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Difficulty trimming for yaw with a CX2.

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Difficulty trimming for yaw with a CX2.

Old 10-14-2008, 01:45 AM
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Terbough Bob
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Default Difficulty trimming for yaw with a CX2.

OK, so I'm not one to just go post on a board about a problem, as evidenced by my post per day count here, but this is just flat out driving me nuts...

I can't get the damn thing to trim out in the yaw axis. I followed the directions in the manual as well as Solo's Wikifaq: http://www.heli-wiki.com/mediawiki/i..._and_CX2_Setup And it continuously yaws to the right. I've played with the mixer, put new rotor blades on it, balanced everything, and have rebound the tx and rx several times.

Nothing.

Nothing changes, not even when I turn the mixer full counterclockwise or clockwise; it's the same thing all the time. While I fly, I have to constantly feed in left yaw, which I guess is suppose to simulate having to keep a foot on the left anti torque pedal in the real thing? But I thought these things were hands off, set the transmitter down and marvel at the stability? Also, I find that some times it'll yaw right even with full left stick and will only come left after I bring the stick back to neutral, let it spin around to the right a bit and then feed in some left stick.

Everything else is fine- no bent shafts or flybar, cyclic roll and pitch respond and trim out fine, and the gyro works as it should. I've done everything I can think short of trimming a bit off the top blades to reduce torque going to them even more.

Do I have a dud, or is this a common problem to which I'm overlooking the solution?
Old 10-14-2008, 02:18 AM
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Default RE: Difficulty trimming for yaw with a CX2.

Is the helicopter Used or New? Has it flown correctly before? When you spin the blades by hand do they move freely or have some drag. If you have a voltmeter you can check the motor output pins and see if the voltage is changing with rudder inputs and by how much. That will determine if you have a bad or good 3in1 or 4in1 which ever one you have. You might have a bad motor for the lower blades. It has been a long time since I have flown the CX to know what the problem could be. Tomorrow the Guru's should be one to help out more.

Nick
Old 10-14-2008, 03:05 AM
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Terbough Bob
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Default RE: Difficulty trimming for yaw with a CX2.

Hi Nick, the helicopter is new, and the guy at the LHS trimmed it for me before I walked out, however, upon flying it at home, it required quite a bit of trim in every direction. Something I forgot to mention- the yaw trim on the tx does make a difference; if I go full left or right with it, I notice a change, but still not enough to compensate.
Old 10-14-2008, 04:19 PM
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soloboss
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Default RE: Difficulty trimming for yaw with a CX2.

Hmmm - I'll go on the presumption that the problem is not electronic. Nick gave you a tip to figure that one out using a voltmeter and checking the motor voltage pins.

Let's go back to the slick table top so you can demonstrate the rotation without actually flying and damaging the helicopter. First thing in my mind it blade tracking. The upper blades are set using the link connected to the flybar. Unless the blades are warped, the upper tracking can be set perfectly. If not perfect, boil the blades to allow them to reshape to original condition.
The bottom rotor do not adjust. If the tracking is not 95% perfect, remove them and try other blades looking for the perfect balance and tracking. Or boil them so they return to original shape.
And check tracking at a high enough rpm that the heli is lifting to the point of almost flying. If you have tracking issues you will have flight issues. Don't give up until tracking is right.

At this juncture, tracking is not NOT the problem.

Not good yet? Remove all the stuff from the upper and lower rotors - blades & flybar. Now spin up just the inner shaft and listen to it. Do the same for just the outer and listen to it. Do they sound the same? Is your gear mesh equal? Don't hold the motor at max rpm because it does go over speed, but goose the inner, then the outer shafts and listen to them slow down. Do they coast about the same length of time? These tests should find any binding or drag. If you have drag, remove the drive gears from the motors and goose the motors again, listening for a difference in rpm and the time required to coast to a stop.

Some have had the screws from the lower blade hub tightened so tightly that they contact the inner shaft. IF you remove the inner shaft and look through the outer shaft you should see more than enough room for the inner shaft to pass through with no drag. The correct screws used to secure the lower head to the outer shaft will not engage deeply enough to contact the inner shaft. If you see the end of a screw when you look through the inner shaft, you may have the wrong screws installed from the factory. Not likely, but we're looking for something that is not likely.

Do you have any vibration in the helicopter? If something is shaking it will certainly throw the flybar out of whack and that will mess up the upper rotor drag and cause TBE and rotational issues. If it shakes, start removing stuff and running up the rpm until you find out what makes it shake. Fix that.

Is your battery balanced? Is it balanced under load? If you have another battery, try that. OK, so if you had another battery, you would have already tried that. Sorry, Your point.

The proportional pot and the Tx trims work in harmony. You should be able to get close with the pot, and then dial it in with the trim. I always charge the pack, run it for a minute, then set the pot for stable hover with the trims centered.

Maybe something in here will lead you to the answer. Tough issue. Keep us posted as you work through ideas.
We're with you - Soloboss
Old 10-16-2008, 01:11 AM
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Terbough Bob
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Default RE: Difficulty trimming for yaw with a CX2.

Thanks for the tips! I haven't had a chance to play with it a whole lot; nine hours of work and then four hours of flight school, five days a week takes a toll... I'll have a chance this weekend and will post my results. If I can't get it dialed in, I'll just return it to the LHS. I suppose that'd be the easy fix, but if I wanted easy, I would have gotten a plane.
Old 10-16-2008, 01:54 AM
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Terbough Bob
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Default RE: Difficulty trimming for yaw with a CX2.

All right... so I decided to forego sleep and take a closer look... the blades are all balanced perfectly per Solo's method, the upper disc tracking is spot on, the voltages are equal, the motor spin downs are the same. Except... the upper bearing on the outer mast. Actually, the bearing is fine, it's the black plastic holder that's not. At first, I thought it was the inner mast that was bent, since it swings around quite a bit when both rotors are going slowly, but when I stopped the upper rotor, it still ocillated quite a bit. I pulled the inner mast out and spun up the outer mast and watched the upper bearing holder go 'round and 'round. I removed everything except the head from the upper mast and spun it on a counter top and it's not bent. The outer mast isn't bent because with the bearing holder removed, it spins true. Soooo... tomorrow during lunch, I'll go pick and aluminum bearing holder up at the LHS and see what happens.
Old 10-16-2008, 05:09 PM
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Default RE: Difficulty trimming for yaw with a CX2.

Been there Bob, And I've done that exact thing. The plastic bearing holder does not run true in some cases. Mine had that issue and I replaced the plastic holder with the Eflight aluminum replacement. Problem solved.
Hat's off to your "sleuthery". I do believe you will have a winner with the new part installed. Then you can get back to eating and sleeping and such.
And of course I'd appreciate you posting the results.
Curious minds need to know.

Soloboss
Old 10-16-2008, 09:53 PM
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Default RE: Difficulty trimming for yaw with a CX2.

Well, it flies a lot smoother now once I readjusted the tracking. However, it's still yawing to the right. So, off to the hobby shop with it tomorrow. It's brand new, has done it since day one, and I don't feel that I should have to buy "optional hop up" parts to correct something that should be fixed out of the box.
Old 10-17-2008, 01:00 PM
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Default RE: Difficulty trimming for yaw with a CX2.

My CX2 yaws to the right, and although I haven't taken it apart or performed any serious upgrades, I have noticed a few things. When I got the bird in August, it flew really well. Still flies fairly nicely, which I supposed has helped prevent any crashes and the need to replace any parts. (So far all I've done to it is replace the skids & boom with boomtown parts.) After flying it awhile, I noticed the bird developed a strange squeal. The kind of squeal a bearing would say "lubricate me!". So I lubed up the bird with some dry super lube. The squeal went away, but the bird began to yaw to the right. Over a course of several weeks, I adjusted the prop. trim to compensate for the yaw, and tried low and high gyro settings. Right now I have my prop. trim all the way to the left and the bird still yaws to the right. I have to constantly fly the tail. Then while flying the tail, the gyro tries to take over and sends the tail in the opposite direction fairly quickly. The bird has been like this since I lubed it.

In looking it over without disassembling it, I notice the upper rotor turns so much more smoothly and freely as compared to the lower rotor. I suspect the extra drag on the lower rotor is the reason I have my prop. adjusted the way it is. Both motor's gear mesh looks good, but I have not taken it apart to inspect any bearings or assembly anomalies.

I'm thinking here that I have a bearing / shaft issue, or the upper rotor motor is that much more powerful than the lower. I'm just going to take it slow and check / adjust / replace one item at a time, as well as memorize the solo wiki guide which I have.

I know the Extreme motors will probably make a difference and maybe an aluminum bearing holder as well. What I'm wondering if anyone has any experience or knowledge concerning the Cryo Hobby Cryo Drive parts for the CX2? Would a drive system such as the Cryo Drive be a better alternative?

DrS
Old 10-18-2008, 01:06 PM
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Default RE: Difficulty trimming for yaw with a CX2.

I had the same issue, but I solved it by modding the transmitter and adding an extra variable resistor pot to the rudder potentiometer. I tuned it so that the yaw is correct with the outside trim at the center. My issue improved after I bought a new swashplate, but my swashplate was all worn off after like 40 flights with 3-cell battery so that is probably not your case.Inspect the motor and the outer bearings though. Exchange the motor functions, move the pinions appropriately and swap connectors to the 4 in 1. If the yaw reverses, it was the motor.
Old 10-18-2008, 06:13 PM
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Terbough Bob
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Default RE: Difficulty trimming for yaw with a CX2.

I'm not trouble shooting it anymore... I bought the damn thing BRAND NEW and I shouldn't have to do all this. If you bought a brand new car, how would you feel if you had to do an alignment and buy new tie rod ends and ball joints because the factory didn't get it right before they sold it to you?
Old 10-19-2008, 09:06 AM
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Default RE: Difficulty trimming for yaw with a CX2.

Hey Terbough;

Not to get too far off topic, but welcome to the modern industrial world where bean counters reign! Quality is not something you find in many products because the parts business is more lucrative. Speaking of brand new cars, in 04' I bought a brand new minivan, took it back after 500 miles as the interior started to fall off! Made the dealer take it back and give me a better deal on an 05'. But already I'm on my third set of front brakes, had a recall, leaking oil pan, tires about worn out, a few other minor items, and there's only 34K miles on the thing! I know how you feel! I could go on and on about product quality. I'm going through the same thing with an Axe CP. (Three flights and the forward swash servo locked up!) You really have to research purchases anymore in this day and age. I bought the CX2 because of the radio, recommendations, watching one fly in my LHS, and to have something to learn on. So I'll continue to tweak & learn. Sorry to hear about your experience, at least mine flew pretty well until it started squealing.

Hey Zdenek;

I was thinking of pulling the motors and swapping them, but I'd rather spend the time installing new Extreme's. The outer bearing also makes sense, but I'd rather upgrade if I go that route. That's why I'm looking for anyone with info on the cryo drive or cryo-carbon. I'd also like to hear about experiences with the cryocarbon flybar. Never thought adding more resistance to the rudder pot would help. Cool idea.

DrS


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