My cpp2 had been vibrating really bad recently, and upon further inspection I noticed that my main gear is no longer moving in the constant plane parallel to the fuselages that it should be in. That is, as the main gear spins, you can see it go up and down relative to the fuselage. In turn, when looking straight down on the helicopter, you can see the main rotor head center pin is not stationary, as it should be, but rather moves in a circular manner.
It's hard to explain, but it is keeping me from flying. I put a new man shaft& main gear in, so I know that that isn't bent. Is there a trick to levelling the main gear relative to the fuselage, or could I have messed something else up?
If you don't understand what the problem is let me know, I'll uplad some videos to YouTube when I get the chance. Regardless, this is keeping me from flying so whatever help you can offer is greatly appreciated!
Thanks
steve

Hi Steve,

When you rebuilt your heli, did you possibly leave something out? The blade frame has an upper and lower bearing for the main shaft (2 bearings) and also the main shaft retaining collar, are those still there? Those would be the first 3 things I would check for if I had a wobbly shaft that I knew was straight. Hope this helps,

Mark

Great idea! I looked, though, and they were all in place. Could they or the housing become misaligned or bent?

Steve,

I've never had the housing itself get bent in a crash, usually everything else will get busted before that could happen. Have you stripped all the head components off and left just the main shaft and gear on? Look closely at that when you add just a bit of throttle (enough to get it spinning), is there any wobble? Also check to see if the gear is firmly against the bottom bearing and the retaining collar is flush with the tapered end pointing down towards the upper bearing, also make sure the grub screw is tightened. Also, are you able to physically move the shaft side to side or up and down at all? You shouldn't, it should be locked in place nice and snug by the retaining collar. Hope this gets your problem solved.

Mark

The stock gear is know for being out of round and not straight height wise,and will not cause any wobble at the rotor head.possible causes for a wobble are unbalance blades,or the plastic center head is bent due to a crash,or a bent spindle.Kiwi4

If you look up from the heli and spin the main blade slowly, does the shaft spin straight? Might be that the shaft is actually bend, bearings are worn body is aging (where bearings are housed. I just rebuild my CPP2 and replaced body and tail. Much less vibration and very stable. A video would be interesting to diagnose the problem.

+1.....


Beanyo ~

What Kiwi4 said is exactly the first things I was going to also say to you. For one, the main gears are hardly ever "true" and perfect but still won't cause the wobble your describing, especially once the rpm's get up to speed. I don't have a CPP2, but I have two of the original CP Pro's and learned with the first one 2 years ago. So it sounds like you crashed it, and then got the wobble ? Or did the wobble just start occuring ?

The plastic rotor head is a weak part also, and after a crash or two will get some slop or tweaked and will usually need to be replaced. For one, when you crash and that little tiny retaining pin going into the plastic housing will usually ream out that hole in the rotor head making for some nice slop and eventually getting things loose which causes wobble. I've been through many of those ! To help save the rotor heads, most use a softer paper clip cut to size to use instead of that stronger retaining pin so that when a crash happens that softer paper clip pin will then break ASAP and save usually your main gear from stripping, and save your rotor head. So just a thought.

Also I've had some serious wobbles before, and I've gone mad before trying to find the cause with lots of new parts and swapping them out one at a time. Well guess what ? All it came down to before was unbalanced blades... So if you did crash it, and are now using different blades, that will definately cause some wobble if there unbalanced for sure. And yes, if your spindle is even bent a little you'll also get that wobble along with even a bent flybar or the flybar not perfectly centered, or even the flybar paddles not perfectly spaced.

But I would definately check that plastic rotor head. With the faster headspeeds that the newer CPP2's have, I bet its that possibly... Just with the slower headspeeds of the CP-Pro's, those things were a weak-link as far as getting loose and sloopy and bent from a mishap.

Its also a good idea to have a very, very tiny gap where your retaining collar is resting with that lip on the bearing... Say a paper thickness, or even 1mm... To tight, even resting just on the bearing will cause some drag even though its just resting on the inner race of the bearing. We also do this with our bigger birds...

You didn't take your spindle out before did you, and forget to put one of the washers in, or put them in the wrong order did you... ? Anyway, a video would possibly help if need be...


~ Jeff

Thanks for all the help!

A couple things; I'm pretty sire my main gear is warped really badly, so I'll replace that with my last spare when I get the chance
Two crashes ago I broke my plastic rotor head and replaced it with the aluminum one. My last crash was due to these vibrations, so I replaces my main gear & shaft, and my wooden blades with carbon fiber ones, bit neither eliminated the problem

The bearings holding the shaft popped out quote a bit, so it's possible I mixed those up. Would that make a difference? Also, (this might be relevant, I have no idea) I put the retaining collar in with the concave down, since that seemed logical, though I am not sure if that's correct. I'll run it a little looser and see if it helps.

I loosened the whole set up and spun the shaft by hand, and I couldn't really see the head moving too much. It's possible that I mistook the rotatating of the head DUE to the vibrations for a bent shaft CAUSING the vibrations, but understand that the diameter of the circle the center pin makes when spinning really fast is about 1cm.

When I put the aluminum head on my helicopter. I didn't use a pitch gauge at all. I'm kind of unfamiliar with that concept thusofar, bu would that have an effect on the balancing of my blades?
That being said, my blades are new and unscathed (and probably weigh the same ), so I don't know how else they could be unbalanced. There's probably some bit of knowledge I'm lacking, though, becaus I imagine so many people wouldn't have said it if it was that simple... Could be wrong idk

I'll experiment with the different suggestions, and definitely post a video tomorrow when I'm near my computer.

Thanks again for all the help so far

Some good advice for you Steve.

The upper and lower bearings are the same so not to worry.

Jeff had a good point, are you still using the same blades that were involved in the crash? If so they were probably damaged and you should think of replacing them. I would also recommend a blade balancer so you can throw your new CF blades on and make certain they are balanced before using them. A pitch gauge is nice but if you haven't messed with your pitch links then I'm sure your factory set pitch range is okay. Did you also track your blades? Out of track blades will also be a cause for vibration.

Mark

Alright, so i finally got a video up;
http://www.youtube.com/watch?v=Qxai_ChWqCw

EDIT: I put a new main gear & shaft on, too. the old gear was really warped. I left a little gap between the retaining collar and the shaft housing, making sure the tapered end was down. it seems as though im able to move shaft from side to side a little, but only a negligible amount... Also, the rotation seen when looking down on the rotor head doesn't seem to be present anymore, for whatever reason.

My biggest concern (since its expensive ) now is that it kind of looks like the rotor head is bent, which i didn't notice before. If you look in the beginning of the video the blade that starts on the right seems to be up higher than the one on the left... though i don't know enough to tell if that's true, if it would cause a problem, and if it would cause this problem...

I didn't check my tracking before, come to think of it, but it didn't seem too bad... I forgot to give it a close look this time (brain dead from college ) but i did glance at it and it didnt seem too bad. I couldn't tell from my own video cause of the angle & my lack of experience, maybe someone else can...

Anyway, is there any particular blade balancer i should look into, or a price range?

I also forgot to try my helicopter without the blades tonight, which would have made sense. I have too much work tonight, so ill do that tomorrow and see what happens.

Thanks, still

Steve

Have you balanced your blades? Could be that one is heavier than the other. Also check to see if the spacing between motor pinion and the main gear is even all around. The sound is not even from the motor as the main gear makes one turn.

Also, put a weight on the landing gear (or hold the heli down), and give it more throttle to see if the vibration stops as it gains speed.

Steve ~

Just as the others keep hinting about balancing your blades, it will make a big difference in the flying performance of your heli, and if not balanced will show exactly what yours is displaying in your video, although the shaking could still be a few other things also. When I was in Cali last year working there for the year, I had both my CPP's up and flying good, and then I stored them and took the CF blades off of them during this. The last time I flew them both, they flew perfect.... Well, when I got back home to Washington State, and got ready to take one of my CPP's for a spin after putting on the CF blades back on, I couldn't figure out why the darn heli was shaking so badly... Worse than yours in fact... So since I had a bunchload of new parts, I started the process of elimination and started swapping parts... Dang I gave myself a headache because I couldn't for the life of me figure out why this thing was still shaking... Heh... It drove me mad, because usually I can troubleshoot a heli in my sleep !

Well, as you can see in my pics below, I have CF blades for both of them... And there tracking tape is similiar on both sets of the blades... And guess what ? I had accidently mixed those sets up, and so those blades had variances then in the weights / balances than from when I flew them last with the right sets balanced for each bird. There was a difference in half a gram, and with all new parts on my CPP's (the original CPP's) it didn't matter, as it made the heli's vibrate like a big dog from having imbalanced blades. So I put on the correct set after weighing and balancing, and then the heli's flew very smooth with no more shakes...

I was so discouraged that I even flew one of the CPP's with that bad shaking, and even crashed at the end... This was 8 months ago... And as you can tell, at the end of the video when I crashed, that soft paper clip, snapped ASAP and saved my main gear and shaft... It beats that very strong stock retaining pin that will usually take out your main gear, and stress out your rotor head. The "paper clip mod" is really a saver, and so think about that also for the future...

Its hard to tell in the video, but the CPP was shaking violently... If you look at the antenna you can kind of see it then shaking :



http://vimeo.com/3464598


I wish I would have been able to learn on the newer CPP2's as those things have so much more power and especially tail control from the upgraded stuff now used on them. Not to mention already equipped for the Spektrum TX's... The original CPP's are VERY underpowered, and tail control on them is near to nothing ! Not to mention they had the famous glitching from the old school 72mhz systems that they had and used.... Eh....! I still fly them though for fun still to this day however, there all stock still except for CF main and tail blades...

My recent video then of one of them was 4 months ago at a bigger field, and although underpowered, there still a fun little craft to take out once in awhile... In this video now, you can see what a CPP fly's like with a set of blades that are balanced ! No more shaking !



http://exposureroom.com/members/J-MI...f14216dcf7b36/



~ Jeff

One thing you'll find is that even a brand new set of blades will never hardly be balanced perfectly. I've had some for my bigger heli's be close to perfect, but those are the higher end CF blades... Especially with any woody blades, the density could be different from one blade to another in the set you buy. Even if cut from the same tree ! Balance your blades....

When I first started out, I didn't have a balancer either, and so I just did my best to try and balance the blades by other methods... However, nothing beats a good balancer as I've learned and found out today. But back then, I'd just balance them like in the picture below from those plastic blades I tried for a bit :





The best way to track your blades is getting the headspeed up or even better yet, while the heli is under load and in a hover. Tracking tape of different colors really helps see which blade is the lower one, or the higher one. Remember, that even a small piece of tape weighs something and will then change the weight of the blade... It may be hard to imagine, but weights and balances play a big part in the rotating mass of these heli's... They like perfection, especially with the high RPM's, that there cranking... They don't like things that aren't balanced throwing them off.





You did good putting the tapered edge of the retaining collar toward the bearing... You don't want to much of a gap, and really you want it kinda snug, but most will still have about a piece of paper's width between the collar and the bearing to free up any extra drag or load from the bearing. I do the same, and like that very, very, small tiny gap there. Here is a picture just in case to show you that "lip" of the collar, and those step washers, and how they rest on the inner housing of the bearing :





This principle will apply to all your future heli's also, just like it even does for the CX2, as you can see in the picture below :





Here are a few more pictures that are from the original CPP's, but will still apply I believe for the newer CPP2's.... Just make sure you have everything in order since you may have taken that stuff apart :

Steve ~

Also make sure your spindle isn't bent.... You can roll it on a piece of glass to test it to see if it still remains "true"... Also, like most metal heads, just because there metal doesn't make them bulletproof... It just means when they take a good enough hit, they bend instead of the plastic just flexing, or eventually even just snapping... Even on my little Trex 450, in 5 crashes, I've had to replace my Microheli CNC rotor head twice now.... And the one that's even on now, I've bent back already a couple times. Metal is nice, but just more expensive to fix from those bad crashes especially from a pilot who is learning and crashing all the time... And the Microheli stuff isn't the greatest anyhow, as like others have said they use a very soft metal... [:-]

The best way to check if that rotor head is bent, is just stripping everything off the main shaft, but leaving just the rotor head to see if it still spins true and without wobble. A good set of digital calipers is also going to be something your going to need... For one, you want that flybar that you installed to be PERFECTLY centered as you installed it back on... And then, you also want those flybar paddles to be PERFECTLY centered also as you measure from the end of one to then the flybar cage... Everything has to be perfect, as that heli is spinning its rotors, and nothing can be off or else...... It all matters.... Trust me....


Hope this helps some,

~ Jeff

I apologize in advance for the lack of continuity; but with all the information from so many people its hard to keep my thought processes easy to follow... ;

Yeah, so i checked the spacing, and it isn't even all around. I noticed that sound, too, but thought it was all part of the same problem. Anyway, that means of the three gear & shaft parts i have, all of them are warped. Each one also seems to have quite a bit of wobble on each end of the shaft... Is there any easy way to fix the spacing? Could it be a sign something is screwed up, or should i just keep replacing gears until i get a good one?

I ran my helicopter at various speeds without my blades (just my flybar & paddles) and it seemed to be alright. There were slight vibrations and a very small range of throttle, but it seemed insignificant.
I'll probably get some digital vernier calipers and double check, though, cause i'll use them in my school's machine shop too probably.

Next step is balancing my blades on the wine glasses looks a lot cheaper and quicker than ordering a scale offline, hah.
After that, ill put them on and check tracking, and also run my helicopter at a higher speed to see if the vibrations go away...

And jeff, thanks for the pictures and videos, they helped conceptualize everything pretty well. Also, the new controllers and their lack of interference are incredible. I can't even fly my airplane here because of all the interference

Alright, i guess i should have picked up on this before, but i didn't realize when people were saying "bent spindle" they may meant the thing inside my rotor head...

I took an alan wrench to the inside of my blade grip, and something is definitely bent in there, i just can't figure out how to get my blade grips off...

Even on our bigger heli's, there is going to be variances of that gap between the main motor pinion and the main-gear... When you set the gear mesh, make it a habit to check the mesh from a few points on the main gear. And then find the inbetween and go with that.... To help you maybe understand a bit further in detail here is a quote from RC-Heli magazine and the link to the tip :



http://www.rchelimag.com/pages/howto...owto=29&page=2


The gear mesh won't have anything to do with the wobbling your having on the heli, but will wear out your gears faster, and also creating excess drag and heat problems, reduced flight times, etc. etc...

What will make your heli wobble is your spindle / feathering shaft (same thing) and they almost always need replaced in a crash. Definately check it and roll it on a piece of glass... After a crash, I don't even check mine, I just replace it... Just a very slight tiny bend will cause havoc with your heli without a doubt. To remove the spindle, it best to use 2 alan wrenches on each end of the spindle to break them free... Usually one will free up, and then allowing you to slide the spindle out as the blade grips should loosen up then to remove them also.

Most likely, if that spindle is bent then that is the big cause of your vibrations, following then by imbalanced blades. But the spindle would be the #1 cause at this point...

Yeah, i think it is the spindle... i managed to get one of the alan screws out, but i can't get my blade grip to come off my rotor head... the second one is still locked in so im having trouble getting that out, too.
i shouldn't need to take both out, right? should i just pull harder on the blade grip to try and free it up?

im just afraid of damaging it further, or sending small parts flying


EDIT: nvm, i just pulled it off...

Yeah, definitely the problem...

although, my rotor head was brand new the last time i crashed, so it couldn't have been the problem before. i was flying wooden blades that had been in a crash before, though, and lost uneven amounts of their plastic coating. i'm convinced that the crash was due to unbalanced blades, or poor tracking before.


It was a mess;


I'm going to order whatever parts i need and hopefully get it fixed this weekend. Ill post a (hopefully) success video

Thanks everyone!

except i dropped the center-ball part of the three piece ball bearing things you see in the top right of this picture http://www.helihobby.com/commonImage...n/EFLH1182.jpg and i cant find it so i might have to buy a whole new grip set

EDIT: I was wondering if someone could confirm thisare the ball type bearings (top right most bearing in the picture i linked to) called thrust bearings?
I'm going to try to find the same dimension bearing online somewhere so i don't have to drop $35 on something i pretty much already have :/

Thanks, still!
Steve