mCPx: Known issues, fixes, information rollup

[litehawkdown]

Originally Posted by Sky Blue Lou

Google is my friend.

You know there's lots of facets to this hobby that aren't about flying. New terminology and technologies, skills learned or relearned... I don't think reflowing a board will be one of them for me.

I have to draw a line somewhere. I'll pay the sixty bucks and get a new one.

New V1 boards are becoming harder and harder to find. And if the 3in1 is pooched there is not much too lose by trying.

[Sky Blue Lou]

Originally Posted by litehawkdown

New V1 boards are becoming harder and harder to find. And if the 3in1 is pooched there is not much too lose by trying.

You're right there. Will a v2 board work? Everything else is the same, right? I just can't imagine how one would do that at home unless you have experience or special equipment already. Good on you for giving it a shot. Post the results - I'm curious as hell about this.

[litehawkdown]

Update after a re-flow with hotair rework station.

First the issue my MCPX V1 was having was swash tilt when throttle/pitch was risen. As soon as I applied throttle the swash would run to the extreme end of travel on the bottom of right cyclic servo.

First thought was to add subtrim to counter the swash movement. This worked for a bit. But soon the swash would start to tilt to the left. A reset of the trims to center or less trim would not last long. Yet again the swash would tilt to the right or to the left in time.

I tried everything one does to fix a finicky MCPX. Then I tried the reflow of the 3in1 as a last resort. Result was the tilt was still there. But now the subtrim entered to counter the unwanted movement held strong. But further testing is needed as only 2 batteries were ran with out issue so far.

I also noticed one of my chips is on a angle. Not sure but I am wondering if it is my gyro chip that is not sitting level. (Front of the board left bottom corner) Not sure why it would matter if it was or not. But it could be why it wants to drift. Also come to think of it my other MCPX board sits funny and that would explain the way it dives back at me in flips

Anyhow I hope this holds up. Right now the bird has been brought back to stock to test. But the ultimate goal with this heli is to turn it into a DBL spin 15500 with a 12000kv tail

Edit: There was trim still on the TX from me trying to counter it earlier. I removed it and the MCPX now has no more tilt on the swash what so ever. Seems the re-flow fixed it.

[skinney2]

Originally Posted by skinney2

My MCPx with a brushed motor suddenly started spinning. I first suspected a bad tail motor, but that (a new one) is working fine. When I hold the MCPx and spool it up, it works fine for a while, but then the frequency of the sound of the main motor drops and the tail jerks back and forth. I probably have more than 100 flights on this main motor. Is this problem likely caused by worn out brushes? Is it difficult to replace the main motor?

I replaced the main motor and the problem went away. I don't understand how a bad main motor can cause spinning.

[jcmo]

Originally Posted by skinney2

I replaced the main motor and the problem went away. I don't understand how a bad main motor can cause spinning.

Semi-Educated guess here - I'll take a crack at it... I would say the gyro is constantly trying to maintain a constant heading using the tail to counter the torque generated by the rotation of the main rotors. It requires a small amount of time to adjust to large changes in torque.

From reading your description it sounds like the main motor is experiencing intermittent performance, running for a while, then stopping momentarily, then running again in brief intervals. This would cause the gyro to detect that suddenly the tail motor was starting to overpower the torque of the main blades because the motor is spinning down mid-flight, causing clockwise yaw. The gyro slows or stops the tail motor to stop clockwise motion.

When the motor kicks back in, the reverse process happens, and the heli wants to yaw counterclockwise against the torque of the main blades. The heading-hold gyro wants to resist this rotation, and starts spinning the tail faster.

You may have a bearing seizing or binding in your motor, and it "freezes up" the motor from spinning freely for a fraction of a second every hundred (or thousand) or so times the motor's shaft completes a rotation. That sort of thing can get better or worse based on the temperature of the parts.

So simplifying things, when the motor is cool, the problem is better. As it heats up, the parts in the motor start binding, and the gyro detects the need for tail on - tail off - tail on - tail off - tail on. Sounds like the kind of thing that would cause a wag or 180/360 degree kickouts to me

Edit: The Gyro's reaction time may be faster than the motor's stopping and starting. The Tail motor, however, would require a little longer to get to the speed the gyro indicates. That's pretty much all the brain power I can muster at the moment. Time for a nap.

[Razskidoo]

What causes intermediate wobbles?
Thanks
Rick

[mejmea]

Originally Posted by Razskidoo

What causes intermediate wobbles?
Thanks
Rick

Can you be more specific? There are a lot of things that can contribute to wobbles but can you clarify what you mean by "intermediate" wobbles?

Have you checked this thread?

[Razskidoo]

I tried searching and that post didn't show up. Then agin I'm typing with an iPhone. Thanks
Anyway,
I think it's call TBO?
In hover and forward flight it wobbles then stops, wobbles then stops.
The shaft, gear, bearings, rotor assembly all new.
I have two other MPCXs and they fly perfect!

Dirty servo?

My 130x started doing the same thing.

I'll clean both Heli servo's and see if that helped.

[mejmea]

It's definitely worth cleaning the servos. One other thing beyond what you mentioned that I would definitely check is the feathering shaft (pull one blade, put the other one straight out, and then use a screwdriver to turn the feathering shaft. If the blade tip goes up and down then the feathering shaft is bent). The previously mentioned thread has a bunch of ideas so hopefully one or some combination will help you! Just for grins, have you tried swapping 3 in 1 boards with one of your good ones to isolate whether the problem may be board/gyro related?

[Razskidoo]

Cleaned all the servos and no change. New shaft assembly also was installed. I did find one servo's threaded rod was slightly bent. I can see the part that connects to the link from the servo move in and out, not as smooth as the others. So wondering if this caused the wobbles due to trying to compensate the extra movement?! Are these servo that sensitive that a slight bend in the travel rod it will cause issues? I have a replacement servo on order. Let you guys know if this worked. Only thing left is the board settings or the board itself!

Thanks

[Stubbz]

A bent servo rod will make the heli not have zero pitch at mid stick, mine have bent a couple times from crashes so i just tweak them back until im at zero pitch at mid stick again. Unless it's rubbing on a servo somewhere, that could cause issues. The rear servo rod is very close to the servo but a lil pull on it should move it far enough from it to not rub on the servo. Servos do not come with the rods either they are bought sepertely.

[mejmea]

Are you saying that the lead screw that is the driving mechanism for the servo is bent? If so then it seems like it could potentially cause issues due to extra friction/binding/interference. You can buy just the replacement servo "mechanics" which are slightly cheaper than buying the whole thing so if it turns out that is the issue you might be able to repair that servo and thus have a spare.

I had a bad case of intermittent wobbles yesterday after a couple of crashes. I was pretty sure it was a bent feathering shaft and so checked it (yup, blade wobble) and replaced it. Although the weather isn't great today I managed to get a couple of flights in between downpours and so far so good.

I'll be curious to hear what you ultimately figure out.

http://www.horizonhobby.com/products...9-gram-SPM6833

[Razskidoo]

The servo screw is what's slightly bent. The links/rods are perfect and swash is level at all travels. That's why replacing the servo's mechanics might resolve my issue.
Thanks for the in-site though.

[Razskidoo]

After swapping parts, the issue followed the the rotor assembly.
Found the rotor hub have a crack. Replaced and problem solved.

[mejmea]

Originally Posted by Razskidoo

After swapping parts, the issue followed the the rotor assembly.
Found the rotor hub have a crack. Replaced and problem solved.

Nice job, glad it's fixed!

[cpmboy]

Just recently mine started having this sudden-turn-45 deg right-then-lost power syndrome (it happened before). Maybe some loose wire at the batt connector?...

[ercapoccia]

Try to replace the main motor.

Inviato dal mio GT-N7100 con Tapatalk 2

[bobbygz]

I just picked up an mcpx from a friend of mine for a really good price. Never been flown, complete with a case for it. I had to get a smaller heli to fly in the culdesac while my 130x board is being fixed at MegasMicros (2servo connectors came off). The trouble I've been having (it's a v2 btw) is when I start doing 3d with it, I never know what the tail is going to do. Sometimes it's rock solid while other times it will tail spin. Both positive and negative pitch are set to 75% and for that matter it's set up per the manual. I've heard about the extended boom fix. Is there anytning else I can do for better tail hold? 2d flight is flawless, it only happens when I start flipping her and I am just now getting proficient at inverted flight so it's not like I'm banging her around with hard 3d. I am so glad I got the 130 first, she flies so much better than the mcpx (cough, cough, uh, once you get her tweaked) and the mcpx almost seems like toy grade when comparing the 2. No offense to hardcore mcpx fans, I just really love my 130

[Stubbz]

I agree with the toy feeling, the V2 is same way when compared to the BL just because of overall headspeed.

V2's are gutless. It's just your collective pitch management that needs work. at 75% pitch you should be pretty good to use it a bit but you still have to be smooth in transitions. put it up to 85 or 90% and it's even harder to fly in and out of inverted without losing the tail but it does help to teach you the management you need to not gain or lose height while doing manuvers. A brushless main is about the only thing that may really make it better, i've seen some videos of guys throwing the V2 around a lot it seems(not sure if there brushed or been modded to BL) but seems almost like that kind of flight would be impossible after flying mine a lot. I have no probly flipping in and out with mine and even doing inverted circuits and 8's but it's no 3d machine thats for sure, you can even hear when your about to blow the tail out.

Check for loose connection where the tail wires hookup to the board i've heard that can be a factor also.

[linklemming]

The extended boom helps a little but it still seemed to me to happen when the motor really bogged and moreso when the battery got low. I actually started having fun with TBO and could do some pretty creative manuevers like a quick stop from high speed pass, would get TBO, modulate it which would rotate the heli 180 and then take off in that direction.

One of my V2s stock had a weaker motor and would do it more. Replaced the motor and it was better but its really a luck of the draw.

Astroid designs sells both a 7mmm motor and mount which might help, unfortuantely they are always out of stock and I got mine from overseas (oversky). I have them on both my V2 M5 11000kv with an extended tail boom. Didnt try the motor and mount and extended motor without the BL motor though so others could comment.