim adjust - the upper rotor turns more easily and requires less power. And if you make the change I'd really like to know how this mod works for you. Other guys have other good mods. This works for me. It's what I fly. There has been a flurry of activity on my email with guys asking for my thoughts on how this thing works and the changes I've made. It's sort of flattering, and I know that my mods work for me, but I NEED feedback. Anyhow, here ya go. Take your time, good luck and enjoy your heli.

THE MOD: If you are able to get a good hover, you don't need the stock flybar weight. Stick a tiny screwdriver or wire down between the brass weight and the rubber boot in the flybar end weight. Pop the brass thing out. Don't loose it. Try to hover. If you're OK with it that way, you should see far less blade damage. Lighter Flybar = Less Clack.
Then, if all goes well, get more serious.
With the weights out of the rubber things, slide the rubbers up onto the flybar and cut the flybar ends off. A Dremmel works great for that. Slide the rubber things off the ends of the flybar rods.
Go to the local hobby shop and get a set of locking collars. They are about 3/16 in diameter, about a quarter inch long with a hole in the center for a 1/16 inch wire. And they have a setscrew to lock them on.
I started with two weights on each end. That worked well so I changed to one collar on each end and one halfway between the end and the center on each side. When I got good enough to hover that way, I went to just one collar on each flybar rod, located at about 1 1/2 inch from the outboard end on each side. That's pretty lightweight and it's a handful, but it rocks. I am not only using about 36% of the original weight, the weigh is spinning in a smaller circle.
The response is very good. The tendency of the heli to go 20 feet, then stop is far less than it was.
And there is NO MORE BLADE CLACK!

Because my flybar is so light, I don't think that it can force the blades to clack. You will find that the hover is just a bit more work with just one collar on each end of the flybar, and the heli is a bit less stable, but I'm OK with it and I'm not a very good pilot. With two collars on each end it hovers just like stock. If you go a step at a time, you'll find a place where you are comfortable. The lighter the flybar the less it fights the heli. That seems to be a good thing. NOTE: If you get TBE, check for flash on the upper blade linkage ball. That plastic flash on the ball can make the link stick and the flybar MUST move with no friction.

As near as I can tell, the stock flybar weights are 2.326 grams EACH (rubber and brass insert combined). I don't have a scale that weighs that close, but I have a cool 3D cad system here, so I created a model of the rubber part, and the brass part, inserted the brass into the rubber and analyzed the whole thing. That's where the weight came from. If you have a better weight let me know.
I did the same thing for a collar. I got .8305 gram each.
Two 2 collars equals 1.661 gm.
Two of the factory weight assemblies equals 4.652 gm.
I did shorten my flybar rods to 3 3/8" (measuring just the exposed metal part).

I haven't trimmed the upper blades... In fact, I'm a bit curious to know what might happen if I did. If my upper blades get "clipped" on the tips, I'll give it a try and see what happens...

The LHS lad was wondering about making stiffer blades. I'm sure that would increase performance, but where might a person get such a blade? Then I got thinking about your clipped blades. A shorter blade will spin faster and make the same lift as stock. A short blade won't clack. A short blade has less flex - flex per inch over less inches = less flex. So a short blade will give equal lift without the flex. Or maybe I'm just nuts. I'll start collecting broken blades until I have a set to trim. I'm pretty hard on blades. No clack, but I keep trying to thread needles and I'm not that good. And ceiling fans are really hard on helis.

After my crash I lost one of the brass weights and it was too late to go buy a new one but I did have blades. I taped up the body and threw on new blades but you can't test fly without the flybar so I straightened it out the best I could and put it on with just the rubber end pieces. It flew o.k. with just the rubber pieces but I have a very limited space to fly in my house so I couldn't really test it. I went to the hobby shop and bought wheel collars and a new fly bar. I cut the ends off of the old fly bar right at the bend in the end and put on the collars. With this configuration I was getting eratic behavior. I took it apart and balanced the blades and the fly bar and then put it back on, big difference! It takes a little more to keep her steady but I can't wait for the weather to clear so I can take her out for a real test. I'll let you know the results and I will try the blade thing also. I would like to try a stiffer/more airfoil shaped blade cause the stock blades are basically fan blades.

Most people who cut the flybar add heavier weights.

Either larger metal pieces or you can also use the flybar paddles from an XRB Llama.

You will like the performance from the shorter flybar =D.

Thanks for the reply.
One thing that you absolutely have to have is VERY loose flybar connection. ANY friction in that flybar assembly will cause TBE with that new setup on top. And the lighter the flybar the more sensitive it is to TBE. But as your read, TBE can be controlled. You'll know when you get it right. The devil's in the details. But it's worth it, so scrape the flash off the link balls and make sure there is no bind anywhere.
Two collars at the end of each rod will hover like a stock heli, but it will have better performance. When you are ready to advance, leave one collar on the outer ends and move the inner collar steadily inboard an inch at a time until it's all you can stand. When you can fly that, loose the second collar and start moving the remaining collar toward the center a little at a time. And MEASURE the locations so both ends are exactly the same. Any imbalance will cause TBE. But you read about that, right? And you probably don't want to move the linkage to an outer hole in the servo arm.
Some will say you can't invert a CX/2.
Wrong.
Truth is that you can't FLY it inverted.
And upside down is expensive.

I would surmise that with some of the mods being discussed that you are correct. However, once inverted, no matter which way you moved the throttle, it will make the copter go down (very quickly in one direction, 32 fps the other). However if you could fly it out over a very deep hole, you may be able to right the copter after it was inverted.

Anyone (else) want to try this?? I'm curious...

Regards,
Marc

I did fly mine out of an upside down situation. I had a tree twig stuck through the skids on one side, hanging upside down over a river maybe 50 -60 feet up. The blades weren't stuck, so I goosed it and pulled loose from the stuck skid (leaving the skid in the tree) and I had a heli upside down heading for the river. I instantly killed the throttle, then snapped the right and left sticks froward fully. When it's right side up, that maneuver causes an inversion and it lands on its rotors upside down. This time it inverted and righted itself. Talk about dumb luck!

Hi soloboss, that would have been a neat thing to see! Glad it came out good for you.

In regards to trimming the blades, would you trim upper, lower, or both? Has anyone trimmed their blades along with the shorter lightweight flybar...what results did you see as far as clack goes?

I rolled my cx while turning sharply with yaw and right cyclic stick while flying in the wind, dropped about 15 feet, then added 1/4 throttle and full right cyclic stick, and it righted itself. Sadly Idid not apply enough throttle to recover, so it hit the ground (right side up) and took off the tip of both landing gear.