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mCX Blade (eFlite) Micro CX Helicopters Information and Help


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Old 03-10-2012, 10:28 PM   #1
Marine6680
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Default [How to] fix vibration on mCX 2 with Carbon fiber Tail Boom

Ok got your attention... Now I need some others to test and confirm this fix.

I also added some more info and a video demonstrating this.

I installed the tail boom today and was getting the bad vibration everyone talks about. The vibration was so bad it was audible and the tail wagged at least an inch or so.

I tried different locations for the tail weight, secured it so it couldn't cause vibration. I made sure the shafts did not have play. I tried rebinding... nothing worked. I then noticed that the vibration did not happen at all throttle positions. After some more tinkering I noticed the vibration is coming from the front canopy.

So I think I narrowed it down... Removing the old tail changes the way air flows around the heli, this causes vibration.

I first tried removing the canopy but that didn't help. I then took the canopy off the rear top posts, and rotated the canopy on the forward lower posts so the nose pointed down and was touching the ground.

That fixed all the vibration, completely. The tail was as stable as before putting on the new carbon fiber tail boom.

I then tried just leaving the canopy off the top posts but basically in its normal position, and the vibration came back slightly, but wasn't too bad, just a slight amount.

Rotating the canopy up a little so the mounting holes are about 3/8 inch above the posts fixed all the vibration. Or resting the bottom edge of the canopy on the posts works.

It seems like the vibrations from the canopy are transferring into the frame. When you have it connected on both the top and bottom posts, the vibrations coming from both connection areas combines and amplifies. Basically wave amplification.

I noticed this because the vibration does not happen at full throttle or low head speeds, only during the normal flight head speed. I also noticed the vibration does not start immediately, when applying throttle from a stop, but after about half a second. The vibration has to have a little time to get into the feedback amplification effect.

Can someone else give this a try, and report back their findings?

I know it sounds crazy, but it works.

The only thing different that I have, is that I trimmed the bottom of the canopy so the MaxAmps 150mAH batteries fit. I did that a few days ago, so that didn't fix any vibration itself, though it could aid the fix by letting air flow better.

Using the mCX canopy may help, if anyone has one, try that as well.

Here is a video showing the fix. It is in HD and full screen will be best.

Last edited by Marine6680; 03-17-2012 at 08:36 PM..
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Old 03-11-2012, 09:10 PM   #2
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Anyone else been able to test this?
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Old 03-11-2012, 10:52 PM   #3
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Never had the vibration.
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Old 03-11-2012, 11:39 PM   #4
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A lot of people have. I am going to try the mCX body next.
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Old 03-12-2012, 09:56 AM   #5
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I had the vibration you described. Two things fixed it. The bottom of the main shaft can rub against the top of the battery holder. It main not be noticable without a battery in place. This can be easily fixed by placing a rubber grommet on each of the two back posts of the landing gear/battery holder piece. Some people have slightly shaved the center piece of the battery holder. The other thing that I believed helped was to make sure the tail boom was fully seated forward. It rests on a piece of the main frame when fully seated forward.
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Old 03-12-2012, 10:44 AM   #6
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Some also reported that rebinding it helped.
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Old 03-13-2012, 12:52 AM   #7
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Yeah... I fixed my vibration. It wasn't the shaft rubbing or anything like that. Just wondering if my fix helps others.
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Old 03-14-2012, 11:58 PM   #8
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An interesting possibly related observation. My upper canopy posts broke off before I installed the carbon tail boom and I have not experienced and tail shakes like I have read about. I will report back when I replace the frame which now seems like maybe not bothering with? Hmmm
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Old 03-14-2012, 11:59 PM   #9
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An interesting possibly related observation. My upper canopy posts broke off before I installed the carbon tail boom and I have not experienced any tail shakes like I have read about. I will report back when I replace the frame which now seems like maybe not bothering with? Hmmm
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Old 03-15-2012, 02:32 AM   #10
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I feel this is the root cause of the vibrations, but I need others to test.

I can make the vibrations come back and fix them again, all on the same battery pack, and never powering off the heli or transmitter, simply by adjusting the canopy like I described.

Seems the farther down on the posts I slide the conopy. (closer to center/tighter on the frame) the worse the vibrations.

It isn't caused by interference with the controls, as I trimmed the canopy to ensure there is clearance to the servo push rods and linkages.
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Old 03-16-2012, 02:54 AM   #11
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Have you taken a close look at the rotor main gears? One of my MCXs has a slight vibration problem and it is caused by one of the main gears not being totally straight on the axil. The top gear has a slight wobble and this causes the tail to vibrate a bit. In my case, it wasn't that bad so I didn't attempt to mess with the gears.
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Old 03-17-2012, 01:32 AM   #12
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If the gear was the problem, then I would always have vibration.

When I adjust the canopy the vibrations come back or go away based on how I put the canopy.

I will post a video soon showing the fix.
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Old 03-17-2012, 02:55 AM   #13
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Maybe your frame is cracked or warped.
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Old 03-17-2012, 03:27 AM   #14
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It is a brand new mCX.

I really need others to try this out.

I am not complaining about having vibration and needing help... I am saying I may have found the main cause for everyone's vibration and that I need people to test it out to see if it helps others as well.

Yeah it sounds crazy... but improper airflow can affect even full size aircraft.
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Old 03-17-2012, 03:43 AM   #15
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Quote:
Originally Posted by Marine6680 View Post
If the gear was the problem, then I would always have vibration.

When I adjust the canopy the vibrations come back or go away based on how I put the canopy.

I will post a video soon showing the fix.
Cool! It was just a suggestion since as I said... Both of my MCXs had the same gear wobble issue. Typical Blade QC issues out of the box!

On mine, the wobble smooths out at higher RPMs due to centrifugal force acting on the gear, but at idle speeds just before takeoff speeds the wobble and the resulting tail shimmying is very noticeable.

I've found with my models that the body will often times amplify the problem either visibly or acoustically, or both, especially with the mCX2 cause of the larger body area, primarily the tail.
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Old 03-17-2012, 07:10 AM   #16
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Quote:
Originally Posted by GG07 View Post
Cool! It was just a suggestion since as I said... Both of my MCXs had the same gear wobble issue. Typical Blade QC issues out of the box!

On mine, the wobble smooths out at higher RPMs due to centrifugal force acting on the gear, but at idle speeds just before takeoff speeds the wobble and the resulting tail shimmying is very noticeable.

I've found with my models that the body will often times amplify the problem either visibly or acoustically, or both, especially with the mCX2 cause of the larger body area, primarily the tail.
Did you check out the vid?

I think it is a bit of feedback and resonance amplification. Two sets of hard point mounting areas magnify the vibration fed into the board.
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Old 03-17-2012, 09:52 AM   #17
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Quote:
Originally Posted by Marine6680 View Post
Did you check out the vid?

I think it is a bit of feedback and resonance amplification. Two sets of hard point mounting areas magnify the vibration fed into the board.
Not yet. You hadn't yet posted one when I posted the last reply.

Where is the link to the video?
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Old 03-17-2012, 02:40 PM   #18
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Vid is in the OP, down at the bottom.
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Old 03-17-2012, 04:37 PM   #19
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Since you are changing the configuration of the mcx2 using the tail boom, ever try rebinding it..worked for a few people.
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Old 03-17-2012, 08:36 PM   #20
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Rebinding didn't fix it.
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