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mCX Blade (eFlite) Micro CX Helicopters Information and Help


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Old 04-02-2012, 12:39 AM   #1
GG07
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Default Question about MCX needing constant rudder trim adjustments during flight

I thought I would put this question out there in case anyone can point me towards the most likely cause.

My newest MCX that I converted over to an S300 and recently swapped in an MCX2 swashplate has developed an odd problem over the last few days.

Bascially, my rudder trim seems to be drifing off center first when putting in a new battery, and later as the flight session progresses. I adjust the rudder to stop the heli from slowly turning to the left or right, but after a few minutes of flying around, it starts doing it again when placed in hover. I recenter the trim again and it stays for a few minutes then drifts out again.

When I put a new battery in and take off, the trim always needs to be adjusted, and the above cycle repeats itself each session. I am also noticing that if I push forward stick with no rudder or aileron command, the heli will begin tracking to the left and I have to hold right rudder/aileron to keep it going straight. When I come back into hover, the heli will be trimmed, but when pushing forward stick again, it starts out flying straight, but after about 6-8 feet of travel, it starts to veer to the left again.

I also notice some minor left spin if I step on the throttle hard, but I assume that this is caused by torque from the rotor? Is all this a torque issue? Is this problem common with a hopped up MCX? My MCX2 flies about the same speed as this updated MCX without any of these trim problems. Both are set to the longer balls on the MCX2 swashplate.

Anyway... Not sure what to make of this issue. Does this sound like the lower rotor motor may be starting to go south, or am I just pushing the limits of the MCX frame? The stock version could never fly this fast with the stock MCX swashplate, even with a major servo arm adjustment. I know because I squeezed as much forward speed out of the stock parts as I could, but it was only about 60% of what I am getting now with th MCX2 swashplate installed.

I welcome any input as to what may be the cause.

So far, I have replaced the flybar and the inner shaft with brand new parts, but I am still seeing the trim issue, and a small amount of Toilet Bowl effect in hover.

Are there any GYRO settings I can try with the DX6i that can make it more forceful in maintaining course? Up till now, I am running completely manual, with just a boost to servo travel and rudder input actually backed off to 75% in the D/R EXPO section.

Thanks in advance!
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Old 04-02-2012, 03:03 AM   #2
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That is normal with an electric heli. As the battery wears down, yaw trim is needed.
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Old 04-02-2012, 09:50 AM   #3
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Originally Posted by Pfloyd View Post
That is normal with an electric heli. As the battery wears down, yaw trim is needed.
How come none of my other (5) models behave like this then? I only have to set trim ONCE at the start of the session with a new battery, and with my newer MCX2, I rarely need to adjust the rudder trim at all, even between battery changes..

Appreciate the input, but I was actually looking for a little more complete and informative answer than that.

Hopefully someone out there with experience over the "specific" problem/symptoms I describe can help.

Cheers.
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Old 04-02-2012, 10:32 AM   #4
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You have to remember the age of the mcx...the mcx2 and above most likely has been upgraded to fix that problem. I know on my 120sr after 2 mins., I have to keep adjusting the yaw. Also remember that the yaw drift on the mcx is not controlled mechanically.

You could have a weak motor, bad set of blades..change out the blades and see what happens....how does it piro?
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Old 04-02-2012, 01:08 PM   #5
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You have to remember the age of the mcx...the mcx2 and above most likely has been upgraded to fix that problem. I know on my 120sr after 2 mins., I have to keep adjusting the yaw. Also remember that the yaw drift on the mcx is not controlled mechanically.

You could have a weak motor, bad set of blades..change out the blades and see what happens....how does it piro?
Thanks for the additional input!

It piros fine with equal amounts in both directions. I am leaning towards a weak lower rotor motor since the blades are new. The model tends to favor heading to the LEFT in forward flight, and this is usually the direction it is turning when the trim gets off. Makes me think that the clockwise rotation of the lower rotor may be weaker than the top anti-clockwise rotor, and thus the top rotor is winning in the balance fight. I'm going to be upgrading my other MCX today with an MCX2 swash and a S300 conversion, so I will see if I see any of the same issues.

I did suspect that some of this could be due to the design itself, since this thing is flying about 300% faster than a stock MCX does. It is a handful at top speed. Seems that the tail boom of the S300 is maybe a little on the light/short side for this much torque and forward speed.
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Old 04-02-2012, 01:41 PM   #6
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If it piros both directions equally, then the motors are most likely ok...if it goes to the left on FFF, then you need to adjust the left servo rod a turn or two.
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Old 04-03-2012, 01:09 PM   #7
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My suspicion is one of the motors is on its way out. I have noticed that toward the end of a motors life it takes more amperage to get to the same.speed..even though it will still reach normal.rpms...it takes a bit longer to get there.....so one motor taking a bit longer to reach full speed than the other will create the effect you are describing...its 3 bucks for a new motor....swapping them both out cant hurt.
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Old 04-04-2012, 11:09 AM   #8
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I see you say the rotors are new. Hover at eye lever and see if either set looks warped. These thin rotors often get warped or come warped before ever installig them. I'd say about 50% of the new ones I've bought and my fried has bought are warped out fo the package. Often causeing HORRIBLE flight behavior.
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Old 04-04-2012, 01:24 PM   #9
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I see you say the rotors are new. Hover at eye lever and see if either set looks warped. These thin rotors often get warped or come warped before ever installig them. I'd say about 50% of the new ones I've bought and my fried has bought are warped out fo the package. Often causeing HORRIBLE flight behavior.
Very good points!

I am keeping my eye on the motors and will replace them if it comes to that. Where are you buying motors at 3 bucks a piece? Do you have a link to a store that sells them that cheap? I am always looking for a good source for replacement parts that ask a reasonable price and don't tack on some ridiculous shipping charge at the end which totally erases any perceived deal and then some!

I thought I had found such a site a few weeks ago, but upon receiving the parts I ordered, it became obvious that the parts being sold as NEW were actually salvage off of broken or otherwise defective models! They were not only NOT new retail packaged stock, some of the blades were more chipped and worn than the blades I needed to replace! I coudln't believe that someone culd be so blatant in their deception!

Just goes to show you that you have to be very careful when ordering online, since some unscrupulous online hobby shops will lie through their teeth to get your money! I went ahead and disputed the charges on my CC in advance of this store possibly trying to stick me with some BS restocking fee or other such nonsense!

I don't have any hobby shops wthin 100 miles of where I live, so I have to buy all my stuff online.

Regarding warped blades right out of a factory sealed package...I HEAR YA!! It is a real problem and is made worse sometimes by how some online stores package these for shipping.

I had to send an entire order of blades back to Amazon.com yesterday after discovering that they had shrink wrapped the stack of blade packages to a piece of cardboard as they often will do with small items to keep them from flying around inside the box.

Problem with this is that the heat used to perform the shrink wrapping, will easily deform the blades in the process! A few of the plastic bags the blades come in were actually fused to the shrink wrap plastic! NOT GOOD!

I was pretty sure that the entire shipment of blades (12 pair of both MCX and MCX2 uppers and lowers) were ruined, but I went ahead tested three separate pairs of lower rotor blades for my MCXs and all three pairs were badly warped and the heli was shaking violently before I even took off!

After that, I didn't even bother checking any of the other pairs and just put in a return/refund request. I sent them a note informing them that using any kind of heat in the packaging of this product is a major NO NO!

I ordered the same blades again, and they told me that they would not be using any shrink wrap this time.

An expensive lesson for them, cause that many blade pairs adds up!
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Old 04-04-2012, 06:12 PM   #10
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Hey GG...check valuerc on ebay. Great seller...great prices....reasonable shipping (the same cannot be said for Horizon Hobby and their outrageous shipping costs).

Buying from valuerc has proven to be cheaper than my lhs even with the shipping and he also carries the upgrades from rhk microheli and xtreme.

Edit: also if you dont find what you are looking for at valuerc be sure to check back in a day or two as his inventory seems to change fairly frequently.
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Old 04-04-2012, 07:57 PM   #11
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Originally Posted by newhelicrasher View Post
Hey GG...check valuerc on ebay. Great seller...great prices....reasonable shipping (the same cannot be said for Horizon Hobby and their outrageous shipping costs).

Buying from valuerc has proven to be cheaper than my lhs even with the shipping and he also carries the upgrades from rhk microheli and xtreme.

Edit: also if you dont find what you are looking for at valuerc be sure to check back in a day or two as his inventory seems to change fairly frequently.
Great! Thanks for the info!

Are the parts you get from this guy retail packaged? I ask because of that unpleasant online experience I relayed in my last reply where instead of receiving all the parts I ordered that were listed on the site as NEW and as such assumed we were talking in their retail packages, I received a single plastic bag full of loose unpackaged parts that looked more like a grab bag you would buy at a swap meet for 20 cents on the dollar than a few bucks cheaper than the going rate for the real thing!

I will definitely check this source out on eBay and see what he has to offer.

Thanks again!
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Old 04-07-2012, 11:04 PM   #12
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Yes all the parts are new in retail package. I have purchased quite a few things from him. All good and actually got here pretty quick (3 days both orders that I have placed) and I am in Texas and he is in New York.
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Old 04-08-2012, 02:39 AM   #13
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Originally Posted by newhelicrasher View Post
Yes all the parts are new in retail package. I have purchased quite a few things from him. All good and actually got here pretty quick (3 days both orders that I have placed) and I am in Texas and he is in New York.
I tried searching on eBAY for that store name and came up empty. Can you post a link to his storefront here for me?

Thanks in advance!

P.S. I recently bought some stuff from a store called NITROHOBBIES on there. Got some Tenergy 900 mAH batteries for my CX2 for $9.99 each and only 4 bucks shipping for the lot. They arrived in 3 days too!

Just bought some motors and an MCX2 LED kit from this guy last night and he can do combined shipping to reduce the shipping down to 4 bucks for everything.

Last edited by GG07; 04-08-2012 at 02:14 PM..
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Old 07-18-2012, 08:09 AM   #14
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Default Same here

A real noob, I am. But I do know this much: I bought two new Xieda 9958 and have not modified them. One of them exhibits the same rudder problem you describe and the other does not. And that's right out of the box. Wow! Because of this special circumstance I feel like I provided a constructive contribution to this thread. Anyways, I'm impressed for the amount of helicopter you get for the price. I haven't had any hard crashes, but I have a Walkera coax that's rotor blades will shatter if brought near a blade of grass. These little Xiedas seem very durable from what I can tell so far. Cheers!
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